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The dry anaerobic co-digestion of LW (livestock waste), OFHW (organic fraction of household waste), and AR (agricultural residue) was evaluated in terms of pH stability, organic removal rate, and methane yield. The total quantity of the solids involved in the digestion was adjusted to 25%. All the reactors were inoculated by 20% (in dry weight) of the municipal sludge. The dynamic changes in the pH values of the LW-AR-OFHW mixture co-digestions underwent four stages and differed from those of wet anaerobic digestion. The decrease in VS (volatile solids), volume, and weight of the LW-AR-OFHW mixtures was higher than those in AR and OFHW. The VS, volume, and weight reductions in LW-AR-OFHW co-digestion were 54.7%, 82.2%, and 72.7%, respectively. However, the VS, volume, and weight reductions in AR were only 11.1%, 20.5%, and 19.8%, respectively, and those in OFHW were only 27.4%, 45.0%, and 40.9%, respectively. The LW-AR-OFHW mixture co-digestions enhanced the methane production of the co-digester (256 m 3 /ton VS), whereas AR and OFHW produced only 12 and 93 m 3 methane/ton VS, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-AnGS was prepared by a biologically induced mineralization method. • The effect of Fe-AnGS on performance and microbial community was studied. • Genes abundance for carbon dioxide reduction pathway increased by 29.40-43.54 %. • Inoculation of Fe-AnGS in MEC with glucose improved TMP CE by 11.83–29.30 %. • Fe-AnGS inoculation was an efficient strategy to establish and enhance DIET pathway. The magnetite nanoparticle-anaerobic granular sludge complex (Fe-AnGS) was formed by a biologically induced mineralization method, then applied in microbial electrolysis cells (MEC) to enhance the direct interspecies electron transfer (DIET) pathway via selective enriched electrogenic microorganisms for biogas production. Results showed with the highest Fe loading amount of 325.03 ± 8.40 mg/gVS, the magnetization and conductivity of Fe-AnGS were improved by 30.94 % and 29.16 %, respectively. The MEC with Fe-AnGS enriched the specific electrogenic microorganisms in the anode and cathode chambers. Simultaneously, genes coding for carbon dioxide reduction [M00567] increased by 29.40–43.54 % and 34.29–43.43 %, respectively. Inoculation of Fe-AnGS in MEC with glucose as substrate enhanced the experimental methane production of the cathode chambers (EMP C), and theoretical methane production of the cathode chamber (TMP CE) by 8.00–14.10 %, and 11.83–29.30 %, respectively. Consequently, inoculation of Fe-AnGS in MEC could establish and enhance the DIET pathway for methane production. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion (A co-D) performance of Phragmites australis , feces and kitchen waste with addition of clinoptilolite (one main kind of zeolite) was investigated to evaluate the improvement of biogas/methane production and internal mechanism of nitrogen and organics control. A better biogas/methane production was observed by 10% clinoptilolite (v/v) than bentonite and diatomite, with the shortest lag phase of 0.070 d −1 , the max rate of 15.89 L/(kg VS day) and ultimate biogas production of 308.2 L/kg VS as the modified Gompertz equation predicted. Accordingly, the content of methane in the biogas was increased from 44.10% to 65.30%. Furthermore, the clinoptilolite inhibited the acidification of digestion liquid (optimum pH 7.0–7.5) and enhanced the VFAs (acetic acid, propionic acid and butyric acid) destruction. Moreover, 10% of clinoptilolite optimally enhanced the microbial utilization of Ca 2+ /Mg 2+ , controlled the C/N ratio, and improved the biogas production as well as NH 3 -N/NO 3 -N inhibition efficiency. [ABSTRACT FROM AUTHOR]