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地球能源大未來 ─背面網路全文版及英文版

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【所長的話】 原文版 【Prelude from IAA Director】 (The English version) All sentinent beings, blessed with sensory organs, can appreciate the beauty of our environments, the rhythm of the seasons, and the daily cycle of sun rise and sun set. With the development of the life sciences and the physical sciences, we human beings can start to understand that the miracle of life is precious and is dependent on a delicate balance of many processes. As the first photographs from the astronauts showed, while on their way to the moon, our earth is a most beautiful and colorful home suspended in the lonely dark void of deep space. It is our responsibility, for each and every one of us, to help protect our environments and to conserve the resources for our children and their children and the generations to come.

In the last two decades, the evidence is irrefutable that human beings, in our quest for improvements in life, have made huge changes to our environments. Not only are we consuming the natural resources at an alarming rate, we are polluting the air, the water, and the earth, perhaps in a permanent way. In this IAAQ, we have invited Professor Yuan Lee to remind us of the importance of climate change, sustainable development, and the role of a responsible society.

We have also invited Professor Frank Shu to tell us about how we indeed can help by making nuclear energy safe for humans and safe for the environment, and also how to reverse the damage to our atmosphere by removing carbon dioxide from the air and returning them into the earth.

As astronomers, we can particularly appreciate how we occupy a very tiny space in the vast Universe within a very tiny moment in time. We should use our own unique moments to do our best, not only to be most responsible for our actions, but to recognize and repair the damages from our past, in order to improve our future. This begins with a dialogue, with the pursuit of knowledge, with the commitment to work hard. （Author/Paul Ho）

天聞季報海報版與網路版由中央研究院天文及天文物理研究所製作， 以創用 CC 姓名標示-非商業性-禁止改作 3.0 台灣 授權條款釋出。 天聞季報網路版衍生自天聞季報海報版。超出此條款範圍外的授權，請與我們聯繫。 創用 CC 授權可於以下網站查閱諮詢 https://isp.moe.edu.tw/ccedu/service.php。

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【徐遐生院士談地球新能源─大自然贈與的禮物】 中文網路全文版

作者：徐遐生 1, 蔡駿 1, 羅芬臺 2 1 中央研究院天文與天文物理研究所 2 中央研究院化學研究所 地球能源簡介 ─核能 地球擁有的天文資產讓她富含能源。在海洋裡的水分子包含兩種可回朔至宇宙大霹靂的氫 同位素，輕的氫驅動太陽裡的熱核融合；而重的氫讓人類在地球上有機會應用熱核融合來 發電。氦是宇宙中含量僅次於氫的元素，不過地球上並沒有自大霹靂遺留下來的氦；地球 上的氦都來自於重元素（地球上岩石的組成物）的不穩定同位素釋出的 alpha 粒子（氦的 原子核）。不穩定同位素具有放射性，是超新星爆炸（中子星的前身）的遺骸，存在於地 球內部，提供熱能讓地球內部保持高溫。含有最多中子的重元素是鈾，是目前核能發電反 應爐中，用來驅動核分裂反應的基本原料。核分裂反應的減速材料是由輕的氫組成的輕水， 功能如同冷卻劑，能夠帶走反應爐的熱量，其原理是讓核分裂反應釋出的中子減速。這樣 的反應爐我們稱為「輕水型反應爐」（Light Water Reactors; 簡稱 LWR）。「輕水型反應爐」 發電過程不會釋出二氧化碳，但卻非常具有爭議性，原因是其以下四個缺點（4 S’s）：    

沒有好的核廢料解決方案（solution） 反應爐可能釋出大量放射性物質的安全問題（safety） 核能武器擴散的國安問題（security） 高純度鈾礦不具永續性（sustainability）

─水力 太陽熱核融合反應釋出的熱輻射是維持地球上所有生命的能量來源，太陽光可穿透大氣層 溫暖地表，照射在海面會蒸發部份海水，但蒸發並不帶走鹽分，所以水蒸汽凝結造成的降 雨是純水的來源。若水氣聚集在寒冷的高山，那取而降雨的就是落在山隘上的冰雪了，冰 雪融化後，潺潺細流便能匯聚成奔騰的江河。若把江河之水利用水壩攔在位於高處的水庫， 接著將這些水往低處洩出，便可藉水力驅動渦輪，轉動金屬線圈內的強力磁鐵，進而產生 交流電。

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─風力 風是溫差和壓力差造成的空氣對流現象，而溫差和壓力差則是陽光不均勻照射地表（日夜 交替和地表的高低落差）造成的。風力也可驅動渦輪並發電（效率大約 50%；水力發電效 率約 90%）。風力發電相對於水力發電價位高很多，因為空氣的密度比水小 800 倍。 ─光電效應 陽光照射在太陽能電板上引發的光電效應也能發電（效率最高時為 20%），不過太陽能在 夜間無法發電，天氣多雲時也無法穩定發電，所以使用它時需要從其他基載能原尋求備用 電力。 ─光合作用 陽光照射在綠色植物上產生的光合作用能利用光子裡的能量，把空氣中的二氧化碳（CO2） 和土壤裡的水分（H2O）轉換成有機化合物，讓植物得以生長及繁衍（效率約 1%）。這些 生成的有機化合物含有的氧原子數量與參與反應的二氧化碳及水相比之下較少，因此光合 作用會產生副產物氧氣（O2），並將其釋放到大氣裡。反之，綠色植物死亡後，在有機物 質裡沒有完全氧化的碳和氫會與空氣中的氧氣結合，重新形成二氧化碳與水並放出熱量， 二氧化碳與水都是溫室效應氣體（greenhouse gases；簡稱 GHGs） 。與氧氣結合的反應若伴 隨著火燄則稱之為「燃燒」，其放出的熱量可以讓水沸騰，產生的蒸氣也可驅動蒸汽渦輪 並發電（若直接燃燒生質，發電效率可達 20%）。若與氧氣結合的反應在生物體（單細胞 或多細胞）內伴隨著使用食物的能量（效率低，且不同物種效率不同）緩慢發生，則稱之 為「消化」，再藉由呼氣或排泄釋出不需要的產物，即二氧化碳和水。 ─化石燃料 十億年前被埋在地底深處的生質，在無氧、高溫與高壓的環境下變成今日的化石燃料，即 煤、石油及天然氣，也成為現代化科技社會的原動力。燃煤是最常用的發電方式（效率約 35-40%） ，但是過程中會排放出有毒的易揮發重金屬（如汞） ，因為煤是從地面下挖出來的， 其中含有這類重金屬的小碎塊。 在運輸燃料的原料選擇上，石油佔有幾乎無法取代的地位，因為它具有稱為 ETUDES 的優 點如下：  其能源投資報酬率（Energy Return On Investment；EROI）一向大於 10（Extraction）  運輸石油很划算，因為它是一種富含能量的液體（Transportation）  可藉由提煉分離低和高分子量碳氫化合物，並藉由加工製造出不同的化學產品（例 如塑膠）（Upgrading）  其產品的供應商和商店分佈很廣泛（Distribution）  其市場已深入社會的每一個角落（Establishment）  很容易儲存在汽油桶裡供使用者使用（Storage） 普羅大眾認為天然氣是一種乾淨的炊事燃料，因為其燃燒的過程幾乎不會排放有毒物質， 在提供相同能量的情況下，燃天然氣產生的二氧化碳大約只有燃煤的一半。除此之外，燃

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天然氣產生的膨脹煙道氣也可使渦輪轉動並發電，在所謂的「複循環（combined cycle）」 發電廠裡，煙道氣產生的廢熱可用來沸騰燃煤發電場裡蒸汽鍋爐的水，讓天然氣的發電效 率高達 60%。美國使用頁岩水力壓裂法開採天然氣，此法花費的成本低的驚人，其他國家 特別是中國，則是採用「自噴法」（rush to gas）開採天然氣。 天然氣經常是以通往無碳未來的「燃料之橋」的名義銷售，所謂的無碳未來即人類使用的 能源完全來自像太陽能和風力這樣的可再生能源。有人會問，當風不再吹了或是太陽光不 再在天空中閃耀時，天然氣還是得出面收拾殘局，在這樣的情況下，天然氣如何只扮演這 種暫時的角色？建造越多的風力和太陽能發電廠，其實只會讓人類更加依賴天然氣。 從二氧化碳排放看減緩氣候變遷 人類燃燒化石燃料導致大氣中二氧化 碳的濃度持續增加，到完成這篇文章為 止，濃度已經從工業革命前的 280 ppm， 增加到 395 ppm 了（如圖一），科學家 壓到性的認為，二氧化碳濃度的增加是 造成今日氣候變遷的主因。 從減緩氣候變遷的觀點來看，我們可以 把前面提到地球上主要的能源分成四 個類別： 類別一、會產生大量二氧化碳的能源：  煤  石油  天然氣 圖一、2005 年之前的過去一萬年內，大氣中二氧化碳的

這三個化石燃料常常被混為一談，但其 實它們並不相同。煤驅動了工業革命， 在這個新的時代，我們確實需要一些比 較好的燃料，但如果我們打算停止使用煤，那就得要提出方法挽救所有投在新燃煤發電場 的資金，因為在中國、印度及德國（有鑑於日本被海嘯摧毀三座核電廠，德國正逐步關閉 國內的核能發電廠）燃煤發電廠正如雨後春筍般的建造中。 濃度（ppm）以時間為函數作圖。資料來源：IPCC 。

由於技術面的成熟，文明國家選擇以石油為運輸燃料，因為石油容易被萃取、運輸、提煉、 散佈及儲存，使用很方便，其每單位能量價格是煤和天然氣的十倍。 使用水力壓裂法開採讓天然氣在美國某些地區很便宜，但相較於石油，使用管線運輸天然 氣卻非常昂貴，因為它是氣體密度很低，單位時間內如果要運輸相同質量的石油及天然氣， 天然氣需要較粗的管線。若要船運天然氣到海外，得先將天然氣液化才划算。液化天然氣 （Liquefied Natural Gas；簡稱 LNG）需要低溫並加壓，所以 LNG 一旦從美國運到台灣， 價錢會立刻翻六倍。由於液化及運送困難，頁岩氣產地目前並不輸出 LNG，因此產地會供 過於求，這就是頁岩氣價格很低的原因。此外，萃取天然氣的過程若有外洩的狀況發生，

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其主要成分甲烷（90%；溫室氣體的一種），20 年內對環境的破壞是相同數量二氧化碳的 72 倍，100 年內則是 25 倍。雖然甲烷在大氣裡會慢慢被氧化作用破壞掉，如果沒有明智 地使用天然氣，其對環境還是有潛在破壞力，這在補救人類正面臨的氣候變遷問題上並不 是一個最好的選項。 分類二、可再生、可靠而且不會產生二氧化碳的能源：  水力發電  生物燃料  地熱  太陽熱能 水力發電是 20 世紀一個傑出的科技，但 21 世紀的今日，世界上各大河流幾乎都已被水壩 攔住並建成發電廠，所以水力發電已很難再擴展了。 生物燃料科技的能源投資報酬率是一個經常被討論的議題，巴西聲稱他們生產的甘蔗乙醇 平均能源投資報酬率達 8.3，不過他們沒有把甘蔗渣（甘蔗裡的糖被榨取出來後剩下的殘 渣）算進輸入能源裡，燃燒甘蔗渣也可以增加發電量，若將甘蔗渣也算進來的話，巴西的 甘蔗乙醇能源投資報酬率大概只接近 2。 經濟學家也爭論著美國生產的玉米乙醇其能源投資報酬率是大於 1 還是小於 1，不管結論 是什麼，玉米乙醇造成全球糧食價格上漲因此評價很差。研究人員希望能著手研發第二代 使用非糧食作物為原料的生物燃料，以避免糧食價格上漲的問題，為達成這個目標，以下 兩點是必需的：（a）使用非糧食原料，例如廢棄木材及野草等等；（b）在不適合栽種糧食 作物的貧瘠土地上生產生物燃料。一般來說，每公頃土地栽種出的生物燃料必須足夠多才 能維持合算的生物能源產量，這與需求（b）不一致，貧瘠的土地要不是缺水，就是土壤 缺乏植物生長需要的養份，或是兩者都缺乏，我們可以用水及（或）化學肥料（生產自石 化工廠）灌溉貧瘠土地，但大量化石燃料就必須引進生產系統，這與人類想擺脫對化石燃 料的依賴相矛盾，這樣的意識刺激一些人開始研究海藻煉油技術，此技術目前還在發展的 初期階段。 地底下的熱源如果接近地表（如冰島），開採地熱會是一個可靠而且完備的科技，特別是 使用地熱做為暖氣，不過對位於溫帶地區的台灣而言，夏季從寒冷的深海開採冷氣可能比 較有需求。地表附近沒有地熱的地區，可利用鑽井技術向地表下十公里處開採地熱，不過 有些人提出，有鑑於過去發生過鑽油井嚴重事故，似乎沒必要對環境做這種具侵略性的開 採。 太陽熱能的使用原理是將太陽輻射至地球的熱量先由東西向的碟狀儲存槽捕捉起來，然後 儲存在熔鹽裡，這樣夜晚時也有能源可以使用。太陽熱能發電的缺點是太陽光能量密度不 高，以及跟太陽光電效應（solar photovoltaics；簡稱 solar PV）相比效率不高，光電效應可 以直接將光能轉成電能，而太陽熱能發電只能間接使用光能。 分類三、可再生而且不會產生二氧化碳但不太可靠的能源：  風力  太陽光電。

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我們可以用水壩控制何時要洩水發電，以滿足人類不同時段用電量不同的需求，不過風力 發電不一樣，在不穩定的低大氣層附近，風速和風向說變就變難以預測，在很熱或很冷大 家很需要用電的時節，說不定風連續一個禮拜都不吹。另外，風力在深夜最強，這時冷空 氣自高空沉降下來而且大部分的人都在睡覺，用電需求很小。我們可以說風的行為就像一 台有意識的車，而且紅燈行，綠燈停… 太陽光電發電是間歇的，因為日落後發電會停止，我們這時卻得要打開電燈，就算在白天 它的發電效率也不太可靠，因為只要有雲飄過電板上空遮住陽光，就會干擾它的發電效率。 不過，在我們最需要用電的炎熱正中午，是太陽光電發電效率最好的時候，這點能夠滿足 我們的用電需求。 太陽光電是唯一提供個人化使用的產能技術，換句話說即每個家庭或企業都能擁有自己的 發電系統，以降低對電力網的需求。太陽光電主要的缺點是需要政府補助不少費用（包括 安裝），而補助的政策在民主國家每次選舉過後就可能改變，導致太陽能電板的市場很不 穩定。目前全世界使用的眾多能源當中，太陽光電只佔 0.01%，只要此技術需要政府補助， 那就很難讓此數字上升（請注意，與太陽光電有關的文章通常會引用最理想化的理論功率， 此功率指的是在天氣晴朗的正中午太陽光電的發電效率，但其實其平均功率只有理論功率 的 20%而已）。 分類四、可靠、永續、並且不會產生二氧化碳的能源：  先進的核分裂反應爐  熱核融合 不論核能的來源是融合或分裂，它都不是可再生的能源，因為核分裂的燃料鈾或釷，以及 地球上核融合的燃料重氫經過核反應後，都無法進行逆反應變回反應前的物質。不過海洋 裡重氫的存量非常豐富，用來發電可以供應全世界使用到太陽演化成紅巨星（譯者註：大 約 50 到 70 億年之後），由此看來核融合不是可再生的能源而是永續的能源。不幸的是， 核融合發電技術目前還不到商業化的階段，來不及幫忙解決氣候變遷的問題，因此它仍然 只個地球未來的能源選項。 反之如果鈾-235 是核分裂發電原料的唯一選擇，以 2050 年預計全世界能源需求量來估算 的話，高純度鈾礦的存量只夠使用六年，以這樣的使用率來看，鈾礦甚至在 2050 年之前 就會用盡，所以鈾-235 既不是可再生，也不是永續的地球能源。 核增殖反應爐 熔鹽增殖反應爐（Molted Salt Breeder Reactors；簡稱 MSBR）除了可以解決核廢料及大量 輻射物質外洩的安全問題以外，還可以解決核武擴散的國安問題，另外，它也是一個能永 續發展的核分裂發電選項。在討論 MSBR 之前，我們先大致了解一下增殖反應爐的項目。 ─鈾-238 增殖反應爐 鈾-238 的豐存度是鈾-235 的 100 倍，鈾-238 獲得一個額外的中子後會變成鈾-239，接著鈾 -239 透過兩個貝他（beta）衰變將兩個中子轉變成兩個質子後會變成可裂變的（fissile）鈽

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-239，這種將可孕的（fertile）鈾-238 轉變成可裂變鈽-239 的增殖（breeding）程序，能延 長高純度鈾礦的使用年限到 600 年（前提是所有能量都從分裂反應爐產生）。含有鈾的礦 物可以溶解在海水裡，因此日本建議在海水裡利用聚合物網來捕捉鈾，實驗證明此技術具 有經濟效益，海洋能提供的鈾足夠驅動鈽經濟數百至數千年，因此鈾-238 增殖反應爐是地 球上可發展的能源，比爾蓋茲已經投資了此技術。 ─釷增殖反應爐 釷增殖反應爐具有更好的潛力，釷元素只有一種穩定的同位素釷-232，所以不需花大錢分 離同位素，而且釷-232 的原子核有 90 個質子與 142 個中子，屬於偶-偶核素（even-even nuclide）是一種可孕材料，可藉由吸收一個中子來製造可裂變材料。釷-232 吸收一個中子 後會變成釷-233，接著透過兩次貝他衰變把兩個中子轉換成兩個質子後就變成鈾-233，鈾 -233 的原子核屬於偶-奇核素，內含 92 個質子與 141 個中子，是一種可裂變材料。鈾-233 吸收一個慢中子（註一）以後，其巨大的原子核增加的能量足以讓它產生劇烈的振動，並 分裂成兩塊不穩定的裂變產物，從富含中子的原子核分裂而來的裂變產物也富含中子，如 果它們不丟出 2 到 3 個中子會很難維持穩定的狀態。一個鈾-233 原子核吸收一個慢中子並 分裂了以後，平均會產生 2.49 個裂變（快）中子。 上述一個完整的分裂反應完成後產生的中子平均數量大於 2，其中一個中子可以用來維持 鏈鎖反應，另一個中子則可用來將鄰近的釷-232 轉變成釷-233，釷-233 又可再衰變成新的 可裂變鈾-233。若想有效使用這些中子，可以將反應爐核心建造在一個不會吸收分裂反應 產生的快中子，只將其減速的材料以內，那麼額外的 0.49 個中子可以讓更多的釷-232 轉變 成鈾-233。原則上釷增殖反應爐的數量可以以指數的方式增加，直到其產生的能量能滿足 這個世界需求。 釷元素在地殼的含量大約是鈾元素的 3 到 4 倍，也就是說，若高純度鈾礦的存量可以讓人 類使用 600 年，那麼高純度釷礦的存量還可以使用 2000 年之久。身為一個化學元素釷有 一個重要的性質跟鈾相反，就是釷不溶於海水，因此在海洋中找不到釷，不過釷在一種稱 為獨居石（monazite）的黑色海沙中含量很豐富。台灣的海灘有很多獨居石，如果你覺得 海灘的獨居石不夠多，還可以去海裡找，海底還有很多。由於釷沒有其他商業用途，所以 沒人調查過地球上能用作核燃料的釷究竟有多少，如果我們願意退而求其次使用低純度釷 礦的話，那現有存量還可以使用幾百萬甚至上億年。因此，釷熔鹽式增殖反應爐是可以永 續發展的能源。 熔鹽式增殖反應爐 LWR 運轉了半個世紀以來，其產生的核廢料一直是個問題，在這裡關於 MSBR 的討論將 從它能解決核廢料產生的問題開始，圖二簡單的解釋了 MSBR 如何解決核廢料問題。LWR 廢燃料棒裡的高階核廢料主要是由以下三個成份組成：  鈾-238 及未反應的鈾-235 混合物質、  鈽-239 及從鈾-238 附屬中子放射線產生的錒系元素、  由可裂變原子核分裂而來的裂變產物。

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未參與分裂反應的鈾，可以與鈽-239 及微量錒系元素安全地分離開來，方 法是利用標準的氟化作用程序讓鈾與 氟結合，產生六氟化鈾（UF6）氣體， 氣體會上升並離開熔鹽系統。一旦分 離反應完成，大量的鈾-238 會與鈾 -235 混合在一起（由六氟化鈾的狀態 轉化成更穩定的氧化態） ，這樣的物質 無法用來製作核彈，可以將它們儲存 在地質儲存槽裡（如美國猶卡山或是 其替代地質儲存槽） ，或提供給反應爐 技術（註二）開發單位當成燃料使用。 另 外 有 一 種 稱為 「 高溫 冶 金 加 工 」 （pyroprocessing）的技術在美國愛達 荷國家實驗室研發，這個技術可以將 鈽-239 和微量錒系元素從裂變產物裡 分離出來

圖二、如何解決 LWR 的核廢料問題示意圖，此圖提供一個 起動 MSBR 的方法。©中研院天文所。

裂變產物還包含半衰期是 30 年左右 的放射性元素，我們可以把這些物質 裝進乾式儲存桶，存放在地底下 300 年以後，它們的放射性就會降至低於 背景值，這時就可以打開儲存桶，把 具有經濟與藥用價值的稀有物質回 收。

鈽-239 和微量錒系元素可利用化學反應將其製成氟的化合物（例如氟化鈽；PuF3），若將 氟化鈽溶進共熔的氟化鈉/氟化鈹（NaF/BeF2）熔鹽（一般傾向選擇載體熔劑鹽）裡，便可 製成燃料鹽氟化鈽//氟化鈉/氟化鈹。接著將此燃料鹽灌進熔鹽轉化反應爐裡（Molten Salt Converter Reactor; MSCR）直到達臨界質量後就可維持鏈鎖核分裂反應。此反應產生的中 子數量會超過維持爐心鏈鎖反應的需求量，這些多出來的中子會隨機跑出反應爐心並照射 在包圍住爐心的熔鹽池裡，熔鹽池內含氟化釷（ThF4）溶進共熔的氟化鈉/氟化鈹熔鹽，這 裡的釷全是釷-232，它們捕獲中子再經兩個貝他衰變後，會變成可裂變材料鈾-233。鈽-239 和微量量錒系元素經上述過程完全反應完後，LWR 的核廢料問題便可解決了。 LWR 核廢料的解決方式有兩個優勢：  

它消除現有 LWR 產生鈽造成的放射性武器危機、 它提供一個方法讓 MSBR 起動，因為它可以製造自然界不存在的鈾-233。

人造鈾-233 在熔鹽池裡以四氟化鈾（UF4）的分子狀態存在，為了把它從熔鹽混合物裡萃 取出來，我們可以持續將熔鹽池裡的熔鹽慢慢灌入另一含有氟氣泡泡的腔室裡，氟氣穿過 熔鹽會與四氟化鈾結合形成六氟化鈾氣體，並飄進另一內有金屬鈹的腔室，六氟化鈾遇到 鈹會產生化學反應形成四氟化鈾及氟化鈹，若把四氟化鈾-233 溶進共熔的氟化鈉/氟化鈹熔 鹽裡，新的燃料鹽四氟化鈾/氟化鈉/氟化鈹即形成。接下來將此燃料鹽灌進反應爐心，以

