This paper demonstrates the significant utility of deploying non-traditional biological techniques to harness available volatiles and waste resources on manned missions to explore the Moon and Mars. Compared with anticipated non-biological approaches, it is determined that for 916 day Martian missions: 205 days of high-quality methane and oxygen Mars bioproduction with Methanobacterium thermoautotrophicum can reduce the mass of a Martian fuel-manufacture plant by 56%; 496 days of biomass generation with Arthrospira platensis and Arthrospira maxima on Mars can decrease the shipped wet-food mixed-menu mass for a Mars stay and a one-way voyage by 38%; 202 days of Mars polyhydroxybutyrate synthesis with Cupriavidus necator can lower the shipped mass to three-dimensional print a 120 m3 six-person habitat by 85% and a few days of acetaminophen production with engineered Synechocystis sp. PCC 6803 can completely replenish expired or irradiated stocks of the pharmaceutical, thereby providing independence from unmanned resupply spacecraft that take up to 210 days to arrive. Analogous outcomes are included for lunar missions. Because of the benign assumptions involved, the results provide a glimpse of the intriguing potential of ‘space synthetic biology’, and help focus related efforts for immediate, near-term impact.

Space synthetic biology is a branch of biotechnology dedicated to engineering biological systems for space exploration, industry and science. There is significant public and private interest in designing robust and reliable organisms that can assist on long-duration astronaut missions. Recent work has also demonstrated that such synthetic biology is a feasible payload minimization and life support approach as well. This article identifies the challenges and opportunities that lie ahead in the field of space synthetic biology, while highlighting relevant progress. It also outlines anticipated broader benefits from this field, because space engineering advances will drive technological innovation on Earth.

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"NASA's Advanced Exploration Systems (AES) program is pioneering new approaches for rapidly developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond Earth orbit" (NASA 2012). These forays beyond the confines of earth's gravity will place unprecedented demands on launch systems. They must not only blast out of earth's gravity well as during the Apollo moon missions, but also launch the supplies needed to sustain a crew over longer periods for exploration missions beyond earth's moon. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. Current efforts are focused on improving the current state-of-the-art systems utilizing fixed beds of sorbent pellets by seeking more robust pelletized sorbents, evaluating structured sorbents, and examining alternate bed configurations to improve system efficiency and reliability. These development efforts combine testing of sub-scale systems and multi-physics computer simulations to evaluate candidate approaches, select the best performing options, and optimize the configuration of the selected approach, which is then implemented in a full-scale integrated atmosphere revitalization test. This paper describes the carbon dioxide (CO2) removal hardware design and sorbent screening and characterization effort in support of the Atmosphere Resource Recovery and Environmental Monitoring (ARREM) project within the AES program. A companion paper discusses development of atmosphere revitalization models and simulations for this project.

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Gaseous NH 3 removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH 3 concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH 3 for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH 3 removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH 3 could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO 3 -early in the operation, but later both NO 2 -and NO 3 -accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20-and 50-ppm biofilters, respectively. A partial IMPLICATIONS Biofilters are becoming an acceptable and economical air pollutant control technology for treating air contaminated with low concentrations of certain gaseous volatile organic compounds (VOCs) and inorganic sulfur compounds. Although NH 3 removal in biofilters has also been demonstrated, the mechanism of removal has been unclear. This research demonstrates the mechanisms of NH 3 removal in biofilters and also some of the associated problems. Potential applications include improved treatment of waste gas streams containing NH 3 , such as those from wastewater treatment systems, animal houses, and composting facilities. Another specialized application considered here is the treatment of cabin air and exhaust gas streams from waste treatment, food processing, and plant growth operations for long-duration space missions, where it is important not only to treat the waste gases but also, if possible, to recover nutrients for recycling into biomass production.

This study evaluated the influence of the membrane type on the performance of bioelectromethanogenesis reactors. The functional activities and taxonomic composition of bioelectrochemical systems (BES) with Nafion 117 or Ultrex CMI-7000 membranes were assessed. Functional activity was measured as methane production and current consumption rates throughout operation. Microbial biomass and phylogenetic diversity were characterized at strategic intervals related to the membrane type used. The Nafion-BES reactor showed the best performance in terms of current consumption and methane production in the early operational period and a strong selection for fermentative bacteria. However, the Nafion-BES was not able to sustain this activity over the course of 7 subpassages since methanogenic species were ultimately selected against and did not appear in the community composition for the last two subpassages. In contrast, the Ultrex-BES had a lower pH concentration gradient and lower overall current consumption activity; however, the methane production activity from the Ultrex-BES was equivalent or better than the Nafion-BES reactor and was sustained throughout the seven subpassages. The membrane type appeared to be responsible not only for differences in the electrochemical operation of the BESs but it also influenced microbial taxonomic composition and dynamics. Microbial electrosynthesis has been reported as a promising new technology for the synthesis of value-added products from CO 2 or other organic feedstocks.1 Microbial electrosynthesis relies on microbial population, applied potential, system design and the specific environmental conditions to define the final products and overall efficiencies of these systems.2-7 As a new technology, most of the studies in the area of microbial electrosynthesis address: i) proving the concept of using bacteria as electrocatalysts for targeted synthesis of a given product 8,9 and ii) understanding the mechanisms of "communication" between microbial species and electrode surfaces used as electron donors.10-13 Pure microbial cultures have primarily been used as they can provide selectivity of the synthesis process.2,12-15 However, from a practical standpoint, natural mixed microbial communities may provide a better strategy for bioelectrochemical systems exploring microbial electrosynthesis because they are more robust relative to operational changes, have greater metabolic capacity for converting/synthesizing complex substrates and are less susceptible to contamination during long-term operation. Therefore, investigations into optimal microbial communities along with interspecies interactions have also gained attention in recent years. [16][17][18][19][20][21][22][23][24][25] The practical application of microbial electrosynthesis still requires a deeper understanding of how reactor design may fundamentally impact performance and overall microbial composition. In most cases, a microbial electrosynthesis reactor is a dual-chambered system composed of an anode electrode, a cathode ele...