Carbon on Earth is constantly exchanged between the biosphere, the soil, the geosphere, the hydrosphere and the atmosphere in many forms, in a balanced process called the carbon cycle. Plants absorb CO2 and release oxygen through photosynthesis, animals and humans depend on oxygen and exhale CO2 for their survival; at the same time, all living things release carbon during decomposition or combustion or CO2 is reabsorbed by plants, land and oceans due to its own carbon content. This carbon balance has been maintained for thousands of years.

Climate Change

So what happens if this carbon balance is upset? Quite simply, climate change. Although the Earth has been going through cycles for millions of years, the effects of these cycles have been within the Earth's own control.

The turning point came in the 18th century, and along with the industrial revolution came the rise of fossil fuels. It disrupted this long-held carbon balance by releasing greenhouse gases such as CO2 into the atmosphere at an unprecedented rate, far beyond the Earth's ability to absorb and balance them. This state of imbalance has led directly to a marked deterioration in the global climate: a gradual rise in average temperatures, accelerated glacier melting, rising sea levels, and a high incidence of extreme weather events ...... Such a drastic deterioration of the gasification makes people realise the urgency of saving the planet.

Carbon Sequestration

Natural Carbon Sequestration - As mentioned earlier, forests, soils, and oceans are natural sponges. Carbon flows naturally between the ecosystems of the atmosphere, oceans, and land in a fairly balanced manner. In the absence of human activity, carbon levels will remain roughly at a steady state.

Artificial Carbon Sequestration - Humans are also actively searching for viable measures to achieve carbon sequestration, the main approach being industrial CO2 capture (CCS). Through specific technologies and methods (adsorption, chemical cycling, thin-film gas separation), CO2 is separated from the exhaust gases emitted from industrial production at a high purity and then sequestered. Despite the progress made in industrial CO2 capture technology, it still faces many challenges. For example, the cost of capture is high, there are difficulties in applying the technology on a large scale, and potential pollutants may be generated during the capture process. In addition, how to effectively utilise or sequester the captured CO2 is also a pressing issue.

How can Biochar Achieve Carbon Sequestration? 

Promoting Soil Carbon Sequestration

As one of the most important carbon reservoirs in the ecosystem, the amount and stability of soil carbon storage greatly influences whether we can effectively achieve carbon sequestration. However, as human production activities intensify, land area is rapidly decreasing. Biochar can effectively sequester soil carbon:

Increase the Organic Carbon Content in the Soil: The carbon in biochar is a stable form of carbon converted by high-temperature pyrolysis, which is difficult to be decomposed by microorganisms, so adding it to the soil has a long-lasting and stable effect on carbon storage. In addition, the increase of carbon content in the soil can also effectively improve soil fertility and promote the growth of plants, thus increasing the absorption and fixation of carbon by plants.

Improvement of Soil Structure: Biochar combines with soil minerals to form soil aggregates, which provide physical protection for the biochar, reduce the rate of soil mineralisation and further promote carbon sequestration. It also enables the regulation of beneficial soil microbial activity, minimising CO2 emissions due to soil respiration.

Biochar Reduces Livestock Methane Emissions

The addition of biochar to animal feed can influence the structure of microbial communities in animals, particularly those associated with methane production, as ruminants burp or fart after eating, which accounts for almost 30 per cent of global methane emissions. Studies have shown that biochar can effectively inhibit the activity of methane-producing microorganisms, thereby reducing the amount of methane produced by animals during the digestive process.

Biochar Optimises the Energy Structure

In addition to biochar, a certain amount of syngas is produced during the biochar production process. Both this syngas and biochar are high-performance fuels. They can reduce the use of fossil fuels such as coal and oil. Although syngas and biochar emit carbon when used as fuels, it needs to be clarified that this carbon comes from existing atmospheric CO2 and won’t lead to a net increase in the carbon cycle. Therefore, the use of biochar and syngas from the pyrolysis process can reduce dependence on fossil energy sources and thus optimise the overall carbon emissions of the energy mix.