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可裂變鈾-233 取代 MSCR 的鈽-239，此反應爐便成為 MSBR。利用電解可將 BeF2 分解成 鈹和氟氣，再分別導入上述兩個腔室，便可重複利用把熔鹽池裡的鈾-233 繼續分離出來。 上述的化學過程很簡單，而且可以遠端遙控，如此一來就可避免讓操作員暴露在輻射的危 險當中。另外，維持這些化學反應的能量與反應爐產生的能量相比（10-5）根本微不足道。 燃料鹽在 MSBR 裡不斷地循環直到 耗盡所有可裂變材料，其裂變產物只 有短半衰期的物質，只需掩埋到地底 300 年，因此，MSBR 本身並沒有解 決不了的核廢料問題。 那麼國安問題呢？難道不能用鈾 -233 製作炸彈嗎？答案是不行。因為 如果鈾-233 周圍有高速中子飛來飛 去，那它就無法避免高速中子入射， 接著自身丟出兩個中子並產生鈾 -232 的反應發生，這樣的過程會讓鈾 -232 與鈾-233 一起存在在炸彈裡而 且幾乎不可能分離開來。鈾-232 衰變 的過程會釋出高能伽瑪射線（gamma ray） ，即使有殉道者願意用未分離的 鈾-233/鈾-232 混合物製作炸彈，並試 著利用港口貨櫃走私到某個城市，那 鈾-232 的存在會讓這個炸彈很容易 被蓋格計數器偵測到。伽瑪射線也會 干擾精密的電子控制裝置，必需遠離 任何武器裝置。若有簡單得多的替代 方案存在，不會有國家或恐怖組織想 嘗試用鈾-233 製作炸彈，因此 MSBR 對國安來說是安全的。

圖三、二流體 MSBR 一個可行的爐心設計（專利審核中）。 前方有四個熔鹽泵，用來將燃料鹽循環進黑色的爐心裡， 爐心裡的燃料鹽被減速劑石墨包圍著，所以達到臨界密度

圖三是二流體 MSBR（如圖二的概念 示意圖）一個可行的機械設計圖。核 分裂反應產生的中子會高速離開反 應系統，為了降低中子的速度但不將 其吸收，反應爐心的建材除了金屬螺 栓與螺帽之外，其他部分完全是由碳 基（石墨）材料製成，只要高溫的氟 化鈉/氟化鈹熔鹽裡不含水，石墨便 不受其化學影響。熔鹽池的外牆則是 用金屬（赫史特合金 N，可抵抗熔鹽 侵蝕）建造，在熔鹽池裡隨機遊走的 中子在撞到外牆，把金屬活化成麻煩 的低階核廢料之前，大部份會被釷 -232（以氟化釷的形式溶在氟化鈉/

後便開始穩定的鏈鎖反應。包圍著爐心的熔鹽池和燃料鹽 是以石墨牆隔開，爐心產生的熱可藉由石墨牆傳導至熔鹽 池（此為第一次熱交換） ，接著池裡的高溫熔鹽會流進池外 的第二熱交換器，第二熱交換器的功能是將熱能從具放射 性的熔鹽傳遞到不具放射性的工作鹽裡（例如用在生質超 級烘焙法的醋酸鈉（NaAc）/醋酸鉀（KAc）熔鹽） 。熱能 交換完畢後，冷卻的熔鹽便流回熔鹽池的頂端，這時熔鹽 池裡的熔鹽上冷下熱因而引起熱對流，讓熔鹽能均勻的混 合。另外，冷卻的燃料鹽會離開爐心流進熔鹽泵，在此所 有裂變氣體會被氣態氦經由白色的管道帶走，接著燃料鹽 會經由紅色的管道再流回爐心，並開始另一個新的循環。 ©中研院天文所。

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氟化鈹熔鹽裡）吸收掉。 核能事故 所有的核能反應爐都為因應緊急事故做了自動關閉的設計，MSBR 也不例外，只是它有較 大的安全幅度。沒有反應爐會因為鏈鎖反應失控而發生核能事故（車諾比反應爐除外，此 核電廠的設計有很可怕的瑕疵，從來沒有通過前蘇聯以外的核能管理檢測），大部分的核 能事故是發生在反應爐安全地關閉之後，事故會發生是因為分裂產物產生的衰變熱無法有 效消散。 有固定固態燃料元素的核電廠有可能會出什麼問題呢？福島核電廠提供了一個例子。地震 發生時，雖然該核電廠的反應爐安全地關閉了，但是燃料棒持續地釋出衰變熱（其能量只 有反應爐火力全開時的百分之幾），地震與大規模海嘯讓該核電廠失去了全部的電力網， 等於破壞了用來冷卻燃料棒的冷卻系統，這時電廠裡的輔助緊急設備必須儘快冷卻燃料棒， 不幸的是輔助電力也失效，因為柴油引擎的燃料被海嘯沖走了，加上電池耗盡，而且冷卻 劑水也因沸騰而蒸發掉了，福島核電廠面臨了大麻煩，燃料棒缺乏有效的冷卻開始熔毀， 水蒸氣碰到極高溫的燃料棒便產生氫氣，氫氣離開爐心進入圍阻體後氫爆一觸即發，圍阻 體並沒有建造的很堅固因而被炸開，大量的放射性物質便從圍阻體的裂縫逸散到環境當 中。 以上的核能災害都不會發生在依照圖三設計的二流體 MSBR 身上，因為 MSBR 有以下幾 個安全特色：  MSBR 不使用水，所以不需要建造在靠近大量水的地方，例如海邊或是河川旁，這 些通常是人類喜歡居住的地方。另外，MSBR 可以在地震過後存活，而且不會被海 嘯毀掉。  熔鹽反應爐可以全自動運作，不需操作員介入。  中子減速材料是浮在熔鹽池（冷卻劑）裡，當事故發生失去冷卻劑後，這些減速劑 會掉到爐心底下，中子便無法被有效率地減速，進而停止核分裂反應。  若燃料鹽因任何原因而過熱的話，位於其下方的排液栓塞會融化接著燃料鹽便會流 進一個沒有減速劑且體積較大的氣冷槽裡，在這裡達到意外的臨界是不可能的。 若 MSBR 的核分裂反應太快，熔融的燃料鹽會升溫並膨脹，接著部份燃料鹽會流出爐心， 進而降低反應速率。反之，我們如果需要多一點電力時，可以讓熔鹽池裡的熔鹽（冷卻劑） 循環快一點，如此便可以加速降低燃料鹽的溫度，讓燃料鹽收縮進爐心裡加速核分裂反應。 這跟太陽控制其核心熱核融合反應速率的原理一樣，太陽有個氣態的核心，降溫會收縮， 升溫會膨脹，如此便可平衡從表面被輻射帶走的能量。我們不再需要擔心 MSBR 過熱或過 冷，而是要擔心明天看到的太陽與今日所見不再相同。 排液栓塞的構想最初是由美國橡樹嶺國家實驗室（Oka Ridge National Laboratory）提出， 他們發明了讓反應爐使用液態燃料元素這個概念。如上所述福島核電廠的例子，一個使用 固態燃料元素的核電廠，如果其主要冷卻系統出問題，就必須要使用位於相同位置的裝置 來維修。如果是液態燃料，我們只需將燃料移到另一個地方，也就是已經預備好的分離式 緊急冷卻系統（緊急傾瀉槽）。我們選擇了空氣來當冷卻劑，因為我們可能會失去水、失 去熔鹽池冷卻劑，但幾乎不可能失去空氣。

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若想使用空氣來冷卻核能裝置，那麼分裂產物的衰變熱不能太多，也就是說清除高階核廢 料若能在核電廠運轉的狀態下進行，那麼對核能安全是一個很大的貢獻。一個穩定運作的 MSBR，在火力全開的操作條件下遇到緊急情況而關閉時，相對於傳統核電廠會有較小的 衰變熱，因此讓反應爐更安全。為了讓反應爐達到超級安全，反應爐應該避免建造的太大， 因為其火力全開的產能與衰變熱的多寡成一定的比例。 不過，當核電廠完全停電時（例如福島核電廠）其實連開電扇散熱的電力都沒有，所以流 進氣冷傾瀉槽的燃料鹽還是沒辦法有效的散熱，對於這樣的意外事故，我們以鋼來製作熔 鹽會散佈進去的另一層寬大超薄空間，熔鹽流動的過程會將熱量傳導進鋼裡，這樣的設計 讓熔鹽可以在十秒內凝固，因此燃料鹽裡可能存在的任何分裂產物都會停止流動，加上固 態鹽的蒸氣壓非常低，所以沒有具輻射性的氣體能夠逃逸至大氣，而且系統裡沒有水，所 以不會有氫氣產生氫爆。鹽類是由元素週期表上左右相反的兩個族元素所組成，一個具有 極正電性，另一個具有極負電性，沒有其他元素能夠介入它們，所以鹽類不會與其他元素 產生化學反應進而威脅到反應爐系統，話句話說：鹽類不會著火。 還有一個額外的預防考量：圍阻體的圓頂要能夠抵擋嘗試衝撞反應爐的噴射機。圓頂得要 好好設計以預防意想不到的事情發生，操作員必要時也得要棄守反應爐，就算沒人看守， 反應爐也要是安全的，這意味著我們不能把衰變熱禁錮在圓頂內，而是需要把能量傳遞出 來。Westinghouse AP 1000 的設計就是一個很好的例子，它的水泥製圓頂不是密合而是部 份對外開放，圓頂下方有層薄薄的鋼製蓋子，可將氣體阻擋在反應爐內部，同時將熱量傳 導到蓋子的外部表面，再藉由圍阻體的對外空隙讓空氣循環以對流的方式冷卻反應爐。最 後，MSBR 可以遠端遙控，如此便可將意外事故對人類造成的衝擊減至最低。綜上所述， MSBR 是很安全的核能發電設備。 生質變成生質燃料的超級烘焙法─碳中和或負碳 運輸石油很容易，所以石油 公司很富有而且強大，我們 因此很難用依賴原始微生 物在室溫下進行發酵反應 的科技來取代石油，這樣的 化學反應速率都很慢，因為 如果不慢慢反應，這些有機 體會燒焦。 我們的研究策略就是用火 來對抗火，或者更精確的說， 利用超級烘焙法。烘焙法通 常被認為是利用生質能最 有效的途徑（如圖四），傳 統的方法包括燃燒一種燃 料，在不完全隔絕空氣的環 境下讓煙道氣加熱生質，此 圖四、木本植物的烘焙法。資料來源：Bergman et al. 2005。 環境具很有限的通風口讓 空氣中的氧氣進入，過程中會袪除易揮發的有機化合物（Volatile Organic Compounds；簡

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稱 VOCs）及水蒸氣，最後留下焦黑的 固態殘餘物－木炭。。燃料可以是天 然氣、生質的一部分或者烘焙生質的 產物，VOCs 通常也會被當作補充燃 料。 超級烘焙法的專利申請尚未通過，此 法是專利的第一作者在中央研究院構 想出來，並使其成熟的一個改進程序， 是利用熔鹽來產生替代能源的一般程 序的一部份。超級烘焙法使用熔鹽當 作傳熱媒介，熔鹽直接接觸並將熱傳 給生質，生質完全浸在熔鹽裡以隔絕 空氣裡的氧氣。傳統烘焙法需要很多 小時才能完成炭化過程，超級烘焙法 只需要十分鐘，因為在相同溫度和壓 力的條件下，熔鹽每單位體積的熱容 比煙道氣大 2000 倍。

圖五、桌上型超級烘焙法 Crankberry 機器。©中研院天 文所。

專利的第二作者設計了一個桌上型的 機器（圖五「Crankberry」） ，可以在實 驗室的尺度下讓超級烘焙法自動化進 行。使用 Crankberry，第三作者和其 團隊已經超級烘焙了各式各樣的生質 原料，並且一致得到好的結果（如圖 六） ，根據實驗累積的數據及與巴西蔗 糖乙醇一樣的計算規則，我們估計超 級烘焙法在示範的規模下，其 EROI 是 40:1，如果我們把由可再生材料而 圖六、各式各樣生質原料經由超級烘焙法利用醋酸熔鹽 來的輸入能源算進分母，能源投資報 （醋酸鈉/醋酸鉀）製成的木炭。©中研院天文所。 酬率便下降至約 9.6:1，依照巴西的標 準，這還算非常好的比率，而且可以媲美市面上石油公司的紀錄。由於「石油峰值」 （peak oil；譯者註一） ，我們的 EROI 相對於石油工業的 EROI 將會越來越好，而且燃燒我們的產 品是碳中和（carbon-neutral；譯者註二）的活動。 超級烘焙法使用的熔鹽是醋酸鈉和醋酸鉀的共熔混合物（一樣的組合也用來調味香醋鹽味 薯片），此混合鹽在溫度達到 235oC 時會融化，如果溫度超過 460oC 則會分解成碳酸鈉 （Na2CO3） 、碳酸鉀（K2CO3）及丙酮。當熔鹽的溫度達到 300oC，會產生能完全燃燒且維 持環境碳中和的環保煤（ecocoal） ，可當作自然界中煤的替代燃料；而當溫度達到 500oC， 則會產生生質炭（biochar） ，是一種精細的負碳（carbon-negative；譯者註三）土壤改良物 質（如圖七） 。我們注意到掩埋生質炭是一種負碳活動，不只對掩埋生質炭的國家有益處， 對整個世界都有正面的影響。因此，原則上製造生質炭然後將其掩埋可以變成真實的炭貿 易基礎。舉例來說，石油公司在任何地區提煉一噸石油後，需花錢請某人將一噸生質炭埋 進地底以改善土壤的品質。此行為產生的資金流動，是由富有的企業流向土地面臨沙漠化 的貧窮鄉村，如此便可達成雙贏的局面，大家都可以得到擁有乾淨的生活環境這個好處。

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從生質分離出來的易 揮發有機化合物不是 用來燃燒，而是具有 還原的功能，所以生 質每單位重的經濟報 酬比傳統烘焙法高， 特別是除了水（註三） 以外，醋酸是易揮發 有機化合物裡含量最 圖七、銀合歡經 300°C 超級烘焙 10 分鐘後產生的環保煤（左圖），及 500° 多的成分，如前所述， C 超級烘焙 11 分鐘後產生的生質炭（右圖）透過掃描式電子顯微鏡 （Scanning 如果我們讓醋酸鈉/ 醋酸鉀熔鹽溫度高於 Electron Microscope；SEM）看到的樣子。左圖左下角的比例尺代表 10 微 460oC，丙酮和碳酸鈉 米；右圖左下角比例尺則代表 20 微米。超級烘焙達 300°C 時，易揮發有機 / 碳酸鉀熔鹽就會產 化合物會從環保煤裡被去除，但很多微小結構會留在細胞壁裡；達 500°C 時， 生，藉由醋酸與碳酸 一些醋酸鹽會被分解成碳酸鹽，並且只留下細胞壁。下圖是多孔性的 BET 鈉/ 碳酸鉀熔鹽進行 （Brunauer-Emmett-Teller）測量（每單位質量分布的範圍；單位「平方公 以酸為基底的快速反 尺／克」）。©中研院天文所。 應，我們便能還原出 醋酸鈉/醋酸鉀熔鹽（以及二氧化碳和水）。 丙酮是高價值化學物質，可做為工業用溶劑，也可做為一般飛機燃料的原料，所以超級烘 焙法不只能創造高生產率的固態生質燃料，用來與自然界中的煤競爭；還能製造液態原料， 用來減少運輸工業部份對石油的依賴，我們也得到可以取代天然氣的未壓縮可燃氣體。 超級烘焙法可將用來每天生產一噸生質燃料的設備體積大幅縮小，好處是能顯著降低重要 設備的初期投資。藉由使用足夠小巧的批量處理設備，便可將其用卡車運至偏遠的超級烘 焙位址（採收生質的地方） 。另外， 即使在烘焙過程中會有少部分熔 鹽因流進木炭氣孔裡而流失，也 不會造成太大經濟損失，因此超 級烘焙法的生產率是有可能達到 吸引人的經濟報酬。傳統烘焙法 對小規模公司來說是不可能有利 潤的，但上述超級烘焙法的優點 有可能讓這些小公司賺到錢。 我們的下一個步驟可能是在澎湖 縣進行一個示範計畫，用以驗證 擴大使用可移動式及可批量處理 的超級烘焙法其經濟可行性。我 們的目標生質是一種在澎湖縣過 度生長稱為銀合歡的灌木叢，其 生長範圍占澎湖縣面積的 70% （圖八） ，在日據時期引進台灣， 原本是栽種來當柴火，是一種固

圖八、銀合歡生長的範圍占澎湖縣面積的 70%，剩下 30%的面 積正面臨銀合歡入侵的威脅。秋冬時銀合歡非常乾燥，是將其採 收並超級烘焙的最佳時機（照片攝於 2012 年 10 月 19 日） 。 ©中研院天文所

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氮植物，在貧瘠的土壤不需化學肥料也能生長。現在，大家都使用天然氣或丙烷來做飯， 銀合歡因為具有極強適應力的優勢，已經成為一種威脅到台灣（以及大部分東南亞地區） 本土植物生長範圍的侵略性物種了。使用此生物廢料當做生物資源，完全符合澎湖縣永續 發展的目標。 台灣的農業委員會（Council of Agriculture；CoA）傾向嘗試將銀合歡這個具侵略性的植物 根除，不過如果沒有深入土壤挖除銀合歡的根部，並且清除掉其散佈在土壤裡面及表面能 發育的種子，那根除悠久的銀合歡是不可能的。為了讓 CoA 能夠試驗根除計畫，我們在採 收銀合歡的時候可能要將其樹枝清除乾淨。如果根除計畫失敗了，銀合歡會在接下來的季 節重新生長，約花三年的時間就可以完全復原。 另一個糟糕的情況正在西北美 發生，那裡的冬季太暖和，再加 上夏季偏乾旱，這樣的氣候被認 為是山區森林爆發松樹樹皮甲 蟲病害的主因，此病蟲害從南加 州蔓延到英屬哥倫比亞（如圖 九），每天有數百千計的松樹倒 下。我們提議在這些倒樹造成森 林野火、腐爛釋出溫室氣體、或 電線被倒下的大樹枝擊中造成 昂貴且危險的斷電之前，將其超 級烘焙掉，我們會將產生的生質 炭埋入同一片森林的地底，目的 不只要將生質炭的碳封存數千 年，也要促進新的樹木生長，如 此便可鎖住更多環境裡的碳。

圖九、位於美國科羅拉多州受到樹皮甲蟲侵襲而正在或已經死亡 的松樹。(AP/Colorado Forest Service/Jen Chase)

森林危機影響的不僅僅只有北美，2012 年發表在自然期刊的一個調查報告顯示，全球其中 81 個森林裡，226 個森林物種中有 70%因根部系統缺水而處於垂死的邊緣(土壤含水量太少)。 這個現存的威脅應該要有一個適當的解決方法。 生質炭對土地再生也有幫助，一個在美國科羅拉多州廢棄銀礦進行的實驗顯示，對每公頃 的土地使用 100 噸生質炭處理過後，植物恢復生長所需的水分將比未處理過的土地少 17 ％（如圖十）。我們提議在試驗性的實驗裡使用以超級烘焙法製作出來的炭粉（只要有混 合樹皮與木質莖），測試在土壤生產力方面，使用炭粉做為土壤改良劑是否對澎湖貧瘠的 土地也能促進類似的顯著改善，進而減少部份需要使用在農業灌溉的水分。利用現有的數 據，澎湖縣可以做出更明智的抉擇，是否應該（1）在未來十年內，著手有系統地進行根 除銀合歡的計畫，（2）控制銀合歡擴散的同時被動地將其收割做為生物資源，或（3）主 動地栽種銀合歡，但並不施放由石化原料製成的氨肥。

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圖十、左圖（攝於 2010 年 7 月） ：一個在科羅拉多洲的廢棄銀礦在施放生質炭土壤改良劑之前的整整 一個世紀看起來都是這個樣子，生質炭是由烘焙生病的松樹製成的。右圖（攝於 2011 年 8 月） ：同樣 的位址在施放生質炭土壤改良劑一年後的樣子，劑量約每公頃施放 100 噸生質炭。（圖片版權：Tony Hooper）

重要的挑戰 氣候變遷是 21 世紀一個重要的挑戰，人類文明的命運或許取決於人類是否能提出一個合 理且科學的方法來迎接這個挑戰。我們的最終目的是要結合熔鹽反應爐和超級烘焙法這兩 個技術。因為一些物理及經濟的理由，我們很難用其他能源取代天然氣在渦輪發電裡的地 位，也很難取代其在超級烘焙法輸入能量裡的地位。但是，就 MSBR 來說，我們不一定得 直接使用其產生的核熱量來驅動渦輪發電機（這是一個困難的耦合），反之，我們可以將 具放射性的熔鹽池（氟化釷/氟化鈉/氟化鈹）所攜帶的熱量經由第二轉換器（如圖三背景 所繪，這是一個簡易的耦合）轉換到不具放射性的工作鹽（醋酸鈉/醋酸鉀）裡，如此一來 我們便可得到一個結合，可以取代天然氣在上述兩項工作裡的地位。雖然核電很昂貴，但 核熱量是很便宜的，比天然氣還便宜得多。因此我們可以使用核熱量將生質製造成生質炭、 丙酮和合成氣（具非常高的生產率），這比採礦得到的煤、鑽井得到的石油及水力壓裂得 到的頁岩氣還便宜且乾淨。合成氣可以產生電力的基本負載；丙酮可以用來製作用於運輸 的液態燃料；利用生質炭則可以達成負碳封存。 煤、石油及天然氣是地球上很珍貴的資源，如果我們使用這些資源來製作耐用品，而不是 燃燒它們，其實它們對氣候變遷並沒有影響。我們並不是要化石燃料公司關門大吉，而是 需要這些公司將這些原料拿去做別的事情。其他研究學者或許有更好的辦法能夠落實化石 燃料經濟體的轉型，如果真有這種辦法，那他/她們應該要開始行動了。物質宇宙經過將近 140 億年的演化，原則上大自然已經給人類很多能夠取代化石燃料的能源了，接下來就靠 我們自己著手利用這些能源，讓地球變得更美好。 （作者/：徐遐生、蔡駿、本院化學所羅芬臺；中文翻譯：楊淳惠；審校：蔡駿、黃珞文） 註一、鈾-233 原子核內有奇數個中子，此慢中子與鈾-233 的未成對中子有相反的自旋方向。 註二、例如集成式快中子反應爐（Integral Fast Reactor；IFR）及旅波式反應爐（Traveling Wave Reactor；TWR） 註三、生物炭製成後，我們將水還原並回收用以清洗及還原鹽類物質。 譯者註一、石油產量達到最後的高峰值，並將持續下降直到結束。

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參考資料: http://e-info.org.tw/node/68999 譯者註二、任何組織、營利單位或個人將其釋放到大氣中的二氧化碳藉由某些方式（如植 樹）吸收掉，因此其碳排放量的淨值為零，故稱之為碳中和。 譯者註三、生物或商品在成長或製作過程中排放的二氧化碳比吸收的少，我們稱這種現象 為負碳。最常見的例子就是植物的光合作用。另一個例子是以鎂矽酸鹽為基礎原料的水泥 在硬化過程亦能有效吸收空氣中的大量二氧化碳，使得在整個製程中呈現負碳的現象。 參考資料: http://www.greenmaster.org.tw/web/web_2a_1.php?kk=110

天聞季報海報版與網路版由中央研究院天文及天文物理研究所製作， 以創用 CC 姓名標示-非商業性-禁止改作 3.0 台灣 授權條款釋出。 天聞季報網路版衍生自天聞季報海報版。超出此條款範圍外的授權，請與我們聯繫。 創用 CC 授權可於以下網站查閱諮詢 https://isp.moe.edu.tw/ccedu/service.php。

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【徐遐生院士談地球新能源】 原文海報節錄版 EARTH ENERGY: GIFTS FROM NATURE (The English Poster Version) Mitigating Climate Change Human burning of fossil fuels has increased the atmospheric concentration of carbon dioxide from 280 ppm before the industrial revolution to 395 ppm at the time of the writing of this article (Fig. 1). Overwhelming scientific consensus holds that this increase is the main cause of modern climate change. To avoid climate catastrophe, we need to transition away from burning fossil fuels.

