Chargroforestry - The Carbon-sequestering & Regenerative Agricultural Landscape

Chargroforestry

The Carbon-sequestering & Regenerative Argricultural Landscape

Master of Architecture Thesis Preparation Document

Singapore University of Technology and Design

Student: Joseph Ooi

Master of Architecture, Architecture & Sustainable Design

Thesis Advisors:

Associate Professor Carlos Banon, Architecture & Sustainable Design

Assistant Professor Peter Ortner, Architecture & Sustainable Design

Acknowledgement

I would like to express my gratitude to every individual that has contributed to the discussion and ideation of this thesis.

With a great and sincere thanks to both my thesis mentors, Prof. Carlos Banon and Prof. Peter Ortner whose advise and guidances, knowledge and encourangements has been invaluable throughout this journey.

A warm thank you to my friendly and supportive classmates who made the journey more light-hearted and enjoyable.

Last but not least, I would like to thank you, for taking your time and effort to flip through this booklet.

- Joseph.

Chargroforestry

The Carbon-sequestering & Regenerative Argricultural Landscape

Abstract

The current waste management system appears as a linear process. The refuse flows from the city of high densities to sprawling landscape of waste. As a city grows and densifies, waste infrastructure and processing have to be re-evaluated so to adapt to its latest capacity and objective. Instead of the isolated and linear processes, the urban, environment and waste ecologies can be interweaved into a sustainable and efficient circular system.

This thesis first reviews the current solid waste management strategy and juxtaposition between landfill and incineration. By understanding the nation’s energy market and direction, the thesis argues the necessity of the centralised energy supply and waste-to-energy plant. With the escalating food consumption and waste generated yearly in parallel to the growth of population, the thesis analyses the carbon emission of the population and develops an approach to maximise the carbon sequestration and offsetting carbon footprint progressively. A multi-method research strategy includes reviewing relevant architectural precedents, analysing material waste flows , design strategy and scenario to deepen the knowledge of current waste management landscape and improvise a hybrid intervention to maximise the landuse by integrating various green plots with industrial, commercial and community usage for a better harmony, circular environmental ecology and lifestyle.

All in all, this study aspires to developing a roadmap for regenerative urban agro-forestry with integrated biomass wastes processing and implementing the new norm of “waste-to-daily life” into the urban and sub-urban context.

Landfill & Incineration

Along with the growth of population, the waste disposed in Singapore has accumulated by seven-fold over the past 40 years. According to the statistic from NEA, there are about 7.7 million tonnes of waste generated from both domestic and non-domestic sectors in 2017. (NEA, 2022) The statistic showed that there are improvements in reduction of the overall waste generated from 7.7 million tonnes in 2017 dropped to 6.94 tonnes in 2021. (Anon., n.d.) However, based on the current rate of waste generated and even with the recycling rate of more than 50%, Singapore’s current landfill site - Semakau Landfill was projected to be exhausted by 2035. It was estimated that a new waste-to-energy incineration plant will be needed at every 7 to 10 years and a new offshore landfill will be needed at every 30 to 35 years. (Anon., 2022)

Landfill is the oldest waste management system while having a large environmental impact. It is the affordable solution as it requires less initial cost and does not involve any complex equipment and procedures. It is the most convenient way as no high fundings for advance technology is required. However, the process takes longer period to degrade the solid waste within the soil and takes up more land space to fill the solid waste throughout the process. During the degrading process, methane gasses and leachates are being produced. The by-products can be harness for fuel. Nevertheless, the emissions will create land and marine contamination if they are not being handled properly.

On the other hand, the incineration of solid waste, converts solid waste into energy by combustion. The process reduces the solid waste mass as much as 95% in just a few hours’ time. While the process is more efficient to reduce the solid waste mass in a shorter period, incineration emits flue gases containing heavy metals, nitrogen oxides and carbon dioxide, which is detrimental to public health and the environment, contributing to climate change.

Neither do landfill nor incineration is an environmental solution, but with both still being the necessary evils, which is the lesser? Incineration might be a slightly better solution as compared to landfills. However, if assessing based on IPCC’s (Intergovernmental panel on climate change) protocol to tackle for climate change, it is very clear that there is not much to choose between the landfill with landfill gas (methane) utilisation and the nett greenhouse gas emissions of an incinerator with energy (heat energy) recovery.

Hence, by increasing responsible recycling commitments and considering for accessible yet cost effective alternatives to plastic that reduces the non-recyclables use, we can gradually reduce the amount of wastes to be sent to bury or to burn.

1:

Figure

Direction of Energy market in Singapore.

Is centralized waste-to-energy plant still necessary?

