Nannochloropsis for the bioremediation of brewery side streams and co-production of aquaculture feed and bio-Fertiliser: A comprehensive review

Abstract

The brewing industry produces a large amount nutrient-rich wastewater. This review proposes a framework that harnesses autotrophic microalgae to establish a circular brewing industry. The study focuses on Nannochloropsis due to their high omega-3 polyunsaturated lipids and protein content, enabling the upcycling of brewery wastewater into aquaculture feed and biofertiliser. In the proposed system, Nannochloropsis is cultivated on brewery wastewater under mixotrophic conditions, and the resultant biomass is used as a fishmeal replacement or biofertiliser. This approach reduces chemical and energy demands for brewery wastewater treatment, while also alleviating aquaculture's reliance on fishmeal derived from unsustainable wild-caught fishing and agriculture's dependence on carbon-intensive mineral fertilisers. A summary of the research to-date on the cultivation of microalgae on brewery wastewater, the use of brewer's spent grain as widely available and inexpensive carbon for microalgal fermentation, the application of Nannochloropsis in aquaculture and bio-fertiliser, and techno-economic and life-cycle assessments of the proposed system are provided. A mass balance of the system suggests that for every 1000 L of brewery wastewater that is treated, 1.0–1.4 kg of Nannochloropsis biomass can be produced, enabling the removal of 95–100 % of N and P and 60–90 % COD reduction from the wastewater and the direct capture of 0.7–1.3 kg of CO₂, while producing 0.4–0.8 kg of lipids for aquafeed formulations and 0.6–1.0 kg of biomass residue for biofertilisers. An integrated approach that combines laboratory research with pilot-scale validation and iterative techno-economic assessments is needed to inform optimisation and guide scale-up.