Oxygen and food production using a microalgae photobioreactor for a Lunar base

Future human spaceflight missions will go beyond Low Earth Orbit, with one potential scenario being a base on the Moon Surface. A permanently inhabited base might require a further closure of the material cycles involved on the Life Support System (LSS), to reduce dependency from Earth's resources. Current LSS physico-chemical technologies at the ISS can recycle up to 90% of water and regain 42% of O2 from the exhaled CO2, but they are not able to produce food, which can currently only be achieved using biological processes. A future LSS will most likely include some of these technologies currently in use, but will also need to include biological components. A potential candidate are microalgae, which compared to higher plants, offer a higher harvest index, higher biomass productivity and require less water. Several algae species have already been investigated for space applications in the last decades, being Chlorella vulgaris a promising and widely researched species. C. vulgaris is a spherical single cell organism, with a mean diameter of 6 µm. It can grow in a wide range of pH and temperature levels and CO2 concentrations and it shows a high resistance to cross contamination and to mechanical shear stress, making it an ideal organism for long-term LSS. Although several experiments have already taken place, both on Earth and in space, more research is still required, both on the biology and on the technology side, before a microalgae photobioreactor (PBR) can become part of a Moon base LSS. The main challenges for a Moon PBR identified and partially being investigated include: long-term performance and stability, radiation effects on algae, selection of the required hardware, sizing the system, operation under Moon gravity and downstream processing to edible food. This paper will give an overview on the results of the current research at the Institute of Space Systems - University of Stuttgart, and will discuss the challenges and questions still open, to enable oxygen and food production using microalgae on the Moon surface.