The artificial ecosystem MELiSSA, supported by the European Space Agency is a closed loop system consisting of 5 compartments in which food, water and oxygen are produced out of organic waste. The first compartment is conceived as a thermophilic anaerobic membrane bioreactor liquefying organic waste into VFAs, ammonium and CO2 without methane. A 20 L reactor was assembled to demonstrate the selected design and process at prototype scale. We characterized system performance from start-up to steady state and evaluated process efficiencies with special attention drawn to the mass balances. An overall efficiency for organic matter biodegradation of 50% was achieved. The dry matter content was stabilized around 40-50 g L-1 and VFA production around 5-6 g L-1. The results were consistent for the considered substrate mixture and can also be considered relevant in a broader context, as a first processing step to produce building blocks for synthesis of primary energy vectors. (C) 2012 Elsevier Ltd. All rights reserved.