Role of Natural Gas in Energy Transition Diya Handa

Role of Natural Gas in Energy Transition

Diya Handa (Year 12, Anderson)

Natural gas is a fossil energy source that is found beneath the surface of the Earth; consisting of multiple compounds, such as methane, carbon dioxide, water vapour and other natural gas liquids (NGL). It is considered to be the cleanest fossil fuel. Additionally, natural gas is odourless and colourless. When burned, it releases carbon dioxide, water vapour and a minimal amount of nitrogen oxides.

HOW IS NATURAL GAS FORMED?

Natural gas was formed from plants, animals and microorganisms millions of years ago; it is formed underground due to the intense conditions. The organic matter from the decomposition of plants, animals and microorganisms is formed on layers of soil, sediment and rocks. As organic matter decays and becomes more rooted into the Earth’s crust, the temperature gets higher. These conditions of high compression and temperature cause the carbon bonds in the organic matter to break, causing the release of thermogenic methane: natural gas. Methane (CH 4 ) is Earth’s most abundant organic compound and is made up of hydrogen and carbon. It does not necessarily have to be formed underground; instead, it can also be formed by microscopic organisms - methanogens. Methanogens are present in the intestine of mammals, and low oxygen areas near the surface of the Earth. The process of methanogens creating natural gas is known as methanogenesis.

Most biogenic methane escapes into the atmosphere as gas rises through permeable matter and dissipates into the atmosphere; however, new technology is being developed to minimise this, as biogenic methane has an impact on the global carbon ‘pool’ of supply. Most thermogenic methane rises to the surface to encounter geological formations. These formations are too impermeable for the gas to escape as they are sedimentary basins and they are prone to trapping a lot of natural gas. To access this natural gas, holes need to be drilled through the rock to allow the gas to escape and be harvested. You can contain this methane to harvest it into a potential energy source. These basins can be found worldwide, such as in the deserts of Saudi Arabia, Venezuela and the Arctic.

TYPES OF NATURAL GAS

There are two main categories of natural gas: 'conventional' and 'unconventional' gas. Conventional gas is easily accessible and economically viable to extract. Unconventional gas, on the other hand, is found in places where it is not convenient nor practical to perform an extraction. Fortunately, technological advancements have made such extractions possible.

Conventional gas extraction can be done using standard methods which are convenient and inexpensive as it does not require specialised extraction techniques and equipment. It is found in natural porous reservoirs that are blocked with an impermeable rock stratum which can be easily unblocked

Deep natural gas is an unconventional gas located 15,000 ft below the Earth’s surface. This natural gas is trapped in layers under shale, an insoluble fine-grained sedimentary rock. Hydraulic fracturing or horizontal drilling can be carried out to extract the gas. Hydraulic fracturing involves splitting open a rock with a high-pressure stream of water then opening it with grains of sand, glass or silica, allowing the gas to flow freely out of the well. Horizontal drilling is when drilling parallels the Earth’s surface, allowing access to the gas trapped between the rocks. Another unconventional deposit of gas is Tight gas. Tight gas is found underground in impermeable rock formations, making it very hard to extract. It requires expensive and complicated methods of extraction, such as hydraulic fracturing and acidizing. Acidising is similar to hydraulic fracturing but acid instead of water is injected into natural gas deposits, dissolving the rock thus allowing the gas to escape.

Figure 1: Hydraulic Fracturing Diagram

Coalbed methane is also found underground, near coal deposits. Historically, when coal was mined, natural gas was unintentionally freed out of the mines. However, it is now a popular method of collecting methane; it is complicated to mine, but they contain large amounts of natural gas. Another interesting unconventional source is gases from geopressurized zones formed 10,000-25,000 ft below the Earth’s surface. Layers of gas form on top of a porous material such as sand.

Furthermore, a newfound source of natural gas, which is found in ocean sediments and permafrost areas of the Arctic, are methane hydrates. Much like hydraulic fracturing, this process too requires high pressure and low temperatures. In ocean sediments, methane hydrates form on the continental slope as the bacteria on them allows other microorganisms to sink into the ocean floor and decompose into the silt. In permafrost ecosystems, they form as bodies of water freeze and water molecules trap individual methane molecules. There is a lot of energy stored in them; however, they are fragile geological formations, meaning that they must be extracted with extreme care.

Figure 2: Conventional and unconventional gas formations in NSW

Natural gas is domestically-abundant and offers multiple environmental benefits over other energy sources such as coal. It is considered to be one of the cleanest fossil fuels as it emits relatively fewer harmful chemicals into the atmospheres. It can potentially mitigate some of the environmental issues such as greenhouse gas emissions, smog, air quality and acid rain.

ENVIRONMENTAL IMPACT OF GREENHOUSE GASES

Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth. They include water vapour, carbon dioxide, methane, nitrogen oxides (NO x ) and engineered chemicals such as chlorofluorocarbons (CFCs). The most damaging greenhouse gas is carbon dioxide, and it is currently at its highest level recorded.

