A review of dewatering and drying energy requirements in microalgae production: Pathways towards industrial uptake and bioeconomy integration

Microalgae gain increasing attention due to growing demand for diversified products such as food, feed and biotechnology systems aimed at addressing climate change and promoting sustainable production processes. They produce high quality fatty acids, amino acids and pigments, which can be utilized as ingredients across various industries. However, energy-intensive dewatering and drying technologies remain a significant barrier to cost-effective, large-scale microalgae production. This review aims at providing insights on how to possibly overcome such barriers, to enable and promote large scale industrial uptake of microalgae. Hereby, it summarizes current dewatering and drying methods, discussing their benefits and limitations. Pathways that can help overcome these barriers and enable industrial microalgae production are then discussed. Principles such as process optimization, exhaust drying heat recirculation, heat pump integration and industrial symbiosis are viable pathways that can enable industrial applicability. The review also presents how industrial side-streams, like wastewaters, excess heat and fume gas can be utilized in circular ways to promote cost-effective production and increased sustainability of different industries. The review aims to complement existing literature on microalgae harvesting, by adding and highlighting the importance of scaling-up and the necessity of removing barriers related to high production costs to achieve a sustainable circular economy. These insights into currently applied technologies and possibilities for industry symbiosis are beneficial for researchers, policymakers, and industry stakeholders striving to align microalgae production with the United Nations Sustainable Development Goals (SDGs), particularly SDG 7, SDG 12, and SDG 13, by offering practical pathways to reduce energy demands, promote circular economy principles, and mitigate greenhouse gas emissions in industrial systems.