ABSTRACT
According to the International Biochar initiative, biochar is the solid material obtained from thermochemical conversion of biomass in an oxygen-limited environment. Biochar is useful as a soil amendment and effects soil improvement, improved resource use efficiency, long-term carbon (C) storage in soils, remediation and/or protection against environmental pollution, and is an avenue for greenhouse gas (GHG) mitigation. Application of biochar has been shown to reduce soil erosion, and result in overall improvements to soil quality by raising soil pH, increasing soil organic matter and moisture holding capacity, attracting beneficial microbes, improving cation exchange capacity (CEC) and retaining nutrients. These benefits have ultimately increased yield in biomass and crops under diverse agro-climatic conditions. Chemical and physical characteristics of biochar are greatly affected both by choice of feedstock (crop waste, energy crop, wood chip, municipal waste, manure, etc.) and process conditions (mainly temperature and time). Biochar-C is more stable as compared to other biological forms of C, and estimates on the mean turnover time of biochar in soil vary from decades to centuries. Reduction in emissions of GHGs, particularly nitrous oxide and methane through biochar production and application to soil, requires further research. In spite of the benefits associated with this ‘tried and tested’ product, various concerns (cost, feedstock availability, takers of the technology, etc.) still exist regarding the upscaling of biochar to cover larger areas, which need to be addressed so as to maximize its benefits.
