Combined hydrothermal pretreatment of agricultural and forestry wastes to enhance anaerobic digestion for methane production.

[Display omitted] • The methane production increased by 14-37% after the CHTP-AD process. • Chem-degradation & biotransformation pathways were simulated by Multiomics. • Carbohydrate-Protein-Lipid interaction has been revealed in CHTP. The dense structure and significant differences in the properties of agricultural and forestry wastes make it difficult to achieve anaerobic conversion. This study employed hydrothermal pretreatment (HTP) and combined hydrothermal pretreatment (CHTP) to enhance the anaerobic digestion (AD) performance of agricultural and forestry organic wastes. At a specific hydrothermal condition of 140℃ for 30 mins, the cumulative methane production of garden waste (GW), chicken manure (CM), duck manure (DM), and pig manure (PM) increased by 14.70%, 14.18%, 27.48%, and 21.81%, respectively. Under the same conditions, CHTP of garden waste with livestock and poultry manures showed noticeable synergistic effects, resulting in the methane production potential of garden waste mixed with chicken manure, duck manure, and pig manure increased by 28.82%, 36.59%, and 37.56%, respectively, compared with the untreated group. Metabolomic analysis showed that CHTP could significantly promote the decomposition of biomass carbohydrates, proteins, and lipids, leading to increased levels of small molecular metabolites. Analysis of microbial community diversity showed that HTP and CHTP increase the abundance of specific functional microbial communities, such as hydrolysis bacteria and methanogens, thereby promoting the anaerobic production of methane from biomass waste. Energy balance analysis shows that HTP-AD and CHTP-AD have a positive net energy benefit. This study provides an efficient CHTP technology and theoretical support for the resource utilization and energy conversion of agricultural and forestry wastes. [ABSTRACT FROM AUTHOR]