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, are used in this project to produce microalgae. With photobioreactors and pure CO2 as carbonsource, 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-emissions 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).
The start-up 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 for the bioeconomy.

In the first step of this project, requirements for the photobioreactor-system were worked out. In order to find a design optimally matched to the process, the Prototye was abstracted into partial functions like aeration, nutrient input, lighting, mixing etc. and partial solutions were sought. Subsequently, three concepts were 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 had to be determined. Therefore, a techno-economic tool was developed. The latter allowed an analysis over a life cycle of the reactors of 20 years. Based on these findings, a detailed utility analysis with weighted criteria was performed by applying the techno-economic tool. Subsequently, the concepts were evaluated, and the 2 best rated concepts were identified and roughly designed. After that, one concept (LOTUS) was designed in detail and implemented on a farm in Rothenburg (LU). In various batch experiments, the energy consumption per kilogram of produced biomass was determined. When extrapolated to continuous operation, this results in an energy consumption of approximately 2.7 kWh per kilogram of dry biomass. This value could be further reduced in the future by using conventional or semi-transparent PV-modules above the reactor. With LOTUS, the largest thin-layer cascade photobioreactor in Switzerland was successfully developed and commissioned. The results are promising; however, significant further development is needed (e.g., reducing investment costs, CO concentration) to enable scaling to a larger system. As the next step, an advanced reactor based on the Cascade Raceway Pond (CRP) design will be built and tested in Rothenburg. If this reactor is also successfully commissioned, the focus will be on scaling up to a pilot plant. To facilitate this, in collaboration with the Greenhouse Gas Fund of V-Zug AG, we initiated a project to identify a suitable location in Portugal with the Portuguese company Algae for Future SA (A4F). The site evaluation has been completed, and two locations have been identified: Lisbon (PRT) and Matacães (PRT). In Lisbon, several different reactors covering a total area of 14 hectares exist. To minimize technical risks, one of these reactors, based on the CRP principle, will first be adapted and equipped with the necessary hardware. Such a reactor has a cultivation area of approximately 1,500 m . Microalgae will be cultivated over a period of about two years to collect as much data as possible.