PNNL

Abstract

This review considers developments over the past five years in which there has been a tremendous expansion of the research and development focused on the thermochemical processing of whole algae for the production of fuels. There are several key elements to this expanded interest in thermochemical processing: 1) the processing is applied to whole algae, not just lipid extracts, and as a result higher product yields have been demonstrated; 2) the feedstock composition is not so critical to the process, so that a wider range of algae growth scenarios have been considered; and 3) the envisioned products are actual hydrocarbon fuels, which are infrastructure compatible. Based on these three elements one can envision a more widely expanded utilization with more flexible growth options and more direct market applications of products. Algae can be processed by dry pyrolysis or in water slurry by hydrothermal liquefaction. In either case, the liquid oil product can be hydroprocessed to liquid hydrocarbon fuels. Recovery and recycle of nutrients is possible through treatment of the aqueous byproduct to promote sustainable production of the algae feedstock. In all cases the cost of the algae feedstock is the primary uncertainty in the economic analysis of such processing.