The next agricultural frontier: Developing black soldier fly frass as fertilizer for food crops grown on Mars

Recently, global interest in space exploration has surged, necessitating the consideration of what agricultural systems on future space installations will look like. Insects offer many ecosystem services such as waste conversion that will inevitably be necessary for food production systems to function. This study envisioned a hypothetical food web motif consisting of black soldier fly larvae, (Hermetia illucens), that upcycle organic waste into nitrogenous fertilizer (frass), which could then be used to grow English peas (Pisum sativum) in Martian regolith to feed astronauts. To validate the concept and test the suitability of frass supplementation, we planted peas across a gradient of frass-regolith mixtures, ranging in combinations from 0%-100% to 100%-0%; respectively. This was compared to a control of peas potted in a gradient of frass mixed with commercial potting soil. Measures included germination rates, plant height, leaf counts, and dry biomass. Results indicate that pea growth occurs readily in Martian regolith, but only at levels of frass addition below 25% and was certainly not optimal compared to the potting mix-control. In addition to nitrogen burning, the large particle size of the regolith simulant was also likely an issue. Therefore, while this research indicates that food plants can be grown in regolith, the system stands to be substantially improved. To better optimize pea plant growth in regolith, future research should investigate the effect of finer particle regolith, that has higher moisture retention, or utilize plants that uptake high amounts of nitrogen, including pok choy (Brassica rapa).