Biomass energy expert from the Chinese Academy of Sciences: To achieve the "dual carbon" goal, carbon zero emission and carbon negative emission are the key factors

China has fully established the goals of reaching a carbon peak by 2030 and achieving carbon neutrality by 2060. As one of the low carbon pilot cities approved by the state, the 8th Plenary Session of the 13th CPC Chengdu Municipal Committee proposed to build a green low carbon life circle, striving to take the lead in building a carbon peak and carbon neutrality demonstration city in the country.
What is carbon neutrality?
On a large scale, carbon neutrality refers to achieving a balance between the amount of carbon dioxide emitted and the amount of carbon dioxide absorbed and utilized, involving carbon emission reduction, carbon zero emission, and carbon negative emission technologies. Carbon emission reduction refers to reducing the consumption of traditional fossil resources by improving efficiency, thereby reducing emissions; Carbon zero emission refers to the use of primary energy without emissions such as wind energy, water energy, light energy, biomass energy, etc. However, the reality is that we cannot completely eliminate the use of underground fossil resources, so we need carbon negative emission technology to convert and utilize the carbon dioxide already generated.
"Zero and negative carbon emissions are the key to achieving the 'double carbon' goal," said Dr. Li Dong, Biomass Energy Project Team of the Chinese Academy of Sciences Chengdu Institute of Biology. The POWER TO GAS technology developed by its team over five years can capture carbon dioxide generated by factories and biogas digesters, utilize renewable electricity to hydrolyze hydrogen, and then use hydrogen to reduce carbon dioxide in biogas to convert carbon dioxide into methane, "completely replacing natural gas.".
From zero carbon emission technology to negative emission technology
"Carbon neutrality is not a new word," Li Dong said. As early as 2008, his team had been engaged in technological research and development in the field of carbon emission reduction. At the beginning, the research direction of the team was "urban and rural organic waste resource utilization", which is a carbon zero emission technology. Later, they found that just zero emissions was not enough, and they had to offset the carbon dioxide they had already generated. Therefore, they began to study negative emission technologies.
"Bioenergy with CO2 capture and storage is one of the important carbon neutralization technologies. The experience of European countries has shown that biomethane and hydrogen are important technologies for achieving long-term climate goals." Li Dong mentioned that, from the perspective of China's situation, China is a large population and agricultural country, with great demand for energy supply and environmental protection. Although China has extremely rich biological natural gas resources such as various types of production and domestic organic wastes, its dependence on natural gas imports is still increasing.
On December 4, 2019, the National Energy Administration issued the Guiding Opinions on Promoting the Industrialization Development of Biological Natural Gas, proposing that by 2025, domestic biological natural gas will have a certain scale and form a green, low-carbon, clean, renewable gas emerging industry; By 2030, biological natural gas will achieve steady development, ranking among the top in the world in terms of scale. "However, currently, biological natural gas is mainly obtained through biogas purification, that is, about 40% of the carbon dioxide in biogas is separated and discharged into the atmosphere, which not only causes a large amount of greenhouse gas emissions, but also seriously wastes carbon resources." Li Dong said.
On the other hand, China is a large power country with abundant hydropower, photovoltaic power, wind power, and other power resources. However, large-scale storage of electricity is relatively difficult. Hydrogen production through electrolytic water can achieve large-scale storage of electricity. Although hydrogen is a clean energy source, compared to natural gas with well-established transmission and distribution networks and terminal utilization facilities, China's hydrogen utilization is still in a distributed small-scale pilot, with transmission and distribution networks not established and terminal utilization facilities imperfect.
At the same time, he mentioned that our society is a carbon based society, and people's food, clothing, housing, use, transportation, and even human life are inseparable from carbon.
"Renewable electricity to biological natural gas" technology is in the pilot stage, which is precisely based on the above background of greenhouse gas emission reduction, lack of gas and rich electricity energy structure, imperfect hydrogen utilization system, and carbon based social attributes. In 2016, Li Dong proposed a carbon based resource coupled CO2 capture and utilization technology for renewable electricity to biological natural gas, namely the POWER TO X technology, which can be carbon based energy, chemicals, food, and materials. Generally speaking, it means converting CO2 into new and available carbon based resources through renewable electricity. Under the POWER TO X technology system, taking POWER TO GAS (Renewable Electricity to Biological Natural Gas) as an example, renewable electricity is used to hydrolyze hydrogen, and then hydrogen is used to reduce carbon dioxide in biogas to convert carbon dioxide into methane. This "can completely replace the use of natural gas", not only eliminating the carbon dioxide separation equipment required for biological natural gas production, but also reducing carbon dioxide emissions and increasing biological natural gas production. Through this technology, hydrogen that is not convenient for transmission, distribution, and utilization is converted into natural gas that is convenient for transmission, distribution, and utilization, electrical energy that cannot be stored on a large scale is converted into natural gas that can be stored on a large scale, renewable electricity is converted into carbon based resources, and the biological fixation of greenhouse gas carbon dioxide is realized. Of course, the application scenario of this technology is in places with carbon dioxide emission sources, such as factories with carbon dioxide emissions, and places with large-scale biogas projects. Li Dong revealed that at present, the technology is in the pilot stage, and the team is contacting relevant enterprises to promote demonstration, which may be promoted on a large scale in the future. "The final cost of this technology depends on the electricity price." Li Dong said that 80% of Sichuan's electric energy is hydropower, and the advantage lies in its rich hydropower resources. It is worth mentioning that in addition to POWER TO GAS, under the POWER TO X technology system, Li Dong and his team are also studying projects such as POWER TO Protein. More results may emerge in the future.