A pilot plant is capable of producing bioproducts from microalgae grown in wastewater

The Environmental Engineering and Microbiology Research Group (GEMA) of the Polytechnic University of Caluña (UPC) has built a 30 m3 pilot plant for the production of bioproducts and bioenergy from microalgae grown in wastewater.

In the bioproduct generation plant that has been built in Agrópolis, located in Viladecans, research is being carried out on how to produce new energy resources and valuable products from agricultural and domestic wastewater, within the framework of the Innovative Eco-Technologies for Resource Recovery from Wastewater (INCOVER). This project includes the recovery of energy in the form of biomethane and the obtaining of other products such as bioplastics, biological fertilizers and water for irrigation.

With the capacity to treat a volume of 2,000 to 8,000 liters of contaminated wastewater per day, the equivalent of the consumption of a small residential building, the pilot plant consists of three tubular photobioreactors – transparent and closed production systems – of 10 m3 each. , fed with agricultural and domestic wastewater that serves for the growth of microalgae.

 Likewise, it includes a lamellar decanter that allows the biomass to be subsequently separated from the treated water. A part of the biomass is digested by a 1 m3 anaerobic digester from which biomethane is obtained, and another part is destined for the accumulation of bioplastics (polyhydroxyalkanoats, PHA). The solid residue from this digestion is stabilized in a 6 m2 artificial wetland, also built in the Agropolis, where biofertilizers are produced. Finally, the water treated in these photobioreactors is subjected to ultrafiltration and solar disinfection, followed by phosphorus adsorption columns. Finally, the treated water can be reused in crops (up to 250 m2 of field) through an intelligent irrigation system.

The richness of the biomethane obtained is much greater than that obtained in conventional digestion processes, where it passes through an absorption column that retains volatile gases and other contaminants that reduce the richness of the product.

Algae to generate bioplastics
Researchers have experimented and demonstrated the capacity of a certain type of microalgae – cyanobacteria – to produce and accumulate bioplastics. By adapting the conditions of the photobioreactors, the increase in the population of these organisms can be promoted, capable of synthesizing and accumulating bioplastics in the form of granules in the cytoplasm of the cell as a nutrient reserve. The properties of these bioplastics are very similar to those of traditional plastics that come from the petrochemical industry and with the advantage that they are completely biodegradable. Now they are also investigating how to use them in the packaging and packaging market. The forecast is to achieve 1.5 kg of bioplastics per day.