The crescent urbanization generates large volumes of solid residues and wastewater, more and more geographically concentrated. This worldwide trend has also created new challenges regarding energy generation and consumption. Renewable energy sources can be strategic to keep up with the increasing energy demand, especially for under developing countries whose population is large. This study focuses on designing a hybrid system based on photovoltaic energy, biomass gasifier, and electricity grid to optimize the energy supply and the costs of a wastewater treatment plant (based on activated sludge system with extended aeration, high energy-demanding process). The optimal combination of energy technologies, with and without electric energy generation from biogas combustion derived from anaerobic digestion of sewage sludge, was assessed to define the better cost-effective arrangement. The cost of energy for an off-grid biomass gasifier standing alone is USD 0.0426/kWh. However, in a grid-connected system including photovoltaic energy and biomass gasifier, the cost was reduced to USD 0.0298/kWh with an energy surplus available to supply the whole facility requirement and enough to supply 788,000 residential power consumers. The hybrid combination with biogas combustion can be an alternative for medium-sized wastewater treatment plants, promoting economic and environmental benefits. Moreover, the results of this case study could be applied to other similar facilities towards cleaner and optimized sewage sludge recycling.
Keywords: Biogas; Circular economy; HOMER software; Hybrid systems; Renewable energy.
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