**8. Implications of circular bioeconomy for the space food system**

In low gravity, e.g., onboard spacecraft, and celestial body (Lunar-, Asteroid-) surfaces, providing food is more taxing than on earth. Humans operating in space face the dynamics of microgravity, radiation, and restricted activity [120–122]. In near-earth missions lasting days (Apollo, Space shuttle, Shenzhou), weeks (Skylab, Salyut), or even months (Mir, International space station, Tiangong space station), food could be carried at liftoff and resupplied from earth. Even in these cases, the space food system is mediated by biological, engineering, environmental, operational, and psychosocial factors. The specific constraints such as safety (biological); mass/volume (engineering); ergonomics (operational); and others have been discussed [122–128]; and detailed for the Apollo food system [129]. Longer durations and interplanetary

#### *Dialing Back the Doomsday Clock with Circular Bioeconomy DOI: http://dx.doi.org/10.5772/intechopen.113181*

destinations make food supply from earth onerous for various reasons. On cost for example, depending on the destination orbit, payload launch cost may range from \$2719/kg for Falcon 9 launch destined to low earth orbit (LEO), to \$28964.52/kg for Delta IV heavy launch destined to geosynchronous transfer orbit (GTO) [130]. Nevertheless, the performance of a launch system is governed by its mass fraction (ratio of the mass of propellants to the total mass of the launch system). The larger the mass fraction, the farther the destination and/or longer the duration. A larger rocket, such as the SpaceX Starship under development, would be able to carry more food, go farther, and last longer than the Saturn V rocket used for the Apollo moon program. But for a given launch system, the larger the food component of the payload, the nearer the destination and/or shorter the mission duration. With no infinite mass fraction launch system, onboard and in-situ food production become vital for successful long-time deep space missions, and extraterrestrial body habitations. To achieve this, space farming would need to benefit from circular bioeconomy technologies and concepts such as AD [131–133]; IRA [116, 134]; circularity [77–82, 135]; bioregenerative life support system (BLSS) [136, 137]; controlled ecological life support system (CELSS) [138–140]; and note by note cuisine (NNC) [141, 142]. For greater plant utility and optimization, molecular pharming [143, 144] could be applied as well.

#### **8.1 Sample study efforts on earth and in space**

Research efforts have been expended both on earth and in space to ascertain the possibility of cultivating plant and animal food stocks in the space environment. Some examples are stated below.

In Apollo quarantine tests of moon soil (regolith), a wide variety of biological species from the animal and plant kingdoms were utilized. Researchers [145–147] concluded that no microbe or harmful agents were found in the tested Apollo Luna regolith; some benefits could be associated with lunar soil cultivation; and that Lunar soil material is a potential source of nutrients for many plants. But experiments with Apollo 11, 12, and 17 Luna regolith reported challenging performance for *Arabidopsis thaliana* (Arabidopsis). Luna regolith seedlings demonstrated normal stems and cotyledon development. However, roots were found stunted after day 6, and the plants showed stress morphologies indicative of ionic stresses [148].

Lettuce (*Lactuca sativa* L. cv. Dasusheng) was grown onboard Tiangong II Spacelab [149]. Germination rate was 37% for space and 78% for ground control. Plant morphology and number of leaves were similar but produced biomass fresh weight differed notably (space-grown lettuce was 40% lower). In nutrition, magnesium (≈ 33%), iron (≈ 35%), and calcium (≈ 45%) were lower, while potassium (by about 10%) was higher in space-grown samples. In food safety, pathogens such as *Staphylococcus aureus*, and *Salmonella* were not detected in both groups. But ground control lettuce presented a higher net colony count. Also, space lettuce grew taller, and had more deep green appearance without transitions (**Figure 4**).

Parabolic flights were used to conduct microgravity research. An interesting discovery was made when thick-toed geckos were flown. Apart from a few rodents that could move by clinging to their container gratings, virtually all objects, mammals (including humans), amphibians, and reptiles float when exposed to the space environment without restraints [122]. However, when the thick-toed geckos were flown in parabolic flights, it was reported that geckos had the ability to remain attached to smooth surfaces. This peculiar capacity apparently allows the geckos to keep normal activities and behavior during weightlessness [150].

**Figure 4.** *Lettuce plant growths and appearances. In space (left), and on earth. Source: [149].*

Future studies: Planet Mars' regolith & rocks are now being gathered by the perseverance rover. These would be studied in detail when delivered to Earth following a future sample return mission [NASA Science: Available @ Video Gallery: Perseverance Rover - NASA Mars; Accessed 12th August 2023]. I venture to speculate that the Martian regolith would be analyzed for agricultural services once in earth's laboratories.
