Techno-economic analysis of a novel hydrothermal liquefaction implementation with electrofuels for high carbon efficiency

This study describes a techno-economic analysis (TEA) to evaluate the feasibility of developing an electrofuel (eFUEL) system based on hydrothermal liquefaction (HTL). The system is developed to make use of the carbon in the aqueous and gas phases of an HTL process as inputs for the production of renewable transportation fuels, supplementing those from the ‘traditional’ HTL pathway. An Aspen Plus® model of the eFUEL system is developed containing a partial oxidation gasifier (POX), a reverse water gas shift (RWGS) reactor, and a Fischer–Tropsch (FT) process. The combined HTL, upgrading, and eFUEL (Electro-HTL) system is designed with a capacity of 1000 tonne of organic matter per day as input. The electro-HTL system increases carbon efficiency to 84.81% and the plant's fuel mass yield by 69.2% (from a yield of 27.8 to 47.0%) compared to a stand-alone HTL and upgrading system. The TEA of the electro-HTL system shows a minimum fuel-selling price (MFSP) of 26.06 USD GJ ⁻¹ , with a carbon efficiency of 84.91%. A sensitivity analysis is performed identifying hydrogen as the key cost influence on the MFSP. The study shows that the incorporation of the eFUEL system decreases the MFSP by 8.9% compared to the standalone HTL and upgrading system. The price generated by the electro-HTL system is 1.5–2.2 times higher than the price of fossil gasoline. In conclusion, the study shows that the production of renewable drop-in fuels using the electro-HTL system is not only cost competitive with other alternative fuel processes, but also with fossil fuels.