In this article, we introduce two alternative paths that are being developed at ASIAA. Nuclear Breeder Reactors

Figure 1. The concentration of CO2 in the atmosphere in ppm as a function of time during the past ten thousand years

Conventional nuclear energy based on (up to 2005). Data source: IPCC fissioning U-235 (enriched relative to natural uranium) in light water reactors (LWRs) is not a sustainable replacement for fossil fuels because there is only six years of energy use at the levels needed globally in 2050 if all that energy were to come from U-235 in high-grade uranium ore. In addition, LWRs are (unfairly) perceived to possess a nuclear waste problem, safety issues against the massive release of radioactivity into the environment, and security issues against weapons proliferation.

U-238 is more than 100 times as abundant as U-235, and adding a neutron to U-238 makes U-239, which becomes Pu-239 after two beta decays to turn two neutrons into two protons.

Pu-239 is fissile. Such a program of “breeding” to turn a fertile (U-238) into a fissile (Pu-239) raises the high-grade uranium ore use (if all power came from fission reactors) to 600 years.

Uranium-bearing minerals are soluble in seawater, leading to Japanese proposals to use polymer filters to trawl for uranium from seawater. The supply of uranium in the oceans suffices to power a “plutonium economy” for hundreds of thousands of years.

The potential for thorium breeder reactors is even better. Thorium has only one stable isotope, Th-232, which eliminates the need for expensive isotope separation. Moreover, while Th-232, an even-even nuclide with 90 protons and 142 neutrons, is only fertile, it can be made fissile by absorbing a neutron. This turns Th-232 into Th-233, which, after two beta decays that convert two neutrons into two protons, produces U-233. An even-odd nuclide with 92 protons and 141 neutrons, U-233 is fissile. When U-233 has a slow neutron added to it (one with a spin opposite to the unpaired neutron that must be in U-233 because it has an odd number of neutrons), the increase in the energy of the large nucleus is enough to cause the resulting nucleus to vibrate

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violently into two uneven pieces, called fission products. Fission products from the breakup of a neutron-rich parent are too neutron rich to remain in such states without spitting out an additional 2 or 3 neutrons. When a U-233 nucleus absorbs a slow neutron and fissions, an average of 2.49 (fast) fission neutrons will be produced in the aftermath.

Because this average output of neutrons per fission is greater than 2, apart from the 1 neutron needed to sustain the chain reaction, another is available to turn a neighboring Th-232 nucleus into Th-233, that then decays into a new fissile U-233. If the neutron economy is managed properly by building the reactor core out of materials that do not absorb fission neutrons parasitically while slowing them down to low speeds, the extra 0.49 neutrons on average per fission reaction can make more U-233 from Th-232 than we started out with. In principle, then, thorium breeder reactors could exponentially expand their numbers until we have enough to supply the total energy needs of the world.

Thorium is 3 to 4 times as abundant as uranium in the crust of the Earth. What is a 600 year depletion time for high-grade uranium ore becomes something more like 2000 years for the depletion of high-grade thorium ores. As a chemical element, thorium behaves oppositely to uranium in one important respect: thorium minerals are not soluble in seawater. Thus, they are not found in the oceans of the Earth, but are ample in beach sand of a variety black in color called monazite. Lots of monazite exits on Taiwan beaches. If you think it is not enough, just go out in the ocean and get some more from the ocean bottom. Because thorium has no other commercial applications, no one has surveyed how much thorium might exist in the world as potential nuclear fuel. The reserves are likely to last millions of years, if not billions, if one were to go to lower grades of ore. Thus, thorium MSBRs are sustainable.

Molten Salt Breeder Reactor Our more detailed discussion of MSBRs begins with the observation that it offers a solution to the nuclear waste problem that has accumulated from half a century of operating LWRs. Figure 2 schematically provides the solution. The high-level nuclear waste from the spent fuel rods of LWRs consists of three main components:  Unreacted U-235, mixed with U-238,  Pu-239 and higher actinides from collateral neutron irradiation of U-238,  Fission products from the splitting of fissile nuclei.

MSRs Can Rid LWR Waste & Safely Breed for U-233

Chain reaction, breeding, and processing in liquid salt

• LWR spent fuel – U-238, U-235 – Pu/actinides – Fission prod’s

Th-232 Blanket Enough in Lehmi Pass for 1,000 yr of USA energy use

Core

• Th-232 Yucca

IFR or

300 yr

Mtn

TWR

Ground

Blanket processing: UF4 (liquid) + F2 (gas) ! UF6 (gas) both U-233 & U-232

Pu in core turns Th-232 into U-233 U-233 in core gives breeder

2/15/13 Frank H. Shu Figure 2. Schematic diagram of how solving the nuclear 9waste problem of LWRs provides a method to start up MSBRs.

©ASIAA

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Unreacted uranium can be safely separated from the Pu-239 and minor actinides by the standard process of fluorination to produce a gas UF6 that rises out of a molten salt system. Once separated, the large amounts of U-238 mixed in with the U-235 (converted from the UF6 form to more stable oxide forms) makes this material unsuitable for bomb making, and it can either go to a geological repository (like Yucca mountain or its replacement), or be given as fuel for proponents of reactor technology like the integral fast reactor

(IFR) or traveling wave reactor (TWR). A process called “pyroprocessing” developed at the Idaho National Laboratory then safely separates the Pu-239 and minor actinides from the fission products.

With a few unimportant exceptions, the fission products contain radioactive elements that have half-lives of order 30 years or shorter. Such material can be packed in dry casks and stored underground for 300 years, after which their radioactivity has dropped below background levels.

The casks can be opened to retrieve rare substances that have great economic and medical value.

The Pu-239 and minor actinides are chemically made into fluoride compounds, such as PuF3, and dissolved in eutectic NaF/BeF2 molten salt (our preferred choice of the carrier solvent salt).

We pump enough of PuF3/NaF/BeF2 fuel salt into the core of a molten salt converter reactor (MSCR) to achieve a critical mass and to sustain a chain fission reaction. The excess neutrons above what is needed to sustain the chain reaction (against parasitic neutron captures by non-fissiles in the system) random walk their way out of the core to irradiate a blanket salt in a pool surrounding the reactor core that consists of ThF4 dissolved in molten eutectic NaF/BeF2.

The thorium is entirely in the form Th-232, and neutron captures by Th-232 result, after two beta decays, in U-233. When the Pu-239 and minor actinides are consumed, we have solved the nuclear waste problem of LWRs. The solution for LWR waste has two side benefits:  It has eliminated the “dirty bomb” risk from the existence of LWR plutonium.  It offers a way to start up MSBRs when U-233 does not exist in nature.

The manufactured U-233 in the blanket salt exists chemically as UF4 in the pool. To extract it, we continuously pump small amounts of the pool salt to a chamber where gaseous F2 bubbled through the molten salt combines with UF4 in solution to form a gas UF6 that bubbles out of the liquid. The UF6 then flows to another chamber where it attacks metallic Be to produce UF4 and BeF2. When we dissolve the 233UF4 in eutectic NaF/BeF2 molten salt and pump this fuel salt into the core of the reactor, the replacement fissile has turned a MSCR (converter reactor) into a MSBR (breeder reactor). Electrolysis of the BeF2 can recover the Be and F2 needed to process the next batch of 233UF4. The chemical processing is straightforward and can be carried out remotely without endangering the operators. The energy needed for the chemical processing is minuscule (~ 10-5) compared to the nuclear energy benefit.

Because the fuel salt in MSBRs circulates indefinitely until all fissiles are consumed, there are only fission products to deal with by underground storage for 300 years. Thus, MSBRs have no waste problem of their own without a good solution.

What about security? Cannot U-233 be used to make bombs? No, when one has fast fission neutrons flying around, one cannot avoid reactions with one fast incoming neutron and two outgoing neutrons. Such reactions create U-232 that accompanies the U-233. In its decay chain, U-232 is a powerful gamma emitter, and U-232 is almost impossible to separate from U-233.

Even if martyrs were willing to make a bomb using unseparated U-233/U-232, the presence of the U-232 would make the bomb easily detectable by Geiger counters if one tried to smuggle it into a city, say, in a port container. The gamma rays would also interfere with the sensitive electronic control mechanisms that must be part of any weapons assemblage. No nation or terrorist organization would attempt to make a bomb this way, when much simpler alternatives are possible. Thus, MSBRS are secure.

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Figure 3 shows a possible design for a two-fluid molten-salt breeder-reactor of a type described schematically in Figure 2. To slow the fission neutrons from the fast speeds at which they emerge from the fission reactions without absorbing them, we build the reactor core entirely out of carbon-based materials (except for metallic nuts and bolts). Graphite is impervious to chemical attack by hot NaF/BeF2 as long as there is no water in the salt. Doubled for safety of containment, the walls of the pool are made of metal (Hastelloy N resistant to attack by the salt). The random walking neutrons in the pool will be mostly absorbed by Th-232 (in the form of ThF4 dissolved in molten NaF/BeF2 in the pool) before they can strike the walls of the pool and activate the metal to become nuisance low-level waste.

Nuclear Accidents All nuclear reactors are designed to shut themselves off automatically in the case of an emergency. The MSBR is no different, it just has larger safety margins. No reactor accident has ever occurred because of a runaway chain reaction (with the exception of the Chernobyl reactor, which had a horrible flaw in its design that could never pass the nuclear regulatory review outside of the former Soviet Union). Most nuclear accidents occur after the reactor has shut down safely.

They arise because of problems in dissipating the decay heat from the fission products.

Figure 3. One design possibility for a two-fluid MSBR (patent pending). Four molten-salt pumps in the foreground, fuel salt circulates into the vertical channels in the black-colored core.

Reaching a compact configuration with moderator graphite all around it, the fuel salt sustains a chain reaction. Pumps in the background pull blanket salt through the core in horizontal channels that alternate with the vertical channels, but separated from them by walls of graphitic material. Heat from fission reactions in the vertical channels conducts across the graphite into the blanket salt in the horizontal channels. The blanket salt then flows into a secondary heat exchanger in the background outside the pool. The secondary heat exchanger transfers the heat from the radioactive blanket salt to a non-radioactive working salt (e.g, the NaAc/KAc used for supertorrefaction of biomass). After the secondary heat transfer, the cooled blanket salt flows to rejoin the pool at the top. The cooler blanket salt lying above the hotter blanket salt induces a convection patter that keeps the blanket salt well mixed. In the interim the cooled fuel salt flows out of the core into the foreground pumps, where any fission gases in the salt are flushed out of the system by helium gas flowing through the white pipes. The fuel salt then circulates back into the core via the red pipes to begin the process anew. Š ASIAA

For reactors with fixed solid fuel elements, the possible problems are exemplified by Fukushima.

An emergency arises (a tsunami of historical proportions strikes the station). The reactors shut down safely, but the fuel rods continue to put out decay heat that is a few percent of reactor full power. Something knocks out the cooling systems normally used to cool the fuel rods (the whole electrical grid goes down because of the earthquake and tsunami). Emergency equipment has to cool the fuel rods while they remain in the same cramped space of the operational configuration.

The auxiliary power goes out (fuel for diesel generators swept away, batteries run down), and there is a loss of coolant fluid (because the water boils away). Now, the plants are in big trouble.

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Without active cooling of the fuel rods, the rods melt down. Steam interacts with the superhot fuel rods, generating hydrogen. The hydrogen escapes into the containment buildings and explodes. Not designed to be strong, the buildings blast apart. Containment is breached, and massive amounts of radioactivity escape into the environment.

None of these events would have occurred in two-fluid molten-salt breeder-reactors of the design in Figure 3 because of the following safety features:  MSBRs do not use water, so they do not need to be located near large bodies of water, like rivers or ocean sides, where people like to live. They can survive earthquakes and cannot be overwhelmed by tsunamis.  Molten salt reactors run themselves, without operator intervention needed;  Neutron absorber elements buoyant in the blanket salt automatically descend into the core if the pool loses coolant (the blanket salt of the pool).  If the fuel salt overheats for any reason, a drain plug melts that dumps the fuel salt into an air-cooled tank absent of moderators and of a geometry where reaching accidental criticality is impossible.

In MSBRs, if reactions run too fast, the fuel salt heats up. The molten fuel salt will then expand partially out of the core, and the reactions will slow. Conversely, if we need extra power, we pump on the blanket salt harder. This cools the fuel salt, causing it to contract into the core more, thereby making the reactions run faster. These principles are exactly how the Sun, having a gaseous core that expands when heated and contracts when cooled, regulates its thermonuclear fusion reactions in the core to balance what is lost in radiation from the surface. We no more have to worry about a molten salt reactor overheating or overcooling than we have to worry that the Sun tomorrow won’t be the same as it is today.

The idea of a drain plug originated at Oak Ridge National Laboratory, who invented the concept of reactors with liquid fuel elements. With solid fuel elements, as we have seen in the example of Fukushima, if something goes wrong with the primary cooling system, the problem needs fixing with the equipment in the same place where something broke. With liquid fuel, we can move it to another place (the dump tank) where we have prepared a separate emergency cooling system. We choose the coolant to be air, because although we can lose water, and we can lose molten salt, it is almost impossible to lose air.

To be able to use air to cool nuclear power equipment, however, the decay heat cannot be overwhelming. This is where online cleaning of the fission products (needed to maintain the breeding ratio above unity) makes its contribution to reactor safety – it allows even reactors with fairly large full-power operations to have relatively little decay heat when one has reactor shutdown in an emergency. To be supersafe, we should avoid building reactors that are too big (because the amount of decay heat scales with operational full power).

Nevertheless, it is conceivable that with complete station blackout (as happened with Fukushima), the power needed even to run fans won’t be available. Suppose the fuel salt then melts through the air-cooled dump tank. For this contingency, we’ve added a steel salt catcher into which the molten salt will spread into a thin sheet, conducting its heat to inside the steel as it flows. The design is such that the salt freezes in less than 10 seconds to immobilize any fission products that the fuel salt might contain. Because solid salt has a very low vapor pressure, no radioactive gases will escape.

One extra precaution must be taken: a containment dome that can prevent intrusion by jet

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airplanes that try to crash into the reactor. We have to design the dome so that in case the unthinkable happens, and the operators have to abandon the site, the reactor is walk-away safe.

This means that decay heat cannot be trapped inside the dome, but needs to be able to work its way out. A good design is exemplified by the Westinghouse AP 1000, which has a thin steel cap that traps gases inside but allows conduction of heat to the upper surface, which is cooled by convection in a protective concrete dome partially open to circulating outside air. Finally, MSBRs can be located in remote places where any accident would have a minimal impact on surrounding human populations. Thus, MSBRs are walk-away safe.

Supertorrefaction of Biomass into Biofuel Torrefaction is generally recognized as the most efficient way of harnessing biomass energy (Fig. 4). The traditional method involves burning a fuel and letting the flue gas heat biomass in a partially enclosed environment that has a limited intake of oxygen in air. The process drives out volatile organic compounds (VOCs), including water vapor, leaving behind a blackened solid residue, charcoal. The VOCs are usually burned to supplement the fuel, which can be natural gas or a portion of the biomass or its torrefaction products.

Supertorrefaction (patent pending) is an improved process conceived as part of a general program using molten salts to generate alternative energies by the first author and brought to maturity at Academia Sinica.

Supertorrefaction uses molten salt as a medium to transfer heat to the biomass with which the salt is in direct contact. Immersion beneath the surface of the salt excludes oxygen and air.

In contrast with traditional torrefaction, where many hours are required for the

Figure 4. Torrefaction of woody plant material. Data source: Bergman et al. 2005).

Figure 5. The Crankberry machine for tabletop supertorrefaction. ŠASIAA 23/66

completion of the charring process, supertorrefaction requires typically only ten minutes because the heat capacity of molten salt per unit volume is about 2000 times larger than that of flue gas if both heat-transfer fluids are at atmospheric pressure and a given temperature.

The second author of this article designed a tabletop machine (“crankberry”, Fig. 5) which automates the process of supertorrefaction on a laboratory scale. Using the crankberry, the third author and his group have supertorrefied a wide variety of biomass feedstocks, with uniformly good results (Fig. 6).

If the temperature of the salt is 300 oC, a product ecocoal results that is a clean-burning, carbon-neutral, replacement for natural coal; whereas if the temperature is 500 oC, the product biochar is a fine carbon-negative soil amendment (Fig. 7). We note that burying bichar is a carbon-negative activity, beneficial not only to the host country, but to the whole world.

Because the VOCs Figure 6. Examples of charcoal making by supertorrefaction with molten acetate driven from the biomass salt (NaAc/KAc) from different biomass feedstocks. ©ASIAA are recovered rather than burned, the economic return per unit weight of the biomass is higher than in traditional torrefaction. In particular, apart from water (which we recover and recycle for washing and recovering the salt in the finished biochar), acetic Figure 7. Scanning electron microscope (SEM) images of (left) ecocoal made acid is the most from leucaena supertorrefied at 300 oC for ten minutes, and (right) biochar made abundant component of from leucaena supertorrefied at 500 oC for eleven minutes. The bar at the bottom the VOC yield. We are left of the left image ois 10 microns; of the right image, 20 microns. able to generate acetone Supertorrefaction at 300 C drives out VOCs from ecocoal, buto leaves many microstructures within cell walls, whereas supertorrefaction at 500 C decomposes and Na2CO3/K2CO3 if some acetate salt into carbonate salt and leaves behind only cell walls. Below the we take NaAc/KAc image we give the Brunauer-Emmett-Teller (BET) measure of porosity (area per above 460 oC. By unit mass) in m2/g. ©ASIAA reacting the Na2CO3/K2CO3 with acetic acid, which is a fast acid-base reaction, we are able to recover the NaAc/KAc that we decomposed (plus CO2 and H2O).

Acetone is a high-value chemical, useful as an industrial solvent as well as a feedstock for 24/66

general aviation fuel, so the technique not only creates a high-throughput solid biofuel to compete with natural coal, but also a liquid feedstock to lessen the dependence on petroleum for one segment of the transportation industry. We also get uncondensed gases combustible as a replacement for natural gas.

Supertorrefaction allows a greatly reduced size of the equipment needed to produce a given throughput (tonne per day) for the biomass processing, even when the slight loss of the salt encased in the pores of the charcoal is taken into account. This reduction lowers considerably the initial investment of capital equipment. Indeed, it is possible to have supertorrefaction throughputs that generate attractive economic returns with batch-process equipment compact enough to be transportable by truck to remote batch supertorrefaction sites where the biomass is harvested. These capabilities make commercialization of supertorrefaction possible in startup environments that hold many barriers for traditional torrefaction technologies.

For example, a bad situation exists in Western North America, where winters that are too mild, combined with drought-like conditions in the summers, are blamed for an outbreak of pine bark beetle disease in mountain forests stretching from Southern California to British Columbia.

Hundreds of thousands of pine trees fall per day. We propose that the felled trees should be supertorrefied before they become ground tinder for wildfires, or rot and release greenhouse gases into the atmosphere, or have falling limbs that bring down power lines and cause expensive and dangerous outages. We would bury the resulting biochar in the same forests, not only sequestering for thousands of years the resulting carbon, but also encouraging new growth that would lock up more carbon.

The forest crisis affects more than just North America. A survey published in Nature magazine in 2012 found that 70% of 226 forest species in 81 forests of the world are on the verge of dying from the stress placed on root systems when there is too little water in the soil. This existential threat deserves an adequate response.

The Grand Challenge Climate change is the grand challenge of the twenty-first century. The fate of human civilization may well depend on whether we rise in a rational and scientific manner to meet this challenge.

The ultimate goal of our group is to marry the technologies of molten salt reactors and supertorrefaction. We can transfer the heat carried in the radioactive blanket salt (ThF4/NaF/BeF2) to a non-radioactive working salt (NaAc/KAc) via a secondary heat exchanger (an easy coupling depicted in the background of Fig. 3). We can then use nuclear heat to produce from biomass, at very high throughputs, biochar, acetone, and syngas cheaper and cleaner than the highly invasive processes of extracting coal by strip mining and mountain-top removal, petroleum by drilling in the ocean deeps, and natural gas from the hydraulic fracturing of shale rock. Baseload electric power can be generated from syngas; liquid transportation fuels can be made from acetone; and carbon-negative sequestration can be achieved with biochar.

Coal, oil, and natural gas are valuable Earth resources, and they would not contribute to climate change if they were used to make durable goods, rather than burned. We do not need fossil-fuel companies to go out of business; we need them to go into a different business. Other researchers may have even better ideas for effecting a realistic transition from an economy based on fossil fuels. If so, they should get to work. Through nearly fourteen billion years of the evolution of the physical universe, nature has given us a bounty of Earth energy that can, in principle, replace fossil fuels. It is time for us to do our part.

