Sustainable production of biodiesel by lipase catalysis in supercritical carbon dioxide: Revealing key research gaps, process engineering, scale-up, sustainability, circular economy perspective and challenges.

Presently, the world energy economy is gradually shifting from fossil to renewable energy economy because of climate change issues and shortfall of fossil fuel resources that demands the cleaner biobased energy production with consideration of circular bioeconomy. In context to this, the widespread research is already undergoing to launch the possible effective protocols for biodiesel synthesis. Among all important methodologies, the lipase catalyzed production of biodiesel in the supercritical carbon dioxide (sc-CO2) is the possible sustainable long-term alternative to obtain the bio-based fuel which eventually reduces the dependance of fossil fuels. However, effective lipase catalyzed production of biodiesel in sc-CO2 is challenging and attributed to various gaps in research (conceptual, methodology, practical, interdisciplinary) that impacted sustainable production of biodiesel. Addressing the research gaps in terms of challenges lead to open the door for more competent, economic and scalable protocols for the sustainable biodiesel production in sc-CO2 media. In view of this, the present review focuses on all aspects (i) market scenario, (ii) reaction engineering, (iii) media engineering, (iv) reactor uses, (v) scale-up approaches (vi) techno-economic (vii) life cycle assessment, and (viii) circular bioeconomy features that involving in biocatalytic synthesis of biodiesel in sc-CO2. Moreover, this review also reports the fulfillment of United Nations Sustainable Development Goals No. 7,9,11,12,13,14,17 (UN-SDG), green criteria parameters and challenges/opportunities considering the economic viewpoint for the cost-effective and sustainable lipase catalyzed production of biodiesel in sc-CO2.