Towards biofuel generation III+: A sustainable industrial symbiosis design of co-producing algal and cellulosic biofuels

Abstract

The emergence of environmental and sustainability regulations as well as the limited availability of fossil fuels have brought the notion of gradually substituting petroleum products with biofuels into the limelight. The commercialization and large-scale adoption of cellulosic biofuel (second-generation biofuel) and microalgae biofuel (third-generation biofuel) have been hampered by their poor economic performance. Although the production wastes of biofuel can be utilized as input materials to enhance resource utilization efficiency, environmental sustainability and economic viability in each generation, rarely existing research has been conducted on the integration between these two generations. To fill this research gap, a novel industrial symbiosis (IS) design for the co-production of second- and third-generation biofuels is proposed in this paper. The material flow, energy flow, cost performance, and environmental impact models are established considering the interactions of stakeholders in the IS system. Four scenarios, consisting of the baseline case without IS and three IS cases with different microalgae species, are comprehensively compared in terms of various economic and sustainability performance indicators. Compared to the baseline case, the results reveal that the synergies in the bioenergy IS system render an annual manufacturing cost reduction of >10% in all IS scenarios. It is also discovered that the symbiotic design can lead to a 36% reduction in greenhouse gas (GHG) emissions, a 9.4% decrease in eutrophication potential (EP), and a 7.5% reduction in acidification potential (AP) when adopting the same species of microalgae. The synergies among the bioenergy IS system stakeholders are proved to be viable and beneficial to enhance the economic viability and environmental sustainability.