Referring to the report from National Climate Change Secretariat (NCCS), Singapore is a resource constraint country and has limited renewable resources option due to its geographical context. The average wind speed in Singapore of about 2m/s makes it hard to adopt the commercial wind turbines which requires at least 4.5m/s to operate. With its narrow tidal range and calm seas, the nation is limited from commercial tidal power generation. Much of the sea space is also used for ports, anchorage, and shipping lanes, which limit the application of ocean energy technologies. In addition, hydroelectric power is almost impossible to be harnessed as the topography of its river system does not encourage fast flowing water throughout the year. The country do not have any geothermal energy sources too. With its small physical size of approximately 728 km², high population density and land scarcity limits the potential for sustainably grown domestic biomass. It also constrains the safe deployment of nuclear power in Singapore. (Anon., 2022)

Over the past decades, Singapore has shifted from oil to natural gas for a cleaner power generation. Nearly 95% of its electricity are generated from natural gas, and the remaining are contributed by renewables, coal, and petroleum products. (Anon., 2022)

Further to the first switch, the country is focusing on the renewable, solar energy along with the energy storage systems for intermittency of renewable energy sources. The country is targeting to achieve at least 2 gigawatt-peak (GWp) by 2030, and an energy storage deployment target of at least 200MW beyond 2025. (Anon., 2022) Through bilateral cooperation and regional initiatives, Singapore is also exploring to connect to the regional power grid to access energy for optimising energy and cost efficiency.

While exploring to decentralise the power grids, Singapore is also diversifying its energy supply by identifying low-carbon alternatives to help reducing the country’s carbon footprint in energy supply, such as carbon capture, utilisation and storage technologies, hydrogen etc.

Hence, the solid waste management solution of waste-to-energy plant need to be reviewed. While solving the issue of reducing solid waste volume, the solution creates the environmental problems of the drop in air qualityv and carbon emission which eventually leads the environment to a non-optimistic future.

Figure 2: Ratio of carbon footprint by an average adult and carbon abosrtion of tree.

Carbon Emissions

As a nation and population grow, the carbon footprint projects in parallel to the growth. In Singapore context, an average adult emits approximately 8 tonnes of Carbon Dioxide per annum. (Anon., n.d.) The emission happens from various activities in our daily life, includes utilities, waste, food, spendings and commute. In natural carbon cycle, the carbon dioxide is absorbed by plants through photosynthesis and gives out oxygen in return, at the rate of averagely 22kg over a year by each matured tree. (Anon., 2012) To project the relationship into a ratio scale, the carbon dioxide emitted by each adult in a year requires about 400 trees to absorb. (See Figure 1)

Based on Singapore’s population of 5.45 million in 2021 (Anon., 2022), the amount of trees required to offset the carbon footprint is reaching about 22 hundred million trees. With the estimated 8 million trees in the nation to come (Anon., 2020), it is still a long way to achieve carbon neutral and further to carbon negative. (See Figure 2)

5.45mil. : 2,200 mil.

Figure 3: Ratio of carbon footprint by an average adult and carbon abosrtion of tree in Singapore’s context.

By encouraging the use of lower or zero carbon sources to minimize the emission of greenhouse gases, the government has implemented the Carbon Pricing Act (CPA) with its accompanying regulations, and imposed carbon tax to all taxable facilities from 1 Jan 2019 onwards for reckonable GHG emissions. Under the Carbon Pricing Act, the responsibility rests with any industrial facility that emits direct greenhouse gas (GHG) emissions equal to or above 2,000 tCO2e annually to register as a reportable facility and to submit an Emissions Report annually. The current on-going tax of S$5 per tonne of GHG emissions (tCO2e) will increase to $25/tCO2e in 2024 and 2025, and $45/tCO2e in 2026 and 2027, with a view to reaching $50-80/tCO2e by 2030. (Anon., 2022)

Besides the increase of carbon taxation that serves as a momentum for greater commitment to the enhanced waste management, the industry should investigate ways to achieve carbon neutral or negative to minimize the impact to the mother nature and the crisis of global warming. Understand and adopt a better process and technology is important to minimize the emission during the lifecycle of a material.

In waste management, new processing technology such as pyrolysis, gasification can help to minimize and slows down the carbon emission by sequestering them within its product and by-product. While implementing a better technology in processing and sequestering carbon to offset the emissions, reconsidering the daily activities and strategies in urban planning to reduce the direct carbon emissions is equally crucial.

Figure 4: Pyrolysis and its product.

Process : Pyrolysis & its Product

While reviewing the process of incineration of general solid waste that will emits large amount of greenhouse gases including carbon dioxide, there are some low-carbon technology that can be adopted for specific type of solid waste that can help to reduce the overall load of the general solid waste accumulation. One of the convincing process is pyrolysis. Pyrolysis is a thermochemical treatment process to organic (carbon-based) product in high temperature and in the absence of oxygen. (Biogreen, n.d.)

Instead of the conventional combustion process, pyrolysis is the thermal degradation process in the absence of oxygen. In such way, there is no chemical reaction to bond the carbon molecules through the process and hence remain the carbon as its original solid form from being released into the gas.

