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This paper presents results generated from an EXCEL based static mass balance model for the incorporation of a higher plant chamber to the MELiSSA Pilot Plant. The model was parameterized using empirical data collected from beet and lettuce production trials and from trials conducted with Pilot Plant or bench scaled MELiSSA compartments. Of particular interest were the daily mass balances of CO2, O2 and nitrogen in the loop for a given set of input variables. The results allow the loop’s designers to foresee the range of conditions for which closure of the mass balances can be expected. This information will be used in the next phases of the MELISSA Pilot Plant integration project.

The MELISSA (Micro Ecological LIfe Support System Alternative) project of the European Space Agency (ESA) is a tool for the development of a simplified biological life support system. In order to achieve this purpose a loop of four interconnected bioreactors and a higher plant compartment has been designed. The target of the loop is to recycle the wastes, mainly CO2 and organic materials, generated in a closed environment such as in manned space missions, into oxygen, water and edible material. Light is the only energy source used to reach this goal. As a part of the development of the project, a Pilot Plant laboratory has been set up. The role of this pilot plant is to demonstrate the feasibility and robustness of the Melissa concept. In order to study the system two kinds of experiments are required. On one hand, each compartment has to be well characterized and, on the other hand, the performance of the connection between compartments has to be evaluated.

MELISSA (Micro Ecological Life Support System Alternative) is a research project for the development of advanced life support systems, conducted by the European Space Agency. Its basic design is based on a loop of bioreactors with the main objective of the regeneration of the wastes generated by a crew into an edible material, with concomitant regeneration of the atmosphere for human respiration. The MELISSA Pilot Plant is a European facility to study and validate advanced life support systems. It has as main objectives the ground demonstration and characterization of a closed loop concept. This includes the development of the associated technology for its successful continuous operation such as water treatment, pathogen detection, food preparation, and other related items. At present time, the main research project developed in the Pilot plant is the MELISSA project.

Successful implementation of the MELISSA loop requires the optimum performance of each of its compartments. Preliminary studies on the behaviour of the photoheterotrophic compartment have been performed. The previously suggested strains have been tested for growth on the carbon and nitrogen sources expected to be components of the influent. The results indicate that of the organisms tested Rs.rubrum should become the organism of choice for the photoheterotrophic compartment while R.capsulatus is more appropriate for the photoautotrophic anaerobic compartment. Biomass analyses, determination of yields and growth rates have also been performed in the preliminary batch and continuous cultures.