Biomethane Recovery Potential from Brewer’s Yeast Using Two-Stage Anaerobic Digestion

The brewery industry is a major global industry which produces several waste by-products, one of which is Residual Beer Yeast (RBY). After series of treatments, the RBY, because of its high nutritional content, is either sold as animal feed to generate some revenue or disposed of in the landfill. The treatment of RBY is an additional expense for the brewery sector as it involves chemical and thermal treatments. This makes it crucial to explore alternatives such as biogas production from the Anaerobic Digestion (AD) process to generate revenues that can aid in sustaining the brewery sector. In this study, an evaluation of the single-stage and two-stage anaerobic digestion process using Biomethane Potential Assay on RBY has been performed to assess the methane production from RBY. Before setting up a two-stage reactor, the RBY was pre-treated using the High-Rate Hydrolysis/Acidification (HRHA) process to further evaluate the effect of HRHA on RBY treatment. The average Total Suspended Solid (TSS) solubilization of 15.54% for TRBY had resulted in the increase in methane production from 68 ± 8 L CH4/L sample for the single-stage reactor to 74.9 ± 10 L CH4/L sample in the two-stage reactor for the pre-treated RBY. It also reduced the time to half (10.8 days) for treated RBY as compared to untreated RBY (21 days) for the 402 mL substrate. Furthermore, the TSS solubilization did not increase in soluble COD, implying that mostly colloidal aggregates were formed. The Total COD (TCOD) removal efficiency was 7% higher in the two-stage AD process as compared to the single-stage AD process