Producing a biofertilizer with microalgae and wastewater
February 29, 2016 — by Jorge Miñón, and Pablo Lázaro
he high concentration of nutrients in wastewaters and in effluents of agro-industrial processes, particularly total N and P, is an environmental problem, and requires costly chemical-based treatments to remove them during wastewater treatment. The ability of microalgae to effectively grow in nutrient-rich wastewaters and to efficiently accumulate nutrients, make them an extremely attractive tool for sustainable and low cost wastewater treatment.
The European Project “LIFE+ Integral Carbon: Development and global enforcement of Greenhouse Gases (GHG) capture photobioreactors in agro-industrial activities” aims to demonstrate the efficiency of microalgal cultures to achieve the fixation of atmospheric CO2 using plant nutrients present in wastewater effluents. The algal biomass would be used as a biofertilizer in substitution of inorganic fertilizers improving C-footprint of the agro-industrial sector.Since September 2015, an industrial prototype has been established in the winery La Fontana, belonging to the AC Wines of Uclés (Cuenca, Spain), containing two portable modules:
(i) the Anaerobic Digestion Module (ADM), in which wastewater and organic wastes generated at the winery are transformed into biogas and digestate, and
(ii) the Photo-Bioreactor Module (PBM) in which algal biomass is produced introducing the burning gases of biogas and applying clarified digestate as a nutrient source (Figure 1).
Exhaust gases of biogas burning and the liquid phase of the digestate, rich in nutrients, are used for growing algal biomass which are being applied to vineyard soils as a biofertilizer (Figure 2).
This project can be a valuable tool for the management of organic residues and wastewater produced in the winery, to reduce the external dependence on inorganic fertilizers, to increase the C-stock in vineyard soils frequently depleted in Southern European Areas, and to improve C balance of the winery sector.
A.C. Wines of Uclés is a pioneering Appellation Controlee in applying C-footprint to all of the associated wineries in Spain. After grape harvest, the total amount of grape pomace produced during the vinification process is stored in a silo and is used daily to feed the ADM mixed with winery wastewater and chicken manure, in a ratio optimized to maximize the biogas production with a methanogenic yield ranging between 30-90 m3/day.The PBM has a production capacity of 30 m3 of biofertilizer with a growing cycle between 15-30 days, depending on ambient temperature and photoperiod duration. The biofertilizer produced has a concentration of algal biomass between 0.8-1.4 g DM/L and is applied to vineyard soils spreading the algal suspension in the inter-rows spaces at two rates: 5 and 10 m3/ha and with one or two frequencies of application: winter and winter and spring, respectively. A total amount of 240 ha vineyard soil will be treated during the actual crop year.
This Project is coordinated by the University of Burgos (UBU) and the consortium involves the University of Valladolid (UVA), Kepler Engineering and Ecomanagement, the Agro-Food Technological Center of Extremadura (CTAEX) and the Appellation Controlee (AC) of Wines of Uclés (Cuenca). With a total budget of 1,253,361 €, the Project has received 650,725 € from the European Commission and is scheduled to last until December 2016.
Jorge Miñón is an Agricultural Engineer at the University of Valladolid (Spain) and Pablo Lázaro is a Chemical Engineer at A.C. Wines of Uclés (Cuenca, Spain). They can be contacted at Área de edafología y Química Agrícola. Facultad de Ciencas. Universidad de Burgos.