Performance of second-generation microbial protein used as aquaculture feed in relation to planetary boundaries

Carbon and nitrogen present in residual water streams can be converted into microbial protein and used as animal feed in aquaculture. While microbial protein is thought to be more environmentally sustainable when compared to proteins made from fish residues or plants, nothing is known about how it performs in an absolute sustainability perspective, relative to planetary boundaries. Here, a systems-oriented analysis using life cycle assessment (LCA) linked to the planetary boundaries framework was conducted to assess environmental performance of a pilot-scale microbial protein production from starch-rich process water using aerobic heterotrophs. Results showed that while this microbial-protein indeed performed significantly better than just fishmeal or soybean meal for impacts related to nitrogen (N) and phosphorus (P) flows, none of the three feeds were found sustainable in relation to all planetary boundaries. This constitutes an opportunity for technology developers when the microbial protein production is scaled up and matures.