1 The Bionetics Corp. (clm. jlg). NASA Biomedical Operations Office (rmw), Kennedy Space Center, FL 32899, and UCLA, Laboratory of Biomedical and Environmental Sciences (wlb), Los Angeles, CA 90024-1786
Wheat, soybean, potato, and lettuce crops were grown in a large (20 m2), closed chamber to test plant production for life support in a Controlled Ecological Life Support System (CELSS). Plant crude protein levels were about 15% in wheat and potato biomass, 20% in soybean biomass, and 27% in lettuce biomass at harvest. Nitrate levels were not assayed, but likely contributed to the protein estimates. Nitric acid (used in hydroponic system pH control) contributed 43% for wheat nitrogen needs, 33% for soybean, 30% for potato, and 27% for lettuce. Lettuce contained the highest percent ash (22%) and wheat the lowest (10%). It was likely that the continuous nutrient supply in the hydroponic systems resulted in high ash values. The percentage of plant macronutrients in the inedible biomass was 7% in lettuce, 50% in soybean and potato, and 80% in wheat. Based on these values, perhaps 50% of the macronutrients needed in a multi-crop system could be removed from the inedible biomass and recycled back into the hydroponic system. Applicable technologies for nutrient recovery would include wet or dry oxidation (ashing), water soaking (leaching), or bioreactor degredation. The mass of reagent-grade salts needed in place of nutrient recycling could equal about 30% of the dry food mass required per person day-1.