Enhancing methane production from anaerobic co‐digestion of cow manure and barley: Link between process parameters and microbial community dynamics

Abstract

The effects of selected process parameters (i.e., temperature, inoculum to substrate ratio [I:S], and inoculum source) on methane production and microbial community structure were investigated in lignocellulose-based anaerobic digestion tests. The results highlighted that dynamic response of microbial communities in changing process parameters subsequently affected anaerobic digestion performance. Co-inoculation of cow rumen fluid to the seed sludge improved the methane yield by 18%. The overall highest methane yield (278 mL CH 4 /g volatile solids) was obtained when cow rumen fluid was co-inoculated with anaerobic seed sludge with an I:S ratio of 1:2 at mesophilic temperature. Based on 16S rRNA gene amplicon sequencing results, Clostridium, Bacteroides, and Bacillus were the predominant bacterial genera in all anaerobic digesters. The highest relative abundances of Clostridum and Bacillus were detected in the thermophilic anaerobic digester. The relative abundance of Rikenella; known for high cellulolytic activity, was significantly higher only in the cow rumen fluid-added digester. Comparatively higher abundances of these lignocellulose-degraders synergistically affected volatile fatty acids as well as methane production in these anaerobic digestion set ups. Methanobacterium was the most abundant methanogen in the digesters inoculated only with anaerobic seed sludge; whereas, Methanobrevibacter dominated the digester that was co-inoculated with cow rumen fluid.

Comparative Assessment of Biogas Production Potential of the Most Abundant Agro-residues in Turkey

“…Thus, appropriate inoculum should be used during the start-up period which includes necessary microbial communities having an ability to degrade lignocellulosic feedstock. The bacterial community structure of the inoculum seems to be consistent with other research that found a similar bacterial profile in the anaerobic systems [22,27] and provides an ability to degrade a wide variety of carbohydrates under anaerobic conditions. The bacterial community of inoculum was dominated by Cloacimonetes, Bacteroidetes, Firmicutes, and Proteobacteria species.…”

“…The physicochemical characterization of the inoculum and feedstock were presented in Table 1. Bacterial and methanogenic archaeal community patterns of the inoculum were determined by nextgeneration sequencing-based metagenomics by the Ion Torrent PGM ® platform as described in Ince et al [22]. operated in batch mode for 30 days under mesophilic conditions (37°C).…”

In search of the optimal inoculum to substrate ratio during anaerobic co-digestion of spent coffee grounds and cow manure

“…In addition, manure-based anaerobic digesters may pose stability problems since the microbial group is highly susceptible to the environmental and operating conditions (Turker et al, 2018). Comparatively high concentrations of propionic acid were often reported in anaerobic digesters fed with cow manure (Akyol et al, 2014b; Cavinato et al, 2017; Ince et al, 2020). Accumulation of propionic acid is considered as a good indicator of unstable AD processes (Roy et al, 2009).…”

“…Although an I:S ratio between 1:1 and 3:1 is often suggested and applied (Lesteur et al, 2010), this ratio obviously varies depending on the substrate composition (Fabbri et al, 2014; Wang et al, 2013). A proper balance between the substrate and the inoculum is important, since excess organic loading may result in VFA accumulation and substrate inhibition, while slow methanation may occur due to lack of inoculum (González-Fernández and García-Encina, 2009; Ince et al, 2020).…”

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

“…Agricultural residues with a high lignocellulosic content and a low moisture content may represent an excellent potential energy resource [82] to produce biogas as a valuable fuel if the proper conversion can be attained at a reasonable cost under a solid-state configuration. In addition, co-digestion with manures may take advantage of the synergistic effects reported by several authors [83][84][85][86], particularly when the solid content of the system is increased. However, some difficulties still need to be solved, such as the higher degradation time needed, the high inoculation rate required to start up this process, and the low degradability of lignocellulosic biomass.…”