Biochar for soil amendment

Abstract Biochar is the solid product of the thermochemical decomposition of biomass at moderate temperatures (350–700°C) under oxygen-limiting conditions. Biochar is used as an amendment in agricultural soils due to many interesting characteristics, including high carbon content, high pH, high stability, high porosity, and high surface area. Therefore, several research studies have been carried out over the last few years to assess the global impact of biochar on various agricultural soils. It was reported that biochar can improve soil's chemical, physical, and biological properties, increasing crop productivity. Moreover, biochars with a high specific surface can be used as a remediation tool in soil to adsorb both organic and inorganic contaminants as pesticides and heavy metals, reducing leaching to water courses. In addition, carbon in biochar, which is highly stable, can be sequestered for more than 1000 years once applied to the soils. Many studies also demonstrate that biochar amendment to agricultural soils can contribute to reducing greenhouse gas emissions. However, each biochar is unique and has different chemical and physical properties. Therefore, not all biochars can provide the benefits listed above. The biomass feedstock and the operating parameters have to be selected with care to obtain a biochar with the desired properties. Moreover, there are many challenges to the use of biochar as an amendment in agricultural soils, because the regulations often consider biochar as a waste or a hazardous material. It is also a challenge to produce biochar on a large scale with minimum costs. This chapter highlights the benefits of biochar used as an amendment in agricultural soils. The key properties of biochar needed and the related production parameters are identified. Finally, the challenges for sustainable production of biochar are pointed out.