(593b) Thermochemical Conversion in Space: Developing Mars Regolith- Activated Hydrochar Composite for Enhanced Water Retention in Mars

While the increasing global population translates an increasing need of freshwater on Earth, researchers have been recently applying hydrothermal carbonization (HTC) of biomass to derive hydrochar that has demonstrated key role for soil amendment purposes by increasing the water holding capacity of soil when mixed with it. However, while thinking beyond the scope of Earth, the question that intrigued our research was the possibility of enhancing water retention capability to boost plant growth in outer space to facilitate life there, for example on the International Space Station (ISS) or at human outposts on Mars. In order to limit transport cost while conserving energy, NASA’s advanced life support system research is pursuing native materials mined on Mars to be utilized for plant growth in future outpost where terrestrial porous materials might be useful to grow plants onboard during future space missions. Hence, this study stemmed in developing composite from exceptionally porous biomass-derived carbon material and Mars regolith to determine the effect of porous carbon material on the water holding capacity of Mars regolith with different mixture proportions. For this study, loblolly pine was used as biomass precursor where HTC was done at 260°C to derive hydrochar which was then chemically activated using KOH at 800 °C to fabricate exceptionally porous carbon material, named activated hydrochars. Activated hydrochar was then mixed with Mars regolith where mass proportion followed was 0, 5, 10, 25, 50 (wt.%) of activated hydrochar in 1g of Mars Regolith. KOH was then added to the mixture following a mass ratio of 1:4 (mixture: KOH) while adding 25 to 50 ml of water to create a suspension for homogenous mixing during ultrasonication. The mixture was ultrasonicated for 6 hours followed by hot-plate magnetic stirring for 12 hours in order to evaporate the water off prior to activation in tube furnace for a residence time of 2 hours at 800 °C. The activated hydrochar-composites hence produced were characterized by N₂ adsorption–desorption for surface porosity quantification, scanning electron microscopy for morphology appearance analysis, X-ray powder diffraction for crystallinity analysis, proximate and ultimate analysis for detailed chemical composition analysis. Eventually, the applicability of the composites was explored by assessing the water holding capacity where the individual composites were saturated with water while gently agitating until excess water was observed. Then, the water-composite mixture was allowed to rest for 24 hours to facilitate a homogenous mixture with water where the mixture was then allowed to be drained by gravity through filter paper (Whatman 41) for another 24 h. The wet composite mixture was then weighed prior to drying and then again weighed to determine the dry mass from which the water holding capacity of each mixture was determined.