Search Results

In order to support effective recycling of resources in a bioregenerative life support system (BLSS), the processing of inedible agricultural wastes into edible food products must be included. The process of converting agricultural waste into usable food resources is called secondary food production. Secondary food production offers a way to reclaim part of the energy and nutrients already sunk in inedible biomass, thus increasing the efficiency of the BLSS and crop harvest index. However, multi-step processes and lower yields and acceptability have made some secondary food production processes in the past problematic and costly. This paper presents preliminary process descriptions for secondary food products which are likely to be cost effective and well accepted: sugar syrup prepared from biomass hydrolysate, single cell oil produced from biomass hydrolysate, and Pleurotus mushroom fruit bodies grown on recalcitrant biomass and unused substrate.

Wet cabin trash, including food residues, moist hygiene wipes and wet paper towels, poses two problems on long term space missions: first, the generation of odors and potential health hazards by microbial action (spoilage); second, the diversion of water from the available recovery loops. We have developed an energy-efficient closed air-loop heat-pump dryer to remove moisture from the wet material. Circulation of hot air can pasteurize the trash in the original bag without water recovery. In drying mode, a gravity-independent Porous Membrane Condensing Heat Exchanger (PMCHX) traps condensate to be passed to the water recovery system. The DRYER system is suitable for stabilization of wet cabin waste in an advanced life support system, and may be adapted to drying of crew laundry and water recovery from water-reprocessing brines.

Food processing will have a significant effect on both system performance and crew habitability on long-duration human space missions. To maximize habitability, the food processing system must be able to utilize available food items for producing a palatable and diverse menu, while minimizing equipment, consumables mass, and manpower requirements. The authors' goal was to minimize the equivalent mass cost (as defined in earlier work) of the food processing system under constraints of nutritional adequacy, variety and hedonic acceptability. In a companion paper, we have developed a concept for organized analysis of food processing at a Lunar or planetary station. In this paper, we propose a way to optimize the cost-effectiveness of this concept for a Lunar base. A four-man ten-year Lunar base was assumed for performing this analysis, based on previous work by Drysdale on regenerative life support systems.

Three distinct food system paradigms have been envisioned for long-term space missions. The Skylab, Mir and ISS food systems were based on single-serving prepackaged foods, ready to rehydrate and heat. Bioregenerative food systems, derived from crops grown and processed at the planetary station, have been studied at JSC and KSC. The US Antarctic Program’s Amundsen-Scott South Pole Base uses the third paradigm: bulk packaged food ingredients delivered once a year and used to prepare meals on the station. The packaged food ingredients are supplemented with limited amounts of fresh foods received occasionally during the Antarctic summer, trace amounts of herb and salad crops from the hydroponic garden, and some prepackaged ready to eat foods, so the Pole system is actually a hybrid system; however, it is worth studying as a bulk packaged food system because of the preponderance of bulk packaged food ingredients used.

In bioregenerative life support systems, crop residues represent a source of biochemical energy for production of chemicals, pulp products and secondary foods. Hydrolysis of the structural carbohydrates in biomass produces edible glucose as well as various 5-carbon sugars usable by microorganisms. However, the biomass must be pretreated before hydrolysis to remove minerals useful as plant nutrients, break down lignin, and improve access of the enzymes to the carbohydrates. Some pre-treatments also hydrolyze part or all of the hemicellulose, leaving purified cellulose. For use in space, pretreatments must be safe, rapid and as complete as practicable. This paper will present a process comparison of three “space-compatible” pretreatment methods for lignocellu-losic crop residues from bioregenerative life support systems. Ozonation, alkaline hydrogen peroxide, and strong alkali treatment use only regenerable materials and mild processing conditions.