Techno-economic assessment of an integrated sewage treatment system for waste-to-ammonia and electricity generation†

Abstract

A techno-economic assessment was carried out for a novel system that combines anaerobic digestion, electrodialysis, electrochemical ammonia stripping, vacuum membrane distillation, and a direct ammonia-fed solid oxide fuel cell to generate electricity from sewage treatment. Traditional wastewater treatment systems focus primarily on removing contaminants with limited resource recovery opportunities. The current study presented an innovative wastewater treatment system designed to address the limitations of conventional plants. An assessment was performed to determine the scalability of the proposed system to effectively produce ammonia from municipal wastewater, which can be further used for electricity generation. The levelized costs of ammonia (LCOA) and electricity (LCOE) were determined along with the net present value, payback period, return on investment and benefit-cost ratio. Detailed evaluations of the cost and performance of each processing unit indicated that long-term cost savings can be achieved despite substantial initial capital investment. The proposed system can produce ammonia at 0.11 Mt per year, which can further generate around 254.58 GWh of electricity per year. The findings demonstrated that at a discount rate of 5% and assuming plant life to be 25 years, LCOA and LCOE were estimated at US$ 238.09 per ton of ammonia and US$ 0.16 per kWh of electricity, respectively. A sensitivity analysis was conducted by varying the discount rate (0–20%), which demonstrated that ammonia production was comparatively more financially stable at high discount rates under a certain threshold. The study provided a model for modern wastewater treatment plants aiming for energy neutrality and resource recovery, aligning with global sustainability goals. Future research can explore renewable energy integration with the assessed system to sustain long-term operations.