Biochar

Biochar is the lightweight black residue, made of carbon and ashes, remaining after the pyrolysis of biomass, and is a form of charcoal. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment". Biochar is a stable solid that is rich in pyrogenic carbon and can endure in soil for thousands of years.

The refractory stability of biochar leads to the concept of pyrogenic carbon capture and storage (PyCCS), i.e. carbon sequestration in the form of biochar. It may be a means to mitigate climate change due to its potential of sequestering carbon with minimal effort. Biochar may increase the soil fertility of acidic soils and increase agricultural productivity. Biochar is mainly used for soil application and is known to improve soil nutrient availability, aeration in soil, and soil water filtration. There exist various approaches for utilizing biochar, including but not limited to soil amendment, slash-and-char, water retention, stock fodder, and concrete additive.

Biochar has been widely viewed as an environmentally positive material for soil. However, it is crucial to take into account the potential adverse effects of biochar, such as disturbing soil pH levels, or introducing harmful chemical characteristics that cause problems at the micro dimension. Therefore, caution should be exercised when considering the applications of biochar as research continues to explore the positive and negative effects of biochar.