MELISSA – The European Pilot Plant key for the living in Mars

For more than 30 years the European Space Agency (ESA) is active in the field of regenerative life support systems. MELiSSA (Micro-Ecological Life Support System Alternative), is a model system conceived as a tool to study and develop a biological life support system, aiming at complete recycling by taking advantage of the combined activity of different types of organisms and inspired by an aquatic ecosystem. 

The system would allow air purification, food production and water recovery. The concept has evolved with the separation of the different biological functions into different subsystems (or compartments) and the integration between them through a systems engineering approach. Research is focused on finding mechanisms to generate oxygen and food, while revalorizing wastes.

The MELiSSA Pilot Plant, located at the School of Engineering of the Universitat Autònoma de Barcelona, has reached the demonstration level, consisting of the interconnection of compartments based on different types of bioreactors and technologies. The Pilot Plant allows recreating the closed atmosphere, where mice act as “crew”, and where photosynthetic bacteria, known as cyanobacteria, have been incorporated to generate oxygen. The project has recently completed an 18-month experiment that demonstrates the possibility of generating the oxygen needed to meet the respiratory needs of mice and the needs of the ammonium nitrification process.. The project paves the way for creating stand-alone systems in spacecraft for long duration manned trips or even bases on celestial bodies such as the Moon or Mars.

The closed-loop system involved in the experiment consists of an 83L photobioreactor that modulates oxygen production by regulating the intensity of the lighting system, depending on the respiratory needs of mice. In turn, the nitrogen source for photosynthesis is supplied by a nitrifying bioreactor that transforms ammonium from salts simulating urine into nitrate. The nitrification bioreactor consists of a 13 L packed bed reactor where nitrifying bacteria grow forming a biofilm attached to a support. In this way, a closed circular system of obtaining resources from the recycling of others is created. To these first three compartments, during the whole integration process, three more will have to be incorporated to reach a total of six, including the photosynthetic compartment of higher plants, which will allow satisfying a higher oxygen demand.

The closed-loop system involved in the experiment consists of an 83L photobioreactor that modulates oxygen production by regulating the intensity of the lighting system, depending on the respiratory needs of the mice. In turn, the nitrogen source for photosynthesis is supplied by a nitrifying bioreactor that transforms ammonium from salts simulating urine into nitrate. The nitrification bioreactor consists of a 13L packed bed reactor where nitrifying bacteria grow forming a biofilm attached to a support. In this way, a closed circular system of obtaining resources from the recycling of others is created. To these first three compartments, during the whole integration process, three more will have to be incorporated to reach a total of six, including the photosynthetic compartment of higher plants, which will allow satisfying a higher oxygen demand.

Currently, ships or bases such as the International Space Station already have recycling systems, but all of them are based on physical-chemical processes. In contrast, the MELiSSA project is based on biological processes, which are considered the only alternative for long duration space exploration.

In order to achieve the goal of completing the integration of the entire loop and reaching the final concept demonstration, the Melissa Pilot Plant needs constant technology development and the adaptation and improvement of existing bioreactors. In order to achieve this goal, TECNIC Bioprocess Equipment Manufacturing has been validated as a provider of Engineering Services including modification and interconnection of existing equipment, upgrading of compartments and bioreactors, supply of new equipment and parameterization through 3D design.