Leachate recirculation effects on solid‐state anaerobic digestion of Pennisetum hybrid and microbial community analysis

Abstract

BACKGROUND A leach‐bed reactor (LBR) with leachate recirculation is a suitable technology for lignocellulosic biomass anaerobic digestion. In this study, the effect of percolate reflux strategies (continuous recirculation and intermittent recirculation) on methane production from Pennisetum hybrid, a type of energy crop, was investigated using a two‐layered LBR. RESULTS Compared to a solid‐state anaerobic digestion batch test, LBRs with percolate recirculation provide a stable process with a short lag phase by avoiding inhibition of volatile fatty acid accumulation and inoculation effect. The results also indicated that continuous reflux led to a lower accumulative methane yield (56.20 L kg−1 VS) compared to intermittent reflux (78.50 L kg−1 VS), resulting from washing effect and poorer distribution on the lower layer. According to microbial analysis, Bacteroidetes, Firmicutes, Proteobacteria and Synergistetes were the most predominant bacterial phyla in each LBR test sample and aceticlastic methanogen (at least >55%) plays a predominant role for methane production in all samples. CONCLUSIONS The results indicate that leachate recirculation could provide stable conditions for methane yield; however, two‐layer reactor designs which cannot guarantee the desired distribution in the lower layer result in a low methane yield. Suitable design of LBRs to maintain a well‐distributed reflux leachate should be further investigated. © 2019 Society of Chemical Industry

Biogas Production from Organic Wastes: Integrating Concepts of Circular Economy

“…Qian et al [100] reported that leachate recirculation favored hydrolysis and acidogenesis by its inoculating effect and improved mass transfer, but it also created a washing effect when excessive recirculation was applied, leading to a fast VFA accumulation. Xing et al [89] also reported a detriment in reactor performance when increasing the recirculation frequency of a solid phase reactor treating lignocellulosic biomass (energy crop Pennisetum hybrid). Even if homogenization and biomass wash-out problems are solved, the process still has to deal with the operating conditions.…”

Methane production of rare earth element‐rich Dicranopteris dichotoma and effects of La(III) on anaerobic digestion performance of lignocellulose

“…On the 5th day, the most abundant archaeal were Methanosarcina , Methanothrix , Methanomassiliicoccus , Methanobacterium , and Methanoculleus in the control experiment. Methanosarcina and Methanothrix belonged to aceticlastic methanogen, and Methanobacterium , Methanoculleus , and Methanomassiliicoccus were hydrogenotrophic archaea 28,41,42 . Both aceticlastic methanogen (25.91%) and hydrogenotrophic archaea (27.48%) were the predominant methanogens in the control experiment.…”

“…Microbial DNA was extracted using a E.Z.N.A™ Mag‐Bind Soil DNA Kit; results were quantified using a Qubit 3.0 DNA test kit. Primers (341F and 805R) were used to amplify the V3‐V4 hypervariable region using a polymerase chain reaction (PCR) 28 . Two rounds and three rounds of PCR were used to amplify 16S rRNA genes for bacteria and archaea, respectively.…”

“…Methanosarcina and Methanothrix belonged to aceticlastic methanogen, and Methanobacterium, Methanoculleus, and Methanomassiliicoccus were hydrogenotrophic archaea. 28,41,42 Both aceticlastic methanogen (25.91%) and hydrogenotrophic archaea (27.48%) were the predominant methanogens in the control experiment. Under the 500 mg/L La(III) conditions, the relative abundance of Methanothrix increased from 11.73% to 16.65% and Methanobacterium increased from 8.69% to 15.63%, while that of Methanosarcina decreased from 14.18% to 8.87%.…”

High-Solid Anaerobic Digestion: Reviewing Strategies for Increasing Reactor Performance

“…However, these authors pointed out that when recirculation was excessive, then a negative outcome was observed because it then caused microbial biomass washout and VFA accumulation. Xing et al [54] also evaluated the recirculation of leachate, treating lignocellulosic biomass (Pennisetum hybrid) as a substrate. They found a similar detriment in reactor performance when the frequency of recirculation was increased.…”