Scenedesmus obliquusmicroalga‐based biorefinery – from brewery effluent to bioactive compounds, biofuels and biofertilizers – aiming at a circular bioeconomy

Abstract

The circular bioeconomy concept relies on the exploitation of wastes as a feedstock of different biotechnological processes to obtain, as much as possible, a huge spectrum of biochemical components through a biorefinery platform. This work deals with the treatment of brewery effluent through the cultivation of Scenedesmus obliquus microalga and the use of the biomass in a complex biorefinery. The treatment proved efficient in the removal of nutrients (N, P and COD removals of 88, 30 and 71% respectively). Several compounds and products were obtained from the biomass, such as: (a) phenols (0.249-1.016 mg GAE mL −1 ) and flavonoids (0.05-0.167 mg CE mL −1 ) by subcritical water extraction (SWE) at 120 °C, the extraction efficiency being five times higher at 200 °C; (b) biohydrogen by dark fermentation (67.1 mL H 2 g VS −1 ); (c) bio-oil (64%), biochar (30%) and biogas (6%) by pyrolysis; and (d) enhanced capacity of germination/growth of wheat and barley seeds by S. obliquus culture and biomass (pellet, after centrifugation); better results were obtained with the biomass cultivated in brewery effluent (when compared with synthetic medium), and the biomass pellet was better than the whole culture; barley seeds 1170 A Ferreira et al.In the Field: Scenedesmus obliquus microalga-based biorefinery aiming at a circular bioeconomy treated with the pellet from the brewery effluent had the highest germination index (GI) of 85 compared with the control (tap water) GI of 35. The innovative study emphasis was on reducing microalgae production costs, providing environmental benefits in a biorefinery-based S. obliquus platform.

Biostimulant Potential of Scenedesmus obliquus Grown in Brewery Wastewater

“…The composition of this wastewater is presented in Table 3. The fresh biomass used was the one obtained from the brewery effluent treatment and was already applied in biofuel production trials and was already published elsewhere [3][4][5].…”

“…Wastewater remediation by microalgae is widely described as an efficient nutrient removal, cost-effective and sustainable process, which avoids secondary pollution by using the biomass produced for different applications such as biofuels, bioplastics, biofertilizers and including animal feed and aquaculture [1][2][3][4][5][6][7]. This strategy is a win-win process that benefits both parts because (i) wastewater treatment with microalgae has lower energy demand, GHG emissions and costs than conventional systems, whereas (ii) the utilization of wastewater as nutrients source allows the reduction of microalgae biomass production cost below 5 €/kg [6,8].…”

Statistical Methods for Rapid Quantification of Proteins, Lipids, and Carbohydrates in Nordic Microalgal Species Using ATR–FTIR Spectroscopy

“…Three major classes of compounds are found in microalgae, which together contribute to more than 50% of their total biomass: amino acids (25–70%), carbohydrates (8–65%), and fatty acids/lipids (0–45%). Amino acids and proteins can be supplied as high nutritional value ingredients in the human diet and animal feed [3,4,5], but also used as organic biofertilizer to sustain crop productivity and preserve soil fertility [6,7]. Carbohydrates, including starch and polysaccharides, can be transformed into fermentable sugars for bioethanol production [8], used as emulsion stabilizer and bio-coagulant or as precursors for synthetic rubber and bioplastic generation [9,10].…”

Mapping the performance of photobioreactors for microalgae cultivation. Part II: equatorial and tropical climate zone

“…For example, global CO 2 emissions associated with energy could be reduced considerably with the use of microalgae biofuels; in 2019, thanks to the expansion of renewable energy sources, such emissions decreased by 1.3% 6,7 . Among microalgae species, Scenedesmus obliquus is particularly attractive for its carbon dioxide bioconversion rates (0.44 kgCO 2 m –1 d –1 ), bioremediation [nitrogen (N), phosphorus (P) and chemical oxygen demand (COD) removals of 88, 30 and 71%, respectively] and biomass production (0.36 kg m –1 d –1 ) 8,9 …”

“…6,7 Among microalgae species, Scenedesmus obliquus is particularly attractive for its carbon dioxide bioconversion rates (0.44 kgCO 2 m -1 d -1 ), bioremediation [nitrogen (N), phosphorus (P) and chemical oxygen demand (COD) removals of 88, 30 and 71%, respectively] and biomass production (0.36 kg m -1 d -1 ). 8,9 Technological advances in past decades have demonstrated the commercial potential of microalgae. A significant number of researchers have focused on optimizing physical parameters that induce the production of target products.…”