Study on Anaerobic Digestion Characteristics of Hulless Barley Straw and Livestock Manure

Co-digestion performance of hulless barley straw mixed with pig, fowl, sheep, and cow manure induced by microbial changes were studied based on mesophilic batch anaerobic digestion (AD) experiments. The mixed AD of hulless barley straw and four kinds of manure yielded the synergistic promotion effect of materials. The highest methanogenic performance was achieved by AD of hulless barley straw mixed with pig manure, and the digestion process was the fastest when mixed with fowl manure. When the volatile solids (VS) ratio of hulless barley straw to pig manure was 1:3 (H1P3), the maximum cumulative methane production was 356.55 mL·g−1 VS. The composition of raw materials could significantly impact on the microbial community composition. In terms of bacteria, Syner-01 and Synergistaceae_unclassified were the most abundant in H1P3 group. Proteiniphilum and Ercella were the most abundant in the AD system supplemented with pig manure. Fermentimonas, Sulfurovum and Desulfomicrobium were the most abundant in the AD system supplemented with fowl manure, cow manure and sheep manure, respectively. In archaea, the concentration of hydrogenotrophic methanogens, such as Methanobrevibacter, Methanoculleus, Methanospirillum and Methanoplanus, could be enriched in the mixed AD system. In addition, the digestate nutritional content exerted significantly positive influence on Syner-01, Methanobrevibacter and other seven genera, while volatile fatty acids and ammonia nitrogen positively influenced the concentration of Smithella and Fermentimonas, respectively.