The products of biomass pyrolysis will be generated in 3 forms: the solid – biochar, liquid –bio-oil and gas – synthesis gas. Biochar can be produced at scales ranging from large industrial facilities down to the individual farm (Lehmann, 2009), and even at the domestic level (Whitman, 2009) , making it applicable to a variety of socioeconomic situations.

The bio-oil and synthesis gas generated from the process can be recirculated back to the system to be used as the fuel for heating and electricity generation to sustain the process, contributing to the overall material circular economy. Lab tests are still being carried out to finalize the possibility of refining excessive synthesis gas or bio gas with further process such as methane pyrolysis which can convert the gaseous into component hydrogen and solid carbon which can be used for aluminium, steel and construction industries or graphite substitute for battery materials. (BASF, 2022)

As such, there will be no greenhouse gas emissions from the process and also linking the circularity of the waste to material flow towards carbon neutrality. The production of Biochar and storage in soil has also been suggested as a means of abating climate change by sequestering carbon, while simultaneously providing energy, improving soil nutrients, and increasing crop yields.

According to the European Biochar Certification (EBC) guideline, the conservative average degradation rate of biochar is approximately 0.3% per year should the biochar be applied directly to soils or indirectly into agricultural soils via use in animal feed, livestock bedding, slurry management, compost, or anaerobic digesters. In general, 100 years upon the biochar application to soil, 74% of the original carbon contained in the biochar could still be accounted for as sequestered carbon. (EBC, 2020)

Figure 5: Classification of pyrolysis methods with various factors. (Clifford, 2020)

There are 3 types of pyrolysis, the flash/ ultra-fast, the fast and the slow process, which refer to the speed at which the biomass is being altered. According to the article by Nature Communications, the fast pyrolysis, with biomass residence times of a few seconds at most, generates more bio-oil and less biochar than slow pyrolysis, for which biomass residence times can range from hours to days. (Dominic Woolf, 2010)

Figure 6: Effect on product distribution of different pyrolysis conditions.(Clifford, 2020)

With the various pyrolysis conditions and methods, the process can be modified from time to time to suit the demand of its products, either to generate more solid (biochar) for the agricultural or built environment sequestration process, or to produce more bio-oil or synthesis gas for energy and heat source for the district or regional grids. However, this thesis emphases on the slow pyrolysis so to sequester as much carbons as possible to compensate with the carbon footprint generated by the population.

Figure 7: Singapore’s food supply.

Based on the projections by United Nations and the researchers, the world will need upto 70 percent more crops to feed the increase of 2 billion more global population by 2050. (Hunter, 2017) The current strategies of securing food supply in Singapore includes diversifying the sources of food imports, growing food overseas while increasing the local food production. (Anon., 2022) As part of the “30 by 30” vision by Singapore government, the nation has targeted to increase the local food supply from 10% in 2019 to 30% by the year 2030. (Anon., 2021) By such push, it is also in line with the objective to reduce food wastages by eliminating part of the upstream process such as handling, storage and logistics that may degrade the condition of the fresh goods along the processes.

Figure 8: Singapore’s food consumption.

From the data collected by Deloitte and A*STAR in year 2009 and 2018, the food consumption patterns in Singapore have not been deviated significantly between the 10 years apart. In Singapore, less than 10% of the food source are produced locally while the remaining food consumption are imported. Out of the overall 13 food items form the chart, only eggs, fish, beansprouts (within “other vegetables” category) and leafy vegetables are both locally produced and imported, the rest of the food items are completely imported from other Asia Pacific region. In Singapore, 367 kg of food is consumed per person per annum, consisting of 46% fruits and vegetables, 25% grains and 29% meats, eggs and seafood. Based on the report, the embodied carbon from the annual food consumption amounts to approximately 954kg kg CO2-eq of GHG per capita which is equivalent to an average passenger car drive of 3,600km. (Deloitte & SIMTech, 2019)

While the food consumptions pattern in Singapore leans toward the source from vegetables, fruits and grains with about half of its total consumptions, its utility consumption and GHG emissions are much lower than the production of meat products.

Figure 9: Singapore’s consumption. (Deloitte & SIMTech, 2019)

As the food consumption patterns and demand may vary by intangible factors such as social habitats, cultural and culinary economy, the tangible solution by producing the food source closer to its consumption to reduce the embodied carbon of the process can be implemented in the lens of masterplan and architecture.

With the trend of food consumption, impact of food production and properties of biochar in improving soil fertility and increasing crop yields, the thesis look forward to integrating local urban agriculture with the organic waste management plant within the proposed district. While providing a circular trend between the organic waste management and the local agriculture food supply chain, the integration provides a solution by simplifying the upfront food supply processes, cutting short the process between production and consumption, thus reducing the potential wastages along the processes. From the socioeconomic and socio-environmental lenses, this is a win-win condition for the supplier, consumers, and the environment. In addition, with the advancement of artificial intelligence (AI), the food demand trend and season can be stipulated and projected for the operation and production of each crops to minimize the surplus and storage issues that were also contributed to the current food loss and waste.

