Duration: 18 months
Sustainable space exploration relies on CLSS for extended missions and potential extra-terrestrial habitation. Lignocellulosic biomass processing is crucial for CLSS to maximize resource use and foster sustainability. The MELiSSA project exemplifies decades of research, advancing regenerative life support systems. The microbial bioreactor converts biomass sugar fraction into simple sugars and gases, with challenging lignin fraction largely untouched. Overall conversion peaks at 70wt%, but high-temperature liquefaction boosts it to >90 wt%[1]. Thus, separating sugars and lignin, enhances conversion and reduces waste for a more sustainable closed-loop system. Various fractionation pathways employ alkaline conditions (kraft) to separate sugars from lignin. However, harsh treatment results in poor-quality lignin, often incinerated. The organosolv process, dissolving lignin in organic solvents, offers a milder alternative. Despite high yields (70-95%)[2], drawbacks include excessive solvent use and fixed bed operation, making it bulky. As a more compact alternative to harsh liquefaction, we propose a reactive extruder for lignocellulosic fractionation. The reactive extrusion system, with continuous operation, utilizes two screws for efficient biomass decomposition, overcoming mass transfer limitations. This compact system could synergize with the MELiSSA bioreactor, using carboxylic acids for biomass fractionation and enhancing overall yields. While reactive extrusion research has focused on high temperatures, combining it with organosolv extraction is innovative. The resulting sugars and lignin can be separated and valorized. Sugars fuel the bioreactor, producing short-chain fatty acids. Lignin's aromatic structure, flame-retardant and UV-blocking properties make it a compelling feedstock for developing extra-terrestrial materials. This integrated approach signifies a significant step towards sustainable and efficient resource utilization in space exploration.
