Quality of biogas generated through co-digestion of Brewer’s spent grain and cattle dung

Abstract

Anaerobic Digestion (AD) of mono-substrate is reported to be ineffective due to nutritional imbalance and lack of a variety of microbes. Anaerobic co-digestion of substrates is the advised alternative to mono-digestion to boost the generation of quality biogas. Brewers’ Spent Grains (BSG) contain high organic matter content and can be used in the production of biogas towards reducing the reliance on fossil fuel-based energy sources. Biogas generation from BSG can be improved through the co-digestion process via the inclusion of extra substrate. The current study explored the quality of biogas generated through co-digestion of BSG and cattle dung (CD). Digestion of two substrates was managed at a retention time of 10 days at BSG: CD ratios: 1:3, 1:2, 1:1, 2:1, 3:1, BSG and CD control experiments with substrates combination of 4.5 kg in each setup. Plastic bottles (10 L) were used as bio-digesters with substrates and water at a 1:1 ratio to allow anaerobic digestion (AD) to proceed. Results showed that BSG: CD ratios of 1:3 and 1: 2 with total solids (TS) content of 9.24% and 8.95% produced the highest quality raw biogas rich in methane. Both ratios 1:3 and 1:2 produced Methane which exhibited a 100% lower explosive limit (LEL) at an average of 40.3 ± 29.88 % LEL d−1 and 40.28 ± 33.39 LEL d−1 respectively; with a respective methane content of 54.7 ± 10.74% CH4d−1 and 51.9 ± 8.67% CH4d−1. The current study provides a facile and convenient optimal ratio between BSG and CD for the production of high-quality biogas using environmentally prevalent materials.

Keywords

• Anaerobic co-digestion
• Biogas
• Brewer’s spent grain
• Cattle dung
• Flammability