Sustainable Mars agriculture: Fertilizer production from cyanobacterial biomass via anaerobic digestion

Abstract

A settlement on Mars would need to be self-sufficient in food production, but crop farming is constrained by the availability of local resources. Producing fertilizer through the anaerobic digestion of cyanobacterial biomass—cultivated using Martian resources such as regolith, water, sunlight, and atmospheric gases (N₂, CO₂)—offers a promising solution. The present study aimed to characterize and improve this process and assess the suitability of the resulting carbon-depleted digestate for crop hydroponics. Several process parameters were studied: biomass pre-processing (no treatment, sonicated, autoclaved); operational temperature (25, 30, 35, 45 °C); and substrate concentration (1250, 2500, 5000, 9000 mg COD L−1). Autoclaving and 35 °C maximized organic carbon removal. Substrate concentration tests established a linear correlation between biomass input and ammonium output. Martian regolith simulant (MGS-1) was tested as a mineral nutrient source for anaerobic digestion, both when added directly to cultures (10, 20, 50 and 200 g L−1) and as a 10 g L−1 leachate, with and without trace element supplementation. The leachate supplemented with trace elements enabled the highest recovery of phosphate, ammonium, and methane. The bacterial and archaeal communities were characterized throughout testing to assess the contribution of specific taxa to digestion performance. The digestate supported the growth of a candidate space crop, Lemna sp., yielding 27 g wet mass per g of cyanobacterial dry mass (roughly half the yield on a standard medium). These findings advance the development of in-situ fertilizer production for sustainable crop farming on Mars.