Use of CO2 from biogas production and upgrading as source of nutrients for algae
In the W2R project, Algal Line is the last system in the modular demo plant in Matadero del Sur (Spain). Algae will be used to recover the remaining nitrogen and phosphorus from the anaerobic digestate and subsequently act as the bio-stimulant and bio-fertiliser in agricultural production. To utilize the algal ponds also as CO2-sinks, the AlgaBioGas (ABG) technology, which has been validated in the frame of Eco-innovation pilot and market replication project (www.algaebiogas.eu), will be employed.
ABG system in Matadero del Sur consists of the 400 m2 main algal pond and two 9 m2 inoculation ponds for maintaining the inoculum culture. The cultures will be mixed by the custom-made paddlewheels to enable illumination to all algal cells and prevent the settlement or unmixed anaerobic areas in the pond. The waste stream’s treatment and main biomass production will be performed in the main pond. All ponds will have a fully automated control system measuring input and output parameters of the water substrate.
The produced biomass will be harvested by sedimentation and DAF (dissolved air flotation). An innovative CO2 diffuser will be employed to optimise CO2 dispersion into the algal ponds, leading to mitigation of the GHG emission during treatment. The algal system is designed as a module in the large-scale demonstrator, making it applicable also as a separate system or part of other treatment systems.
Currently, the main and inoculation algal ponds are already installed at the demonstration site. The main pond needs another protective coating to be finalised. The sedimentation system is also there but have to be installed and connected to the ponds. DAF has to be transported to the site. The system is also missing electrical lines and water piping as well as connection to the other systems.
Once the ponds will be finalised, the initiation of the algal cultivation will be performed. In Algae Park (Slovenia), partners from AlgEn and Biotechnical Faculty (University of Ljubljana) established a pilot algal system that already enables the production of biomass by feeding the algae with anaerobic digestate. Three 9 m2 ponds are used to compare different culturing conditions for the optimal production of biostimulant substances or compounds for the organic fertilisers.
The algal culture from Algae Park will be used for the initiation of Matadero-del-Sur culture. First, algal culture will be adapted to the demo site conditions and waste stream (digestate) in the inoculation ponds. Although the existing culture from Algal Park is already adapted to the digestate stream, the algal composition in culture depends also on the geographical area and weather conditions. The inoculation culture will be grown to adequate cell density (minimal OD 0.7) before inoculating the main pond. If all goes well, the main pond will take approximately two weeks to achieve culture density suitable for the harvesting. At that time, the harvesting systems will be started to begin collecting the biomass.
The produced biomass will be processed by the partner Kimitec before starting agricultural trials. The biostimulative effects of algal biomass have already been evident from the laboratory and pot agricultural tests done by the partners from University of Ljubljana. In the meantime, algal growth on the digestate and biostimulants’ production is being further optimised and tested in the Algae Park in Slovenia by the Slovene partners Algen and University of Ljubljana.