Fourth-generation (4G) biodiesel: Paving the way for a greener and sustainable energy future in emerging economies
Ajeet Kumar Prajapati, Annanya Mahajan, Shraddha M. Jadhav, Karan Kumar
Abstract
Biofuels have gained increased attention in the context of sustainable development and the pursuit of net-zero emission goals amidst the ongoing global energy crisis. Consequently, there is a growing exploration of biobased substitutes for sustainable feedstocks to produce biomass-based bioenergy. The primary focus has been on fourth-generation (4G) biodiesel, which stands out as a promising renewable energy resource with significant potential as a new alternative fuel. This interest is coupled with a focus on various biological processes, including genetic modification and engineering strategies, aimed at enhancing the accumulation of lipids, alcohols, hydrocarbons, polysaccharides, and other energy storage compounds in photosynthetic organisms such as microalgae, yeast, and bacteria. This review comprehensively covers the entire biological process of producing 4G biodiesel, including genetic engineering or stimulation of genes. Additionally, it encompasses various aspects, such as feedstock availability, chemical compositions, market analysis, anticipated demand, and program policy. Furthermore, it examines potential avenues of a biological approach, such as genetic engineering, which can improve the production of 4G biodiesel and different elements that influence product yield and quality, including feedstock-related properties and different system conditions. The review also outlines the future availability of 4G biodiesel and hydrotreated vegetable oil (HVO), emphasizing their potential contributions to meeting the sustainable development goals. • Accelerating fourth-generation (4G) biodiesel development as a sustainable energy solution. • Reviews state-of-the-art genetic-engineering strategies in algae, yeasts and energy crops to maximize lipid productivity. • Compares edible, non-edible, waste-oil and microbial feedstocks on yield, cost and life-cycle sustainability. • Quantifies 4G biodiesel's potential to displace fossil diesel and cut greenhouse-gas and criteria-pollutant emissions. • Critically evaluates blend mandates, fiscal incentives and market mechanisms to scale 4G biodiesel in emerging economies.