Utilizing conductive materials for reducing methane emissions in postharvest paddy rice soil microcosms

Area of Science:

• Agricultural Science
• Environmental Science
• Microbiology

Background:

• Paddy fields are a significant anthropogenic source of global methane (CH4) emissions, a potent greenhouse gas (GHG).
• Understanding mitigation strategies for CH4 is crucial for addressing climate change.
• Conductive materials (CMs) are being explored for their potential to influence soil microbial processes and greenhouse gas emissions.

Purpose of the Study:

• To investigate the efficacy of organic and inorganic conductive materials (CMs) – biochar, fungal melanin, and magnetite – in mitigating CH4 emissions from paddy soils.
• To assess the impact of these CMs on key microbial populations during rice straw decomposition under anaerobic conditions.
• To elucidate the mechanisms by which CMs influence microbial interactions and CH4 production pathways.

Main Methods:

• Microcosm experiments using postharvest paddy rice soils from the Ebro Delta, Spain.
• Incubation under anaerobic conditions simulating postharvest season with rice straw amendment.
• Analysis of CH4 emissions, isotopic signatures (δ13C-CH4, δ13C-CO2, δ2H-CH4) to determine methanogenesis pathways.
• Microbial community analysis, including archaeal populations and specific bacterial linkages using LefSe.

Main Results:

• Fungal melanin significantly reduced CH4 emissions by 29%, and biochar by 10%.
• Magnetite showed a non-significant 3% increase in CH4 production.
• All treatments confirmed acetoclastic methanogenesis; CMs altered archaeal abundance (Methanobacteria, Methanosarcina, Bathyarchaeia).
• Specific microbial linkages were identified: fungal melanin with Geobacter, biochar with Clostridia, and magnetite with Thiobacillus and Bathyarchaeia.

Conclusions:

• Fungal melanin and biochar are effective in mitigating CH4 emissions from paddy soils, likely through influencing microbial electron transfer and metabolism.
• CMs can modulate soil microbial communities, promoting interactions that may suppress methanogenesis.
• The findings suggest potential for CMs to facilitate direct interspecies electron transfer (DIET), offering a novel approach for managing greenhouse gas emissions in agriculture.