Carbon offset potential of biochar based straw management under rice- wheat system along Indo-Gangetic Plains of India

The Paris Agreement goal of a net-zero equation will require decarbonization technologies in agriculture. Agri-waste biochar offers huge potential for carbon abatement in agricultural soils. The present experiment was carried out to compare the effects of residue management, viz., no residue (NR), residue incorporation (RI), and biochar (BC), as well as nitrogen options for emission reduction and carbon capture under the rice-wheat cropping sequence (RWCS) of the Indo-Gangetic Plains (IGP), India. After two cycles of cropping pattern, the analysis revealed that the biochar application (BC) reduces the RWCS's annual CO₂ emissions by 18.1 % over residue incorporation (RI), while CH₄ and N₂O emissions were reduced by 23 % and 20.6 % over RI and 11 % and 29.3 % over no residue (NR), respectively. The application of biochar-based nutrient composites with rice straw biourea (RSBU) at 100 % and 75 % significantly reduced greenhouse gases (CH₄ and N₂O) compared to commercial urea at 100 %. The global warming potential of cropping systems recorded with BC was 7 % and 19.3 % lower than NR and RI, respectively, while 6-15 % under RSBU over urea 100 %. The annual carbon footprint (CF) under BC and NR decreased by 37.2 % and 30.8 % over RI, respectively. The net CF under residue burning was estimated to be the highest (132.5 Tg CO₂-Ce), followed by RI (55.3 Tg CO₂-Ce), showing net positive emissions; however, net negative emissions were found under a biochar-based system. The estimated annual carbon offset potential of a complete biochar system over residue burning, incorporation, and partial biochar as calculated was 189, 112, and 92 Tg CO₂-Ce yr^-1, respectively. A biochar-based approach to managing rice straw had great carbon offset potential through a large drop in greenhouse gas emissions and an improved soil carbon pool under the rice wheat system along the IGP, India.