“Cities are the defining artifacts of civilization, but they are also dangerous parasites, with a capacity to harm regions far beyond their own boundaries. The ecological impact of cities on the global environment is out of proportion to their size.” (Ferrao & Fernandez, 2013, p. 28) The development and growth of a city has always been a major driver of anthropogenic resource extraction, consumption, and waste production.

The culminating urbanization in developed countries such as Singapore is undergoing densification of its urban fabric. With limited land space and natural resources, Singapore is one of the most densely populated country in the world, with approximately 7,485 persons per km². (Anon., 2022) In terms of Carbon Dioxide Emissions Per Capita, Singapore ranked 13th within Asia and 30th in the world, with the average of 8.40 metric tons. (Anon., n.d.)

Figure 10: Stages of Urbanization & associated materialenergy consumption (Anon., 2013)v.

Figure 11 : Urban metabolism framework guide. (Anon., 2013)

Based on Ferrão & Fernández interpretation, urban metabolism framework can be examined by the input (consumption) and output of energy and material flows devoted to three broadly inclusive sets of urban activities, which involves in the urban living and working of:

i) the habitable space (built environment); ii) the goods and services of all types (products); iii) the movement of goods and people (transportation). (Anon., 2013)

The interconnectivity between the three factors above is the key consideration in socioeconomic context as well as the socio environment context which relates to the carbon footprint. (refer to Figure 6)

The agriculture food crops are being seeded at the eastern parcel of the longitudinal plot along with forestry landscape and neighbourhood park content. The strategy of agroforestry park is being implemented to integrate several green functions into the same plot of land catered for greenery, to optimize its efficiency without compromising the urban plot planning ratio.

The ripe fruits and vegetables are then be harvested and sent to the southern wing of the central zoning for collection, sorting and separation:

a) The deteriorated/ lowest quality products will be sent to the pyrolysis process at the western parcel of the plot as biomass feedstock. Together with the horticulture & wood waste collected from the district, the feedstocks will be processed by the pyrolyzers to sequester the carbon.

b) The not-so-appealing/ medium quality products will be separated and be marketed at the fresh food market beside the sorting facility at a lower price to reduce the potential food loss;

c) The products that passed the standard quality will then be sent to the distribution branch for supermarket and food court supply, or be distributed to the other retail in the district or other neighbourhood.

With the simplified process within the same plot, the intervention reduces the carbon footprint of the upstream and downstream activities, minimizing the direct and indirect emission for the process while sequestering carbon through the biomass waste of the process to reduce the overall carbon emissions.

By implementing this prototype to the other districts islandwide, the intervention will contribute the carbon offset of the population gradually along with other implementation and incentives, such as carbon credits and carbon tax along the route to the future.

i) How can the local agriculture food source, upstream agriculture food loss, and food supply be integrated to minimize its carbon footprint while sequestering carbon?

In the pyrolysis process, the biomass waste mass will be reduced while converting into 3 forms: Bio-oil (liquid), synthesis gas (gas) and bio-char (solid). 50% of the carbon content within the biomass will be surpressed within the solid form, bio-char, while the remaining of it will be released as the bio-oil and synthesis gas (Lehmann, 2009), in which they can be recirculated as the fuel to generate energy back to the system.

Biochar application to soil is a means of sequester carbon while improving the soil fertility. The improved soil can be applied to landscape plantings and agricultural use for local farming. Besides soil amendments, biochar can also be used for water remediation in water treatment plant and odour control for industrial, waste handling and treatment facilities. It can also be used in poultry farming as feed additives and odour control for poultry litter. (Yarrow, 2015)

In the built environment, Biochar can also be premix into building materials such as concrete to fabricate concrete blocks, pavement tiles, (Draper, n.d.), non-load-bearing walls, light weight roof tiles (Brownell, 2017) and even street furnitures.

ii) How can a Singapore district sequester carbon with biochar?

Biochar and its carbon circularity can be introduced to the community through public participation activities such as community farming, developing landscaping features or sculptures at Jurong Lake Garden and other co-creation activities. Through a better understanding and awareness about biochar, the community can engage with the development of the district green and create the identity of the carbon neutral neighbourhood by the residents.

Besides, soil amendment initiatives around the neighbourhood and the existing parks (Chinese Garden & Japanese Garden) can also elevate the awareness of the community about the benefits of the carbon sequester.

Pop-up events and workshops for public participations for instance plant repotting or propagation workshops, light weight concrete planter pots and furniture making using admixture of biochar also engage the community to create a piece out of biochar that they can bring home and circulate the knowledge to their inner circle.

iii) How can pyrolysis and carbon circular economy be experienced and understand by the community stakeholders?

