Economic and Environmental Analysis of the Hydrothermal Liquefaction Process of Animal Byproducts

Animal byproducts consist of parts of animals or products of animal origin not intended for human consumption. The recovery and treatment of this kind of waste are a challenging problem because of its high volume and heterogeneous nature. In this sense, previous studies have shown that hydrothermal liquefaction (HTL) can be a viable technology for transforming these wastes into a valuable biofuel. In this paper, a comparative preliminary analysis of costs and resource consumption (water and energy) between HTL and pyrolysis for this type of byproducts has been performed. The results indicate that HTL with aqueous phase recycled is the most favorable treatment. Additionally, a life cycle assessment has been developed for the selected option, including the combustion of the liquid biofuel obtained. Gas combustion, HTL gas phase, aqueous phase, solid fraction, and electricity demanded have been the five burdens analyzed to evaluate the corresponding environmental impacts and damage categories at different levels. Thus, at the aggregated endpoint level, the analysis indicates that the use of the biofuel obtained from HTL produces a strong reduction in the CO2 emissions per kilowatt hour of electricity produced compared with fossil fuel.