Assessing the Mitigation Potential of Biochar as a Permanent Carbon Storage Solution: A Comparative Analysis of Natural and Artificial Storage Methods
Carbon sequestration has become an increasingly important topic in recent years, as we try to find ways to mitigate the effects of climate change. Each year, agriculture fixes 30 gigatons of carbon, but when the plants die, 30 gigatons of carbon return to the atmosphere, resulting in little net change. One potential solution that has gained attention is the use of biochar as a more permanent storage of carbon in the soil compared to natural ways of carbon cycling and other bio inputs like composting.
The recent IPCC report documents Biochar as not being in the list categorised by high risk of non-permanence category even compared to Afforestation, Reforestation and Soil Carbon Sequestration through altered methods in agriculture. In this article, we will explore why biochar is a more permanent storage of carbon in the soil compared to natural ways of carbon cycling and other bio inputs like composting.
Slow and Fast Carbon Cycle
Carbon is both the foundation of all life on Earth, and the source of the majority of energy consumed by human civilization. Firstly, let’s understand how carbon cycling works in nature. Carbon is an essential element for life on earth, and it cycles through different reservoirs, including the atmosphere, oceans, and terrestrial ecosystems.
The carbon cycle can be broadly divided into two categories: the slow carbon cycle and the fast carbon cycle. The slow carbon cycle takes millions of years to complete, and it involves the movement of carbon from rocks and minerals into the atmosphere through volcanic activity and weathering. In contrast, the fast carbon cycle is much quicker and involves the movement of carbon between the atmosphere, oceans, and terrestrial ecosystems. This cycle is driven by biological and physical processes, such as photosynthesis, respiration, decomposition, and combustion.
Slow and Fast Carbon Cycle
Carbon is both the foundation of all life on Earth, and the source of the majority of energy consumed by human civilization. Firstly, let’s understand how carbon cycling works in nature. Carbon is an essential element for life on earth, and it cycles through different reservoirs, including the atmosphere, oceans, and terrestrial ecosystems.The carbon cycle can be broadly divided into two categories: the slow carbon cycle and the fast carbon cycle. The slow carbon cycle takes millions of years to complete, and it involves the movement of carbon from rocks and minerals into the atmosphere through volcanic activity and weathering. In contrast, the fast carbon cycle is much quicker and involves the movement of carbon between the atmosphere, oceans, and terrestrial ecosystems. This cycle is driven by biological and physical processes, such as photosynthesis, respiration, decomposition, and combustion.
Natural process of Carbon storage in Soil
One of the primary ways in which carbon is stored in the soil is through the process of photosynthesis. Plants absorb carbon dioxide from the atmosphere and use it to produce organic matter through photosynthesis. This organic matter is then decomposed by microorganisms, releasing carbon back into the atmosphere in the form of carbon dioxide. However, some of the organic matter is not decomposed and remains in the soil, contributing to soil carbon storage. This process is known as natural soil carbon sequestration.
Composting is another method of carbon sequestration that is commonly used in agriculture. Composting involves the breakdown of organic matter by microorganisms, which releases carbon dioxide and other gases into the atmosphere. However, some of the carbon is stabilized in the form of humus, a stable form of organic matter that can persist in the soil for hundreds of years. While composting can be an effective method of carbon sequestration, the amount of carbon stored in humus is much less in comparison to Biochar and is less permanent.
Carbon capture and Storage (CCS)
Carbon capture is a process of capturing CO2 from industrial processes, such as power plants, and storing it underground or in other geological formations. The process involves capturing the CO2 before it is released into the atmosphere, compressing it, and transporting it to the storage site. The CO2 is then injected into the storage site, where it is stored permanently. However, carbon capture is an expensive and energy-intensive process, and the storage sites need to be carefully selected to prevent leakage of the stored CO2 making it less feasible for widespread implementation. Unlike Biochar, CCS has found to have no benefits for soil health and agriculture and is vulnerable to leaching , Overall, biochar presents a promising alternative for long-term carbon storage that can also provide
Now, let’s turn our attention to biochar. Biochar is a type of charcoal that is produced by heating organic matter, such as wood chips or agricultural waste, in the absence of oxygen. This process, known as pyrolysis, results in a carbon-rich material that is highly porous and stable. Biochar can be added to the soil as a soil amendment, where it can improve soil fertility, water retention, and nutrient availability. However, the most significant benefit of biochar is its ability to sequester carbon in the soil for long periods.