Research Methodology

The thesis looks forth to develop an integrated strategy among the context of urban, architectural, industrial technology and landscape, which weave the urban environment of a new district with the existing neighbourhoods while celebrating the circularity of agricultural food.

The research first adopts the methodology of analysing several relevant precedent typologies to understand the design strategy and considerations used by the relevant projects. By synthesising the essence of the relevant typology, it helps to rationalise and crystalise the idea of integration.

Then, the research further inclines towards the understanding of biomass waste flow analysis, the process of pyrolysis and how it can be integrated into the current resource, energy and carbon flow to maximise the potential of carbon sequestration while improving the output properties of the recycled and disposed biomass waste.

By incorporating the knowledge of the biomass waste flow and the food supply-loss process, the research will then explore a prototype to simulate and visualize for a circular and regenerative process which can be enjoyed by the community.

To navigate the project further, the prototype can be implemented in other districts and existing neighbourhoods to weave up the carbon-zero connectivity while celebrating the circularity of food. In the long-term vision, the progression will resonate and bring the nation one step closer to the resilience for its food security circularly.

Review of relevant precedents 2.0

Figure 12: Axonometric study of Amager Bakke WTE plant.

Waste Management: Amager Bakke WTE Plant

The Amager Bakke WTE facility was being established by Amager Resource Centre (ARC) as an important step to meet future demands by supplying low-carbon electricity to 550,000 people and district heating to 140,000 households. (Anon., n.d.) It was completed in 2018. As a recreational bonus, the designer vastly expands the de nition and expectation of an energy-sector facility, featuring a ski slope, hiking trail, and green terrains on its roof, sporting the world's tallest arti cial climbing wall on its vertical facade as well as hosting a rooftop bar, cross- t area, and a viewing plateau of the city. The plant emits a ring of smoke, 70 feet in diameter, every time it releases a ton of carbon dioxide. It's a visual reminder to the public about the emissions created by waste.

From waste to electricity, heat and clean water

The combined heat and power producing plant can treat more than 400,000 tonnes of waste every year. Flue gas condensation and heat pumps will be established to optimise the production of heat. The new facility can export energy for two di erent purposes: hot water for three separate district heating networks and electricity for the power grid. In addition 15-20% of the incoming waste can be reused for road construction.

Building roads with ashes

At Amager Bakke, the incineration process provides the opportunity for material recycling through recovery of resources that would not otherwise be recycled. Metal segregation from bottom ash reaches more than 90% of the potential for most ferrous and non-ferrous metals when modern techniques are deployed. Bottom ash is used for road construction and similar construction purposes under strict requirements for heavy metal content and leaching behaviour. Thereby, the bottom ash can replace natural resources of a similar nature, i.e. sand and gravel.

Precedent Takeaways:

i) Form follow functions: Building layout and spatial massing arranged to suit the function of a skii slope at the rooftop.

ii) Flexible facade modules: Without affecting the overall facade consistency, the modular facade system allows the building skin to be porous or concealed depending on the spatial function beneath the skin. Porous facade at main mechanical sections allow passive airflow and heat released without additional energy.

iii) Spatial layout: Arrangement of space to allow visitor’s to be able to oversee the overall process in a glance without interferring the building operation.

Consisting of two iconic greenhouses, the conservatories mimic the cold and dry climate of the Mediterranean, the cold and humid climate of the semi-arid subtropical and tropical Montane regions. They are home to a diverse collection of plants not often found in this part of the world, some of which have a high conservation value. The development adopted combination of sustainable engineering and advanced technologies for energy e cient solutions in cooling that allows the garden to reduce its energy consumption by approximately 20% as compared to typical buildings using conventional cooling technology.

System Sustainability: Gardens by the Bay

The conservatories were designed to reduce solar heat gain in the form and material chosen. The use of spectrally selected glass panels maximizes daylight while minimizes solar heat penetration into the greenhouse. This operation generates heat and electricity for the chiller using a biomass- red plant that is fed with horticultural waste collected from around the garden, including tree branches and dry leaves. Cold water pipes were laid on the ground to cool the earth while the air inside the dome was dehumidi ed by the heat generated from the biomass processing plant. This strategy can reduce the amount of energy used in the cooling process by settling cold air only at the lower occupied areas.

As for the super trees, the canopies are installed with solar panels to capture and convert the energy to illuminate the super tree at night. Water bodies were introduced to commemorate the landscape design. While ltering the water run-o , the lake system also serves to maintain an aquatic ecosystem and habitat of the ora and fauna around the district while providing evaporative cooling to the garden. Besides, the lakes also help to reduce the nutrient load of the gardens, maintaining a balance soil nutrient for the habitat.

Figure 13: Axonometric analysis of Gardens by the Bay.

