SAT’s innovative production system employs a special feature to match light and nutrient supplies optimally to the algae life cycle. This helps to maximise biomass production, greatly enhancing system efficiency and cost-effectiveness. The technology can operate in any climatic conditions with a variety of micro-algae species.
A pilot plant is running at the Timelkam power station in Austria. The system includes three stages: separation of CO2 from flue gas, algae cultivation and biomass harvesting. During the first stage, CO2 is removed from the plant’s waste gas emissions and diverted to a nutrient solution for the micro-algae, which are then cultivated in a compact system of bioreactors. The bioreactors, the heart of the SAT process, include a start-up biosphere, photo-bioreactors and a mixotrophic process stage where the microorganisms can use a mix of different sources of energy and carbon.
Algae cultivation in the biosphere takes place as part of a ‘closed pond’, which helps to mitigate environmental influences and to protect against contamination by other organisms. The system is also fitted with automatic temperature controls, an automated CO2 feed and a special pump system to ensure a uniform distribution of nutrients within the ponds, optimising the growth of the algae culture.
The photo-bioreactors, in which the algae are grown to maturity, are another core part of SAT’s technology. These are silos equipped with an agitator and a CO2 feed as well as temperature control elements. The reactors are illuminated by a combination of sunlight and high performance light-emitting diodes (LEDs). The light is evenly distributed within the bioreactors to ensure perfect growth conditions for the algae, helping to reduce overall space requirement and investment costs.
The mixotrophic process involves the introduction of alternative carbon nutrient sources, while reducing ambient light and the supply of CO2. This allows for optimisation of algal properties such as oil content, fatty acids and enzymes. SAT harvesting is carried out in two steps. Firstly, a specially designed coagulation process concentrates the algal mass at the bottom of the bioreactor. Water and algae biomass are then separated using a highly efficient but low energy harvesting system.
The biomass produced has a variety of potential applications, including in the production of biofuels, in the biochemistry, bioplastics, pharmaceutical and cosmetics industries, and as an animal feed. The SAT system also has a potentially important role in reducing greenhouse gas emissions. It offers a biomass CO2 conversion factor of 1:2, meaning every tonne of biomass consumes about two tonnes of CO2 during its growth cycle.
European Commission, press release, 2012-02-13.