Abstract:
The present study intends to evaluate a synergy towards enhanced biogas production
by co-digesting municipal sewage sludge (SS) with brewery spent grain (BSG). To execute this,
physicochemical and metagenomics analysis was conducted on the sewage sludge substrate. The
automatic methane potential test system II (AMPTS II) biochemical methane potential (BMP) batch
setup was operated at 35 ± 5
◦C, pH range of 6.5–7.5 for 30 days’ digestion time on AMPTS II
and 150 days on semi-continuous setup, where the organic loading rate (OLR) was guided by pH
and the volatile fatty acids to total alkalinity (VFA/TA) ratio. Metagenomics analysis revealed that
Proteobacteria was the most abundant phyla, consisting of hydrolytic and fermentative bacteria. The
archaea community of hydrogenotrophic methanogen genus was enriched by methanogens. The
highest BMP was obtained with co-digestion of SS and BSG, and 9.65 g/kg of VS. This not only
increased biogas production by 104% but also accelerated the biodegradation of organic matters.
However, a significant reduction in the biogas yield, from 10.23 NL/day to 2.02 NL/day, was
observed in a semi-continuous process. As such, it can be concluded that different species in different
types of sludge can synergistically enhance the production of biogas. However, the operating
conditions should be optimized and monitored at all times. The anaerobic co-digestion of SS and
BSG might be considered as a cost-effective solution that could contribute to the energy self-efficiency
of wastewater treatment works (WWTWs) and sustainable waste management. It is recommended to
upscale co-digestion of the feed for the pilot biogas plant. This will also go a long way in curtailing
and minimizing the impacts of sludge disposal in the environment.
