Environmental Sustainability Assessment of a Microalgae Raceway Pond Treating Wastewater from a Recirculating Aquaculture System: From Upscaling to System Integration

Microalgal bacterial flocs (MaB-flocs) in an outdoor raceway pond operated as sequencing batch reactor are an innovative wastewater treatment system based on photosynthetic aeration. Recently the technical potential of this system was demonstrated in a pilot study treating aquaculture wastewater (Belgium). Not only the technical potential but also the environmental sustainability of this system needs to be known before implementing it on industrial scale. Therefore a life cycle assessment of this raceway pond at pilot scale and industrial scale (hypothetical upscaling) was performed. Furthermore, two integration scenarios were compared, using MaB-flocs as shrimp feed or to produce biogas. Upscaling reduces significantly the environmental impact of the plant, e.g. by consuming 68% less resources. At industrial scale, the valorisation of MaB-flocs as shrimp feed is preferable over biogas but improvement should be made to reduce the energy use of the system, especially by improving the energy-efficiency of the pond stirring system.