(2025) Energy_Integrated microalgae–insect cultivation for enhanced carbon-negative biodiesel production

Park G.; Kim J.Y.; Choi Y.; Sim S.J.; Park W.-K.; Kwon E.E.

(Elsevier Ltd) Energy ISSN: 3605442 Vol.335 Issue. Article No.138225 DOI: 10.1016/j.energy.2025.138225

Black soldier fly larvae (BSFL) are promising feedstocks for large-scale biodiesel production owing to their short growth cycle and high lipid content. However, the CO₂ emissions associated with BSFL cultivation compromise the overall process sustainability. To mitigate this issue, this study used the CO₂ fixation capability of Chlorella sp. HS2 by using defatted microalgae as feed for BSFL. Despite using a defatted substrate, BSFL synthesized 20.9 % lipid. Therefor, the integrated cultivation system can enhance lipid productivity by providing lipids from microalgae and BSFL. Microalgal lipids, which are rich in free fatty acids, challenge conventional alkaline-catalyzed transesterification because of the side reactions. To circumvent this, we introduced a thermally induced transesterification process, which achieved a biodiesel yield of 55.1 wt% from Chlorella lipids within 1 min at 380 °C (an eight-fold increase in yield from microalgal lipids compared with conventional catalytic methods). The same process applied to BSFL lipids yielded 87.5 wt% biodiesel, indicating greater reaction selectivity. The blended biodiesel derived from microalgal and larval lipids exhibited improved oxidative stability and flash point. The integrated cultivation system achieved a net CO₂ reduction of 3.7 g per gram of biodiesel. © 2025 Elsevier Ltd

This work was supported by the National Institute of Biological Resources (NIBR), funded by the Ministry of Environment (MOE) of the Republic of Korea (grant number NIBRE202505 ); and the National Research Foundation of Korea (NRF), funded by the Korean Government ( MSIT ) (grant number RS-2023-NR077231 ).