Techno-economic and environmental assessment of anaerobic co-digestion plants under different energy scenarios: A case study in Morocco

Abstract

Developing countries face major challenges related to energy management and environment preservation, which have sparked interest in anaerobic digestion. Therefore, this study evaluates the techno-economic and environmental feasibility of anaerobic co-digestion plants in four Moroccan cities (i.e., Casablanca, Agadir, Temara, and Essaouira). These plants treat the organic fraction of municipal solid waste and sewage sludge under different energy scenarios. The considered scenarios involve burning the entire volume of the produced biogas in combined heat and power (CHP) units for electricity and heat co-generation (scenario 1), combusting a fraction of the biogas to meet the plants’ energy needs and upgrading the rest into biomethane (scenario 2), and upgrading all of the biogas into biomethane while satisfying the plants’ electric and thermal needs through electricity purchase and solar thermal systems (scenario 3). The economic evaluation results indicate that the AD plants in very large Moroccan cities (e.g., Casablanca) can be financially feasible only if scenario 3 is adopted, with an internal rate of return (IRR) of 10.14%. Concerning large, midsized, and small Moroccan cities (e.g., Agadir, Temara, and Essaouira, respectively), scenario 2 is the most economically viable, with IRR values of 13.85%, 13.64%, and 12.18%, respectively. Furthermore, the sensitivity analysis shows that the capital cost and biogas volume have the biggest impact on the profitability of the considered AD plants. From an ecological standpoint, findings show that scenario 1 is the most environmentally friendly for all the considered cities, followed by scenarios 2 and 3 (1.95, 2.02, and 2.30 kg CO2-eq/m3biogas, respectively). Additionally, using biogas as a fuel for energy production has been shown to reduce the emitted greenhouse gases by up to 37% compared to coal and by 24% compared to oil.