Biochar addition in rice farming systems: Economic and energy benefits

This study investigated economic returns and energy use of alternative rice production systems in North Vietnam with various residue management options. The traditional practice of open burning of rice residues (System A) was compared with the alternative of converting residues to biochar, which was returned to the paddy fields (System B). It was assumed that households used improved cook-stoves and drum ovens to produce biochar, and that the agronomic impacts of biochar compound with increasing biochar applications until reaching maximum benefit at 18 Mg ha−1. This amount of biochar would take eight years to be produced in pyrolytic cook-stoves and drum ovens using the rice residues produced on-site. The net present value (NPV) of producing rice in the two systems was calculated based on their expected streams of costs and benefits. Biochar addition enhanced the NPV of rice by 12% and reduced the non-renewable energy intensity by 27%, relative to System A, after eight years of application. The difference in NPV values between production systems significantly increased to 23% and 71% by crediting GHG emissions abatement in low and high carbon price scenarios, respectively. These findings demonstrate the potential economic benefits of converting rice residues to biochar for soil application.