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（ Authors/Frank Shu, Michael Cai, Fen-Tair Luo; Translator/Chun-Hui Yang; Reviewers/ Michael Cai） For full article, please check online https://sites.google.com/a/asiaa.sinica.edu.tw/iaaq-on-web/

天聞季報海報版與網路版由中央研究院天文及天文物理研究所製作， 以創用 CC 姓名標示-非商業性-禁止改作 3.0 台灣 授權條款釋出。 天聞季報網路版衍生自天聞季報海報版。超出此條款範圍外的授權，請與我們聯繫。 創用 CC 授權可於以下網站查閱諮詢 https://isp.moe.edu.tw/ccedu/service.php。

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【徐遐生院士談地球新能源】 原文網路全文版

EARTH ENERGY: GIFTS FROM NATURE (Online English Full Version) Frank H. Shu1, Michael J. Cai2, Fen-Tair Luo3 1 Institute of Astronomy and Astrophysics, Academia SInica Research Corporation, University of Hawaii2 Institute of Chemistry, Academia Sinica3 Introduction The astronomical heritage of the Earth makes it rich with energy. In its oceans are water molecules that contain two isotopes of hydrogen that date back to the big bang. The light form is what powers thermonuclear fusion in the Sun; the heavy form underlies the hope behind thermonuclear fusion on Earth. Helium is the second most abundant element in the Universe after hydrogen, but none of the helium remaining on Earth came from the big bang; they all come from the alpha particles (helium nuclei) spit out from unstable isotopes of heavy elements that make up the rocks of Earth. These radioactive elements are relics from supernovae that made neutron stars and provide the heat that keeps the interior of the Earth hot. The most neutron-rich of these heavy elements, uranium, forms the basis of fission reactions that power most of today’s terrestrial nuclear reactors. The moderator that slows down fission neutrons is the same as the coolant that carries away the heat from the core of these reactors, water with the light form of hydrogen. This use gives these machines their name: light water reactors (LWRs). LWRs have no emissions of carbon dioxide, but they play a controversial role in Earth energy because of misconceptions that they lack 4 S’s:  Solutions (for the nuclear waste problem)  Safety (with respect to massive release of radioactivity to the environment)  Security (with respect to weapons proliferation)  Sustainability (of high-grade uranium ore) Radiation from the thermonuclear powered Sun is the natural energy source that sustains all life on Earth. Sunlight passes through an optically transparent atmosphere to warm the surface of the earth. If sunlight falls on the oceans, heating the water causes some of it to evaporate. The salt of the seawater is left behind, so when the water vapor precipitates, the rain is a source of fresh water. If it is cold, and snow instead falls on high mountain passes, when the snows melt, the streams of fresh water collect into mighty rivers. If the rivers are dammed, high reservoirs of water build up behind the dams. Released from these great heights, the falling water can rush

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past water turbines that turn powerful magnets inside coils of wire that hum with alternating current.

On inhomogeneous terrain, and because of night and day variations, the heating by sunlight is uneven and gives differences in temperature and pressure that create wind, which can power turbines also generating electricity (at about 50% efficiency versus 90% for hydroelectricity).

Because air is 800 times less dense than water, wind-electricity is considerably more expensive than hydroelectricity.

If sunlight strikes solar panels, the photovoltaic effect generates solar electricity (at efficiency up to 20%). Solar electricity ceases at night and is highly variable during cloudy days, so it requires backup from other sources of “base-load” power.

If the sunlight falls on green plants, photosynthesis is able to take the energy in the photons to convert the carbon dioxide in the air and water in the ground into the organic compounds necessary for plant growth and reproduction (at about 1% efficiency). These organic compounds contain proportionally fewer O compared to C and H than present in CO2 and H2O, so free molecular oxygen O2 is released to the atmosphere as a byproduct of photosynthesis. Conversely, when plants die, the incompletely oxidized C and H in organic matter can combine with the O2 in air, releasing heat in the process, and reform CO2 and H2O, both of which are greenhouse gases (GHGs). If the reactions occur in a flame, we call the process “burning,” with the heat of combustion used perhaps to boil water that causes the steam to expand past a steam turbine that can again generate electricity (at about 20% efficiency if the biomass is burned directly). If the reactions occur more slowly in animals, we call the process digestion, with the animals (unicellular or multicellular) making use of the food energy (at a low efficiency dependent on the species) and exhaling or excreting the waste products, CO2 and H2O. Biomass that got buried in past eons deep into the Earth, where there is no oxygen but ample heat and pressure, produced the fossil fuels, coal, petroleum, and natural gas that powers the modern technological society. Coal burning is used mostly for electricity generation (at about 35 to 40% efficiency), with noxious emissions of volatile heavy metals (like mercury) because coal is dug out of the ground with small bits of stone in it that contain such heavy metals.

Petroleum holds an almost unassailable position as the feedstock of choice for transportation fuel because it of its advantage in ETUDES:  Extraction, with historical energy return on investment (EROI) ratios > 10  Transportation, worth doing because petroleum is an energy dense liquid  Upgrading, refining to separate low and high molecular weight hydrocarbons and processing to produce a variety of chemical products (e.g., plastics)  Distribution, extensive network of suppliers and outlets for products  Establishment, with market penetration into all segments of society  Storage, e.g., in gasoline tanks, available for usage when one wants In the public mind, natural gas is a clean burning cooking fuel with almost no noxious emissions and yields CO2 about a half that of coal with the same energy content. But natural gas can also be burned so that the expanding flue gas turns turbines to generate electricity at an efficiency that can reach 60% in so-called “combined cycle” power plants where the waste heat in the flue gas is used to help boil water in the steam boiler of a coal-fired power plant. Natural gas in the United States produced by the method of hydraulic fracturing of shale has unbelievably low production costs. Other nations, notably China, are joining the “rush to gas.”

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For these various reasons, natural gas is often touted as the “bridge fuel” to a carbon-free future, where human energy needs are entirely supplied by renewables like solar and wind. One can question how natural gas can serve this temporary role given that it is needed to take up the slack when the wind is not blowing or when the Sun is not shining in the sky. Building more wind and solar makes humans more dependent of natural gas, not less.

Mitigating Climate Change Human burning of fossil fuels has increased the atmospheric concentration of carbon dioxide from 280 ppm before the industrial revolution to 395 ppm at the time of the writing of this article (Fig. 1).

Overwhelming scientific consensus holds that this increase is the main cause of modern climate change. Because of space limitations, we do not discuss the evidence that supports this conclusion. We hope that a future issue of the ASIAA Quarterly can focus on this important subject.

From the perspective of mitigating the effects of climate change, we can divide the major terrestrial energy sources mentioned above into four categories:

Figure 1. The concentration of CO2 in the atmosphere in ppm as a function of time during the past ten thousand years (up to 2005). Data source: IPCC

Category I, sources that produce copious emissions of carbon dioxide:  coal  oil  natural gas Although always lumped together, the three fossil fuels are not equal. Coal powered the Industrial Revolution; for the Age of Innovation, we need something better. But if we are to stop using coal, thought has to be given to how we salvage the investment made on all the new coal-fired power plants that are springing up in China, India, and Germany (which shut down its nuclear power plants because a tsunami disabled three nuclear reactors in Japan).

For sound technical reasons, civilization uses oil as the transportation fuel of choice. Easy to extract, transport, upgrade, distribute, and store, it is priced per unit energy at ten times the value of coal and shale gas for its convenience of use.

Natural gas is cheap in some parts of the United States because of the practice of hydraulic fracturing. In its low-density state as a gas; transporting it in pipelines is very expensive compared to doing the same for oil, because to carry the mass mass-flow the natural gas pipes have much larger diameters. Shipping natural gas overseas is economically feasible only if it is liquefied into a denser state. Liquefied natural gas (LNG) requires cryogenically low temperatures and high pressures, so by the time LNG reaches Taiwan from the United States the cost of natural gas has increased by a factor of six. As a result of these difficulties, shale gas is

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not today transported from where it is produced, with the result that local supply greatly exceeds the local demand, which explains why current prices for shale gas are so low. Moreover, if there are leaks during extraction, then methane, which makes up 90% of what is in natural gas, is, as a GHG, 72 times worse than the equivalent amount of CO2 for 20 years, and 25 times worse for 100 years. Methane is gradually destroyed by oxidization in the atmosphere, but its potential for harm in the environment if not used wisely does not bode well for it being a panacea for humanity’s problems with climate change.

Group II. Sources that are renewable and reliable, that produce essentially zero emissions of carbon dioxide:  hydroelectric power  biofuels  geothermal  solar thermal Hydroelectricity is a wonderful twentieth century technology. It has little room for expansion in the twenty-first because almost all the large rivers of the world have already been dammed.

Biofuel technologies are often judged on their ratio of energy return on energy invested (EROI).

Economists argue whether corn ethanol is being produced in the United States with EROI > 1 or < 1. Brazil claims that its EROI for producing sugar-cane ethanol averages about 8.3; however, their calculation does not count as input the bagasse (the material left after the sugar has been pressed out of the cane) burnt in the fields to help power the plant. If this input is included, the Brazilian EROI is probably closer to 2.

Corn ethanol is notorious for driving up worldwide food prices. Researchers hope to proceed to second-generation biofuels where the feedstock does not compete with food. To accomplish this aim requires using (a) non-food feedstocks, e.g., waste wood, wild grasses, etc; (b) marginal lands not suitable for the planting of food crops. The second requirement is at odds with having biomass yields per hectare high enough to sustain economic biofuel production. Almost by definition, marginal lands either lack water or lack the soil nutrients necessary for productive vegetative growth, or both. To supply this water and/or the chemical fertilizer (which is today produced by the petrochemical industry) requires large fossil-fuel inputs that may be self-defeating if the goal is to reduce our dependency on fossil fuels. This realization has spurred some to look at oil produced by algae, where the effort is in a state of relative infancy.

When the source of Earth heat is close to the surface, as in Iceland, geothermal is a reliable, established technology, especially when used for space heating. In warm climes, like Taiwan, it makes more sense to look at using cold seawater at depth as a source for air chilling in the summertime. To drill ten km deep to tap geothermal heat where it is not available from the surface, as some have proposed, seems an unnecessary invasion of the environment, given the bad accidents that have occurred with deep drilling for oil.

In solar thermal, the heat of the Sun is captured by parabolic east-west troughs and stored in molten salt for energy conversion at night. Solar thermal suffers from the dilute nature of sunlight and the inefficient use of its energy compared to photovoltaics, which directly converts sunlight into electricity.

Group III, sources that are renewable but unreliable, and produce essentially zero emissions of

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carbon dioxide:  wind  solar PV With hydroelectricity, we can control the release of water behind dams to satisfy the timing of human demands. The wind changes speed and direction according to the vagaries of a turbulent lower atmosphere of the Earth. During hot or cold spells, when one needs electricity the most, the wind can stop blowing for weeks on end. Wind is strongest at night, when the cold air is descending and everybody is sleeping with little need for electricity. Thus, wind behaves like a car with a mind of its own, starting when the traffic light is red, and stopping when it is green.

Solar photovoltaics (PV) is intermittent because it ceases when the Sun sets, which is when we need to turn the lights on. It is not completely dependable even during the daytime because passing clouds can interfere with the efficient operations of solar panels. Nevertheless, because electricity demand is highest around noon, solar PV is well matched to “peak-load” power.

Solar PV is the only energy generation technology that offers personalized action, i.e., each family and business can own and control their own system to reduce the electricity demand on the power grid. The main failing of solar PV is its heavily subsidized costs, including installation.

As long as solar PV needs government subsidies, which can change in democracies with each election cycle, making the market for solar panels highly volatile, it cannot have an impact much greater than its current contribution of about 0.01% of total world energy usage. (Beware that articles about solar PV usually quote nameplate power. Nameplate power refers to electricity generation on a clear day at noon when the Sun is highest in the sky. The average contribution is typically only 20% of nameplate power.)

Group IV, sources that are reliable, sustainable, and have essentially zero emissions of carbon dioxide:  advanced fission nuclear reactors  thermonuclear fusion Nuclear power based either on fission or fusion are not renewable because the fuel – uranium or thorium in the case of fission, deuterium in the case of terrestrial fusion – are irreversibly transformed into non-fissionable and non-fusionable substances. Nevertheless, the stock of deuterium in the oceans is so large that fusion could supply all the world energy needs until the Sun turns itself into a red giant. In that sense, fusion energy is not renewable, but it is sustainable.

Unfortunately, fusion power is unlikely to become a commercial reality in time to help with climate change. Thus, it remains a terrestrial energy source for the future.

In contrast, if U-235 continues to be the world’s sole source of fissile material, then the stocks of high-grade uranium ore are sufficient only to supply about six years of total projected world energy needs in 2050. We cannot even make it to 2050 at that rate. Fissioning U-235 for terrestrial power is neither renewable nor sustainable.

Nuclear Breeder Reactors Molted salt breeder reactors (MSBRs) offer solutions for the nuclear waste problem, safety against the massive release of radioactivity into the environment, security against weapons proliferation, and sustainability of the nuclear fission option. Before we discuss MSBRs,

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however, we briefly review the subject of breeder reactors more generally.

U-238 is more than 100 times as abundant as U-235, and adding a neutron to U-238 makes U-239, which becomes Pu-239 after two beta decays to turn two neutrons into two protons.

Pu-239 is fissile. Such a program of “breeding” to turn a fertile (U-238) into a fissile (Pu-239) raises the high-grade uranium ore use (if all power came from fission reactors) to 600 years. .

Uranium-bearing minerals are soluble in seawater, leading to Japanese proposals to use polymer filters to trawl for uranium from seawater. Experiments have been carried out showing that the technology is economically viable. The supply of uranium in the oceans suffices to power a “plutonium economy” for hundreds of thousands of years. Thus, U-238 breeder reactors are a sustainable energy resource for the Earth. Bill Gates has invested money in this technology.

The potential for thorium breeder reactors is even better. Thorium has only one stable isotope, Th-232, which eliminates the need for expensive isotope separation. Moreover, while Th-232, an even-even nuclide with 90 protons and 142 neutrons, is only fertile, it can be made fissile by absorbing a neutron. This turns Th-232 into Th-233, which, after two beta decays that convert two neutrons into two protons, produces U-233. An even-odd nuclide with 92 protons and 141 neutrons, U-233 is fissile. When U-233 has a slow neutron added to it (one with a spin opposite to the unpaired neutron that must be in U-233 because it has an odd number of neutrons), the increase in the energy of the large nucleus is enough to cause the resulting nucleus to vibrate violently into two uneven pieces, called fission products. Fission products from the breakup of a neutron-rich parent are too neutron rich to remain in such states without spitting out an additional 2 or 3 neutrons. When a U-233 nucleus absorbs a slow neutron and fissions, an average of 2.49 (fast) fission Because this average output of neutrons per fission is greater than 2, apart from the 1 neutron needed to sustain the chain reaction, another is available to turn a neighboring Th-232 nucleus into Th-233, that then decays into a new fissile U-233. If the neutron economy is managed properly by building the reactor core out of materials that do not absorb fission neutrons parasitically while slowing them down to low speeds, the extra 0.49 neutrons on average per fission reaction can make more U-233 from Th-232 than we started out with. In principle, then, thorium breeder reactors could exponentially expand their numbers until we have enough to supply the total energy needs of the world.

Thorium is 3 to 4 times as abundant as uranium in the crust of the Earth. What is a 600 year depletion time for high-grade uranium ore becomes something more like 2000 years for the depletion of high-grade thorium ores. As a chemical element, thorium behaves oppositely to uranium in one important respect: thorium minerals are not soluble in seawater. Thus, they are not found in the oceans of the Earth, but are ample in beach sand of a variety black in color called monazite. Lots of monazite exits on Taiwan beaches. If you think it is not enough, just go out in the ocean and get some more from the ocean bottom. Because thorium has no other commercial applications, no one has surveyed how much thorium might exist in the world as potential nuclear fuel. The reserves are likely to last millions of years, if not billions if one were to go to lower grades of ore. Thus, thorium MSBRs are sustainable.

Molten Salt Breeder Reactor Our discussion of MSBRs begins with the observation that it offers a solution to the nuclear waste problem that has accumulated from half a century of operating LWRs.

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Figure 2 schematically provides the solution. The high-level nuclear waste from the spent fuel rods of LWRs consists of three main components:  Unreacted U-235, mixed with U-238  Pu-239 and higher actinides from collateral neutron irradiation of U-238  Fission products from the splitting of fissile nuclei

MSRs Can Rid LWR Waste & Safely Breed for U-233

Unreacted uranium can be safely separated from the Pu-239 and minor Pu in • LWR spent fuel Th-232 Blanket actinides by the standard process of core Enough in Lehmi Pass for – U-238, U-235 fluorination to produce a gas UF6 that turns 1,000 yr of USA energy use – Pu/actinides Th-232 rises out of a molten salt system. Once into – Fission prod’s separated, the large amounts of U-238 U-233 Core mixed in with the U-235 (converted • Th-232 U-233 Blanket processing: from the UF6 form to more stable oxide in core UF4 (liquid) + F2 (gas) forms) makes this material unsuitable gives 300 yr ! UF6 (gas) Yucca IFR or breeder for bomb making, and it can either go both U-233 & U-232 Mtn TWR Ground to a geological repository (like Yucca 2/15/13 Frank H. Shu Figure 2. Schematic diagram of how solving the nuclear 9waste mountain or its replacement), or be problem of LWRs provides a method to start up MSBRs. given as fuel for proponents of reactor ©ASIAA technology like the integral fast reactor (IFR) or traveling wave reactor (TWR). A process called “pyroprocessing” developed at the Idaho National Laboratory then safely separates the Pu-239 and minor actinides from the fission products.

Chain reaction, breeding, and processing in liquid salt

With a few unimportant exceptions, the fission products contain radioactive elements that have half-lives of order 30 years or shorter. Such material can be packed in dry casks and stored underground for 300 years, after which their radioactivity has dropped below background levels.

The casks can be opened to retrieve rare substances that have great economic and medical value.

The Pu-239 and minor actinides are chemically made into fluoride compounds, such as PuF3, and dissolved in eutectic NaF/BeF2 molten salt (our preferred choice of the carrier solvent salt).

We pump enough of PuF3/NaF/BeF2 fuel salt into the core of a molten salt converter reactor (MSCR) to achieve a critical mass and to sustain a chain fission reaction. The excess neutrons above what is needed to sustain the chain reaction (against parasitic neutron captures by non-fissiles in the system) random walk their way out of the core to irradiate a blanket salt in a pool surrounding the reactor core that consists of ThF4 dissolved in moleten eutectic NaF/BeF2.

The thorium is entirely in the form Th-232, and neutron captures by Th-232 result, after two beta decays, in U-233. When the Pu-239 and minor actinides are consumed, we have solved the nuclear waste problem of LWRs. The solution for LWR waste has two side benefits:  It has eliminated the “dirty bomb” risk from the existence of LWR plutonium  It offers a way to start up MSBRs when U-233 does not exist in nature The manufactured U-233 in the blanket salt exists chemically as UF4 in the pool. To extract it, we continuously pump small amounts of the pool salt to a chamber where gaseous F2 bubbled through the molten salt combines with UF4 in solution to form a gas UF6 that bubbles out of the liquid. The UF6 then flows to another chamber where it attacks metallic Be to produce UF4 and BeF2. When we dissolve the 233UF4 in eutectic NaF/BeF2 molten salt and pump this fuel salt into the core of the reactor, the replacement fissile has turned a MSCR (converter reactor) into a

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MSBR (breeder reactor). Electrolysis of the BeF2 can recover the Be and F2 needed to process the next batch of 233UF4. The chemical processing is straightforward and can be carried out remotely without endangering the operators. The energy needed for the chemical processing is minuscule (~ 10-5) compared to the nuclear energy benefit.

Because the fuel salt in MSBRs circulates indefinitely until all fissiles are consumed, there are only fission products to deal with by underground storage for 300 years. Thus, MSBRs have no waste problem of their own without a good solution.

What about security? Cannot U-233 be used to make bombs? No, when one has fast fission neutrons flying around, one cannot avoid reactions with one fast incoming neutron and two outgoing neutrons. Such reactions create U-232 that accompanies the U-233. In its decay chain, U-232 is a powerful gamma emitter, and U-232 is almost impossible to separate from U-233.

Even if martyrs were willing to make a bomb using unseparated U-233/U-232, the presence of the U-232 would make the bomb easily detectable by Geiger counters if one tried to smuggle it into a city, say, in a port container. The gamma rays would also interfere with the sensitive electronic control mechanisms that must be part of any weapons assemblage. No nation or terrorist organization would attempt to make a bomb this way, when much simpler alternatives are possible. Thus, MSBRs are secure.

Figure 3. One design possibility for a two-fluid MSBR (patent pending). Four molten-salt pumps in the foreground, fuel salt circulates into the vertical channels in the black-colored core.

Reaching a compact configuration with moderator graphite all around it, the fuel salt sustains a chain reaction. Pumps in the background pull blanket salt through the core in horizontal channels that alternate with the vertical channels, but separated from them by walls of graphitic material. Heat from fission reactions in the vertical channels conducts across the graphite into the blanket salt in the horizontal channels. The blanket salt then flows into a secondary heat exchanger in the background outside the pool. The secondary heat exchanger transfers the heat from the radioactive blanket salt to a non-radioactive working salt (e.g, the NaAc/KAc used for supertorrefaction of biomass). After the secondary heat transfer, the cooled blanket salt flows to rejoin the pool at the top. The cooler blanket salt lying above the hotter blanket salt induces a convection patter that keeps the blanket salt well mixed. In the interim the cooled fuel salt flows out of the core into the foreground pumps, where any fission gases in the salt are flushed out of the system by helium gas flowing through the white pipes. The fuel salt then circulates back into the core via the red pipes to begin the

Figure 3 shows a possible design for a two-fluid molten-salt breeder-reactor of a type described schematically in Figure 2. To slow the fission neutrons from the fast speeds at which they emerge from the fission reactions without absorbing them, we build the reactor core entirely out of carbon-based materials (except process anew. Š ASIAA for metallic nuts and bolts). Graphite is impervious to chemical attack by hot NaF/BeF2 as long as there is no water in the salt. Doubled for safety of containment, the walls of the pool are made of metal (Hastelloy N resistant to attack by the salt). The random walking neutrons in the pool will be mostly absorbed by Th-232 (in the form of ThF4 dissolved in molten NaF/BeF2 in the pool) before they can strike the walls of the 34/66

pool and activate the metal to become nuisance low-level waste.

Nuclear Accidents All nuclear reactors are designed to shut themselves off automatically in the case of an emergency. The MSBR is no different, it just has larger safety margins. No reactor accident has ever occurred because of a runaway chain reaction (with the exception of the Chernobyl reactor, which had a horrible flaw in its design that could never pass the nuclear regulatory review outside of the former Soviet Union). Most nuclear accidents occur after the reactor has shut down safely. They arise because of problems in dissipating the decay heat from the fission products.

For reactors with fixed solid fuel elements, the possible problems are exemplified by Fukushima.

An emergency arises (a tsunami of historical proportions strikes the station). The reactors shut down safely, but the fuel rods continue to put out decay heat that is a few percent of reactor full power. Something knocks out the cooling systems normally used to cool the fuel rods (the whole electrical grid goes down because of the earthquake and tsunami). Emergency equipment has to cool the fuel rods while they remain in the same cramped space of the operational configuration.

The auxiliary power goes out (fuel for diesel generators swept away, batteries run down), and there is a loss of coolant fluid (because the water boils away). Now, the plants are in big trouble.

Without active cooling of the fuel rods, the rods melt down. Steam interacts with the superhot fuel rods, generating hydrogen. The hydrogen escapes into the containment buildings and explodes. Not designed to be strong, the buildings blast apart. Containment is breached, and massive amounts of radioactivity escape into the environment.

