Estimation of carbon sequestration potential and air quality impacts of biochar production from straw in China

Aiming to optimize straw resource utilization and to reduce air pollutant and greenhouse gas emissions in China, the environmental benefits of biochar production using straw and utilization need to be assessed. Two biochar production scenarios were studied: centralized production scenario (CPS) utilizing an industrialized production method with advanced air pollution control devices, and decentralized production scenario (DPS) based on a distributed production method of biochar at the village level, compared to an open-burning scenario (OBS). The potential GHG emission reductions under DPS, including the benefit of soil biochar application, were evaluated as 680 Tg CO2-eq yr-1, which was lower than the reductions under CPS (780 Tg CO2-eq yr-1). Although the attentional centralized production method of biochar has more potential environmental benefits, at present the distributed production method is more practical in China due to its convenience, management ease, and lower costs. Modeling on air quality in China showed that in comparison with OBS, DPS could reduce the average monthly PM2.5 concentration of key regions by 19%, and about 190 Tg yr-1 biochar could be produced with 150 Tg C yr-1 sequestered in biochar. Our findings support widespread biochar use in China for improved air quality and climate neutrality.