Optimization of biogas production through anaerobic digestion of municipal solid waste: a case study in the capital area of Reykjavik, Iceland

Abstract

BACKGROUND Biogas is a valuable carbon-free renewable energy source that can be produced from anaerobic digestion of organic waste. Accordingly, biogas production is promoted worldwide in efforts to reduce carbon emissions and optimize the recovery of resources from waste streams. In this paper the biogas production from bioresidues collected in the capital area of Reykjavik was modelled in Aspen Plus v10. RESULTS Municipal solid waste (MSW), food waste (FW) and lignocellulosic biomass (LCB) were the feedstocks used in this research. A total of 16 scenarios were simulated at thermophilic temperature conditions of 55°C. Each scenario accounted for different inlet mass flows, varying the kind of feedstock, i.e. MSW, FW, LCB, or co-digestion of various feedstocks, using two model approaches: (i) one digestion stage and (ii) two stages coupled in series. Sizing, costing and environmental aspects were analysed for all the scenarios. A sensitivity analysis was carried out by changing the substrate concentration and studying its effect on the methane mass flow. Simulations showed biogas yields measured in millilitres per gram of volatile solids (VS) in the range 305.5-406.4 mL g-1 VS (single-stage approach); and biogas yields ranging from 64.78 to 358.8 mL g-1 VS (two-stage approach). Maximum methane yields were obtained using LCB as feedstock resulting in 106.0 mL g-1 VS. CONCLUSIONS From a technical viewpoint the highest biogas yield is obtained when using MSW whereas optimum calorific value of biogas and electrical power potential is achieved working in co-digestion of various feedstocks.