None of these events would have occurred in two-fluid molten-salt breeder-reactors of the design in Figure 3 because of the following safety features:  MSBRs do not use water, so they do not need to be located near large bodies of water, like rivers or ocean sides, where people like to live. They can survive earthquakes and cannot be overwhelmed by tsunamis  Molten salt reactors run themselves, without operator intervention needed  Neutron absorber elements buoyant in the blanket salt automatically descend into the core if the pool loses coolant (the blanket salt of the pool)  If the fuel salt overheats for any reason, a drain plug melts that dumps the fuel salt into an air-cooled tank absent of moderators and of a geometry where reaching accidental criticality is impossible In MSBRs, if reactions run too fast, the fuel salt heats up. The molten fuel salt will then expand partially out of the core, and the reactions will slow. Conversely, if we need extra power, we pump on the blanket salt harder. This cools the fuel salt, causing it to contract into the core more, thereby making the reactions run faster. These principles are exactly how the Sun, having a gaseous core that expands when heated and contracts when cooled, regulates its thermonuclear fusion reactions in the core to balance what is lost in radiation from the surface. We no more have to worry about a molten salt reactor overheating or overcooling than we have to worry that the Sun tomorrow won’t be the same as it is today.

The idea of a drain plug originated at Oak Ridge National Laboratory, who invented the concept of reactors with liquid fuel elements. With solid fuel elements, as we have seen in the example of Fukushima, if something goes wrong with the primary cooling system, the problem needs fixing with the equipment in the same place where something broke. With liquid fuel, we can move it to 35/66

another place (the dump tank) where we have prepared a separate emergency cooling system. We choose the coolant to be air, because although we can lose water, and we can lose molten salt, it is almost impossible to lose air.

To be able to use air to cool nuclear power equipment, however, the decay heat cannot be overwhelming. This is where online cleaning of the fission products (needed to maintain the breeding ratio above unity) makes its contribution to reactor safety – it allows even reactors with fairly large full-power operations to have relatively little decay heat when one has reactor shutdown in an emergency. To be supersafe, we should avoid building reactors that are too big (because the amount of decay heat scales with operational full power).

Nevertheless, it is conceivable that with complete station blackout (as happened with Fukushima), the power needed even to run fans won’t be available. Suppose the fuel salt then melts through the air-cooled dump tank. For this contingency, we’ve added a steel salt catcher into which the molten salt will spread into a thin sheet, conducting its heat to inside the steel as it flows. The design is such that the salt freezes in less than 10 seconds to immobilize any fission products that the fuel salt might contain. Because solid salt has a very low vapor pressure, no radioactive gases will escape. There is no water in the system, so hydrogen will not be generated to cause an explosion. The salt is composed of elements on opposite sides of the periodic table, one being very electropositive and the other being very electronegative. No other element can get between them, so there are no chemical reactions that can threaten the system. In other words, salt cannot catch on fire.

One extra precaution must be taken: a containment dome that can prevent intrusion by jet airplanes that try to crash into the reactor. We have to design the dome so that in case the unthinkable happens, and the operators have to abandon the site, the reactor is walk-away safe.

This means that decay heat cannot be trapped inside the dome, but needs to be able to work its way out. A good design is exemplified by the Westinghouse AP 1000, which has a thin steel cap that traps gases inside but allows conduction of heat to the upper surface, which is cooled by convection in a protective concrete dome partially open to circulating outside air. Finally, MSBRs can be located in remote places where any accident would have a minimal impact on surrounding human populations. Thus, MSBRs are walk-away safe.

Supertorrefaction of Biomass into Biofuel With oil’s advantages in ETUDES (which have made them rich and powerful), oil companies are tough to displace with technologies that depend on primitive micro-organisms performing fermentation reactions at room temperature, where all chemical reactions are slow. (If they were not slow, the organisms would char.)

The strategy of our research group is to fight fire with fire, or more accurately, with supertorrefaction. Torrefaction is generally recognized as the most efficient way of harnessing biomass energy (Fig. 4). The traditional method involves burning a fuel and letting the flue gas heat biomass in a partially enclosed environment that has a limited intake of oxygen in air. The process drives out volatile organic compounds (VOCs), including water vapor, leaving behind a blackened solid residue, charcoal. The VOCs are usually burned to supplement the fuel, which can be natural gas or a portion of the biomass or its torrefaction products.

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Supertorrefaction (patent pending) is an improved process conceived as part of a general program using molten salts to generate alternative energies by the first author and brought to maturity at Academia Sinica.

Supertorrefaction uses molten salt as a medium to transfer heat to the biomass with which the salt is in direct contact.

Immersion beneath the surface of the salt excludes oxygen and air. In contrast with traditional torrefaction, where many hours are required for the completion of the charring process, supertorrefaction requires typically only ten minutes because the heat capacity of molten salt per unit volume is Figure 4. Torrefaction of woody plant material. Data source: Bergman about 2000 times larger than et al. 2005). that of flue gas if both heat-transfer fluids are at atmospheric pressure and a given temperature.

The second author of this article designed a tabletop machine (“crankberry”, Fig. 5) which automates the process of supertorrefaction on a laboratory scale. Using the crankberry, the third author and his group have supertorrefied a wide variety of biomass feedstocks, with uniformly good results (Fig. 6). From data that we have accumulated from such experiments and using the same rules of calculation as Brazilian sugar cane ethanol, we estimate that the EROI ratio for a demonstration-scale supertorrefaction project is of order 40:1. If we include internal inputs of energy from renewable sources in the denominator, but not the crude glycerol that should be charged to biodiesel making, the EROI drops to about 9.6:1, still very good by Brazilian standards, and comparable to the record of established oil companies. With “peak oil,” our EROI will improve relative to that of the oil industry. Moreover, burning Figure 5. The Crankberry machine for tabletop supertorrefaction. our products is a carbon-neutral ©ASIAA activity.

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The molten salt we use for supertorrefaction is a eutectic mixture of sodium acetate, NaAc, and potassium acetate, KAc. (The same combination is used to flavor “salt-and-vinegar” potato chips). This salt mixture melts at 235 oC and decomposes to sodium carbonate, Na2CO3, and potassium carbonate, K2CO3, plus acetone if the temperature exceeds 460 oC. If the temperature of the salt is 300 oC, a product ecocoal results that is a clean-burning, carbon-neutral, replacement for natural coal; whereas if the temperature is 500 oC, the product biochar is a fine Figure 6. Examples of charcoal making by supertorrefaction carbon-negative soil amendment (Fig. with molten acetate salt (NaAc/KAc) from different biomass 7). We note that burying bichar is a feedstocks. ©ASIAA carbon-negative activity, beneficial not only to the host country, but to the whole world. Thus, in principle, biochar production and burial can become the basis of true carbon trading, where, for example, oil companies that extract a tonne of petroleum from anywhere in the world are required to pay someone else to bury a tonne of biochar on land in need of improvement in soil quality. The resulting flow of money from the rich to the poor in rural communities facing desertification is a win-win proposition, with everyone receiving the benefits of a cleaner environment.

Figure 7. Scanning electron microscope (SEM) images of (left) ecocoal made from leucaena supertorrefied at 300 oC for ten minutes, and (right) biochar made from leucaena supertorrefied at 500 oC for eleven minutes. The bar at the bottom left of the left image is 10 microns; of the right image, 20 microns. Supertorrefaction at 300 oC drives out VOCs from ecocoal, but leaves many microstructures within cell walls, whereas supertorrefaction at 500 oC decomposes some acetate salt into carbonate salt and leaves behind only cell walls. Below the image we give the Brunauer-Emmett-Teller (BET) measure of porosity (area per unit mass) in m2/g. ©ASIAA

Because the VOCs driven from the biomass are recovered rather than burned, the economic return per unit weight of the biomass is higher than in traditional torrefaction. In particular, apart from water (which we recover and recycle for washing and recovering the salt in the finished biochar), acetic acid is the most abundant component of the VOC yield. As mentioned earlier, we are able to generate acetone and Na2CO3/K2CO3 if we take NaAc/KAc above 460 oC. By reacting the Na2CO3/K2CO3 with acetic acid, which is a fast acid-base reaction, we are able to recover the NaAc/KAc that we decomposed (plus CO2 and H2O).

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Acetone is a high-value chemical, useful as an industrial solvent as well as a feedstock for general aviation fuel, so the technique not only creates a high-throughput solid biofuel to compete with natural coal, but also a liquid feedstock to lessen the dependence on petroleum for one segment of the transportation industry. We also get uncondensed gases combustible as a replacement for natural gas.

Supertorrefaction allows a greatly reduced size of the equipment needed to produce a given throughput (tonne per day) for the biomass processing, even when the slight loss of the salt encased in the pores of the charcoal is taken into account. This reduction lowers considerably the initial investment of capital equipment. Indeed, it is possible to have supertorrefaction throughputs that generate attractive economic returns with batch-process equipment compact enough to be transportable by truck to remote batch supertorrefaction sites where the biomass is harvested. These capabilities make commercialization of supertorrefaction possible in startup environments that hold many barriers for traditional torrefaction technologies.

The next step may be to conduct a demonstration project in Penghu County to prove the economic feasibility of scaled-up, mobile, batch-process supertorrefaction.

Our target biomass is a bush called leucaena that has over-grown 70% of Penghu County (Fig. 8). Introduced to Taiwan under the Japanese occupation, leucaena was originally cultivated for firewood.

Leucaena is nitrogen-fixing and requires no chemical fertilizer to grow in poor soil. Now that everyone uses natural gas or Figure 8. Leucaena fields occupy 70% of the land area of Penghu propane for cooking, the leucaena, and threaten to invade the remaining 30%. In autumn and winter the with its adaptive advantages, has plants are very dry, in optimum condition for harvest and become an invasive species that supertorrefaction. (Photo taken Oct 19, 2012). threatens the habitats of the native vegetation of Taiwan (and, indeed, much of Southeast Asia). Using this biowaste as a ŠASIAA is consistent with the sustainable development goals of Penghu County. bioresource Taiwanâ&#x20AC;&#x2122;s Council of Agriculture (CoA) prefers to try to eradicate this invasive species.

Eradication of established leucaena is impossible without digging up its deep roots, and killing all viable seeds dispersed on and in the soil. To harvest the leucaena, we would therefore clear-cut the branches, allowing the CoA to experiment with eradication schemes. If eradication efforts fail, as is likely from experience in other parts of the world, each topped bush will regenerate new growth in ensuing seasons, recovering fully in about three years.

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Another bad situation exists in Western North America, where winters that are too mild, combined with drought-like conditions in the summers, are blamed for an outbreak of pine bark beetle disease in mountain forests stretching from Southern California to British Columbia (Fig. 9). Hundreds of thousands of pine trees fall per day. We propose that the felled trees should be supertorrefied before they become ground tinder for wildfires, or rot and release greenhouse gases into the atmosphere, or have falling limbs that bring down power lines Figure 9. Pine trees in Colorado dying or dead from bark beetle infestation (AP/Colorado Forest Service/Jen Chase). and cause expensive and dangerous outages. We would bury the resulting biochar in the same forests, not only sequestering for thousands of years the resulting carbon, but also encouraging new growth that would lock up more carbon.

The forest crisis affects more than just North America. A survey that appeared in Nature magazine in 2012 found that 70% of 226 forest species in 81 forests of the world are on the verge of dying from the stress placed on root systems when there is too little water in the soil.

This existential threat deserves an adequate response.

Figure 10. Left (picture taken in July 2010): how an abandoned silver mine in Hope, Colorado looked for a century before the addition of biochar soil amendment made by torrefying diseased pine trees. Right (picture taken in August 2011): how the same mine tailings site looked a year later after the application of biochar soil amendment at a rate of about 100 tonne per hectare. (Photo credit: Troy Hooper).

Biochar is also useful for land reclamation. Experiments carried out at an abandoned silver mine in Hope, Colorado show that each hectare treated with 100 tonne of biochar will permanently require 17% less water to rejuvenate vegetative growth (Fig. 10). We propose to use charcoal fines, generated by supertorrefaction whenever one has bark mixed in with the woody stems, in experimental trials to see whether the use of charcoal fines as a soil amendment stimulates a similar dramatic improvement in soil productivity of Penghuâ&#x20AC;&#x2122;s infertile soil while decreasing the share of water that needs to be devoted to agricultural irrigation. With the data in hand, Penghu County can make better informed decisions whether it should (a) undertake a systematic effort to eradicate leucaena over the next decade, (b) passively harvest leucaena as a bioresource while

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controlling its spread, or (c) actively cultivate leucaena, but without the application of ammonium fertilizers that are based on petroleum feedstocks.

The Grand Challenge Climate change is the grand challenge of the twenty-first century. The fate of human civilization may well depend on whether we rise in a rational and scientific manner to meet this challenge.

The ultimate goal of our group is to marry the technologies of molten salt reactors and supertorrefaction. There are physical and economical reasons why it is hard to beat natural gas for turbine electricity generation, or to beat natural gas as the input heat for supertorrefaction.

But we do not have to use the nuclear heat from a MSBR for turbine electricity generation (a difficult coupling). Instead, we can transfer the heat carried in the radioactive blanket salt (ThF4/NaF/BeF2) to a non-radioactive working salt (NaAc/KAc) via a secondary heat exchanger (an easy coupling depicted in the background of Fig. 3). Then we have a combination that can beat natural gas at both tasks. Although nuclear electricity is expensive, nuclear heat is cheap – much cheaper than natural gas. We can therefore use nuclear heat to produce from biomass, at very high throughputs, biochar, acetone, and syngas cheaper and cleaner than mined coal, drilled petroleum, and fracked shale gas. Baseload electric power can be generated from syngas; liquid transportation fuels can be made from acetone; and carbon-negative sequestration can be achieved with biochar.

Coal, oil, and natural gas are valuable Earth resources, and they would not contribute to climate change if they were used to make durable goods, rather than burned. We do not need fossil-fuel companies to go out of business; we need them to go into a different business. Other researchers may have even better ideas for effecting a realistic transition from an economy based on fossil fuels. If so, they should get to work. Through nearly fourteen billion years of the evolution of the physical universe, nature has given us a bounty of Earth energy that can, in principle, replace fossil fuels. It is time for us to do our part. （ Authors/Frank Shu, Michael Cai, Fen-Tair Luo; Translator/Chun-Hui Yang; Reviewer/ Michael Cai）

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【從地球和人類發展看臺灣的永續能源選擇─李遠哲前院長專訪】 網路版專訪全文 前言 2011 年接任聯合國際科學理事會會長的本院前 院長李遠哲院士，近年來在國內外不斷宣導「永 續發展」的重要性並推動落實。藉本期季報地 球能源主題之便，我們很榮幸專訪到李前院長 和讀者們分享他對「永續發展觀點下，臺灣的 永續能源選擇」的建議。專訪議題有以下三個 主軸，分別是（1）人類與地球的永續發展（2） 臺灣永續能源的利用與發展（3）如何落實永續 發展。 ©APANAC

議題一、人類與地球的永續發展 「永續發展」小辭典（摘錄李院長過去相關演講中對於永續發展的解釋）： 1.

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永續發展是指「滿足當代的需要（包括需求、國家主權、國際公平、自然資源與生態承載力、 環境和發展相結合），同時不損及後代子孫滿足其本身需要」的發展。 永續發展並不排斥經濟成長，但要加上「社會轉型」及強調「社會公平」。 永續發展要從「環境保護」的角度來倡導人類社會的進步與發展，在號召人們增加生產的同時， 必須注意「生態環境的保護與改善」 。 要永續發展，就必須改變人類沿襲已久的「經濟生產方式」和「社會生活方式」，尤其是工業 革命之後的高消費高消耗生活方式，並調整現行的「國家經濟關係」 。

問：李院長您近年來一直在宣導永續發展的觀念，發表的相關演講中曾提到：人類在地球 上活動所帶來的影響已經遠遠超過大自然回收量可以承受的範圍。 李：是的，再過半個世紀，溫室效應帶來的極端氣候說不定就會突破臨界點，進入「不連 續期」─也就是所謂「失控的斷層期」 ，這時海水中的二氧化碳和甲烷就會像咳嗽一樣，不 停地被咳出來。西伯利亞凍土中的甲烷一旦釋出，溫度就會突然上升，人類和很多生物都 無法存活；這是本世紀內就可能會發生的事。2007 年聯合國氣候變遷跨國小組（IPCC； Intergovernmental Panel on Climate）獲頒諾貝爾獎的評估報告指出：和西元 1750 年工業革 命前相比，溫室效應已經讓全球均溫上升大約 0.7°C。如果上升超過 2°C 這個臨界值，氣 候及地球上的生命就會遭到很大的衝擊。目前全球努力想將升溫程度控制在這個臨界值之 內，也就是要將溫室氣體的濃度控制在 450 ppm（註一）以下─但即便這樣，將全球年升 溫控成功制住的機會也只有 50%。依現在的情況來看，2°C 這個夢想已經達不到了，若再 不努力控制，本世紀結束前溫度甚至可能會增加 4°C 到 5°C 左右。

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2°C，很多人不瞭解這個數字的意義，認 為僅僅「2 度」而已有什麼大不了，早上 起來到下午，溫度變化就不只 2 度，春夏 秋冬溫差更大。很多住在北方（像東京、 瑞典、莫斯科、溫哥華等）的人甚至以為 溫度升高 2 度氣候更舒適。可惜事實不是 這樣，所以大家不瞭解這裡「2 度」的嚴 重性，這裡我們講的「2 度」指的是「全 球年平均溫度上升 2°C」 。若以人體作比喻， 平均體溫 36.5°C，上升 2 度就發燒了，躺 在床上不能上班上課。上升 4 度，到達 40.5°C，醫生就會要求趕緊泡冷水或打點 圖說：目前全球努力想將升溫程度控制在 2°C 這個臨 滴降溫，不然生命會有危險。地球是一個 界值之內，也就是要將溫室氣體的濃度控制在 450 有生命的體系，從某個觀點來看和人類很 ppm 以下。 即便這樣，將全球年升溫控成功制住的 像。溫度升高 2°C，各大洋的海水會大量 機會也只有 50%。背景圖片©www.port.ac.uk。 蒸發，海水蒸發後儲存在雲氣中的能量非 常大，能量一旦釋放出來，表現出來的就是颱風、或者是很多的氣候變化（fluctuation）， 結果造成很嚴重的極端氣候，例如乾旱好一陣子，然後突然下起大豪雨氾濫成災。 問：面對隨著極端氣候變化而來的，諸如海平面上升、乾旱、洪水、暴風、生物多樣性消 失等等現象對未來地球生物及人類生存帶來的威脅，多數國家已經覺醒，同意「經濟發展」 應轉型為「永續發展」（sustainable development）。但何謂永續發展？請問李院長您怎麼看 「永續發展」這個問題？ 李：每次提到「永續發展」 ，大家就會想到 1987 年聯合國世界環境與發展委員會（WCED） 主席 Brundtland 在「我們共同的未來」（Our Common Future）報告書─又名布蘭特報告 （Brundtland report）中提出的概念：「永續發展為：滿足當代需求，同時不損及後代子孫 滿足其本身需要的發展」。 對這個布蘭特報告的「永續發展」，我就有兩個疑問，「滿足誰的需求」？「何謂發展」？ 我到非洲的時候有人問我：「滿足現代人的需求」是滿足「誰」的需求？美國人的需求， 還是非洲人的需求？比如說美國洛杉磯，如果沒有汽車就很多地方去不了、不能買日常生 活用品、很多事都辦不成，所以汽車就是他們生活的基本需求。但是非洲很多地方連吃的 東西都沒有，所以他們的需求就是「食物」。世界各角落人們的差異那麼多，所以到底要 滿足「哪個地方的現代人」的需求？這是很大的問題，但是全球並沒有共識。 再者，什麼叫做「發展」？人類過去的能源一直都從太陽來。回溯宇宙形成的最初，大霹 靂後 91 億年太陽系形成，然後地球上出現了生命的現象。46 億年來陽光從未停止照射， 透過光合作用，地球上的物質得以循環、生命可以生生不息，才有花草樹和我們人類存在。 如果我們把地球的一部份變成水泥地的話，循環的功能馬上就會大受影響。人類到了工業 革命後才開始利用化石燃料（fossil fuel）取代陽光，製造業開始不斷發展，發展的方法是 把很多自然環境破壞掉，然後大規模促進工業生產。如此下來，也不過短短 250 年左右就 已經走到極限；所謂極限就是說：太陽已經無法透過光合作用把人類產生的廢棄物回收消 化了。

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所以我們一直說的「發展」 （development）到底是什麼？ 歐美發展的方式就叫做發 展嗎？以歐美經濟發展模 式來看，發展是「製造更多 的東西、以便人們有更多的 東西可消耗」 ，但是這個「永 無止盡地增加物質消耗」的 發展模式，在人類社會是不 可行的。人口一直增加，物 質消耗也一直增加，因而產 生的污染，不但陽光已經無 法消化回收循環，而且開始 影響地球的生態環境。所以 我們一直在反問自己：發展 圖說：和公元前相比，全球人口隨著工業革命而快速增加。1950 年代 到底是什麼？國際社會上 地球尚可提供人類舒適的生存環境，但僅僅半個世紀的時間，人口的 歐美都說自己是「已開發國 暴增已經帶來大量資源消耗、飢荒、以及地球生態環境破壞等等危機： 家」，告訴「開發中國家」 資料來源：The U.S. Census Bureau。 說他們可以幫忙開發，像是 促 進 能 力 建 設 （ capacity building）、提供技術轉移，幫助往已開發國家目標前進。但從地球現在的觀點來看，人類 已經「過度開發」到地球承載不了的地步了；已經過度開發的國家還來跟尚未過度開發的 國家說：「你們跟我的腳步走」，這樣下去只有死路一條。 所以我們在討論永續發展時首先該有的認知是「人類的活動，地球承受的了嗎？」；此外 要好好地思考：人類應用科技來發展究竟想要達到什麼樣的目的？在達到目的的同時，也 要讓地球及生態環境不受破壞，這樣我們才能夠繼續在這個地球生存下去。 工業革命之後人類開始使用化石燃料，這是人類社會的一個轉折點。脫離太陽、脫離自然， 然後以為人定勝天，就這樣一直走下來，直到今天終於發現走不通了：因為人太多、消耗 太多、污染太多、環境改變太多！所以 現在大家都在說我們應該要走入「低碳 社會」 。低碳社會是什麼意思？就是不要 用會產生二氧化碳的礦物燃料，要低碳， 因此要回到太陽的懷抱、回到大自然的 懷抱。 所以，所謂的永續發展就是：人類處在 太陽系裡面，就要知道這個太陽能夠給 我們什麼？太陽能夠給我們的能量很大 很多，一個小時內送到地球表面的能量 就可以供應人類社會一年所需。也就是 說，每年地球從太陽接收的能量，是目 前人類社會所需總能量的一萬倍左右。 若能善加利用太陽提供的能量以及由太

