Techno-economic and environmental assessment in wastewater valorisation to recover green value-added products towards circular economy: Hydrogen, ammonia, and methanol

Circular economy is a promising future across various sectors to solve environmental issues such as global climate change by recovering and recycling the resources. In the globe, various industrial sectors are highly dependent on the fossil fuel-based electricity generation causing global warning potential. In this context, hydrogen utilization is highlighted to substitute fossil >ired energy resources. However, hydrogen production has relied on as byproduct from petrochemical industry; this grey hydrogen production emitted anthropogenic greenhouse gases (GHGs) such as carbon dioxide (CO₂). Hydrogen delivery is additionally problematic issue due to large volume of hydrogen gas. In this context, methanol and ammonia are promising hydrogen carrier to accelerate hydrogen delivery and utilization; they face problems of 1) non-greener process to produce ammonia and 2) insuf>icient biomass to produce methanol. Wastewater treatment plant (WWTP) treat mainly organic pollutants, and it can recover energy from treated organic pollutants. Furthermore, anaerobic digestion (AD) in WWTP provides abundant biogas including CO₂ and CH₄. The biogas from AD can be reformed to produce methanol and hydrogen; furthermore, reject water from AD includes strengthened ammonium and it can be stripped and converted to ammonia. This study aims to conduct comparative analyses to identify the implementable pathways towards circular economy among wastewater to hydrogen, ammonia, and methanol. This study uses techno-economic assessment (TEA) and life-cycle assessment (LCA) for hydrogen, ammonia, and methanol recovery from WWTP. Considering technology readiness levels, diverse methods for hydrogen, ammonia, and methanol recovery such as steam methane reforming (SMR), biogas upgradation system, and stripper were considered. This research indicates H₂, NH₃, and MeOH production from wastewater can reduce the production cost of 28.5%, 38.3%, and 18.6% than conventional production methods, with acceptable GHGs emission.