Agro-Industrial Wastewaters for Algal Biomass Production, Bio-Based Products, and Biofuels in a Circular Bioeconomy

Abstract

Recycling bioresources is the only way to sustainably meet a growing world population’s food and energy needs. One of the ways to do so is by using agro-industry wastewater to cultivate microalgae. While the industrial production of microalgae requires large volumes of water, existing agro-industry processes generate large volumes of wastewater with eutrophicating nutrients and organic carbon that must be removed before recycling the water back into the environment. Coupling these two processes can benefit the flourishing microalgal industry, which requires water, and the agro-industry, which could gain extra revenue by converting a waste stream into a bioproduct. Microalgal biomass can be used to produce energy, nutritional biomass, and specialty products. However, there are challenges to establishing stable and circular processes, from microalgae selection and adaptation to pretreating and reclaiming energy from residues. This review discusses the potential of agro-industry residues for microalgal production, with a particular interest in the composition and the use of important primary (raw) and secondary (digestate) effluents generated in large volumes: sugarcane vinasse, palm oil mill effluent, cassava processing waster, abattoir wastewater, dairy processing wastewater, and aquaculture wastewater. It also overviews recent examples of microalgae production in residues and aspects of process integration and possible products, avoiding xenobiotics and heavy metal recycling. As virtually all agro-industries have boilers emitting CO2 that microalgae can use, and many industries could benefit from anaerobic digestion to reclaim energy from the effluents before microalgal cultivation, the use of gaseous effluents is also discussed in the text.

Current and future perspectives of a microalgae based circular bioeconomy to manage industrial wastewater– A Systematic Review

“…In their light-dependent and independent reactions, microalgae grown on the effluent absorb CO 2 and convert it into biomass and the precursor to carbohydrates (Ghaffar et al, 2023). For instance, research has shown that 4000 m 2 of a microalgal pond can sequester up to 2.4 tonnes of CO 2 per year under daylight (16 h of light) conditions (de Carvalho et al, 2022). The most contributing parameter for carbon dioxide absorption in microalgae is their ability to grow rapidly and their simple cell structure, performing multiple roles for the synthesis of essential compounds (Bhandari et al, 2023).…”

Biodiesel Production from the Marine Alga Nannochloropsis oceanica Grown on Yeast Wastewater and the Effect on Its Biochemical Composition and Gene Expression

“…Microalgae cultivation coupled with wastewater treatment has many benefits, including waste remediation, low-cost microalgal biodiesel generation [ 16 , 17 ], and a high-value end product rich in polyunsaturated fatty acids (PUFAs) [ 18 ]. Since massive amounts of water and nutrients can be recycled for algae growth in wastewater-based algal cultivation systems, this integration may offer an economically viable and environmentally beneficial approach for sustainable algal biodiesel generation [ 19 , 20 , 21 ].…”

Microalgae Production on Biogas Digestate in Sub-Alpine Region of Europe—Development of Simple Management Decision Support Tool

“…The large-scale cultivation of algal biomass in wastewater streams is an attractive technology for putting circular bioeconomy theory into practice. Algae extract and recycle nutrients, organic carbon, and minerals that would otherwise be lost to the environment [1,2]. They also sequester CO 2 from the atmosphere.…”