Abstract
Three anaerobic reactors using pig manure (PM), maize straw (MS), and a mixture of the two as substrates were compared for archaeal community structure and diversity, and for methanogens response to increased organic loading rate (OLR, expressed in the mass of volatile solid (VS)). Methanogenic archaeal richness during codigestion of pig manure with maize straw (ACE: 2412) was greater than that during the others (ACE: 1225, 1467) at an OLR of 4 g L−1 day−1, accompanied by high specific methane yield. Euryarchaeota and Crenarchaeota predominated during overall digestion of different substrates; with relative abundances of 63.5%–99.0% and 1.0%–36.3%, respectively. Methanosarcina was the predominant genus that accounted for 33.7%–79.8% of the archaeal community. The diversity in the PM digester decreased with increase in OLR, but increased in the MS digester. The diversity was stable during the codigestion with increased OLR. The relative abundances of hydrogenotrophic methanogens increased by 2.6 and 2.1 folds; the methanogenic community shifted from acetoclastic to hydrogenotrophic methanogens during digestion of MS, and of the mixture of MS and PM. Canonical correspondence analysis revealed a strong relationship between reactor parameters and methanogenic community.
Highlights
China is a large agricultural country in which abundant biomass resources are generated during agricultural processes
It is expected that the results presented would enable the optimization of operational conditions in order to achieve high efficiency Anaerobic digestion (AD) for agricultural applications
The average specific methane yield (SMY) of R2 (PM and maize straw (MS)) was 218 and 254 ml g−1 day−1 at OLR of 2 and 4 g L−1 day−1, respectively, which were 7.4%, 10.4%, and 33.7%, 192.0% higher, respectively, compared with that in R1 and R3
Summary
China is a large agricultural country in which abundant biomass resources are generated during agricultural processes. The production of livestock manure was around 3.49 billion tons in 2016 (National Bureau of Statistics of the People’s Republic of China, 2017; Zhang, Bo, & Geng, 2012). Large amounts of livestock and poultry manure have become concentrated in certain areas over the last few decades, as agricultural land is not sufficient for their recycling via the soil-plant system. This fact together with the inadequate management of these wastes, has caused serious land, water, and air pollution problems (Chen & Liu, 2017; Li, Liu, et al, 2016) that have received increased attention from environmentalists, economists, and policymakers (Li, Cheng, Yu, & Yang, 2016)
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