Improving yields, compatibility and tailoring the properties of hydrothermal liquefaction bio-crude using yellow grease

Low quality waste feedstocks like food wastes, waste fats, manures etc. offer huge potential for replacing an appreciable quantity of petroleum crude. Owing to high water content of some of these feedstocks, hydrothermal liquefaction is the preferred route for its transformation. The present work performed in a continuous pilot scale hydrothermal liquefaction system studies the influence of yellow grease on the yields and quality of bio-crude, properties of bio-crude/blends, and its compatibility with petroleum fractions. Blends of food waste, yellow grease, and algae were used as feedstocks. Key fuel properties such as density and viscosity of bio-crudes and its blends with diesel and butanol were evaluated. Compatibility of different bio-crudes with petroleum fraction was investigated using microscopy imaging of blends of bio-crude and commercial diesel. Enhanced yields of bio-crude and lower asphaltene content were observed with the addition of waste lipids in the form of yellow grease while also decreasing the viscosity and density of bio-crude. Bio-crude from food wastes showed regions of compatibility at higher bio-crude concentrations while lower concentrations of bio-crude were incompatible. A combination of feedstock mix and blending of bio-crude could be used to improve the properties and compatibility of bio-crude for specific end-use devices and processes.