The reason biochar is more permanent is due to its chemical composition and physical properties. Biochar is highly stable and resistant to biodegradation, which means that it does not break down easily over time. This is due to the fact that biochar is composed mostly of carbon, which is a very stable element that does not readily react with other compounds. In addition to its chemical stability, biochar also has physical properties that make it an effective long-term carbon storage medium. Biochar has a very high surface area, which means that it can adsorb and hold onto large amounts of nutrients and organic compounds.
This creates a habitat for beneficial microorganisms in the soil, which further enhances its stability and long-term carbon storage capacity. Another important factor that contributes to the permanence of biochar as a carbon storage medium is its ability to resist leaching. Biochar is insoluble in water, which means that it does not easily wash away or become transported to other locations in the environment. This helps to ensure that the carbon stored in the biochar remains in the soil for a long period of time.
- Biochar is a highly recalcitrant form of organic carbon, meaning that it resists degradation and is therefore more stable in soil than other forms of organic matter.” (Lehmann and Joseph, 2015)
- “Biochar has a high resistance to decomposition due to its chemical structure, which is dominated by aromatic compounds, and its high surface area, which can promote the adsorption of microbial enzymes and protect it from microbial attack.” (Biederman and Harpole, 2013)
- “Biochar can enhance soil carbon sequestration by reducing the mineralization of organic carbon and increasing its retention in the soil, resulting in a more stable pool of soil organic carbon.” (Laird et al., 2010)
- “Biochar has been shown to increase soil carbon stocks and reduce carbon losses through leaching and gaseous emissions, indicating that it can be an effective long-term strategy for carbon sequestration in soils.” (Spokas and Reicosky, 2009)
- “Biochar’s high stability and resistance to decomposition means that it can remain in soil for centuries to millennia, making it an effective long-term strategy for mitigating climate change by sequestering carbon in soil.” (Lehmann et al., 2015)
This stability makes biochar a more permanent storage of carbon in the soil compared to natural soil carbon sequestration and composting. Additional advantage of biochar is its ability to reduce greenhouse gas emissions from agriculture. When organic material is burned or decomposed, it releases carbon dioxide and other greenhouse gases into the atmosphere. By converting this organic material into biochar, we can capture and store this carbon in the soil instead of releasing it into the atmosphere.
Several studies have demonstrated the effectiveness of biochar in sequestering carbon in the soil. One study conducted by Lehmann et al. (2006) found that adding biochar to soil increased soil carbon sequestration by up to 12 times compared to unamended soil. Another study by Woolf et al. (2010) found that biochar could sequester carbon for up to 1000 years.
In addition to its environmental benefits, biochar can also have economic benefits for farmers and other land managers. By improving soil health and fertility, biochar can increase crop yields and reduce the need for inputs like fertilizers and pesticides. This can lead to cost savings for farmers and other land managers, as well as improved profitability.
In recognition of these benefits, biochar use can qualify for carbon credits under various carbon offset programs, including the Clean Development Mechanism and the Gold Standard. This can provide an additional source of income for farmers and incentivize the adoption of sustainable practices. Furthermore, integrating biochar use into global climate funds can help scale up the adoption of this technology and support sustainable agriculture in India and beyond. While biochar is not a silver bullet for addressing climate change, it is one tool in the toolbox that can help us move towards a more sustainable future.
— Written by Dr.Kshithij Urs, Executive Director, India Biochar and Bioresources Network