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.

At the bioproduct generation plant built in Agrópolis, located in Viladecans, researchers are investigating 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) project. This project includes energy recovery in the form of biomethane and the production of other products such as bioplastics, biofertilizers, and irrigation water.

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.

 It also includes a lamellar clarifier that allows for the subsequent separation of the biomass from the treated water. Part of the biomass is digested in a 1 m³ anaerobic digester, from which biomethane is obtained, and another part is used for the accumulation of bioplastics (polyhydroxyalkanoates, PHA). The solid residue from this digestion is stabilized in a 6 m² constructed wetland, also located in the Agropolis, where biofertilizers are produced. Finally, the water treated in these photobioreactors undergoes ultrafiltration and solar disinfection, followed by phosphorus adsorption columns. The treated water is then reused in crops (up to 250 m² of field) through a smart 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 decrease the richness of the product.

Algae for Bioplastic Production:
Researchers have experimented with and demonstrated the ability of certain types of microalgae—cyanobacteria—to produce and accumulate bioplastics. By adapting the conditions of photobioreactors, it is possible to encourage an increase in the population of these organisms, which are capable of synthesizing and accumulating bioplastics in the form of granules in the cell's cytoplasm as a nutrient reserve. The properties of these bioplastics are very similar to those of traditional plastics from the petrochemical industry, with the advantage that they are completely biodegradable. Researchers are now also investigating how to use them in the packaging market. The goal is to achieve a production of 1.5 kg of bioplastics per day.