Microalgae Oil Production: A Downstream Approach to Energy Requirements for the Minamisoma Pilot Plant

Abstract

This study investigates the potential of microalgae oil production as an alternative renewable energy source, in a pilot project located at Minamisoma City in the Fukushima Prefecture of Japan. The algal communities used in this research were the locally mixed species, which were mainly composed of Desmodesmus collected from the Minamisoma pilot project. The microalgae oil-production processes in Minamisoma consisted of three stages: cultivation, dewatering, and extraction. The estimated theoretical input-energy requirement for extracting oil was 137.25 MJ to process 50 m3 of microalgae, which was divided into cultivation 15.40 MJ, centrifuge 13.39 MJ, drum filter 14.17 MJ, and hydrothermal liquefaction (HTL) 94.29 MJ. The energy profit ratio (EPR) was 1.41. The total energy requirement was highest in the HTL process (68%) followed by cultivation (11%) and the drum filter (10%). The EPR value increased along with the yield in the cultivation process. Using HTL, the microalgae biomass could be converted to bio-crude oil to increase the oil yield in the extraction process. Therefore, in the long run, the HTL process could help lower production costs, due to the lack of chemical additions, for extracting oil in the downstream estimation of the energy requirements for microalgae oil production.

Keywords

• microalgae
• energy requirement
• hydrothermal liquefaction
• energy profit ratio