Biogas production from municipal solid wastes using an integrated rotary drum and anaerobic-phased solids digester system

Abstract: This research was conducted to develop an integrated rotary drum reactor (RDR)-anaerobic-phased solids (APS) digester system for the treatment of municipal solid waste (MSW) to produce biogas energy and achieve waste reduction. A commercial RDR facility was used to provide a 3-d pretreatment and sufficient separation of the organics from MSW and then the organics were digested in a laboratory APS-digester system for biogas production. The organics generated from the RDR contained 50% total solids (TS) and 36% volatile solids (VS) on wet basis. The APS-digester was started at an organic loading rate (OLR) of 3.1gVSL−1 d−1 and operated at three higher OLRs of 4.6, 7.7 and 9.2gVSL−1 d−1. At the OLR of 9.2gVSL−1 d−1 the system biogas production rate was 3.5LL−1 d−1 and the biogas and methane yields were 0.38 and 0.19LgVS−1, respectively. Anaerobic digestion resulted in 38% TS reduction and 53% VS reduction in the organic solids. It was found that the total VFA concentration reached a peak value of 15,000mgL−1 as acetic acid in the first 3d of batch digestion and later decreased to about 500mgL−1. The APS-digester system remained stable at each OLRs for over 100d with the pH in the hydrolysis reactors in the range of 7.3–7.8 and the pH in the biogasification reactor in 7.9–8.1. The residual solids after the digestion had a high heating value of 14.7kJgTS−1. [Copyright &y& Elsevier]