| Abstract | Hydrothermal liquefaction is a promising technology for niche feedstocks like sewage sludge, food-wastes, bio-solids, organic waste streams etc. Availability estimates of these low or negative value waste feedstocks in the United States include: 15.2 million ton per year of food wastes, 5.9 million ton per year of waste fats and oils, 41.5 million ton per year of animal manure, and 13.8 million ton per year of sewage sludge. Collectively, these wastes have a potential of replacing a significant portion (up-to 25 % in some estimates) of US aviation kerosene demand. Bio-crude produced from HTL is generally heavier than conventional crude, with a high heating value as high as 35-40 MJ Kg-1 , heteroatom content around 10-12 weight percent, mostly oxygen and/or nitrogen depending on feedstock. Akin to crude oil upgrading in petroleum refineries, following various complex and interdependent hydro-processing, separations, and finishing steps, HTL bio-crude could be transformed to fungible biofuels (green diesel, sustainable aviation fuel, etc.) in standalone bio-refineries or co-processed in existing petroleum refineries thus eliminating significant capital investments and exploiting economies of scale offered by large existing upgrading facilities. There is also a possibility to use HTL bio-crude or its fraction directly in turbines and engines with minimum upgrading. Despite great potential and opportunities, HTL technology is still at a low readiness level and significant challenges exist that have hindered commercialization: lack of understanding of feedstock specific characteristics of complex bio-crudes and how these influence upgrading and end-use applications; its compatibility with petroleum crudes; challenges around upgrading catalyst performance; potential improvements in yields and quality of bio-crude to improve economics, and make it more amenable for upgrading/end-use; and ultimately its demonstration for end-use. The presentation will focus on some of these challenges with examples of recent research at NRC to bridge these gaps. |
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