The Use of Electric-Field Can Effectively Reduce Greenhouse Gas Emissions and Promote Carbon Conversion in Compost

This study focused on the effect of electric field intensity on carbon transformation in aerobic composting of biochar–pig manure. Four treatment groups were set up with voltages of 0 V (CK group), 2 V (L group), 4 V (M group), and 5 V (H group). The physicochemical properties and carbon forms of the compost were characterized, and how they influence composting was investigated by observing the changes in the functional groups of the compost and the interactions between microorganisms and environmental factors. The results showed that the electric field treatment groups entered the thermophilic phase 2–3 d earlier than the CK group, and the duration of this phase was extended by 3–5 d. The seed germination indices were 95.2%, 106%, 110%, and 121% for the CK, L, M, and H treatment groups, respectively. The DOC content decreased by 11.7%, 11.4%, 16%, and 16.5%. The degradation rates of hemicellulose were 38.6%, 41.1%, 42.7%, and 42.8%, respectively. Those of cellulose were 46.8%, 47.7%, 51.8%, and 54.5%, respectively. Those of lignin were 37.2%, 40.8%, 47.9%, and 53.3%, respectively. Compared to the CK group, the cumulative emissions of CO2 and CH4 in the L, M, and H groups were reduced by 13.8–25% and 47.86–75.76%, respectively, resulting in lower carbon losses. Fourier transform infrared spectroscopy indicated that applying an external electric field induces changes in the functional groups of humic acid, the formation of aromatic functional groups, and the optimization of the maturation process. Compared to the CK group, applying an electric field (L/M/H groups) optimized the microbial communities (especially the Bacteroidota, Chloroflexi, and Acidobacteriota abundances), enriched Proteobacteria and Myxococcota, and regulated the moisture content and C/N ratio. These changes in the electric field treatment groups significantly improved the degradation efficiency of cellulose, lignin, and hemicellulose and reduced greenhouse gas emissions.