Techno-economic analysis of renewable fuels production from sewage sludge through hydrothermal liquefaction

In this work, techno-economic evaluation of renewable fuels production from sewage sludge using hydrothermal liquefaction method is investigated. The process design of the plant includes wastewater treatment for sewage collection, hydrothermal liquefaction for biocrude production, hydroprocessing for biocrude upgrading, and hydrogen production. A steady-state simulation is first conducted to predict the mass and energy flow rates of the plant for the manufacture of renewable fuels. Then, the economic calculation is performed to obtain a minimum selling price (MSP) of the renewable fuels using the results of a steady-state simulation. The MSP of renewable fuels is obtained at US$4.04/ Gasoline Gallon Equivalent (GGE). The predicted value closely matches the literature findings. Furthermore, the analysis of sensitivity is conducted to find the influential parameters that affect the MSP of renewable fuels. It is found that biocrude yield and operating cost have a significant effect on the MSP of renewable fuels. This study provides the feasibility of large-scale production of the renewable fuels from the sludge and also guides future plant design/optimization. This will drive further research and development activities towards to circular economy.