Carbon Footprint Accounting of Biochar-Based Fertilizer Derived from Tobacco Stems: A Life Cycle Assessment Case Study of Bijie, Guizhou Province

Biochar-based fertilizers have attracted considerable attention due to their potential in waste resource utilization, enhancement of soil fertility, and contribution to carbon sequestration and emission reduction. Currently, however, there is a dearth of systematic research on the carbon emissions during their production process. To address this gap, this study employs the life cycle evaluation method. A carbon footprint accounting model was constructed, and both on-site and literature data were collected to calculate the carbon footprint of the production process of tobacco stem biochar-based fertilizers. By comparing the scenario of traditional tobacco stem incineration plus fertilizer application, the study examines the carbon emission reduction potential of tobacco stem biochar-based fertilizers throughout their life cycle. The results indicate that the carbon footprint of the production process of tobacco stem biochar-based fertilizers is 111.56 kg CO2-eq/t, with electricity consumption being the most significant contributor to the carbon footprint. The carbon emission of tobacco stem biochar-based fertilizer was 1 423.06 kg CO2-eq/hm2, which was 1 050.16 kg CO2-eq/hm2 lower than that of non-tobacco stem biochar-based fertilizer. By collecting tobacco stems to produce biochar-based fertilizers and replacing traditional fertilizers, Guizhou Province can achieve a carbon emission reduction of approximately 1.32×105 t CO2-eq. As the proportion of clean electricity increases, the carbon footprint of tobacco stem biochar-based fertilizers is projected to decline to 110.15 kg CO2-eq/t by 2035. This study provides a scientific basis for the resource utilization of tobacco stems from the perspectives of carbon accounting and carbon emission reduction, thereby contributing to the green, low-carbon, and high-quality development of the tobacco industry.