Advancing hydrogen production: A comprehensive review of wastewater reforming techniques, feedstocks, and opportunities
Wastewater is produced across nearly all human activities and requires treatment to safeguard human health and the natural environment. Treatment of wastewater often requires a large amount of thermal energy, resulting in wasted heat after the treatment process. Because hydrocarbon reforming needs both water and heat, the integration of wastewater treatment with hydrocarbon reforming, a process that produces synthesis gas rich in hydrogen, offers an excellent opportunity to utilize this waste heat and the impurities in wastewater to produce valuable hydrogen gas, to minimize waste from industrial processes, and to integrate water treatment with the hydrogen economy. Yet, no comprehensive literature review has been conducted to examine the integration of reforming and wastewater. To address this lack, we summarize the variety of catalytic reforming techniques available in the open literature and review the current literature on wastewater reforming with these techniques. Subsequently, we conduct a review of common types of wastewater contaminants and their possible effects on reforming catalyst performance and life. Lastly, three underexamined wastewater sources are identified, namely, oilfield wastewater, geothermal water, and mining and mineral processing wastewater, and their potential for future study as a reforming feedstock is examined.