A new co-production (biogas& biodiesel) plant under a microalgae-to-biofuel process designed under a hydrothermal disintegration/ deep eutectic solvent process

Abstract

Microalgae-to-biofuel process can be introduced as one of the promising alternatives to non-renewable resources due to its outstanding advantages. However, the industrial feasibility of employing deep eutectic solvents (DESs) for pretreatment of microalgae remains a relatively uncharted territory, which had been acknowledged as a noteworthy research gap in the literature. The purpose of the article is to develop life cycle and energetic analyzes of a co-production (biogas& biodiesel) plant under a microalgae-to-biofuel process. The proposed biofuel production process is based on a hydrothermal disintegration (HD)/DES cycle. An in-depth analysis and comparison between HD/DES of microalgae for the concurrent production and the conventional HD process is developed. Additionally, the effectiveness of recrystallization and membrane filtration for DES recovery was developed. Finally, the sensitivity analyses, focusing on variables like lipid recovery, DES usage quantity, the efficiency of DES recovery, and biogas yield, are provided. When compared to traditional HD, the incorporation of DES during HD led to a substantial 36.8 % improvement in energy output. However, this came at the cost of higher energy input, resulting in a rise in ratio of net energy by 28 %, primarily due to the energy-intensive nature of DES synthesis. Additionally, the introduction of DES contributed to a slight increase in overall released GHG, from −25.86–25.72 g CO₂ (eq.) per MJ. Notably, a combination approach involving both membrane filtration and recrystallization yielded promising results, achieving a low ratio of net energy of 0.46 and even negative overall released GHG. The sensitivity analyses findings emphasized the need for reducing energy utilization in DES synthesis and addressing more energy-efficient recovery processes to further enhance the HD/DES process's environmental performance and energy efficiency. This study provides valuable insights into optimizing the co-production plant under a microalgae-to-biofuel process through HD/DES, highlighting avenues for sustainability improvements in this promising approach.