Public Engagements: City Sprouts @ Bukit Merah

City Sprouts was founded in 2019 with the mission to create a platform to educate and inspire the local community on the awareness and engagement in social and environmental issues through the curated spaces, various programmes, and events. The project has transformed the former Henderson Secondary School into an urban farming redevelopment that rejuvenates the urban with new life to spaces and communities. The approach of the project mainly promotes the community networking, sustainable living in green movement and food independence.

Figure 14: Axonometric analysis of City Sprout @ Bkt. Merah.

Urban biomass flow analysis & Strategies 3.0

Reutilization of the Renewables for the Regeneratives

Figure 15: 2021 Singapore’s Waste Statistic.

Horticultural waste & Wood waste

As Singapore is well known as the garden city, the harmony between the urban and its articulated landscape are important to balance the lifestyle and well-being of its habitants. The co-living between the landscape and the dwellers makes the biomass waste irresistible and surfaces the potential of reutilising these wastes as a regenerative source for agriculture and horticulture. By adopting the system of pyrolysis into this process, the thesis analyses the potential to sequester carbon from the renewable biomass feedstock concurrently with the biomass waste processing. While reducing the biomass waste volume, the process will harness the full potential of biomass waste products by recycling its bio-oil and synthesis gas produced to generate energy back to the process while sequestering its carbon in the bio-char generated. It is killing three birds in one stone!

According to NEA’s waste and recycling statistics in year 2021, there are total of 310 thousand tonnes of wood wastes and 332 thousand tonnes of horticultural waste generated (NEA, 2022). Both wastes are processed into wood chips for composting, cogeneration or used to make new wood products. (Anon., 2022) The amount of both wood and horticultural waste contributed 10.8% of the total waste generated in 2021. Wood waste in Singapore are mainly derived from crates, pallets, boxes, furniture and wood planks used in construction, while horticultural waste refers to tree branches or trunks, plant parts and trimmings generated during the maintenance and pruning of trees island wide. (Anon., 2022)

Figure 16: 2021 Singapore’s Food Loss breakdown.

Food Waste & Loss

With reference to FAO’s (Food and Agricultural Organization of the United Nations) study, the food wastage happens in both processes, the “upstream” contributing 54% during the food production, post-harvest handling and storage; while the “downstream” contributing 46% during the processing, distribution, and consumption stages. (Anon., 2022) Majority of the food lost happens before reaching the consumers. The setback can be minimized by bringing both upstream and downstream processes closer to its consumers, avoiding the expected and unnecessary losses.

In Singapore context, the local Food and Agriculture Organization (FAO) de nes the perishables that were “lost” in the supply chain between producer and the market as food loss. There were 393,000 tonnes of food loss during the upstream (production) and midstream (processing and transportation) which accounts to 53% of the total food waste in 2019. (Lee, 2022) Among the total food loss, approximately 49% of them were fruits and vegetables. (Naguran, 2019)

In view of the wastages and losses in the food chain, it encourages the thesis research to progress towards the direction of bringing the local consumers closer to the local food productions.

Carbon release / year = 5,891 tonnes

Carbon sequester/ year = 477 tonnes

Figure 17: Implementation of carbon sequestration to current waste flow.

Carbon release / year = 3,411 tonnes (-58 %)

Carbon sequester/ year = 2,958 tonnes (+ 626 %)

Figure 18: Implementation of carbon sequestration to the integrated waste flow.

Biomass Waste Flow Scenarios

By projecting the data to the masterplan of Jurong Lake District, the implementation of pyrolysis to the current nett disposal horticultural and wood waste contributed an estimated amount of carbon sequestration within biochar of 477 tonnes per annual. However, the products channelling out from the recycled wood chips into fuel in cogeneration plant, charcoal products and mulch/ compost are contributing 5,891 tonnes of carbon as they went through the conventional processes of combustion and decomposition which will fully release the carbon back into the atmosphere. (refer to figure 17).

As there is only a portion of the recycled wood will be reconditioned and cut into sizes for new pallets, crates, doors or finishes products, the remaining recycled waste were being grinded into wood chips and send to process into fuel in cogeneration plant, charcoal products, and mulch/ compost. For the horticulture and wood waste stream, the result can be further improved by integrating the pyrolysis process to include the recycled wood chips to process and sequester the carbon before repurposing them back into fuel, biochar, and mulch/ compost.

As the contaminated food waste will affect the properties and reduce the efficiency of carbon sequesteration, the thesis is looking into utilising the food losses (uncontaminated wastes) as the biomass feedstock for the pyrolysis process. Based on the research by the team from School of Environment of the Harbin Institude of Technology on August 2021, the research concluded that the addition of biochar to the anaerobic digester, was evidenced to enhance the anaerobic digestion by accelerating, upgrading and improving system stability of the biogas production with lesser carbon dioxide (CO2v) generated and more methane gas (CH4) produced, which can be used as fuel or for further carbon sequestration via methane pyrolysis. (Weixin Zhao, December 2021)

For the foodwaste stream, the integration of food loss into the pyrolysis process before being sent directly to the anaerobic digester can help to increase the volume of carbon sequestration, while the pyrolysed bio-char can improve the anaerobic digestion process of the remaining of food waste (contaminated waste).

