Anaerobic digestion has been used to simultaneously realize pollution control, energy recovery, nutrient cycling, and carbon emission reduction. Among them, biomass anaerobic digestion can also contribute to bio-manufacturing, organic waste pollution in environmental protection, and national energy security in sustainable agriculture. Energy utilization can be expected to transform from conventional single energy to a multi-objective collaborative new-quality mode. Current industrial development was also characterized by technological precision, product high-endization, value diversification, and ecological low-carbonization. This study aims to systematically classify the three purposes of biomass anaerobic digestion technology: rural revitalization and food security, agricultural and rural pollution, and renewable energy conversion. A comparison was made to examine the industrial trends between the European Union and China, including standard certification, equipment manufacturing, business models, and technology breakthroughs. Furthermore, three technical links were also reviewed: the functional microbial synergistic metabolism (covering bioaugmentation of targeted functional consortia and intensification of interspecies electron transfer mechanisms), biomass feedstock pretreatment (including physical, chemical, biological, and combined technologies), and process regulation (involving feedstock solid content optimization, carbon-to-nitrogen ratio adjustment, and temperature gradient control). Four bottlenecks were identified to restrict the high-quality development of the industry: Low conversion efficiency caused by the imbalance of microbial syntrophic metabolism, long-term stability of engineering systems, great difficulty in precise regulation, and low added value of products. Four trends were also given for the new-quality utilization of biomass anaerobic digestion. 1) The "black box" of conventional anaerobic digestion was integrated with synthetic biology, multi-omics technology, and artificial intelligence. Multi-scale precise regulation was realized from microbial metabolic pathways to full engineering. 2) Anaerobic metabolic pathways were directionally regulated to apply carbon chain into high-value bio-based chemicals represented by medium- and short-chain fatty acids. The application boundary of anaerobic technology was expanded in the field of bio-manufacturing. 3) A systematic cascade high-value utilization was constructed for primary and by-products: Raw biogas was upgraded into high-end green fuels, such as liquefied biomethane (LBM) for heavy-duty transportation, shipping, and aerospace applications; Biogas residue and slurry were converted into diversified high-value products, including functional bio-fertilizers, biochar materials, and single-cell protein (SCP) feed additives. 4) Carbon emission reduction was realized for quantifiable and tradable carbon assets in the full-chain anaerobic conversion, according to China Certified Emission Reduction (CCER), thereby realizing the stable and sustainable transformation of ecological into economic value. Finally, the future directions and paths of biomass anaerobic digestion were determined using Technology Readiness Level (TRL), including organic waste treatment over the full chain at the county level. Biotechnology and information technology were integrated to realize the full-component value of biomass resources. The findings can provide important theoretical references and practical guidance for engineering and industrial formulation in the field of biomass anaerobic digestion.

Anaerobic digestion (AD) operating under conditions of organic overload stress typically exacerbates the potential for process instability, thereby resulting in significant economic and ecological ramifications. In this investigation, an augmented substrate-to-inoculum ratio (S/I) along with varying total solid content (TS) levels was employed to replicate diverse organic loadings, utilizing maize straw and cattle manure. The findings reveal that a moderate augmentation in S/I and TS proves advantageous in augmenting methane yield, while an excessive substrate loading diminishes methane yield, hampers the kinetics of methane production, and even induces severe process instability. Kinetic study also displayed the variation of the model parameters for the first-order model, the modified Gompertze model, and the transfer function model. Both the modified Gompertze model and transfer function model exhibited the same environmental stress trend. Thus, both the increase in particulate content and the increase in S/I had a substantial effect on the substrate conversion rate to methane. Microbial analysis demonstrates the dominant influence of Firmicutes and Methanosarcina under different organic loading stresses. From both a kinetic and a microbiological point of view, this work provides novel insights into the fundamental processes that regulate anaerobic digestion (AD) under varying loading stress. Furthermore, it has significant implications for improving the operating efficiency of AD, which is a significant benefit.

In order to enhance the start-up of anaerobic digestion (AD), the propionate-degrading methanogenic cultures were introduced to AD of food waste at a high organic loading rate (OLR) of 3.0 g VS/L∙d in this study, and the efficiency of different bioaugmentation strategies were investigated. The results demonstrated that bioaugmentation significantly improved the start-up efficiency and enhanced the methane production. Specifically, higher dosage and frequency of bioaugmentation had a positive effect on the performance of the AD reactors. Among three bioaugmented reactors, the reactor with a bioaugmentation strategy of 0.675 g VS/L of bioaugmentation seed added every 5 d during the first hydraulic retention time (HRT) performed the best and remained relatively stable for the next three HRTs without bioaugmentation. The 16S rRNA gene sequencing analysis revealed that Methanothrix predominated in bioaugmented reactors. A large proportion of Methanothrix accompanied by a small proportion of Methanospirillum played a key role in volatile fatty acid degradation and contributed to the successful start-up and long-term stability of AD at a high OLR. These findings suggest that bioaugmentation with methangenic consortium is a promising strategy to boost the AD process at high OLRs and achieve higher treatment capacity of food waste.