Biochar-based fertilizer enhances carbon neutrality and net ecosystem economic benefit in tobacco (Nicotiana tabacum L) production

Biochar has great potential to advance carbon neutrality and net ecosystem economic benefit (NEEB), dual priorities critical for global sustainability. Nevertheless, scarce studies have comprehensively assessed the carbon footprint and NEEB based on life cycle assessment (LCA) as well as field crop production. An integrative investigation of five strategies was set up through field experiments: (1) chemical compound fertilizer (CF), (2) biochar-based fertilizer (BF), and (3–5) biochar application rates of 10 (NB10), 20 (NB20), and 30 (NB30) t ha⁻¹ with equal nitrogen inputs in a typical tobacco field with no N fertilizer or biochar as CK. The results demonstrated that biochar amendments (NB10, NB20, and NB30) achieved dose-dependent net negative carbon footprint although they intensified N₂O emissions by 118.7–321.7 % (p < 0.05) as compared with the CF. Moreover, the NB10 strategy reconciled environmental-economic objectives with better NEEB, but the NB20 and NB30 strategies depressed NEEB despite achieving carbon negativity. Importantly, the BF strategy optimally increased NEEB (by 3.9 %, p < 0.05), improved tobacco quality (by 13.9 %), and decreased the carbon footprint (by 22.1 % and 25.9 % on the yield-scaled and income-scaled, respectively, p < 0.05) compared to the CF. Energy consumption was the primary contributor to carbon emissions, accounting for 69.1–83.1 % among all sources based on the LCA framework. Thus, biochar-based fertilizer and optimized biochar amendment strategies lowered the carbon footprint and enhanced NEEB for sustainable production, surpassing conventional local practices.