Supercritical Water Gasification and Oxidation for Waste Treatment: A Systematic Review of Feedstocks, Catalysts, and Scale-Up Strategies

In recent times, Supercritical Water Gasification (SCWG) and Supercritical Water Oxidation (SCWO) technologies are rapidly advancing as promising solutions for solid & liquid waste management. We conducted a systematic review on various feedstocks (sewage sludge, oily sludge, industrial waste, biomass, animal wastes, and pharmaceutical effluents), using multiple types of catalysts (alkaline, Ni-Mo, Ru-based & hybrid), and the scale-up challenges together. The methodology used in this review paper follows the PRISMA guidelines, including literature search, inclusion and exclusion criteria, and content analysis. The dataset for this systematic review paper solely selects journal articles on either SCWG or SCWO published between 2020 and 2025, resulting in 86 papers after screening and excluding irrelevant ones. The findings underscore the critical need for scalable, durable catalysts and reactor design that will address waste issues. This integration of SCWO and SCWG is highly feasible for destruction and energy recovery from waste. Partial advancements include modular heater design, ultrasonic descaling, autothermal operation using methane and ethanol co-fuel, and salt recovery modelling. It will be possible to take this technology to a sustainable and commercial level through low-cost and long-life catalysts, real-time salt control, and hybrid SCWG-SCWO coupling.