Sustainability metrics on microalgae-based wastewater treatment system

This paper presents a life cycle assessment of a simulated large-scale process of agroindustrial wastewater treatment through microalgal heterotrophic bioreactors. The study focuses on establishing sustainability metrics for recovering energy and nutrients from wastewater to produce bulk oil and lipid extracted algae (LEA) in an integrated process. The experimental data, obtained from a benchscale facility, were used to estimate the life cycle impacts of a wastewater treatment plant with a capacity of 16,000 m3/d, with a production of 4.32 ton/d of biomass, fractioned in 0.84 ton/d of bulk oil and 3.45 ton/d of LEA. The sustainability metrics of the integrated process indicate a net energy ratio of 0.41, reduction of 98% of the water footprint, global warming potential of 47 × 106 kgCO2eq/y, eutrophication potential of 5 × 104 kg eq PO4/y, acidification potential of 7 × 104 kg SO2-eq/y and ozone depletion potential of 3.33 kg CFC-11-eq/y. The assessment of the life cycle demonstrated that this technological route presents itself as a new sustainable approach for wastewater treatment plants and their implementation and dissemination can help to support a change towards resource recovery and a sustainable circular economy.