Magnetite-loaded biochar generated
by gasification serves as a
potential additive to facilitate electron transfer and boost methane
production. In this study, the focus was placed on the mechanism of
magnetite-loaded biochar-enhanced methanogens with live bacteria in
real habitats, and the connection between live microorganisms and
the methanogenic pathway was revealed. Magnetite-loaded biochar produced
at a FeCl3-to-woodchip ratio (w/w) of 15/100 presented
maximal methane production, where the daily methane yield was improved
by 157% compared with the control. Magnetite accelerated the consumption
of short-chain fatty acids through dissimilatory iron reduction, and
it was converted into siderite and goethite after anaerobic digestion.
The iron cycle coupling with the organic removal enhanced electron
transfer efficiency and further transmitted electrons to promote methanogenesis.
As indicated from the results, live high DNA (Atelge, M. R.; Atabani,
A. E.; Banu, J. R.; Krisa, D.; Kaya, M.; Eskicioglu, C.; Kumar, G.;
Lee, C.; Yildiz, Y. Ş.; Unalan, S.; et al. Fuel
2020,
270, 117494.) cells with high
viability increased from 21 to 44%, which probably facilitated the
electron transfer and direct interspecies electron transfer via membrane
proteins. Moreover, the activities of the functional enzyme participating
in the acetoclastic and hydrogenotrophic methanogenic pathways were
enhanced. As revealed from the gene abundance from live microorganisms
of the acetoclastic/hydrogenotrophic methanogenic pathway, the magnetite-loaded
biochar facilitated the methanogenesis process, probably due to the
DIET formed between the iron reduction bacteria Ruminococcaceae and methanogenesis Methanothrix and Methanosarcina by the magnetite-loaded biochar.