Using Microalgae to Convert Brewery Carbon Gas Emissions into Valuable Bioproducts

The brewing industry is a major part of the agri-food sector, but its fermentation processes contribute significantly to global CO2 emissions, exacerbating the greenhouse gas crisis. Achieving net-zero emissions requires innovative solutions, and this study explored one such solution by using microalgae to capture CO2 from a brewery while simultaneously generating valuable bioproducts. Two microalgae species, Tetradesmus obliquus and Limnospira maxima, were cultivated in a 1000 L raceway and a 400 L tubular photobioreactor, both powered by the brewery's CO2 waste gas. The specific growth rates reached 0.3 in the raceway and 0.4-0.5 in the photobioreactor for both species. Notably, L. maxima showed higher productivity, achieving up to 0.80 g L-1 day(-1) in the photobioreactor and 0.5 g L-1 day(-1) in the raceway. Operating across 300 brewing days per year, a single module (1400 L) of this system could reduce a brewery's CO2 emissions by 29%. These low-maintenance systems are modular, allowing for easy scaling and operation. The harvested biomass was nutritionally valuable; L. maxima contained up to 55% protein and 3% phycocyanin, while T. obliquus was rich in carbohydrates (36%) and lipids (12%), levels suitable for feeds and fertilizers. A cost-benefit analysis suggests that coupling CO2 removal with bioproduct generation supports a sustainable circular economy while offering financial returns.