Biochar modulates microbial carbon metabolism to mitigate global warming potential during composting.

Biochar addition during composting reduces 100-year global warming potential by up to 19.29 g CO2e·kg−1 through microbial-mediated mechanisms.

• Why it matters: Reducing greenhouse gas emissions from composting is crucial for mitigating environmental pollution and conserving organic carbon for humification, but the microbial mechanisms involved are not fully understood.
• What they did: The study examined the effects of rice husk biochar (RHB) and sawdust biochar (SDB) on CO2 and CH4 emissions in composting, using 11.38% and 16.30% reductions in CO2 emissions, and 45.35% and 81.04% increases in CH4 emissions, respectively, with statistical significance.
• The result: Biochar increased total organic carbon (TOC), shifted microbial communities from r- to K-strategies, inhibited CO2 production, and modulated methanogenesis, collectively decreasing the net global warming potential of composting systems.