With such integration, the amount of biomass feedstock has increased and thus increased the amount of carbon sequestered by 626%. The integration also simultaneously reduce the carbon released by 58%. (refer to Figure 18)

Strategies

“Biochar only becomes a long-term C-sink when it can no longer be burned or when it is used in products with a long life cycle. Only when the biochar containing material is disposed of, destroyed or decomposed may the sequestered carbon be released back to the atmosphere again, causing the C-sink to lose its value and to be removed from the C-sink register.”

- European Biochar Certificate, 2020.

Figure 19: Carbon distribution in a tree.

Carbon Strategy: Carbon Sequestration

Out of all life on earth, trees contributed 80% of the dry carbon biomass weight. Within a tree, carbon constitutes approximately 50% the dry mass of trees. Carbon is stored for the life of the wood product. (Leys, 2022)

As the garden city, every public tree in Singapore will undergo regular maintenance and pruning every 1-2 years. During each maintenance, each tree will undergo pruning of its tree crown range between 25%-90% which will contribute to the horticulture waste feedstock. (Fong & Burcham, 2012). By understanding from one of the NParks officer via email, the consistent output of these horticultural waste are currently being chipped on-site or sent to contractor’s facilities to recycled as mulch to left breakdown naturally around the trees.(Leng, 2022)

The current horticultural waste method is effective and natural. However, the process is recovering 100% of the carbon into the atmosphere by the aerobic decomposition process. The thesis evaluates the potential of integrating this line of waste source into the pyrolysis process to sequester the carbon within the horticultural waste before releasing the processed waste back as mulch ot the streetscape trees. By such integration, half of the carbon from the waste are being sequestered from releasing into the environment while the processed mulch can still function as soil amendments to fertilise the streetscape horticultures.

Figure 20: Carbon sequestration flow model.

By understanding that carbon can be sequestered via biochar in soil mixture and building materials, the thesis intends to incorporate the strategy to sequester the carbon in the prototype that can be implemented in both landscape and building scale.

Based on the European Biochar Certification guideline, the carbon sinking can be assessed in three steps:

i) Removal of carbon from the atmosphere;

ii) Transformation of carbon into a stable form that can be stored; iii) Safe, long-term storage e.g.: in the soil or in materials (carbon capture, trans formation and storage)

Calculations will be basing on EBC’s principles:

i) Planting of biomass (on site agricultural & horticultural waste) + (horticultural waste from street maintenance)

ii) Packaging of biochar including deduction for production-related emissions [Energy & fuel consumption for transportation to plant, preparation of biomass (chipping, homogenization, pelletizing & drying), pyrolysis process and post-treatment of biochar (grinding, pelletizing), transportation to collection depot]

iii) Implementation of biochar to soil or long-lasting construction materials (to be recorded by C-sink broker)

With the strategy of carbon sequestration via the 3 directions:

a) Streetscape & garden maintenance: - biochar mulch to horticultures as soil amendments.

a) Community greenhouse & agroforestry farming: - biochar mulch to agriculture and horticulture as soil amendments.; - biochar admixture materials for planter boxes or pots.

a) Industrial & built environment:

- Biochar can be premixed into building materials such as concrete to fabricate concrete blocks, pavement tiles, (Draper, n.d.), non-structural walls andv light weight roof tiles (Brownell, 2017) and street furniture.

- biochar can be used for water remediation in water treatment plant; - odour control for industrial, waste handling and treatment facilities

3.2.2

Regenerative Strategy: Agroecology - Agroforestry Park

In land-scarce Singapore, the strategy of adopting agroecology is crucial as to incorporate various green plot land use into an integrated landscape fabric for maximising its usage and ecology. Instead of individual green plot usage of neighbourhood park, agricultural land plot or “farming warehouse”, the integration also provides a biophilic approach to be shared by the new district as well as the existing neighbourhoods.

The weaving of agricultural land, forestry and leisure park space within the urban fabric creates an hybrid ecology and lifestyle while synthesising the harmony between urban and sub-urban context. By diluting the sense and scale of the concrete jungle, the agroecology synergizes the urban hardscapes with the accessible lush softscapes, harmonizing the urban lifestyle with a hint of refreshness and distressful physically and mentally.

Figure 21: Agroforesty park vconcept..

