Carbon Footprint of Hydrothermal Liquefaction of Microalgae Biomass Cultivated in Availability and Limitation of Nutrients

Abstract

This work aimed to assess the carbon footprint of microalgae biomass processing in hydrothermal liquefaction (HTL) to produce biopetroleum and co-products. The foreground inventory covered the cultivation in open ponds with availability (C1) and limitation (C2) of nutrients, followed by harvesting and processing in HTL for 1 kg of microalgae biomass in total solids. The ecoinvent™ 3.6 databases and IPCC- 2021 GWP 100 years method were used for background inventory and impact indicator in openLCA® 1.11.0. The carbon footprint of C1 (1.1 kg CO2eq) was more significant than that of C2 (0.7 kg CO2eq). The most considerable carbon footprint contribution per stage was the Production stage (cultivation and harvesting), with 64%-88%, in the evaluated scenarios. In comparison, this per process was the fertilizer (71%) in C1 and the heat (32%) in C2.