Effect of phase-separation and thin-slurry recirculation on flexible biogas production from maize silage and bedding straw

This study investigates a two-stage anaerobic digestion (AD) process to enhance methane production from lignocellulosic biomass, in this case bedding straw, co-fed with maize silage. The system combines phase separation and double thin-slurry recirculation under mesophilic conditions. The first hydrolysis-acidogenesis stage produced over 10 g L^-1 short-chain carboxylic acids (SCCA) at an organic loading rate of 1.3-3.0 g (L d)^-1 when fed with a content of 50 wt% straw. The subsequent methanogenesis stage achieved a maximum methane yield of 260 mL CH₄ gCOD^-1, with 50 % variation in methane production within 24 h. Thin-slurry recirculation was shown to improve the methane content by 20 %. Cell activity and quick recovery of gas production was proven after fasting periods of several weeks. The approach demonstrates the potential for flexible, efficient processing of bedding straw in AD without further treatment beyond cutting.