Process development for green diesel and bioethanol production using Chlorella sp. ABC-001

Abstract

Microalgae are promising as biofuels, but most researches have been focused on the cultivation process (upstream process). For the overall development of ‘microalgae to biofuel’, however, attention to the subsequent process is essential. To this end, in this study, microalga Chlorella ABC-001 was used to develop and optimize technology of the subsequent process, which is extraction process and conversion process. Also, by using the lipid-extracted microalgal solution was established a process to additionally obtain bioethanol. More specifically, 88.6% of carbohydrates of Chlorella sp. ABC-001 50 g/L was hydrolyzed to monosaccharides at 170 °C, 0.1 N H2SO4, and 4 min. Subsequently, the liquid phase and solid phase were separated through low-speed centrifugation of the hydrolysate, thereby significantly reducing the time and energy for lipid extraction using hexane. The extracted microalgal oil was hydro-converted through an in-situ generated MoS2 catalyst to be removed 98.2% of oxygen, and it was confirmed that H/Ceff reached 2.01 to become a saturated hydrocarbon suitable for green diesel. Also, it has been proved that this catalyst is superior to other conventional catalysts and has excellent reusability. And, the hydrolysate solution produced through acid hydrolysis was used as a medium of Saccharomyces cerevisiae KL17 for bioethanol production, and various acids and subsequent processes were compared and selected. As a result, the bioethanol yield of the hydrolysate using H2SO4 and Ca(OH)2 showed a yield similar to that of the conventional medium. Finally, as a result of applying whether a series of developed processes are suitable for other microalgae, it was feasible to most microalgae. Therefore, this study is a significantly improved and superior process than the conventional extraction and conversion processes and will be a great cornerstone for the production of biofuels derived from microalgae in the future.