Role of Biochar on Greenhouse Gas Emissions and Carbon Sequestration in Soil: Opportunities for Mitigating Climate Change

Abstract

Biochar, a pyrolyzed product of biomass, is richer in aromatic carbon (C) and poorer in oxygen which provides structural recalcitrance to it against microbial decomposition in soil. Biochar, being a stable source of C when applied to soil, remains there for longer period of time imparting long-term soil C sequestration. This sequestering effect of biochar has another advantage to mitigate climate change by reducing emission of greenhouse gases (GHGs) from soil. Both the interconnected processes imparted by biochar have its prominent role in climate resilience and environmental sustainability. Researchers around the world have been focusing on this aspect; thus revealing new facts and findings on managing biochar in agriculture. In this chapter, an attempt has been made to describe the biochar-governed mechanisms on emission of GHGs from soil, how the structural and functional properties of biochar regulates that, and the other associated factors like feedstock type and pyrolysis temperature during biochar preparation and soil inherent properties controlling various processes. Similarly, highlights of C sequestration potential of biochar made up of different crop/animal residues and other regulating factors have been described. Increase in pyrolysis temperature and switching over from manure to wood as a feedstock for biochar production increase the stability of biochar and reduce emission of GHGs from soil. The soils low in organic matter trigger C mineralization than that with high organic matter content. Biochar in presence of N fertilizer is reported to enhance CH4 sink/decrease source strength of soil. The strongest effect of biochar on enhancing C sequestration and reducing GHGs emission is evident when it is applied in acid soils than alkaline soils. Both the concurrent processes of C sequestration and GHGs emission bring sanity to soil by physically more stable, enriching soil fertility, biologically more active and resulting to enhanced soil quality and lowering the C-footprint in agroecosystems.