Bio-Based Circular Economy and Polygeneration in Microalgal Production from Food Wastes: A Concise Review

The production of biofuels from microalgae has gained considerable attention due to the rapid diminution of fossil fuels. Despite major advantages, microalgal biofuels deployment still faces obstacles associated with the cost of biomass production and waste disposal. The production could become more cost-effective and feasible if the wastes in the production processes are recycled/reused and the biofuels produced are co-produced with high-value co-products. The aim of this review is to discuss and analyze the importance of recycling/reusing wastes and co-producing high-value products to be implemented with biofuels from microalgal-based processes. Recent advances in circular economy/integration and polygeneration, as proper strategies, are discussed. Circular economy and integration entail the reuse of food wastes, waste biomass, and wastewater in microalgal conversion processes for producing biofuels. The main focus of the section of this review on circular economy is food waste reuse for microalgal production. Polygeneration is the production of multiple products, including a biofuel as the main product and multiple co-products to ensure process cost reduction. The results reported in relevant studies have shown that microalgal growth and metabolite accumulation could be favored by mixotrophic cultivation using wastes from the conversion processes or reused food wastes. The co-production of high-value products, including pharmaceuticals, proteins, carbohydrates, pigments, bioplastics, pellets, and biofertilizers may also favor the sustainability of biofuel production from microalgae.