1) Diversity & Agroforestry :

To integrate the merging of forestry and agriculture within the urban fabric to blur the boundary between urban, agricultural land and forest.v

a) Windbreak/ shelterbelts: slow down the wind, reduce visual and noise impact from industrial/ highways, enhancement of biodiversity, wildlife habitat, carbon storage, pollinator habitat, and soil and water quality protection

b) Riparian forest buffers (by the stream): filtering nutrients, pesticides from agricultural land runoff; stabilizing eroding banks; filtering sediment from runoff;

Figure 22: Riparian Forest Buffer.

c) Forest farming/ multi-story farming: For Crops like ginseng, goldenseal, shiitake, or other mushrooms can be planted under shade of the bigger fruit trees.

d) Alley cropping: Interweaving of crops and trees array like alley to blur the perspective of agricultural land and blend the overall landscape as one.

Figure 23: Alley cropping strategy..

Project Scope

Further to the research and understanding with regards to the carbon footprint, food and agriculture, and waste management, the thesis look forth to stitch the 3 stories, to develope an integrated urban green network which can sequester the carbon while celebrating the circularity of local agricultural food production in the community’s everyday landscape.

The intervention shall also be set as a prototype to be implemented islandwide along with the nation’s growth in the population and their appetites. With the increasing yield crops and horticultures in the near future, the quantum of carbon sequestration will expand parallelly. By progressing along with this footstep, the nation can eventually achieve carbon neutrality and moving forward as a carbon-negative community globally.

4.1.1

Move: Accessibility & Logistic

Improves the inclusivity and co-creativity into the everyday-space of the community in line with UN goal 9.1 & 9.2.

As the mode of transportation for majority of the population, MRT and public busses are the roots of connectivity among the districts and neighbourhoods islandwide. Based on the information compiled by Statista Research Department, the MRT is fetching approximately 2.1mil people daily while the public busses are fetching around 5.26mil people per day. (Department, 2022)

In sync with the car-lite vision and the current & future MRT stations, the green network aims to improve the carbon-free accessibility, weave the connectivity of daily commute and recreation to each and every building within the district and also to part of the existing neighbourhoods.

Sustainable Output: Circularity from waste to supply

- Self-sustainable food production landscape while surpressing the carbon footprint progressively.

- One’s waste, is another’s resources: recycle organic waste products and incorporating into the new function in built environment and landscape

- Carbon sequestration: carbon sink & carbon sequestration

- Resilient of food supply: regional food supply to overcome the imbalance of local food resources and progressively bring Singapore to a self-sustain and resilience to any emergency condition.

Well-being: Physically & Mentally

Integrating recreational spaces and landscape into the daily commute routes of the community around the urban fabric helps to minimize the thresholds between hardscape and softscape, allow ones to immerse into the softscape environment once they step out of the workplace or daily life routine. The simplified transition will ease oneself to destress, relax and recharge their energy along the way home after a long day.

Site Selection & Analysis

Why JLD ?

By 2040 to 2050, the Jurong Lake District (JLD) will be the next largest business district with high density mix-development. The new district witll create 20,000 new homes & 100,000 new job opportunities on top of the existing 1 million population in the West region. (URA, 2022)

With aspirations to be a City in Nature, the district was identified as model of urban sustainability under Singapore’s Green Plan 2030. The district envisioned that working, living and playing in the district with intimate public spaces, lush lakefront greenery and native fauna.

By having fast connections to major hubs islandwide, JLD will be a transit-oriented district where its masterplan has incorporated 2 new public train lines (Jurong Region Line & Cross Island Line) to minimize the travel time and making the district more accessible to all walks of life. Along with the car-lite plan, the new district will dedicate more space for pedestrian, cyclist and public transportation facilities.

In this government-supported Built Environment Living Lab, the district provides opportunities to pilot new urban solutions and refine sustainability-centric initiatives. Companies can conveniently co-locate R&D and commercial trials in one place to facilitate faster lab-to-market prototyping and scaling.

As the vision of this new district and opportunity are aligned with the direction of the thesis research, JLD is chosen as the potential site for the implementation.

Neighbourhoods & Surroundings

Key Transportation & Accessibility

Greenery parcels

Green parcel reconfiguration

Original Central Park

Centric spline & exlusive within JLD district

Redistribution of green parcels & Relocation of main central park within JLD district

pocket parks to be enjoyed by each zones & the relocated central park

Centric spline & inclusive among JLD district & existing neighbourhoods (Teban Garden & Terusan Industrial Area)

Agent-based modelling Simulation - Physarealm

(Simulation & Testing of possible public accessible routes and identifying the centric nodes of gathering for public square/ central courtyard atrium)

Centric Node

collection - distribution - serving

Carbon Sequestration

sorting - process - distribution

Public Community

accessibility - recreation - collaboration

Administrative operation - maintenance - planning

Waterfront Promenade

Green Well roofscape

By integrating the green plots with agroforestry park, the intervention will progressively enforces the resilience for local agricultural supply & sequestering carbon from the environment while providing the community a lush & serene environment along their daily commutes.

Material Testing: modular casting

Light-weight & Brittleness of Mix 04.

Prototype: Modular Planter boxes

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