Sustainable biodiesel synthesis via non-catalytic transesterification of biomass waste-derived oil and ethanol

Abstract

Ethanol (EtOH)-based biodiesel, known as fatty acid ethyl esters (FAEE), offers better fuel properties than methanol-based biodiesel. Given that EtOH can be produced via fermentation of lignocellulosic waste, the use of waste-derived ethanol represents an environmentally sustainable strategy for biodiesel production. In this approach, EtOH and oil are derived from waste materials, such as silkworm litter and discarded silkworm pupae, reinforcing the potential for an integrated waste-to-biofuel platform. This study demonstrated that EtOH production from silkworm litter hydrolysed using yeast was comparable to that from synthetic media, highlighting a green and cost-effective method for EtOH synthesis. EtOH was used in the transesterification process to convert oil extracted from silkworm pupae (which had a high oil content of 32.0 wt%) into biodiesel. Given the presence of impurities in pupal oil, a non-catalytic transesterification process was selected as it remained unaffected by such contaminants. Based on the availability of silkworm litter and discarded silkworm pupae, it was estimated that 50% of the required energy could be supplied by energy production from in situ waste. This innovative waste-to-energy strategy provides a sustainable method for FAEE production and contributes to the environmental and economic sustainability of the textile industry.