• Efficient alternative food systems for earth and space

      Alvarado, Kyle A.; Denkenberger, David; Schiewer, Silke; Karlsson, Meriam (2020-12)
      Alternative foods are a source of human-edible calories derived from an unconventional source or process. This thesis includes two alternative foods: (i) crops grown under low-tech greenhouses in low sunlight environments and (ii) hydrogen-oxidizing bacteria (HOB) in space and Earth refuges, such as to repopulate the Earth. The purpose of alternative foods is to ensure food security for human survival. During a global catastrophic risk (GCR) scenario, such as nuclear winter or super volcanic eruption, the sun may be obscured, causing lack of crop production and therefore global food shortages. The purpose of this thesis was to improve the cost and energy use of producing food during a GCR by avoiding the need to use artificial light photosynthesis. As a solution, a low-tech greenhouse scaling method was designed that could feed the Earth as quickly and cost-effectively as possible during a GCR, such as nuclear winter. Using concepts derived for scaling HOB single cell protein (SCP), a cost analysis was conducted for space that relates to Earth refuges. The cost of HOB was compared to that of microalgae SCP and of dry prepackaged food in a closed-loop system. Low-tech greenhouses were designed with basic materials to continue the production of non-cold tolerant crops at low cost; cold tolerant crops would be able to grow outside of greenhouses where it does not freeze. Scaling of low-tech greenhouses, which would add a cost to food of $2.30 /kg dry, is currently one of the most effective alternative foods for Earth. HOB is an effective method of converting electrical energy into food, having an electricity to biomass energy conversion efficiency of 18% versus 4.0% for artificial light (vertical farming) of microalgae (other crops would be even less efficient).