圖說：太陽能、風力、地熱、洋流這些能量都是太陽 給的。動植物的光合作用、森林土壤和微生物也都是 太陽孕育出來的資源。背景圖片©RPeter Hannam/ brisbanetimes.com.au。

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陽孕育出來的資源，就非常足夠我們生活了，當然這是在「人口數量能夠控制」的前提下。 問：所以，您的意思是，人類生存在太陽系內的地球上，就要想辦法好好利用太陽的能源， 和大自然一起共存走下去，這樣才是人類今後要走的永續發展方式。 李：是的。我們看太陽系形成至今約 46 億年，這 46 億年來地球上的資源、生物、人類都 因為有太陽而形成及演化。人類走入工業僅僅 250 年左右就已經走不通了。以前我們是擔 心礦物燃料終有用盡的一天，但其實在用盡之前，人類社會就會面臨無法生存的困境。所 以我一直說，大家在講的再生能源、新能源等等，其實都是要「回歸太陽」的意思，只是 沒有這樣直接講出來。但是你看，太陽能、風力、地熱、洋流，這些能量都是太陽給的。 當然有些海洋的能量，像潮汐是和地球及月亮的引力有關，但那也是太陽系形成時留下來 的能量。我們補充體力所吃的動物、蔬菜植物的光合作用、森林土壤和微生物，全都是從 太陽孕育出來的資源。總的說來，人類要永續發展，在能源資源的利用上就要回歸到能與 大自然共存的發展方式，這已經是無可避免的結論了。 議題二、臺灣永續能源的利用與發展 50 年後臺灣的能源要從哪裡來？： 李院長在過去的演講中提過：臺灣如果要利用來自太陽的能源，效率也要是美國的 20 倍才行。以 臺灣的地理情況而言，根本不可能單靠太陽能源，所以仍需要倚賴「能源輸入」 。問題是該輸入「何 種能源」─化石燃料、氫燃料、核能？而且隨著能源資源的快速減少，若只靠從國外買進，花費也 會越來越貴。這些問題我們都要開始好好的思考該如何走，科學家們也要好好去研究發明適合臺灣 的能源。不要依賴外國，自己掌握自己的國家社會，這樣才可靠。

問：接下來我們想請李院長談談目前臺灣永續能源（註二）的利用情況。您一直都跟大眾 強調：人類要永續發展就要回歸到大自然的能源利用方式。亦即位處太陽系，就應善加利 用直接或間接來自太陽的資源。在太陽能源的利用上，比如說：與建築設計結合的太陽能 板、小型家用風力發電、絕緣或通風系統、利用人造樹葉來提高光合作用等。以太陽能板 為例，造價很貴；對此您說隨著科技進展，綠建築、節能綠生活方式將來也可能以不同的 方式呈現，節省能源的材料研究也會持續進展，一旦技術成熟及量產，成本就會跟著降低。 在過渡時期，如果政府能夠有積極的配套鼓勵措施，就可以支持研究發展持續下去，民眾 也就可以負擔得起這個能源的利用。所以應該不要拿一開始的高價格就低估其未來的經濟 價值；若純粹從技術觀點來看，數 10 年內臺灣要做到降低利用太陽能源的成本是有機會 的，可不可行端看政府的態度與配套政策。 但是民眾對於在臺灣發展太陽能板可能會有幾個疑問：第一，太陽能的利用，不能只是「靠 天吃飯」。臺灣中南部陽光利用可能比較穩定，但北臺灣多陰雨地區如何穩定利用太陽能 並跨季節儲能呢？有沒有可能克服這些氣候、時間和地理位置的障礙，將中南部儲存的太 陽能源儲存並輸送到北部地區去？在未來的 30~50 年時間，我們的技術有可能做得到嗎？ 第二，技術成熟之前的過渡期，太陽能利用的成本負擔很高，以目前臺灣經濟不景氣的情 況，民間負擔得了嗎？我們政府此時有能力提供鼓勵配套措施嗎？ 李：這個問題很好。我一開始就說，永續發展是全球性的問題，如果全球不一起解決，就 很難做到。臺灣目前 98%的能源靠進口，幾乎所有的能源都是靠進口的化石燃料。化石燃

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料來自地底，不是從陽光來的，也無法再生重複利用；但優點是能量很密集，釋放出來利 用的能量和運輸消耗的能量相比，消耗得比較少，釋放出來的則高很多，所以在全球市場 上，石油、煤炭的使用分布很廣。每個地方需要多少能源，就買進多少煤炭，臺灣就是這 樣。如果有一天人類不再使用化石燃料，對臺灣來說其實影響不大，因為我們大多數的能 源還是得靠進口，差別只在於輸入能源種類換成別的罷了。 臺灣地狹人稠，每平方公里住了 600 人，不像美國地廣人稀，每平方公里只住 30 人，加 拿大、澳洲則只住了 3 人。換句話說，臺灣人口密度是美國的 20 倍，約是加拿大、澳洲 的 200 倍，所以臺灣人可以享受陽光的「人均享受量」是很少的。當然，即便很少，未來 我們還是得盡可能好好利用太陽能源，只不過臺灣的太陽能源使用效率也得是美國的 20 倍才行；以臺灣的地理情況，還是無法單靠本地的太陽能來發展。整體說來，我們還是一 個需要輸入能源的國家。因此政府更應該要好好想的是：50 年之後臺灣的能源要從哪裡來？ 若依照今天國人高消耗的生活方式繼續下去，即使再加上風力、水力、地熱、生質燃料等 等再生能源（註三） ，能夠滿足能源需求的 10%~20%就很了不起了；就算能滿足 20%，仍 有 80%得靠進口，這 80%的能源又要怎麼來？ 20 年前大家都在說人類以後會進入「氫經濟」（hydrogen economy）時代（註四），取代石 油經濟。氫分子在地球上不是以天然氣體的形式存在；大部分的氫與氧結合後存在水中， 所以氫並不是初級能源（註五）。我們利用風力、太陽能這些初級能源來供電或其他方式 （如微生物分解）將氫從水裡分解出來儲存；這個氫可以當作燃料，透過化學反應再產生 電力。因此能量的儲存並不是直接儲存「電」，而是儲存經過化學分解後的「氫」。但是將 來臺灣如果要利用氫來發電是要進口買入氫嗎？可是氣體的運送是很不方便的，如果要變 成液態氫來運送，溫度要很低，所以有很多問題和成本都需要大家來想辦法解決。 臺灣要好好想的還有：未來的能源該從哪裡取得？ 今年我會邀請亞太地區科學家和重要人物一起討論亞洲的未來，包括能源問題，屆時澳洲 一定會說：我們有很大的土地和充足的陽光可以進行太陽能發電，我們可以輸出太陽能給 亞洲！這也是可以，太陽能先轉成高壓直流電再輸送。澳洲用不到那麼多收集到的太陽能 量，但是亞洲很多國家需要。 另外，澳洲廣大土地上生長的尤加利樹，可以做碳化處理（torrefaction） ，就類似徐遐生院 士正要做的「超級烘焙法」，這樣澳洲就是一個很好的幫助進行碳回收的地方。森林不要 燒掉，而應該要把它作為光合作用的碳回收基地。將來回收很多碳，磨成粉之後可以再灑 回土壤，改善土壤的性質。 同樣地，我們政府也應該要想想 30~50 年後該怎麼辦？臺灣如果在半世紀內仍無法脫離化 石燃料，至少得想辦法處理掉煤炭發電所產生的二氧化碳。目前的方法是做「碳收集及封 存」 （carbon capture and storage 或 carbon capture and sequestration；簡稱 CCS） ，把二氧化 碳埋到地底下。我們應努力朝這方面好好研究，可是政府目前進行的非常緩慢。二氧化碳 的封存需要做地層研究，每個洞打下去就是一百萬美金，這絕不是一個學術單位的教授可 以做到的；必須靠政府大規模規劃、與國際合作才有辦法進行。去年十一月召開的『2012 台灣二氧化碳捕獲封存與再利用』國際研討會，林立夫博士廣邀澳洲、日本、馬來西亞、 中國的科學家，希望一起動腦想想應該怎麼解決未來亞洲的能源問題。亞洲應該學學歐盟， 他們很有組織。如果大家無法跨越主權國家利益的藩籬進入「全球」合作、互相支援，一

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切就無解。 二次大戰之前英國以「日不落地國家」來描述自己，他們到處都有殖民屬國，所以陽光隨 時照耀著大英帝國的土地。反觀單一國家各地晝夜雲雨條件不一，陽光或風力供給可能不 穩定，時有時無。如果全球國家能作為「共同體」一起合作，利用大自然提供能源的問題 就可以迎刃而解了。臺灣未來的永續能源也是一樣，要想辦法和全球其他國家合作，建立 起能源網絡。目前各國之間仍有國際藩籬、利益考量，所以藉由更多全球化的組織聯繫， 希望把國界淡化、走向全球化，這是本世紀一定要走完的路。 我們這一世代的人，還沒有能力去做全球的聯繫，但是你們年輕世代的人不一樣。人類有 史以來第一次可以透過網路聯繫全球，以往做不到的事，現在都有可能做到。「阿拉伯之 春」能夠串聯起來，就是因為網路連結，資訊四通八達的緣故。去年有一個科學營在以色 列開會，每次這個會都有一個壁報的競爭，這次以色列在會前就先分配好組別。各組的人 透過網路就先把資料內容都準備好了，一到會場馬上就可以執行。所以說，現在的世代和 以前不同了，現在的世代已經具備打破國家界線、進行全球連結的潛力。我再說一次，不 打破國界走向全球，人類的未來是沒有希望的；主權國家做不了事，必須全球一起來方能 成事。先是歐洲有歐盟、亞洲有亞盟、美洲有美盟，然後再進一步全球化。 問：除了來自太陽能量的再生能源，如太陽能、風力、地熱等，還有其他能源的技術研究， 像核能等等。有些人的主張是只要他們能夠減低轉換能源過程中的耗損就可以減碳，既然 可以減碳就不需要節能，如此一來就可以滿足經濟發展的需求。就這一點您的看法如何？ 此外，您曾經說過再生能源「 不等於」永續發展，請問這是為什麼？ 李：我們通常說人類發展的危機就是人類從地球上滅絕的危機以及核子大戰的危機。今天 的我們已經開始在承受全球氣候變遷帶來的各種衝擊。半世紀前冷戰時期大家最擔心的是 核子大戰危機，現在我覺得核戰的危機仍在，另外還多了兩個危機，就是溫室效應的危機， 和生物多樣性消失的危機。

圖說：大自然提供人類的產值比人類自己生產的 GDP 還高。若我們繼續無限制消耗資源，把森林、綠地 都變成水泥地，將來生態破壞、生物多樣性消失的一天，也就是人類消失的一天。背景圖片左圖©Nature Blog Network；右圖©WallpaperWeb 。

透過科學研發及全球性的政策合作，或許可為減碳及永續的再生能源問題找到出路，但這 仍然只是人類及地球永續發展環節的一部份而已。大自然提供給人類的產值比人類自己生 產的 GDP 還高。比如說，蜜蜂蝴蝶做花粉授粉的工作，我們所吃的食物有三分之一都靠

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他們。的確，如果能源都從太陽來，溫室氣體就可以控制住，但是如果人類無限制地消耗 資源，把森林、綠地都變成水泥地，將來生態破壞、生物多樣性消失的一天，也就是人類 消失的一天。人類是無法單獨存在這地球的。透過科學研發及全球性的政策合作，或許可 為減碳及永續能源的問題找到出路，但這仍然只是人類及地球永續發展環節的一部份而 已。 問：再生能源有很多種，像其中的生質能源（註六），有些必須大量種植某種類的植物， 這也有可能破壞生態系統中的生物多樣性，是嗎？ 李：是的。美國地廣人稀，每平方公里平均只住 30 人，所以他們要發展再生能源還說得 過去。巴西人口密度也不高，所以他們種甘蔗生產酒精燃料，提供很多汽車使用。但是要 大量依賴生質能源就不適合在亞洲人口密度高的國家。想在臺灣利用生質產生酒精當作燃 料，就會影響本土的農業生產，因為我們的土地有限，陽光接收也很有限，因此這類能源 的發展可能就要針對農業廢棄物的利用的方向去探討。 問：徐院士的「超級烘焙法」計畫就需要大量種植某種植物，如銀合歡。但因為臺灣的地 狹人稠，研發成功後，將來也可能需要借用像南美國家等廣大肥沃的土地來種植這些植物， 然後碳化，再進口運回臺灣利用。對臺灣而言，這樣的投資和能源使用的解決辦法，您覺 得可行有效益嗎？ 李：這個計畫倒不是為了用來作為臺灣能源燃料來源的解決方法，主要是作為碳回收的機 制，就是前面提過的「碳化處理」。澳洲和南美洲都有規劃專門在種植二氧化碳的固碳回 收農場，種植生長很快的植物然後進行碳化，這樣碳就被封存保留下來了，這是一個全球 二氧化碳回收封存的機制。把植物買進來進行碳化，就是碳中和（註七）。雖然在燃燒碳 化的過程會釋出一些熱，透過熱交換器可以利用這些熱能，但這個釋出熱能其實相對並不 是那麼多。重點在碳化，一部份的能量和碳可以因此被封存保留下來。 問：所以，徐院士的這個植物碳化計畫主要目的是在碳回收，而不是在提供生質能源？ 李：是的。整個碳化反應其實是「吸熱反應」。碳化反應吸收的能量一部份燃燒掉，一部 份拿來進行碳中和。換句話說，陽光提供能量給植物生長，我們再把植物加熱燃燒變成木 炭。如果拿回收的木炭來燒，那就是一種碳中和措施；如果把製成的木炭保留下來不燒掉， 那就是碳回收。我們小時候，山上種了很多相思樹，人們會把相思樹砍來燒成木炭，用來 煮飯洗澡。大家燒的是木炭而不是木柴，燒木柴排放出來的煙很多，但燒木炭的煙就很少。 所以碳化計畫主要目的是為了「減碳」、回收二氧化碳，不是為了當作再生能源。 問：核能發電方面，最近臺灣核四廠興建、以及其他核電廠的核安和廢料處理問題引起很 大的討論和爭議。徐院士團隊的熔鹽式反應爐計畫（詳見本期徐院士專欄文章內容）願景 是增加核電效能、安全性及對環境的影響所進行的核電研究。熔鹽式反應爐有幾項特色： 使用熔鹽型態的冷卻劑及核燃料，不需要使用水所以不會氫爆，安全性比目前的輕水式反 應爐高；也不需蓋在海邊，不會影響海洋生態；混在氟化物熔鹽中的釷-232 經過核反應轉 換成的鈾-233，作為核燃料幾乎可完全利用，產生的核廢料半衰期只有 30 年左右，裝入乾 式儲存桶存放地下 300 年後還可能成為經濟礦物再利用；可回收現存輕水式反應爐的高階 核廢料鈽-239 當作燃料再利用。這個計畫的理想果真實現的話，看來似乎可以解決核電目 前的一些問題。假如真的必須發展核電來符合低碳、乾淨又可大量供電的需求，同時又要 48/66

改善核安和解決核廢料處理問題，熔鹽式反應爐會是一個解決方案嗎？院長您對這個熔鹽 式反應爐計畫的研究或前景有什麼看法？ 李：熔鹽式反應爐從前美國橡樹嶺國家實驗室（Oak Ridge National Laboratory）就已經試 過，但是因為溫度很高，有些技術問題無法克服，所以當時沒有繼續發展。因此現今看到 的核電廠反應爐運作為了避免核子武器的擴散，反應爐中真正能用來發電的核燃料鈾-235 所含有的能量，用到的不到 5%，剩下的 95%都變成核廢料。純就核能發展來看，目前這 種核電廠是不理想的。為什麼效率這麼低呢？主要是我們提煉鈾-235 之後，會用普通的水 （輕水）來進行讓中子減速、冷卻的調節，利用慢速的中子來作用發電發熱，這是為了避 免反應爐發生核爆，但是會產生很多核廢料。目前臺灣用核能來發電是不合宜的，因為核 廢料產出那麼多，但至今卻還沒有辦法解決核廢料的處理問題，問題全被推給了下一代。 核電廠除了本身不理想之外，安全也是個問題。所以，發展核電是不理想的。 問：提到核安，對臺灣各核電廠運作或核四續建有異議的人，他們的疑慮包括：對過程中 官商專家利益輸送情形有質疑；對電廠興建問題、核電機組零件規格不合的結果不滿；對 臺灣核廢料無法處理、核安運作與管理能力不信任。那麼，假設以上這些問題都不存在， 假如臺灣目前正處於國泰民安、政治清廉、經濟繁榮、四方太平、沒有戰爭陰影的理想狀 況下，我們可以發展核能嗎？ 李：這又是另一個問題。核能「本身」可以做得很安全，這是沒問題的；但是對臺灣來說， 「地震」是另外一個重要考慮因素。在穩定的土地上，核電廠可以做得安全嗎？應該有很 多監視偵測系統可以做得相當安全，然而，一旦「地震」因素加進來，事情就變得很複雜 了。即便不是處在地震帶，光憑臺灣現今核電廠的運作管理，就已經問題叢生，更何況我 們是處在地震帶。所以你問我臺灣能做好核安嗎？其實我不太相信。所以核電在臺灣發展 是不理想的。 對臺灣而言，現今的核能不是永續能源，核電在臺灣發展是不合宜的。但若想進一步研究 如何讓核燃料完全燃燒，不要造成更多的核廢料污染問題，這方面的研究倒是值得推動。 剛才說，熔鹽式反應爐以前就有人做過；徐院士重新估算後，覺得他可以把這個做得更好。 我也同意這個看法，但一定要和歐美的大實驗室合作。但美國方面一直強調像這種核能研 究一定要國務院通過才行，但是他們國務院是不會通過的，所以和美國方面的合作嘗試仍 有困難度。我是不認為臺灣有辦法獨立完成這樣的研究，因為我們的工業技術不夠。所以 這個計畫應該要繼續想辦法找德國、法國或其他有技術及經驗的歐美先進國家合作才行。 徐院士的構想很好，希望合作發展的格局可以更大，才不會侷限完成理想的機會。 在提高核安和解決核廢料處理問題上，其實還有很多新一代的核電研究方案也正在進行， 像是利用加速器控制核反應提高安全性…等等，在這裡我無法一一說明介紹，有很多不同 的構想，熔鹽式反應爐也是其中一個。此外，如果全球大家願意坐下來討論國際合作，一 起開發新一代核能反應爐，而且大家說好這個反應爐不要蓋在海邊和地震帶等不適合的地 區，只蓋在穩定的土地上，生產出來的核電可以利用進出口來供應不適合發展核電的國家， 如此一來核能發電對全球還是可以很有貢獻的。

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議題三、如何落實永續發展 李院長於 2011 年接任國際科學理事會（The International Council of Science Union/ICSU）會長後就 提出：「人類社會考量經濟發展及社會需求的同時，也必須有效地對全球變遷做出應變措施」這個 觀念，對全球大規模宣導推廣，希望普及落實到各地區。 人類社會要如何邁向永續發展？（摘錄李院長過去的相關演講） 1. 面對人類活動帶來全球氣候變遷的這些危機，人類社會應該開始思考永續發展的生活方式，減 少高消費高消耗的生活方式，回歸利用大自然資源的生活方式。 2. 永續發展的生活方式並非回歸原始生活，所以科技發展和回歸大自然兩者並無矛盾，而是應利 用現有科技進行「以能源消耗最少的發明」來達到「高品質的生活」。而「高品質的生活」也 不代表「高消費的生活」 ，而是可以和大自然結合的人文生活。 3. 科學應作為人類和大自然溝通的橋樑。在應用科學的同時，不要讓科學破壞大自然，因為人類 和大自然是共存亡的。 4. 永續發展要結合科學家及關心環境的人文社會學者一起跨領域合作，來評估科學對人類社會帶 來的衝擊和影響，並找出處理及解決問題的辦法，將人類社會帶向永續發展的未來。 5. 「國際化的科學」 （international science）應轉變為「全球的科學」（global science），才能永續 發展。也就是說，科學界應破除「國家發展」的界線，將「全球」當成一個整體目標來考量其 未來及發展。 6. 永續發展是全球性的問題，如果全球不一起來解決，就很難做到。 7. 要由已開發國家援助開發中國家一起來努力。

問：院長您剛才不止一次提到「要打破國界，走向全球」。這個觀念您近年來一直在宣導 推廣，鼓勵科學界不要自己做自己的，應破除國家發展的界線，將「整個地球」當成一個 整體目標來考量人類的未來及發展。強調科學家應該要結合關心環境的人文社會學者，一 起跨領域合作來評估科學對人類社會帶來的衝擊和影響，並找出處理及解決問題的辦法。 您認為「國際化的科學」應該要轉變為「全球的科學」，人類社會才能夠永續發展下去。 請問院長，您覺得這個轉變有何意義？當初是如何啟蒙出這樣的想法的？ 李：隨著人類活動與交流的增加， 慢慢地，人類所面對的問題已經 變成「全球化」的問題，像：流 行病擴散、貧窮飢餓、森林保育、 生物多樣性消失等等問題，都是 跨越國界持續在進行的。以前流 行病方面是亞洲的疾病、美洲的 疾病，但現在每天幾千架飛機到 處往來、海運四處通航、 SARS、 禽流感等到處傳播；紅火蟻這些 問題也是跨國交通帶到臺灣來 的。所以我說現在很多問題常常 都是「全球性」的問題；全球性 的問題，如果是以「主權國家」 為單位來考量的話，是解決不了 的。主權國家之間大家都在競爭， 像美國政界為了選舉，一直想把

圖說：科學界不要自己做自己的，應破除國家發展的界線，將「整 個地球」當成一個整體目標來考量人類的未來及發展。淡化國 界、走向全球化，這是本世紀一定要走完的路。 背景圖片©Henry Mühlpfordt 。

