Abstract
M.Sc. (Environmental Management)
Biogas, a renewable energy source, is generated from biomass under anaerobic treatment. Anaerobic treatment of biomass, which is usually sludge at the stage of anaerobic digestion, occurs within a vessel – also known as a digester – enclosed of air and usually has bacteria derived from the incoming waste for digestion and the production of biogas. The main objective of this study was to investigate the electrical energy potential from digester carbon waste sources utilizing analyses from the gas and a basic excel software model. For this purpose, we used selected wastewater treatment facilities of the East Rand Water Care Company (ERWAT) that had gas reservoirs and sampling points available. The GIZ/WEC model was utilized together with other WWTP-based parameters to calculate potential electricity that could be generated daily in two plants (Vlakplaats and Waterval). The size of combined heat and power (CHP) suitable for each of the WWTPs to generate power from the biogas generated was also estimated. We found four components in the biogas (CH4, CO2, traces of H2S and O2) with CH4 and CO2 being the main constituents. The concentrations of these main constituents were 30%-38% and 63%-70% for CO2 and CH4, respectively. The potential electricity calculated was on average 3 861 kWeh/day for the Vlakplaats plant and 21 777 kWeh/day for Waterval. These values change as the biogas production varies depending on the operational conditions. This study shows that future generation of electricity using biogas is achievable at these plants. Although this study is not new it clearly emphasizes the potential of biogas utilization as a cost saving incentive at the plants where analysis was conducted.