Hydrothermal Liquefaction of Food Waste and Remediation of Aqueous Byproducts

Thermochemical processing via hydrothermal liquefaction (HTL) is capable of processing a broad range of feedstocks, has a favorable net energy ratio, and produces an energy-dense liquid bio-oil product. However, there is an obstacle with current HTL processes that has hampered adoption of this technology—the HTL process produces a considerable amount of aqueous organic byproducts, which limits oil yields and complicates waste disposal. Mainstream’s approach is two-pronged: 1) use heterogeneous catalysts during hydrothermal liquefaction to improve oil yields and decrease aqueous waste and 2) perform hydrothermal gasification to convert aqueous waste to permanent gases. HTG gases (H2, CO2, and CH4) can then be recycled to the HTL reactor to improve oil yields and reduce residence time. In Phase I, Mainstream proved technology feasibility, developing the process to TRL 4, and demonstrating improved oil yields and effective gasification. In Phase II, Mainstream will further develop the combined HTL/HTG reactor to TRL 7, maximize oil yield, minimize aqueous organics, and demonstrate the process with an integrated, continuous reactor. The proposed hybrid HTL/HTG process is focused on the conversion of waste biomass material to a renewable fuel that would displace petroleum-derived fuels, thereby addressing both a waste disposal challenge and a renewable fuel challenge. The public will benefit from renewable energy, less waste entering landfills, and reduced environmental impacts from liquefaction processes.