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美國牛肉、美國豬肉賣到臺灣來，這樣可以增加美國的出口所得和人口就業。為了要滿足 他們國家的人民需求，結果臺灣的農牧業、農民就會受苦。很多臺灣企業家為了賺錢把工 廠移到中國，用那邊的廉價勞力，結果對臺灣社會帶來很多問題，例如：工廠關閉、臺灣 勞工面臨裁員、失業問題，然後這些企業賺的錢，臺灣政府又課不到稅，臺灣拿不到企業 主的稅，靠一般老百姓在繳稅，造成社會的不公平。所以我們常常講「全球化、全球化」， 「政治」上其實並沒有做到全球化，很多問題倒是全球化了。所以你看，常常大家到了國 際會議中提出一堆問題，說大家應該一起來解決，但是一回到自己的國家申請研究經費想 解決這些問題時，各國政府就會問：做這些能幫助「本國的競爭力」嗎？好比美國在審查 計畫經費時，首先的要求就是要能幫助就業率。臺灣也是一樣，如果不能提供就業機會的 話，政府承擔不了。所以很多「國際合作」和「國際間的競爭」是存在著矛盾的。所以國 際間一直說要減少飢餓，千囍年時說想在 2005 年前減少多少飢餓情況，全球觀點規劃說 我們應該如何如何做，但是很多時候，國際的合作到頭來還是各個主權國家為了自己人民 的利益考量，產生很多的矛盾，因此都合作不起來。 所以「國際」和「全球」是不一樣的。國際是以「主權國家」為單位來合作、競爭；而全 球是把「整個地球」當作一個單位來看。比如說溫室效應的問題，如果不是全球一起來解 決的話，是無解的。所以我一直努力想宣導這個觀念，就是：我們要超越「國際」，而推 進到「全球」。 問：有些議題像溫室效應這些，可能大家都會同意「跨越國際到全球規模」這個觀點，可 是其他很多一般議題或研究，既然要考慮國家競爭力，要怎麼說服大家一起合作？ 李：是，所以我說社會必須要有很大的轉變跟進才行。我們的研究成果常常是為了要促進 經濟的進步，但經濟的進步對各國政府來說指的是自身國家的經濟進步，談的是自己國家 的競爭力，卻並不在乎別的國家人民的死活。所以像非洲人民飢餓，美國農產品會提供給 非洲嗎？不會，他們只想賣給亞洲像日本、臺灣跟韓國這些國家。臺灣現在是美國本土之 外，全球人均（平均每個人）消費美國農產品最多的國家。臺灣是農業非常發達的國家， 結果現在臺灣的農產消費竟然只有 28%是來自本土農產品，72%是進口的食品。有些人想 把電子產品賣到美國，因此在自由貿易要求下就得打開臺灣農業市場。我曾參加 APEC， 當時美國布希總統就說要打開亞洲的農業市場。美國的農業是粗放型的，聯邦政府資助很 多，尤其是水的供應。而且美國幅員廣大，像加州在灑肥料、灑農藥是用飛機在灑的，農 地和人住的地方是分開的。但亞洲和美國不一樣，農村是在整個社會組織架構裡面，農村 的人口還是佔人口一半以上。像我們，農產品的出產幾乎是足夠供應全臺灣人口的，但是 現在政府卻為了進口外國農產品，要額外花錢要求自己的人民休耕、廢耕。臺灣的農業精 緻、品質高，外國進口的農產品相對便宜，價格競爭之下，結果台灣農民辛苦研發育種、 種稻、種農產品，卻反而沒辦法過活。美國說要打開亞洲的農業市場，亞洲農業市場一旦 被強迫打開，很多亞洲農村都有可能會破產，農村破產的話，整個社會都會破產的。 問：這一點，日本怎麼做？日本農業也很發達，品質好價格相對高，他們為何可以同時保 護本土農業又能和外國競爭？ 李：是的，日本位處北溫帶，農業產出還沒有臺灣發達，但是他們本土農產品的市場佔有 率是 42%，臺灣的本土佔有率卻只有 28%，所以我們現在的政策和作法是很不對的。臺灣 的農業研究和發展在全球是非常進步，排名很前面的；但是現在政府卻叫大家廢耕不要種 了，很多肥沃的農村土地要被改成工業用地，水的供應也是都供應給工業、大企業，成為

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國際間利益和競爭的犧牲品。 我剛才說的就是「國家利益」和「全世界利益」的相互矛盾。美國農產品為什麼不提供給 非洲呢？因為非洲國家沒有錢，亞洲人才有錢，所以他們才想賣農產品到亞洲。所以國家、 國際的利益和全球利益的矛盾，這個問題，我們老一輩的人沒有解決，年輕一代得要想辦 法解決。 我再舉個例子。像貧窮、飢餓的問題，如果全世界一起每年提供個 2 千億，這些問題都可 以解決。像森林保育的問題，非洲國家都說：給我們個幾千萬，我們就可以好好保護非洲 森林不去開發。印尼、亞馬遜河流域巴西等國也都說：給我們一些錢，我們就可以不開發 森林改做保育，可是，大家卻拿不出錢來。雖然如此，每年我們花在國防上的預算是台幣 1.7 兆 (1.7 trillions)，美國一個國家的國防就花掉美金 7、8 千億（700~800 billions） ，可見 現在很多國家都花很多錢在買武器保護邊境，要對付敵人。但是我剛才說了，溫室效應、 臭氧層的破壞、疾病等都是跨越國界持續在進行的。結果可能不到 50 年，我們就會發現 地球環境已經被破壞到人類無法生存的境地。到時候大家就會知道，我們的敵人其實就是 自己，我們自己要把自己消滅掉了，卻不知去正視這點。 問：所以，國際間有合作也有競爭，也有很多彼此矛盾衝突之處。科學要從「國際化」邁 向「全球化」 ，很多國家還沒有共識。要克服這個問題，是不是需要在國際間有個「協定」 或議定書，來達成共識呢？ 李：是的，所以 2012 年在里約熱內盧的聯合國 RIO+20 永續發展大會中，很多學術界及民 間人士都贊成應該要立個國際協議來訂定二氧化碳減量的標準。但是沒有一個國家的政府 肯站出來帶頭做這個事，因為一旦這麼做，恐怕會影響他們本國的經濟，經濟一受影響， 選票就沒有了。如果政府不介入，單靠學者和民間很多事是無法推動的。所以現在有個很 大的矛盾就是：很多主權國家的政府都說要保護自己的人民，透過經濟稅收好去重新分配 資源，大家就會過得比較好；然而國家之間有競爭關係，因此無法去解決全球性的共同問 題。 問：所以國際科學理事會的成立就是基於這個原因，想要去推動解決全球性的問題嗎？ 李：是啊，80 多年前成立國際科學理事會時，就是希望促進國際科學，每個國家一起透過 科學合作來造福人類社會，但是那是「國際間的科學合作」還是有前面所說的競爭問題。 所以我才一直在講，應該要推動將觀念整合轉變為「全球的科學」。但是聯合國是以主權 為單位的國家所組成，所以每次的議題討論，都得要主權國家同意才行；學術界的人想從 全球觀點著眼，卻只能從旁建議，真正決定政策的是政治界的人，他們卻未必有共識，這 是現存的大矛盾。所以今天科學界的人在說，做研究的人還是得要想辦法影響政策，才有 辦法施力。 問：就像李院長您說的，很多主權國家都是以自己國家的利益為考量，仍然停留在「國際 科學合作」的思維，臺灣也是一樣有這個思維，有自己經濟利益的考量。加上像臺灣雖然 是個經濟已開發國家，因為政治上的關係，一直被排除在很多國際組織之外，無法實際去 參與國際議庭上的討論及合作。即便如此種種，臺灣還是有在推動節能減碳，那麼，您覺 得臺灣目前在這方面的作為，和其他已開發或開發中國家比較起來算合格嗎？有和國際或 全球接上軌嗎？ 52/66

李：這個我想是不合格的。很多二氧化碳排放量的減量控制，政府開出來的減量支票，並 沒有什麼真正具體的政策去落實，也沒有達到所要的目標。 以臺灣為例，僅僅推動個人或家庭的節能減碳，實際減碳效果仍有限，來得及面對 30～50 年內可 能即將面臨的人類危機嗎？在觀念和政策轉型的過渡期，要如何讓政府社會、產業、教育等各方面 有遠見的視野，一起配合推動新價值觀並實際規劃落實呢？

問：臺灣比較弔詭的一點是，一方面配合國際低碳協定，要大家節能減碳、增加油電瓦斯 費嚇阻消耗、鼓勵各種低碳綠能、及再生能源的研究，政府及產業在能源方面繼續強調發 展核電。然而，在鼓勵「減碳」的同時，另一方面又以經濟發展及國家競爭力為考量，縮 減農地以擴大會增加排碳的建築用地及工業用地、鼓勵各種高消耗產品的大量生產，發消 費卷鼓勵消費（增加能源消耗）。在能源方面則繼續擴大發展已經可以說是「全球碳排放 怪獸級」的兩個火力發電廠（排名全球排碳第一、第五） 、繼續開採化石燃料的能源計畫。 這些互相矛盾的政策，似乎都是經濟考量下的作為。 您在過去的一些演講中曾提到：所謂永續發展的生活方式，並不是要人類回歸到原始生活， 而是指在應用科學的同時，不要讓科學破壞了大自然，畢竟人類和大自然是共存亡的。人 類應該要利用現有科技進行「以能源消耗最少的發明」來達到「高品質的生活」 。但是「高 品質的生活」不代表「高消費的生活」，而是可以和大自然結合的人文生活。因此，科技 發展和回歸大自然並非兩相矛盾，科學，應該要作為人類和大自然之間的溝通橋樑。 可是從臺灣的表現看來，政府和人民似乎一直有著「經濟發展與回歸大自然的生活方式， 相互矛盾」 、以及「經濟發展所追求的高品質生活=高消費高消耗的生活方式」的思維。李 院長您覺得應該怎麼做才有辦法宣導轉型呢？如何才能讓政府和產業的政策真正全面能 落實節能減碳，而不是說一套做一套呢？ 李：首先，世界發展至今，人口這麼多、消耗如此龐大，人類社會今後的永續發展，勢必 得朝向「以最少的資源過最好的生活」的方向來走；所以，我們得要改變生產製造和消費 習慣，這對地狹人稠的臺灣來說尤其重要。產業必須轉型，生產製造出來的東西要經久耐 用，不該為了商業利益刻意減短產品壽命，或是不斷推陳出新、大量生產、鼓勵消費，應 該想辦法利用更少的資源來創造更高的價值。對消費者而言也不要追逐流行、喜新厭舊， 要以更少的物質消費來過更好的生活。生活有很多種形式，閱讀、彈奏樂器、社區聚落的 音樂、文化或體育活動、登山健行、在家交流聚會、看藝術展覽、聽音樂會等等，這些活 動消耗的能源都不高，同時也提升了生活品質。開著車到處玩，消耗的能源就比較多。 此外對臺灣來說很重要的一點是：社會組織結構也要跟著改變。比如說：讓走路、腳踏車 車程、大眾捷運系統可達範圍內就能辦妥日常生活的大小事，而不是到哪辦事都要開很遠 的車。這點，像多功能便利商店的普遍設立就很方便，很多都在住家辦公步行或騎車範圍 內就可以到達，這就是社會結構組織改變的成功例子。 降低能源消耗和提高能源使用效率，是人類社會未來該走的方向。臺灣可以為人類社會作 個示範，看如何可以用很少的資源過最好的生活。這個在產業上其實是有很廣的路可以走 的，比如說 20 年前的電冰箱每小時耗電量 1000 瓦，現在約 130 瓦，能源消耗減少 8 倍； 汽車工業現正朝著電動汽車發展；建築業在蓋房子時，則要以日常能源消耗最少又能讓人 們生活過得最舒適的原則來設計。假如生活結構、經濟發展還是持續原來大量生產、大量 53/66

消耗的方式，這樣的未來是走不通的。 問：早年臺灣休閒活動有很多是社區群聚參與的吹簫、拉琴、聽歌仔戲等音樂活動，或是 文化、體育社團等，但是現今生活型態改變了，大家回家多是打手機、看電視、玩電玩、 逛街買東西、吃大餐。大家已經都走到這個地步來了，我們該如何導正大家，叫大家轉彎 回頭呢？請問李院長您的看法如何？或是您是否已經試過，經驗和效果如何？ 李：我的經驗是，臺灣老百姓還沒有感受到「必須改變」的切身需要。比如說年紀較長的 70 多歲企業家，當我談到這個嚴肅的話題時，他們大多看著我說：你為何要這麼認真？反 正我們也不會活著看到這些問題發生。但是我覺得這是不對的，這樣對下一代是不負責任 的作法。有那種說法的應該多是與下一代關係不夠親密、或是沒有小孩不在乎小孩的人。 「債留子孫」是目前最嚴重的問題。所以我都告訴年輕人，不要相信這些 50 年之後就不 在這個地球上的人說的話，自己的未來，要自己去掌握。年輕人要趕快覺醒，不要只是「沿 襲」長輩過去的經驗和想法，或是受到媒體宣傳的左右，要自己主動反省思考，縮短「現 實與理想」的差距，為自己的未來想辦法。 問：但是很多臺灣人對「公共領域」的事似乎很被動，除非侵犯到自身權益了，否則多採 取「事不關己」的態度，或是漠不吭聲等待其他自告奮勇的人先站出來爭取解決。這是民 族性，還是教育的問題？可以改得過來嗎？ 李：這一部份是文化的問題。很多臺灣人的想法是「修身齊家治國平天下」，都是先以自 己的小圈圈為先再往上拓展；先從自己開始，然後齊家，家裡弄好了才考慮治國，然後才 想到平天下的問題。像在美國，我們就發現很多臺灣留學生對公共領域事務的參與很是被 動，不太參與的。美國很多大學自從增加很多亞洲學生之後，他們的學生運動就減少很多， 因為亞洲人比較不參與公共領域的事。 問：「以最少的能源消耗」來達成「真正高品質生活」的轉型應該是很緊急的，因為人類 要面臨的危機很可能是 30～50 年內就會發生的事。但是在這之前，我們除了要扭轉被「長 期教化」出的既有價值觀，還得對已經習慣的高消費高消耗生活方式產生實質的改變作為 才行。這個「去舊思維」的需要已是迫在眉睫了，對嗎？ 李：事實上，10 年之內若不能把現行的發展曲線扭轉過來，就沒有希望了。 問：但是現在很多人熱中電玩、動漫、追星，對公共事務似乎較缺乏關心，怎麼辦？ 李：很有趣的是，從前最不能接受溫室效應造成極端氣候說法的是美國社會。但是去年旱 災之後颱風又過境，慢慢地有些美國老百姓開始覺得極端氣候的來臨可能是真的。所以今 年聽說美國年輕人在思維上有很大的改變，開始認同溫室效應造成極端氣候的說法。 問：對臺灣來說，經歷幾次洪災、風災、土石流等天災後，您覺得這個社會對極端氣候的 影響及嚴重性有比較覺醒了嗎？ 李：沒有。大家應該是沒有深切瞭解到近年這些天災和溫室效應的關係。像 12 年前納莉 颱風過境時，台北不是大淹水嗎？地鐵、中研院、很多地方都嚴重淹水，那時大家都說這

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是百年一次的大雨。可是為什麼過了幾年又來一次？然後再來一次，一個接著一個？表示 頻率很高，這是環境在變遷的一個現象。可能因為這次在台北，下次在南部，所以大家沒 有很切身的感受。 問：臺灣有沒有一個單位，政府的、或是民間組織或學界在整合這些溫室效應、氣候變遷、 永續發展的資訊和規劃呢？ 李：本來行政院有一個永續發展委員會在做這個工作，但後來這個單位的階層被降級到某 個組的架構下面了，沒有真正努力在做這方面的事（編註：經查行政院網頁上仍有國家永 續發展委員會的網頁連結，但機構似已改編制為行政院環保署永續發展室永續發展組）。 這整個國家的能源政策、社會發展政策、永續發展政策、環境變遷這些事，執政者並沒有 真的放在心上。民間方面，近年來確實有不少進步，有越來越多人思考極端氣候和永續發 展這方面的事，但是還沒有凝聚成足以讓執政者覺得若不處理就無法當選的一個壓力。核 四到底該停建或是續建？這個「公共議題」大家能夠提出來討論，我覺得對臺灣是好事， 希望藉此能讓臺灣的人民開始關心公共議題。 總結、以最少的資源過最好的生活 李：臺灣要永續發展，有兩個方向一定得 落實。一是節能、減碳，可再生的永續能 源一定要發展。社會的發展也要同時跟上 腳步，要宣導民眾「以最少的資源過最好 的生活」，從臺灣開始努力，然後可以影 響亞洲和全世界。 此外我們也要往前看，想想以後的能源要 怎麼來？這不僅僅是能源政策，而是整個 國家發展的政策，需要全球大家一起來做。 圖說：世界發展至今，人口這麼多、消耗如此龐大， 政府如果無法行動，大家就只好在公共領 人類社會今後的永續發展，勢必得朝向「以最少的資 域來討論。所以年輕人要覺醒，好好想想 源過最好的生活」的方向來走。©中研院天文所 自己的將來。 （整理撰文/陳筱琪；採訪/陳筱琪、楊淳惠；審稿/前本院院長李遠哲）

註一、ppm 百萬分濃度=溶質毫克數/溶液公升數 註二、永續能源（sustainable energy）：永續能源應該要符合永續穩定、乾淨安全、有效率、 及經濟與社會公平正義發展的需求。該能源不會因持續使用而耗竭、該能源的使用 不會產生對環境造成大幅傷害的污染物、該能源的使用不會對健康與社會公平正義 造成永久性的嚴重危害。 註三、再生能源（renewable energy）：再生能源最主要還是源自太陽輻射的能量，是人類 所使用最古早、也是最現代的能量型態。1986 年 John Twidell 與 Anthony Weir 將再 生能源（renewable energy resources）定義為：從自然環境中獲取的「源源不絕」的 能源。2000 年 Bent Sorensen 則把再生能源擴大定義為：更新與消耗速率相同的能 55/66

量流通（energy flow）。簡單的說，現代對再生能源的看法是：可以長期不斷的供 應，而且不會造成氣候與環境的衝擊的能源。 註四、氫經濟（hydrogen economy）一詞是 John Bockris 在美國通用汽車公司（General Motors） 技術中心於 1970 年演講中提及。 註五、初級能源（primary energy）：取得能源是需要先耗費能源的。也就是說，能源轉換 涉及的過程愈多，能源取得的效率愈低，每個過程中被排放出來的廢熱、廢水、溫 室氣體、懸浮微粒等污染物就愈多。能源轉換過程涉及最少的是初級能源，就是那 些存在於自然界中，不需轉換即可被使用的能源。初級能源又分為可永續循環利用 的再生能源，如：生質燃料、水力、太陽能、風力、地熱等；以及無法再重複利用 的非再生能源，如：煤、石油、天然氣等。 註六、生質能源（biomass energy）：就是利用構成生物體的有機質做為燃料（biofuel） 的 再生能源，依型態可分為固態、液態與氣態三種。目前全球及臺灣主要是發展液態 生質燃料（也就是生質柴油及生質酒精）來做為汽機車燃料。使用生質柴油及生質 酒精做為燃料的優點為燃燒時不產生鉛、二氧化硫、鹵化物，並能大幅降低碳排放， 因此生質能目前已成為世界各國積極發展的替代能源，尤其以巴西和美國為最。但 另一方面，為了製造生質燃料而造成的糧食及用水短缺，使全球糧價不斷上漲。且 為了栽種能源作物而大量砍伐森林，也可能讓原本儲存在樹木及土壤中的許多碳轉 變成大氣中的二氧化碳，使全球暖化更為嚴重。 註七、碳中和（carbon neutral）是指總釋放碳量為零；亦即排放多少碳就作多少抵銷措施 來達到平衡。

天聞季報海報版與網路版由中央研究院天文及天文物理研究所製作， 以創用 CC 姓名標示-非商業性-禁止改作 3.0 台灣 授權條款釋出。 天聞季報網路版衍生自天聞季報海報版。超出此條款範圍外的授權，請與我們聯繫。 創用 CC 授權可於以下網站查閱諮詢 https://isp.moe.edu.tw/ccedu/service.php。

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【從地球和人類發展看臺灣的永續能源選擇─李遠哲前院長專訪】 英文海報節錄版 （本翻譯版未經審訂，僅供參考） The Sustainable Energy for Taiwan, from the Earth and Human Development Point of View- An interview with Professor Yuan-Tseh Lee (English translation for the poster Version) （This English translation is made only for reference; it is NOT officially reviewed.） [The impact of 2°C warming] For 4.6 billion years ever since the Earth was formed, the sun never stops shinning on it, all materials cycle and lives grow. Until the Industrial Revolution, humans started to exploit fossil fuels and stepped into the era of large-scale industrial and commercial production. Natural environment was widely damaged because of our arrogance. Only about 250 years since then, we found ourselves heading towards a no-through road: people start to worry fossil fuels will soon run out one day, but in fact © APANAC before that day, we shall face awkward life-threatening predicaments: exploding human population and consumptions, earth-shattering pollutions, and environmental variations. Nuclear War has been a fear for everyone since half century ago, and we are now facing two more upcoming crises, global-warming and biodiversity-disappearing. For the coming half century ahead, it is likely that the extreme climate brought by global warming will break through a “critical point” and enter an age of so-called "out-of-control fault". At this time, CO2 and CH4 will be coughed up off all oceans. Once CH4 is released from the Siberian tundra, global temperature will shoot up abruptly, no man Global effort is making to control the increase of global annual and only few living creatures can survive. average temperature to below the 2°C critical point, that is, to This is the scene that we humans may meet control the concentration of greenhouse gas to lower than 450 right within this century. So, what is it ppm. But even so, there is only 50% chance to achieve this goal. © www.port.ac.uk marked on the boundary stone of this critical point? -- 2°C! IPCC (Intergovernmental Panel on Climate Change) had an evaluation in 2007 reporting that the average global temperature is 0.7°C warmer than it was before the Industrial Revolution. Lives on the Earth will be heavily frustrated once the warming is beyond the threshold of 2°C, therefore striving to avoid this happening has become the world’s goal (NB#1), which nevertheless has become a fantasy. And if we don’t try harder, we are expecting a 4~5°C warming by the end of this century.

Many people don’t fully understand the meaning of 2°C. They think “JUST 2°C!” -- the 57/66

variation of temperature from dawn to nightfall is more than this scale, not mentioning the variation across four seasons. Those who live in the up North even look forward to this 2°C warming to bring them more comfortable climate.

Unfortunately these are not true. 2°C is the temperature warming scale of global annual average. The Earth is a living system, very similar to human body in some way. 36.5°C is the average human body Comparing with BC, global population has been growing rapidly after the Industrial temperature; a 2°C Revolution. Our earth can still provide human beings a comfortable living warming in body is called environment in 1950s, but after merely half a century, the population explosion has brought consequences such as resource depletion, starvation and worldwide “having fever”; 4°C environmental damage. © The U.S. Census Bureau warming without any cooling handling and your life will be in danger. If the average “body temperature” of the Earth increases 2°C, seawater of all oceans will evaporate enormously into air, up into clouds, where huge energy tanks form. Once the energy is released, it transforms into what we see as typhoon, or many other forms of climate changes, and finally the extreme weather. For example, long drought following by violent rainfall then deluge.

“Can the Earth bear all what human activities bring to it?” this is very important for us to keep in mind when bringing the issue of “sustainable development” into discussion, emphasized Professor Lee. [Sustainable development and sustainable energy] Brundtland stated in report of “Our Common Future” in the 1987 WCED (World Commission on Environment and Development) about the concept of sustainable development: "…the development is that meets the needs of the present without compromising the ability of future generations to meet their own needs."

Regarding this, Professor Lee raised two questions: meet WHOSE needs? WHAT is development?

Are the needs the needs of the West?

Without a car, people in Los Angeles cannot reach most places to buy and do many things, so car is one of the basic needs in their life. Food is in shortage in many area of Africa, so food is the local needs in Africa. The needs of people around the world differ so much; “whose needs are we to meet?” is a big key matter, whereas no global consensus has ever

The sun provides our earth enormous energy, of which one-hour supply can meet human needs for one year. Photosynthesis of plants, animals, forest, soil, microorganisms are all resources nurtured by the sun. © Peter Hannam/ brisbanetimes.com.au

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reached so far.

