Waste-to-biofuel integrated system and its comprehensive techno-economic assessment in wastewater treatment plants.

Combining wastewater treatment and biofuel production is considered the cost-effective way for better waste remediation and lowering the environmental impact for biofuel production. In this study, an innovative integrated system incorporating sludge, scum and centrate treatment and biofuel production was developed. A comprehensive techno-economic analysis was conducted to evaluate the technology and economic feasibility of the integrated system with the consideration of biofuel production, wastewater treatment improvement, tax credits, carbon credit, and coproducts utilization. Benefited from the integrated system that the intermediate byproducts can be used in between the sub-systems, such as the glycerol generated from the scum-to-biodiesel production can be used as an organic carbon for the centrate-to-algae production, the estimated breakeven selling price of the bio-oil ($1.85/gallon) is very close to the 5-year averaged crude oil price. The assessment result showed the payback period and the IRRs of the integrated system are superior in comparison with others.