Anaerobic Digestion of High-Solid Chicken Manure (CM) at Different Temperature: Intestinal Microbiome Efficiency, Inhibition, and Microbial Community Evolution

Abstract

Anaerobic digestion (AD) of high-solid mono-chicken manure (CM) holds great promise for resource utilization. However, the effects of substrate overload (high-solid mixture inside the reactor) on AD performance at various temperatures are still unclear, moreover, the metabolic processes with and without inoculation are also seldom reported. In this study, three key impact factors of different temperatures (4 °C, 35 °C, 55 °C and 75 °C), total solids (TS) inside, and inoculation were conducted to comprehensively explore the process variation. EEM-FRI results revealed that high temps boost coenzyme F420, while TS predominately driver the microbial production. High TS and temperature synthetically result in high free ammonia (FA) (>600 mg/L) associated with free volatile fatty acid (FVFA) (>450 mg/L), reducing CH4 production but increasing VFAs accumulation (12 g/L at 55 °C). Notably, intestinal microbiota alone without inoculation even achieved 11 g/L of VFA. The cross-feeding symbiosis between fermentative bacteria (Caldicoprobacter, Bacteroidetes, Tepidimicrobium) and hydrogenotrophic Methanobacterium enhanced CH4 production (68 mL/gVS at 35 °C). Moreover, high temperatures reduced microbial diversity but made heat-resistant hydrolytic bacteria dominant. This study precisely analyzes the effects of temperature and inoculation factors on the acidification efficiency of high-solid CM digestion, providing a crucial scientific basis for optimizing the resource utilization of CM waste.