Is the development the development of the West way? The model of the West development is to “produce more so people can consume more”. But is this endless consumption feasible? The increasing human population and consumption have exceeded what the sun can bear to recycle and have started to damage the Earth ecosystems. To our mother earth, today’s human development has reached to a level of “overexploitation”.

Professor Lee hopes everyone to think deeply while discussing sustainable development: Indeed what purposes do we humans apply science and technology to develop economics? When we reach our purposes, we should try all the best not to destroy the ecosystems so that we can keep ourselves surviving on this earth. People now say that we should try to build “low-carbon” society, in other words, to not use fossil fuels which generate lots of CO2. The renewable energy and new energy that we keep talking about also means “back to the sun”. Our sun provides this mother earth enormous energy, of which one-hour supply can meet human needs for one-year.

Solar, wind, geothermal, and ocean current powers all come from the sun. Some ocean energy like tidal power to do with earth or moon gravity is also a heritage from the sun. Photosynthesis of plants, animals, forest, soil, microorganisms are all resources nurtured by the sun. If we can make good use of these, our needs for living and life will be fulfilled very well, given that human population is under control of course. All in all, if we want a sustainable development, the use of resources and energy should ensure our coexisting with the nature.

[Where would the energy come from for Taiwan half decade after?]

In general, Taiwan is an “energy-importing” nation, 98% of our energy is imported. In addition, Taiwan is densely populated, its population density is 20 times to the United States, and about 200 times to Canada or Australia, therefore the sunlight per capita we can enjoy is very limited.

All the same, we still have to try making the best of solar energy, although this energy cannot solely support our national development given Taiwan’s geography condition. In fact, if we keep today’s high-consumption lifestyles, it would be lucky enough to satisfy 10%~20% of our energy demands even if we add in wind power, hydroelectricpower and geothermal, biofuels and other renewable energy. Even though we can meet this 20%, another 80% is still depending on imports.

With the rapid decrease in global energy resources, the cost of energy import will become more and more expensive, provided which, how are we going to acquire these 80%?

Currently almost all Taiwan’s energy sources come from the imported fossil fuels. Fossil fuels are an un-reusable but high-efficient energy source, so the global markets of petroleum and coal are large. Each country buys their coals according to their needs, so does Taiwan. If one day humans do not use fossil fuels anymore, Taiwan will actually not be much affected. How come?

It is because most of our energy still relies on importing; the only differences are which type of energy and where from. About this, our government needs to plan carefully ahead. Our scientists also need to study harder to develop new energy that suit Taiwan. Do not count solely on foreign countries. The fate of our own nation and society should be taken full control by ourselves.

[Example Taiwan’s developing sustainable energy] Professor Lee exemplified several of Taiwan’s developing sustainable energy and provided some comments with greater scope: 1.

Solar photovoltaics: Currently solar panels are costly, but with the progress of science

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and technology, green building and energy-saving lifestyle would be presented in various ways. Energy-saving materials will also continue developing. Once the technology is matured and goes mass production, the cost would be reduced. During the transitional period, if our government can provide positive support and incentives, the research and development of solar panels can continue, and people will be able to afford this energy.

Therefore we should not underestimate the future economic values of solar energy because of its current high cost. From pure technical point of view, it is possible for Taiwan to lower the cost of solar energy in the coming several 10 years, as long as the government is acting at positive standpoint to support such development. In addition, an alternative way of acquiring solar energy is to develop the storage and transport of this energy through international cooperation. Professor Lee will meet with some key scientists from Asian-Pacific region this year to discuss future solutions for this area, including the energy issue. Australia is expected to show their potential power of making solar energy from their vast land full of abundant sunshine. They should be able to convert the excess into high-voltage direct current and export to many Asian countries where solar energy is needed.

2.

Hydrogen economy: Hydrogen molecules do not exist on the Earth in the form of natural gas. Most of the hydrogen stays in water after combining with oxygen; therefore we are not using it as primary energy. Instead, we released it from water by applying other types of primary energy such as wind power, solar energy, or decomposed it by microbes. The released free hydrogen can then be used as fuel to produce electricity through chemical reactions. The hydrogen energy we store is not the electricity it produces but the hydrogen itself after chemical decomposition. In other word, if Taiwan needs to import hydrogen energy, we are not actually importing the electricity but the hydrogen. However, it is difficult to transport gas like hydrogen, and so liquid hydrogen is a better form for transportation. To do so, liquid hydrogen has to be kept in very low temperature for delivery, which involves many technical details and the costs are correspondingly high.

Therefore, if Taiwan is to import this energy, we need to plan ahead the best solutions for these issues.

3.

Biomass fuels: It is reasonable for the US and Brazil to develop biomass fuels because they both own big lands and less dense populations. But for Asia countries where population density is very high, it is not such a good idea to depend heavily on this energy type. For example, Taiwan is densely populated on relative small land and received limited sunshine per capita. Under this circumstance, developing biomass fuels in Taiwan will bring significant impact on local agriculture production and food self-supply. Therefore when trying to develop this type of energy here, it is better that we focus on the exploit of agricultural discards as the biomass resources.

4.

Nuclear power: Current nuclear power development in Taiwan is not ideal. In order to avoid the expansion of nuclear weapons, the design of todayâ&#x20AC;&#x2122;s nuclear reactor allows only less than 5% potential power of the real nuclear fuel substance, uranium-235 to be exploited, leaving the remaining 95% the nuclear waste after reaction. The reactor keeps producing so many nuclear wastes that we have so far no way to handle. In the end, all the problems are extended to our next generations to deal with.

Nuclear power plant is not ideal not only because of the way the reactor is designed and operated, but its safety is unsatisfactory either. There are now many innovative ideas and quite a few research teams seeking for solutions to nuclear wastes and nuclear safety problems. Professor Frank Shuâ&#x20AC;&#x2122;s MSBR (molten-salt breeder reactor) is one among them.

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MSBR was tried many years ago by the Oak Ridge National Laboratory in the US, but the development did not continue due to a number of insurmountable technical problems.

After reassessment, Frank’s Academy team thinks they can design it better. There are several features for their new MSBR that they are planning: in the system molten salt coolants are applied and nuclear fuels are dissolved into special molten salt --no water in the system so no hydrogen will be generated to cause any explosion, no need to locate the reactor near ocean or river sides so no risk of affecting marine ecosystem and no risk of tsunami attack after earthquakes; stable isotope Th-232 is used to convert to nuclear fuel U-233 that can be consumed quite completely in the chain fission reaction so to increase the effectiveness of reaction and reduce nuclear wastes; radioactive fission products from MSBR have short half-lives of 30 years and can be packed into dry casks and stored underground for another 300 years to become rare mineral substances with great economic values in future; high-level nuclear wastes from traditional LWRs such as Pu-239 can be recycled into useful nuclear fuels in the MSCR (molten-salt converter reactor) and consumed so that the nuclear waste problems of LWRs may be resolved (please refer the details to Frank’s column in 2013Q2). If all these ideas can be achieved, it may provide solutions to some of the problems of current LWRs. Professor Lee agrees with this, but he does not regard that Taiwan's current industrial technology can achieve this research alone. He strongly recommends that we must seek for cooperation with countries in Europe and America where with advanced science and technology in nuclear power development if we don’t want to miss opportunities for this project to achieve great goals.

Professor Lee believes that in a stable land it is possible to deliver good security to nuclear power plants by well-designed monitoring systems. However, he stressed, for Taiwan, earthquakes are an important variable that can make situations much more complicated and turn down everything. Taiwan’s LWRs has long been denounced having many problems associating with operations and management, not to mention this island being situated on seismic zones. “Do I believe in Taiwan’s nuclear safety? If you are asking me, I would say Not Really!” said Professor Lee. For Taiwan he does not think nuclear energy is a sustainable energy, and it is not an appropriate energy option either.

But it is worthwhile to encourage researches to find better solution to current nuclear power problems, such as optimizing the effectiveness of nuclear power reactors, or reducing nuclear wastes and pollutions, on the other hand, nuclear power can still offer great contributions to the world if global nations can sit down to discuss the collaborations of developing new generation nuclear reactors. If everyone agrees to build nuclear power plants only in stable lands rather than inappropriate area such as where by the sea or on earthquake belts, then countries with suitable conditions to build nuclear power stations can export their nuclear energy to where unsuitable to develop nuclear energy.

5.

Carbon neutral, carbon recycling─carbon capture and storage (carbon capture and sequestration; abbreviated CCS): In addition to developing low-carbon energy, an alternative option for "low carbon” is to recycle or neutralize carbons exhausting from human activities. “Torrefaction” is one of the options besides planting trees or using renewable energy with low carbon emission. Our sun provides energy for the greens to grow, and we burn plants into charcoal through torrefaction. Torrefaction as a whole is “endothermic reaction”, during which a part of the absorbed energy is released into air during the combustion and another part is used for carbon neutral. The released heat can be recycled using heat exchangers but the heat is actually relatively little. The key benefit of torrefaction is that through it the energy and carbon can be captured and retained. Lee

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mentioned an example of torrefaction from his childhood experience. At the time people escaped the war into mountain area, Taiwan acacia (acacia confuse) were chopped off to make blackened charcoals, which then were burned to use for cooking and boiling hot waters. People burn charcoals rather than firewood, so very little smoke.

Carbon farms in Australia and South America and the “supertorrefaction” by Frank’s Academy team are all trying to grow fast-grown plants and then torrefying them into charcoals. The main purpose of doing this is for carbon sequestration rather than making biomass or renewable energy, which benefits the environment not just locally but globally.

Therefore, don’t burn out the forests; keep them as the bases of photosynthesis and carbon sequestration. The recovered carbon can be further grounded into powder and sprinkle back to earth to optimize soil qualities.

If Taiwan cannot avoid using fossil fuels within this half century, we should at least try to reduce carbon dioxide produced by coal power. The current approach is CCS, burying the gas into underground. Professor Lee said, “We should strive towards developing researches for this, but our government works rather slow for supporting it. For example, stratum studies are essential for carbon sequestration, it is one million US dollars for each hole punched into ground. This is by no means a thing affordable by any academic scholar or any university professor, but needs large-scale planning by the government and international collaborations together to make it happen.” Last year in the “2012 Taiwan Symposium on Carbon Dioxide Capture, Storage and Utilization”, Dr Li-Fu Lin invited scientists from Australia, Japan, Malaysia, and China to brainstorm how to resolve Asian energy issues for future. “Asia countries should learn from the European Union, which are very organized." Professor Lee stressed, if we cannot cross the boundaries of sovereign national interests and turn these to 'global' collaborations with mutual support, then nothing can be solved.

[Global collaborations to solve the problems of sustainable development] Britain before World War II used to describe their own Empire as “the sun never sets”, because the Empire has colonies all over the world for the sun to always shine on. By contrast, each single country has its own weather and time-zone condition, the supply of sunlight or wind power can be unstable. Whereas, if all nations work together as one “community”, the problems of use natural renewable energy can easily be solved. Same to this for Taiwan, to develop future sustainable energy, we should find ways to cooperate with other countries to establish “energy networks”. Today there are still international barriers and conflicts of individual interest between countries. Therefore, by means of connecting among more and more global organizations and communities, we hope to lower international boundaries and move towards globalization. This is the road we ought to finish by the end of this century.

With the increasing human activities and communications, problems we are facing today are often “global” issues. Ozone depletion, greenhouse effect, spread of the epidemic, poverty and hunger, forest conservation, biodiversity loss and other issues are all ongoing across borders.

There is contradiction between “International collaboration" and "international competition". If everyone continues focusing on their concerns of self-interest and cannot work together as a global community to deal with problems, we can resolve no issues. Perhaps no need to await another 50 years, we will soon find out that our earth has been degraded to the extent that no man can ever survive in. By then we shall know we are our own enemy. We are heading to a dead-end for this but still don’t see it.

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Professor Lee has been trying to promote the idea of “breaking boundaries, walking to the global world”. Scientific communities should not do their own, but remove international barriers with sovereign national interests, and work for the "whole earth" for the future of humanity and development. He emphasized that scientists should work together with scholars in the area of humanities and social science who concern with global environment. Scientific communities should not do their own, but work for the "whole By means of the interdisciplinary earth" for the future of humanity and development. This is the road we cooperation, we are to assess the ought to touch down by the end of this century. © Henry Mühlpfordt impacts and influences on human society that science brings, and to identify ways to address and resolve the problems. Science development should move from “international” scale towards “global” scale, so that human society can continue developing sustainably. Unfortunately, for this there is still no consensus in many countries. In the 2012 Rio+20, the United Nations Conference on Sustainable Development, a lot of scholars and civil societies are in favor of drawing up a greenhouse gas international standard protocol to reduce carbons. The academia that has global visions can only make suggestions behind the sidelines. Whereas, politicians that not necessarily have the consensus of global perspectives are the actual one in control of the game-- policy decisions.

This is the existing major contradiction now a day. So, to get things working, researchers have to find ways to influence the policy decisions.

Conflicts among the national, international and global interests, “we the elderly were not able to resolve, younger generations need to find your ways”, said Professor Lee in earnest. “We at our time did not manage to connect globally, but younger generation is not the same”. This is the first time in human history that the world is connected together through an internet. What we cannot make in the past, now it is all possible. That is, the current generation already owns the potential to break international boundaries and make a global link. Professor Lee has stressed repeatedly that the future has no hope without breaking the boundaries to the world. Sovereign states cannot work together to achieve anything, but the global links can.

[Carbon reduction+enewable energy≠sustainable development] The GDP that the nature outputs to humans is much higher than the GDP from our own input.

For example, one-third of the food we eat reply on the pollination by bees and butterflies. It is no doubt that we can bring greenhouse gases under control if all energy we need comes from the sun. We may find a way out for carbon reduction and sustainable energy issues by means of scientific research and development and global policy cooperation. Nevertheless if we keep consuming resources endlessly, the day when all the forests and the green lands are replaced by concrete, and when ecosystems are destroyed and biodiversity is disappeared, is the day we human beings vanish from the Earth. Humans cannot live alone; therefore, some old ways of thinking must change!

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The GDP that the nature outputs to humans is much higher than the GDP from our own input. If we keep consuming resources endlessly, the day when all the forests and the green lands are replaced by concrete, and when ecosystems are destroyed and biodiversity is disappeared, is the day we human beings vanish from the earth. Left image © Nature Blog Network; Right image © WallpaperWeb

First of all, so far as the world's development went, the exploding of human population and consumptions has forced humans to face our future. We inevitably have to try “live better, for less” for the sake of the sustainable development of our human society. This is not to ask everyone back to live in primitive ways, but to urge people not to allow science perish nature while we are applying it. Living with the nature is not mutually contradictory with the development of science, technology, and economics. On the very contrary, science should work as a bridge to communicate between human development and nature. Reducing energy consumption and improving energy efficiency are the direction that human society should follow in the future. “How to live the best life with the minimal resource?” Industry can open their gates for various advanced development with this logic. For instance, 20 years ago, refrigerator consumed 1000 watts per hour, and now about 130 watts of electronic power. The automobile industry has been moving towards a new era to develop electric vehicles. The construction industry designs and builds their houses following the principle of “allowing people the most comfortable living with the least daily energy consumption”.

Secondly, it is wrong to believe “high quality of life = high consumption, or high consumption of life”. High quality of life can be a perfect combination of nature and humanity life. Reading, playing musical instruments, cultural, music and sports activities within community settlements, hiking, home gatherings, seeing art exhibitions, etc. These are all the activities with limited energy consumption, but can lift the quality of our life.

Furthermore, social structure, manufacture and production, as well as consumption habits must also change, which is especially important for the densely populated Taiwan. Industry must be restructured. The manufacturing and merchant products should be durable and the warranty and lifespan should not be shortened for commercial interests. The industry should not promote public consumption by means of pushing little improved innovation every now and then and all the time. WE SHOULD THINK OF WAYS TO CREATE HIGHER VALUES BY USING FEWER RESOURCES. Consumers should not consider popular grass always greener and always chase after fashion. We actually can live better life with less material consumptions.

Social structure needs change too, by allowing people to have everything of their daily life reached within easy distances by walking, riding, or MRT. For this, in Taiwan, the establishment of widespread networks of multi-functional convenience stores has set a very successful example. We should be aware that it is a no through road if we continue our way of mass production and mass consumption for daily life and for economic development.

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[Enough time for a change?]

The crisis of extreme climate that humans are to face may be happening in 30~50 years of time.

Before that day, we need not only be able to reverse our existing values coming from “long-term indoctrination", but need also a real and solid change of behavior in daily life. Professor Lee said “we may face no hope for future if the changes cannot be achieved in 10 years.” In Taiwan, there are policy plans for the development of energy, society and sustainability. However, these plans are more as paper works. Professor Lee thinks the Taiwanese rulers didn’t make enough effort to try to make the plans implemented. There used to be a Sustainable Development Committee directly hosted by the Executive Yuan to be responsible for these tasks, but this unit has now been downgraded to a chamber group in an Office section under a subordinate Bureau of the Executive Yuan. In addition, Taiwanese people do not seem to sense the vital need of "need to change". They didn’t realize the fact of relationship between the greenhouse effect and the natural disasters happening in these recent years. This is partly because that Taiwanese people are always passive to the engagement in the affairs of public domain. Many people have the traditional Confucius idea as “self Qijia rule the world”, based on which they give all priority to the interests of their own and their small circle, then consider their family welfare, then the nation, and finally the issues for the peace of the world. To tell the truth, there are indeed quite some civil progresses, more and more people consider extreme climate and sustainable development important matters, but it hasn’t coagulated into a pressure that significant enough to push the government to handle the issues. Whether the new nuclear power plant-IV should continue or cease? This public issue is now put forward for debate. Professor Lee sees this good thing to Taiwan, by which he hopes Taiwanese people begin to care more about public issues.

“Leaving debts to offspring” is currently the most serious problems happening in Taiwan.

Professor Lee said, “I always tell young people to grasp their own future, not to believe people, who are no longer living on this planet 50 years later.” Do not just think following the idea or past experience of the elders, or being manipulated by media propaganda. Young people should take the initiative to reflective thinking, shorten the gap between "the reality and the ideal", and find the best way for their own future well.

[Final words: live better..for less] To sum up, there are two subjects to get implemented for Taiwan’s sustainable development. The first is reducing energy consumption, reducing carbons, and developing renewable sustainable energy.

At the same time, social development also needs to keep up with the pace. We need to act public advocacy “living a better life with minimal resources”, starting from Taiwan and influencing the Asian and then the world. Second, we have to look ahead and think about the future of “where and how the energy comes from?” This involves the policy not only of energy but also of the As the world's development went, the exploding of human and consumptions has forced us to face our future. national development as a whole, and even population We inevitably have to try “live better, for less” for the sake of involves the global world that everyone the sustainable development of our human society. © ASIAA needs to work together to achieve. At the end of the interview, Professor Lee final addressed his wish to young people, “I could not help you with my little influence to urge the government or world to take action, but I hope all young

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people to be awaken and think about what you really want for your future and act to grasp it”.

(Data & Writing /Joyce Chen, Interview/Joyce Chen and Chun-Hui Yang) NB#1. Currently the world tries to control green gas level to the level under 450 ppm, but even so, we only have 50% chance not to let the warming exceeding 2°C.

天聞季報海報版與網路版由中央研究院天文及天文物理研究所製作， 以創用 CC 姓名標示-非商業性-禁止改作 3.0 台灣 授權條款釋出。 天聞季報網路版衍生自天聞季報海報版。超出此條款範圍外的授權，請與我們聯繫。 創用 CC 授權可於以下網站查閱諮詢 https://isp.moe.edu.tw/ccedu/service.php。

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發行人＼賀曾樸 執行主編＼陳筱琪 美術編輯＼蔡殷智 執行編輯＼金升光、曾耀寰、楊淳惠、蔣龍毅 網路版製作＼陳筱琪 發行單位＼中央研究院天文及天文物理研究所 地址＼臺北市羅斯福路四段一號天文數學館 11 樓 電話＼(02)2366-5391 電子信箱＼epo@asiaa.sinica.edu.tw 天聞季報版權所有＼中研院天文所 底圖版權聲明：重力透鏡 SDSS J1004+4112 經影像處理而成，原圖版權 © European Space Agency, NASA, Keren Sharon (Tel-Aviv University) and Eran Ofek (CalTech) 天聞季報編輯群感謝各位閱讀本期內容。本季報由中央研究院天文所發行，旨在報導本所相關 研究成果、天文動態及發表於國際的天文新知等，提供中學以上師生及一般民眾作為天文教學 參考資源。歡迎各界來信給我們，提供您的迴響、讀後心得、天文問題或是建議指教。 來信請寄至『10617 臺北郵政 23-141 號信箱 中央研究院天文所天聞季報編輯小組收』 ；或是寄 至電子信箱：epo@asiaa.sinica.edu.tw。

天聞季報海報版與網路版由中央研究院天文及天文物理研究所製作， 以創用 CC 姓名標示-非商業性-禁止改作 3.0 台灣 授權條款釋出。 天聞季報網路版衍生自天聞季報海報版。超出此條款範圍外的授權，請與我們聯繫。 創用 CC 授權可於以下網站查閱諮詢 https://isp.moe.edu.tw/ccedu/service.php。

發行人＼賀曾樸 執行主編＼陳筱琪 美術編輯＼蔡殷智 執行編輯＼金升光、曾耀寰、楊淳惠、蔣龍毅 網路版製作＼陳筱琪 發行單位＼中央研究院天文及天文物理研究所 地址＼臺北市羅斯福路四段一號天文數學館 11 樓 電話＼(02)2366-5391 電子信箱＼epo@asiaa.sinica.edu.tw 天聞季報版權所有＼中研院天文所 底圖版權聲明：重力透鏡 SDSS J1004+4112 經影像處理而成，原圖版權 © European Space Agency, NASA, Keren Sharon (Tel-Aviv University) and Eran Ofek (CalTech) 天聞季報編輯群感謝各位閱讀本期內容。本季報由中央研究院天文所發行，旨在報導本所相關 研究成果、天文動態及發表於國際的天文新知等，提供中學以上師生及一般民眾作為天文教學 參考資源。歡迎各界來信給我們，提供您的迴響、讀後心得、天文問題或是建議指教。 來信請寄至『10617 臺北郵政 23-141 號信箱 中央研究院天文所天聞季報編輯小組收』 ；或是寄 至電子信箱：epo@asiaa.sinica.edu.tw。

天聞季報海報版與網路版由中央研究院天文及天文物理研究所製作， 以創用 CC 姓名標示-非商業性-禁止改作 3.0 台灣 授權條款釋出。 天聞季報網路版衍生自天聞季報海報版。超出此條款範圍外的授權，請與我們聯繫。 創用 CC 授權可於以下網站查閱諮詢 https://isp.moe.edu.tw/ccedu/service.php。