Integrated techno economic and life cycle assessment of the conversion of high productivity, low lipid algae to renewable fuels

Abstract

As microalgae becomes a feedstock of interest for biofuels production, technologies have advanced to provide a variety of methods for cultivation and processing. This study explores the economic viability and environmental impact of processing high productivity, low lipid, high ash content algae into biofuels using two different production pathways. The two processing pathways explored are, 1) Biochemical processing via protein and carbohydrate fermentation to produce fusel alcohol products, followed by hydrothermal liquefaction to produce a biocrude, and 2) Thermal-chemical processing via whole algal hydrothermal liquefaction and used as a baseline for the biochemical process. For a feedstock, this study considered algae harvested from an algal turf scrubber, which represents a robust high productivity system, at the expense of a producing a biomass with lower lipid content and higher ash compared to conventional algae production systems. Techno-economic results show the minimum fuel selling price of $12.85 and $10.41 GGE−1 for the biochemical and thermal-chemical pathways, respectively. Life cycle assessments shows a global warming potential of 111.2 g and − 2 g CO2eq MJ fuel−1 for the biochemical and thermal-chemical pathways, respectively. Sensitivity analysis on techno-economic model inputs identifies strategic areas for further research in an effort to move towards an economically viable process. Improvements in the system based on sensitivity and techno-economic analysis results show a pathway to $3.85 GGE−1. Discussion focuses on potentials for ash removal, decrease of biomass cost and potential for higher value products.