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

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Carbon loss via CO2 and CH4 emissions during composting negatively impacts compost quality and contributes to environmental pollution.
• Biochar, a stable carbon-rich material, is explored as an additive to mitigate these emissions.
• Understanding the microbial mechanisms behind these changes is crucial for optimizing composting processes.

Purpose of the Study:

• To investigate the impact of rice husk biochar (RHB) and sawdust biochar (SDB) on CO2 and CH4 emissions during composting.
• To elucidate the underlying microbial mechanisms influencing greenhouse gas emissions.
• To assess the overall global warming potential (GWP) of biochar-amended compost.

Main Methods:

• Composting experiments with control (CK), RHB, and SDB treatments.
• Measurement of CO2 and CH4 emissions.
• Analysis of microbial community shifts using redundancy analysis (RDA) and partial least squares path modeling (PLS-PM).
• Correlation analysis between total organic carbon (TOC) and microbial genes.

Main Results:

• Both RHB and SDB significantly reduced cumulative CO2 emissions compared to CK.
• RHB and SDB significantly increased CH4 emissions.
• Despite increased CH4, the overall 100-year global warming potentials (GWP-100s) were reduced for both biochar treatments.
• Total organic carbon (TOC) was identified as a key regulatory factor, influencing microbial communities and gas production.

Conclusions:

• Biochar addition alters microbial community structure and function, shifting from r-strategy to K-strategy.
• Biochar inhibits CO2 production while modulating methanogenesis, leading to reduced net GWP.
• This study provides a theoretical basis and practical guidance for reducing greenhouse gas emissions in biochar-manure co-composting.