The potential of generating electrical energy from digester carbon waste sources at erwat wastewater treatment facilities, South Africa

Biogas, a renewable energy source, is generated from biomass under anaerobic treatment. Anaerobic treatment of biomass occurs within a vessel – also known as a digester – that is fully sealed off from air and usually has naturally occurring bacteria to allow digestion and the production of biogas. The objective of this study was to investigate the potential of generating electrical energy from digester carbon waste sources. A GIZ/WEC model was utilized together with other WWTP^a-based parameters to calculate the potential electricity that could be generated daily in two plants (Vlakplaats and Waterval), and the size of combined heat and power (CHP) suitable for the WWTPs was also identified. In terms of gaseous composition, four components were found in the biogas with CH₄ and CO₂ being the main constituents, having concentrations between 30%-38% and 62%-70% for CO2 and CH4, respectively. The electricity generated was on average 3 861 kWeh/day for the Vlakplaats plant and 21 777 kWeh/day for Waterval. Overall, the generation of electricity through the use of biogas is achievable, primarily when the amount of biogas produced on a daily basis reaches or exceeds the estimated biogas usage. The results obtained from this analysis showed estimate efficacy and consistency in the amount of electricity that can be generated.