Food Production in Space From CO <sub>2</sub> Using Microbial Electrosynthesis

Abstract

Human space survival requires sustainable food production methods. The current food method in space is launching prepackaged food which is costly and unsustainable. Alternatives include growing crops and microalgae single cell protein (SCP) using artificial light photosynthesis, which are also costly and inefficient. Prepackaged food and SCP food growing solutions were compared to microbial electrosynthesis of acetic acid (MES-AA) using electroactive bacteria. The analysis employed an equivalent system mass (ESM) technique customarily used by the National Aeronautics and Space Administration to compare and select from alternative systems. Since the dominant cost of a space mission is the cost of launching mass, components of a system are converted to an equivalent mass, including power, heat rejection, and volume. Distinct three-year roundtrip manned missions were evaluated for the International Space Station, the Moon, and Mars. The average ESM of MES-AA is 1.38x and 2.84x lower than prepackaged food and microalgae SCP, respectively. The alternative food with the lowest average ESM in space, SCP from hydrogen-oxidizing bacteria (HOB), is 1.86x lower than MES-AA. The expected electricity-to-calorie energy conversion efficiency of MES is 19.8%; consuming 3.45 kW to fully feed five astronauts with AA (diets would realistically compose multiple foods). MES-AA has a higher energy efficiency than any currently investigated alternative food in space. The most promising food source is HOB, having the lowest ESM and highest nutritional quality. However, MES can provide diet diversity at a lower cost than customarily storing prepackaged food or growing crops in space.