Effect of the acclimated inoculant on improving the potential for biogas production at room temperature (∼28 °C) subjected to daily variations

Abstract

Agriculture and agribusiness generate waste rich in organic matter that can be degraded by biological processes and used as biomass for bioenergy. Inoculants to improve methane production in anaerobic reactors were developed using the anaerobic co-digestion of livestock manure (cattle, swine, and poultry) as biomass. These inoculants were prepared by anaerobic incubation of biomass with and without heating (constant at 35 °C and room temperature at 28 °C ± 3 °C, respectively) for 72 days. The identification of the microbiota in the inoculants, carried out by sequencing the amplicon of the 16S rRNA gene, showed differences between the inoculants in the two temperature conditions evaluated. Bacteroidetes was the most representative phylum in inoculants acclimated to ∼28 °C and Firmicutes in those inoculants acclimated to 35 °C. The inoculants were used as a starter of the anaerobic digestion process (livestock manure as biomass) in a 1 L anaerobic bioreactor for 77 days. The use of inoculants at room temperature (∼28 °C) improved the production of biogas and methane, reaching similar values to obtained at the ideal temperature (35 °C). The absence of heating probes in reactors conducted at room temperature resulted in a more favorable final energetic balance under this condition. The results are promising and show that it is possible to produce biogas in regions with temperatures slightly below those considered ideal for its production (35 °C) and highlight the economic viability of anaerobic digestion processes in such circumstances.