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Sub-moderate temperature (ranging from low to moderate temperature) anaerobic digestion (AD) could balance fermentation efficiency and energy input. We investigated biogas production and the microbial community in wastewater AD at sub-moderate (15 °C, 20 °C, and 25 °C) and moderate (35 °C; control group) temperatures with the organic loading rate (OLR) incrementally increased over 200 days. The impact of temperature on biogas production was found to be minimal at a low OLR but became more significant at a high OLR. Notably, a temperature threshold ranging from 15 °C to 20 °C exerted a strong inhibitory effect on biogas production and disrupted the microbial community. And, SMT-AD is deemed by this study to be the optimal application strategy of wastewater with low temperature and low OLR. Bacterial richness was positively and linearly related to temperature. There is a relevance between methane production and archaeal diversity under the influence of temperature and OLR. Temperature and OLR shaped the ecological function of predominant bacteria. Anaerolineales, Thermotogales, and Lactobacillales were strongly influenced by temperature. Synergistales had a synergistic relationship with Desulfovibrionales. Clostridiales was responsible for acetate and butyrate production and closely related to Lactobacillales. Acetoclastic Methanosaetaceae was the predominant methanogen. Methanogens could survive and maintain their population even though methanogenesis was limited under high OLRs and low temperatures. [ABSTRACT FROM AUTHOR]

Korshinsk peashrub branches (Korpb) are agroforestry byproducts that accumulate in millions of tons per year and need to be reasonably utilized. To maximate the utilization value of Korpb, an integrated process was proposed and conducted by using Korpb as the main substrate ingredient for Pleurotus tuoliensis cultivation and also performing anaerobic digestion (AD) of spent mushroom substrate (SMS) for biogas production. The results indicated that the cultivation substrate including Korpb could obtain higher mushroom yields than a conventional substrate, and AD of SMS added the value of Korpb. Preliminary calculation suggested that, for every t of P. tuoliensis production, 1.65 t Korpb was consumed and 314 m3 biogas was produced from corresponding amount of SMS, bringing a total economic profit of $906.1. In addition, this integrated strategy has positive ecological and social benefits. The maximization of Korpb value can not only promote the biological conversion of Korpb to circle economy, but also be beneficial for the development of environment, energy conservation and edible fungus industry. • Korpb is a lignocellulose biomass resource with great potential. • Integration of P. tuoliensis cultivation and AD of SMS maximized the value of Korpb. • The economic profit achieved $906.1 for every t of P. tuoliensis production. • The integrated strategy has positive ecological and social benefits. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Continuous stirred-tank reactor (CSTR) has a "short-circuit" problem. • The Gradient anaerobic digestion reactor (GADR) can solve the problem of CSTR. • GADR can stably carry out semi-continuous dry anaerobic digestion. • GADR can improve the biogas yield of straw raw materials that are unique to China. • The biogas production efficiency and microbial community were analyzed. In China, the problem of low biogas yield of traditional biogas projects has become increasingly prominent. This study investigated the effects of different hydraulic retention times (HRTs) on the biogas production efficiency and microbial community under pilot conditions. The results show that the "Gradient anaerobic digestion reactor" can stably carry out semi-continuous dry anaerobic digestion and improve biogas yield. The highest volatile solids (VS) biogas yield (413.73 L/kg VS and 221.61 L CH 4 /kg VS) and VS degradation rate (48.41%) were observed at an HRT of 25 days. When the HRT was 15 days, the volumetric biogas yield was the highest (2.73 L/L/d, 1.43 L CH 4 /L/d), but the VS biogas yield and degradation rate were significantly decreased. Microbial analysis showed that HRT significantly affected microbial community. It provides basic data support for the development of a new anaerobic digestion process and the practical application of the straw biogas project in China. [ABSTRACT FROM AUTHOR]