Figure 3: Carbon dioxide emissions by each country

These gases can trap heat in our atmosphere (known as the greenhouse effect), helping maintain a habitable climate for us; however, they are now imbalanced, and threaten life on earth. Greenhouse gases are linked to climate change which has resulted in rising temperatures, extreme weather conditions, rising sea levels, a decrease in wildlife populations and the destruction of habitats. Furthermore, greenhouse gases can cause respiratory diseases due to smog and air pollution. Smog is formed as a result of a chemical reaction between carbon monoxide, nitrogen oxides and heat from the sunlight, and alongside poor air quality, it can lead to respiratory problems, both temporary and permanent. However, natural gas does not contribute to the formation of smog as it does not release copious amounts of nitrogen oxides. Thus, natural gas can effectively reduce smog and increase air quality.

Acid rain is another major problem that is a result of greenhouse gases. It damages crops, forests and wildlife habitat. Much like smog, it can also cause respiratory problems. Acid rain is a result of the formation of multiple acidic compounds from sulfur dioxides and nitrogen oxides reacting with water vapour and other chemicals in the presence of heat from the sun. Natural gas emits virtually no sulfur dioxide and 80% fewer nitrogen oxides than the combustion of coals.

Using natural gas to generate electricity has significantly more advantages than other means of energy. Firstly, it reduces greenhouse gas emissions when generating electricity as it produces minute amounts of NO x , CO 2 and other particulate emissions. Additionally, it emits virtually no SO 2 . It can be used as a replacement for fossil fuels such as coal and oil, as these produce more harmful toxins. Coal powered plants and industrial boilers reduce SO 2 emission through the use of scrubbers, which produces 'sludge', a semi-solid waste product, while electricity generation using natural gas produces virtually no SO 2 , reducing the production of sludge and eliminating the need for scrubbers.

Furthermore, natural gas can be reburned and injected into coal or oil-fired boilers. This reduces NO x emissions by 50-70% and SO 2 emissions by 20-25%. Additionally, natural gas can combine cycle generations which means that units that usually capture and generate electricity, resulting in wasted heat energy, can now be reused to regenerate electricity. These multiple benefits include aspects such as increased energy efficiency, less fuel usage and fewer emissions. Natural gas-fired combined-cycle generation units can be up to 60% efficient, whereas coal and oil generation units are only around 30-35% efficient. Moreover, natural gas can be used for fuel cells. This application is currently in development for widespread use in the future. The idea is that fuel cells will use hydrogen to generate electricity, which can be obtained from natural gas in abundance. This would theoretically lead to fewer emissions from the generation of electricity.

Figure 4: Hydrogen fuel cell diagram

According to the Paris Agreement, the goal for each country is to restrict global warming levels to below 2°C. This agreement plays a critical role in addressing air quality problems and reducing carbon dioxide emissions globally due to the legal guidelines it puts in place. Presently, 197 countries-all nations- have signed this treaty. This includes countries such as the United States of America, India and China. Each country is responsible for reducing emissions and submitting national climate action plans. The governments agree to meet every five years to assess their progress and evaluate long-term goals. Under the EU’s 2030 climate and energy framework, countries should collectively aim to reduce greenhouse gas emissions by at least 40% compared to 1990.

A growing number of countries are transitioning to use renewable energy and limiting their carbon footprint with an emphasis on the coal-to-gas transition. From 2010 to 2019, more than 550 coal-fired power plants were suspended. In 2016, natural gas generators had replaced coal as the primary suppliers of electricity in the United States of America. This has resulted in a decrease in the CO 2 emissions, which fell by 28% from 2005.

One of the most popular policy solutions to climate change is decarbonisation i.e. shifting towards lower carbon power sources. China has been responsible for over 65% of the worlds energy consumption and over 70% of carbon emissions but the industrial energy consumption has greatly reduced in the past years, which is the most significant contributor to China’s energy and CO 2 emissions. The industry has been implementing energy-efficient and low-carbon development. The decline in energy consumption in 2017 was 4.6% in China.

Figure 5: Sector energy savings in China

India is the third largest-emitter of carbon emissions after China and the United States of America. It is projected to take over the USA by 2030 at its current rate of carbon emissions. India’s CO 2 emissions had increased by 132% whereas other countries increased by an average 40%. India heavily relies on coal for electricity and this demand for energy is anticipated to increase. Current government policies modelled by the International Energy Agency predict that this energy consumption will double in the future. It is projected that by 2040 the transport sector carbon emissions will triple and other industries such as construction are also projected to increase in carbon emissions.

Major countries such as China and the United States of America are only a few of the countries that have made some progress in reducing greenhouse emissions. Nevertheless, stronger actions and policies need to be set in place to allow for a more effective transition. India is predicted to be the largest carbon emitter by 2040 because it is still developing, the country has not yet made major efforts to reduce carbon emissions. Monopolies, businesses and developing countries are only a few hindrances that can affect the decarbonisation goals set by the Paris Agreement. Switching to natural gas will aid countries in meeting these targets, and more collaboration amongst governments and industry leaders will allow for a more successful transition. This pathway to decarbonisation will lead to a more sustainable future.

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