Biochar is found in soils from around the world. It can be formed as a result of vegetation fires and from particular soil management practices, especially in the Amazon region. Sustainable biochar is a carbon-enriched material derived from waste biomass, such as crop residues, manure, and timber and forestry residues. It is made by heating biomass at low temperatures in the absence of air (pyrolysis), usually in a specially designed furnace to drive off volatile gasses, leaving behind carbon or “biochar.” This process also produces other clean energy products, such as bio-oil and syngas, along with the biochar.
Biochar is primarily used as a soil amendment. Research has shown that biochar can increase soil retention of nutrients and agrochemicals for plant and crop production. Biochar can also help to improve water quality by causing more nutrients to stay in the soil instead of leaching into groundwater or surface waters. Soil application of biochar is being tested around the world and more research is needed on its effects on specific soil types and the different properties of biochars made under various conditions and from different feedstocks. Biochar can be important for growing food and improving cropland, especially in areas with depleted soils or lacking adequate water and chemical fertilizer supplies.
Bio-oils and syngas, the byproducts of biochar production, can be used as fuel, providing a source of clean, renewable energy. Bio-oils can also be utilized in the production of other value-added products.
Another potential environmental benefit associated with biochar applied to soil is that it can sequester atmospheric carbon. In the natural carbon cycle, plants take up carbon dioxide as they grow. Carbon dioxide is emitted rapidly when the plants die and decompose -- a carbon-neutral cycle. In contrast, pyrolysis can potentially lock up this atmospheric carbon as biochar for hundreds of years. Considering that carbon dioxide is pulled from air to make biochar, the net process is carbon-negative. Therefore, biochar is an attractive solution to increased carbon in the atmosphere. Research is ongoing in this area of carbon sequestration.