Hydrothermal liquefaction technology for co-processing of wastewater sludge and other solid wastes for bioenergy production

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A promising hydrothermal liquefaction (HTL) technology (PCT patent pending, file # 349-264-P) has been developed, partnering mainly with Trojan Technologies, and a few other industrial partners. The technology realizes co-processing of high-water-content wastewater sludge and other solid wastes such as municipal solid waste (MSW) and forestry/agricultural residues for co-production of bio oils and biogas. In our previous lab-scale tests in both a 100 mL batch reactor and a lab-scale continuous-flow HTL reactor (0.6 kg/h), the operating conditions including reaction temperature, reaction time and solids concentration were optimized based on the response surface methodology for the maximum bio-crude oil production. The two by-products from this process (bio-char and water-soluble products (WSP)) can be used to produce energy as well.Bio-methane Potential (BMP) test on the obtained WSP demonstrated excellent fermentability for biogas production by anaerobic digestion (AD). In this proposed I2I Phase I (reduction-to-practice) project, we aim to advance this HTL-AD process by scaling up the process for treating mixed wastes at 6 kg/h treatment capacity(10 fold scale up). The operating conditions will be optimized for the 6 kg/h scale HTL reactor system for the maximum bio-oil production. Mixtures of waste activated sludge and various types of solid wastes such as wood sawdust, cornstalk, and MSW will be investigated in the 6 kg/h scale HTL reactor system. In addition, a 5 L batch bioreactor will be constructed for AD tests of the water-soluble products for biogas production in addition to the BMP test. Finally, a techno-economic analysis for a full-scale plant (16 t/h sludge treatment capacity) will be performed, and compared with a conventional process (WAS anaerobic digestion digested sludge dewatering - landfill or incineration) as a benchmark. The research results from this I2I Phase-I project can be used for the decision making and design of full-scale HTL plants.