PORTFOLIO

In order to combat human-caused climate change, in addition to reducing new CO2 emissions, it is necessary to use Negative Emission Technologies (NETs) on a global scale. One possible solution to remove CO2 from the atmosphere is through the production and storage of biomass. Microalgae produced in warm water are the most efficient way to produce biomass, as its growth rates are up to 50 times higher than fast-growing plants on land. Photobioreactors, which can be powered by both natural and artificial light, are used in this project to produce microalgae. With photobioreactors and pure CO2 as carbon source, costs are about 0.5 US$ per kilogram of dry biomass, which is equivalent to 0.3 US$ per separated kilogram of CO2. Research has shown that it is possible to produce biomass at a rate of 287 tons per hectare per year using photobioreactors.
The results from Reto Tamburini's Master thesis and a Life Cycle Analysis project have led to the conclusion that the production of microalgae in photobioreactors as a NET (Carbon Dioxide Removal) is environmentally beneficial if the process is powered mainly by natural light. This overall process including CO2 emissons for building the reactors and their disposal after 20 years, the provision of nutrients a.s.o. is CO2-negative, meaning it has a positive impact on the environment. If the process requires a higher demand for technical energy (artificial light, etc.), it is only environmentally meaningful if the generated biomass is used as a raw material to replace fossil raw materials in industrial processes, reducing CO2 emissions. This approach is referred to as Carbon Capture and Utilization (CCU).
A to be founded start-up called Arrhenius AG is pursuing these two approaches with the goal of developing and operating photobioreactor systems on a large scale, both to directly remove CO2 from the atmosphere and to reduce CO2 emissions through the production of biogenic substances.

In the first step of this project, requirements for the system have to be worked out. For example, the specific energy demand of the reactor should be low or less than comparable systems like e.g. helical tubular reactors. A minimum area productivity should still be achieved, the cost per tonne of separated CO2 should be low and under no circumstances exceed 700 CHF/tCO2. A variety of different reactor designs already exist, such as vertical/helical tube reactors, fermenter reactors, plate reactors, hanging bag reactors, open ponds etc. However, in order to find a design optimally matched to the process, the Prototye is abstracted into partial functions like aeration, nutrient input, lighting, mixing etc. and partial solutions are sought. Subsequently, at least three concepts will be developed from these partial solutions. In order to determine the characteristic values such as energy demand, production rate, material costs, operating costs etc. for the evaluation of the concepts, the technical, energetic, ecological and financial influencing factors are to be determined. This is to be developed in the form of a techno-economic tool. This should allow an analysis over a life cycle of the reactors of 20 years. Based on these findings, a detailed utility analysis with weighted criteria is performed. Therefore, the techno-economic tool will be applied to the concepts as soon as the characteristic values are known. The concepts will be evaluated and the 2 best evaluated concepts will be identified.