[Feasibility of the use of degraded inedible biomass of plants as a nutrient liquid for hydroponic cultivation]

Objective. To demonstrate that the recycled liquid, which originated from lettuce inedible biomass degraded by fixed microorganism (correction of microorgannism) and enzyme, can be used as a nutrient solution for lettuce hydroponic cultivation. Method. After biologically degrading the weighted, oven-dried and milled leaves and roots of lettuce in a biological reactor under aerobic condition, the original effluent and its supplemented effluent were used as nutrients for lettuce hydroponic cultivation. Result. The average dried weight (ADW) of lettuce from the original effluent group was approximately half of that from the control group, and the ADW from supplemented effluent group was about equal to that from the control group; some qualities of the lettuce such as a relatively lower content of NO3- from both the original effluent group and the supplemented effluent one improved, and some of those such as a relatively higher content of NO2- dropped. Conclusion. The biologically-degraded effluent was able to be used as nutrient solution for lettuce hydroponic cultivation, although the effects of the inorganic ion-supplemented effluent were much better; the plants of lettuce from the biologically-degraded effluent were safely edible.

[Principle demonstration of nutrient delivery system in a space vegetable planting prototype facility]

Objective. To develop a nutrient delivery system for space vegetable planting prototype facility to be used in future space station, and to preliminarily testify its feasibility through ground-based demonstration experiments. Method. A nutrient delivery system in a space vegetable planting prototype facility was designed and fabricated, and ground based demonstration experiments of plant cultivation were conducted. Result. Nutrient could be steadily delivered to plant cultivation matrixes through capillary action, water content of planting matrixes could be controlled automatically and maintained constant, and the planted material lettuce showed basically normal morphology and color. Conclusion. The nutrient delivery system in a space vegetable planting prototype facility could basically meet the requirements for plant nutrient delivery under space microgravity environmental condition.

[Prospect of the Advanced Life Support Program Breadboard Project at Kennedy Space Center in USA]

The Breadboard Project at Kennedy Space Center in NASA of USA was focused on the development of the bioregenerative life support components, crop plants for water, air, and food production and bioreactors for recycling of wastes. The keystone of the Breadboard Project was the Biomass Production Chamber (BPC), which was supported by 15 environmentally controlled chambers and several laboratory facilities holding a total area of 2150 m2. In supporting the Advanced Life Support Program (ALS Program), the Project utilizes these facilities for large-scale testing of components and development of required technologies for human-rated test-beds at Johnson Space Center in NASA, in order to enable a Lunar and a Mars mission finally.

[Development of an experimental facility for waste treatment by microorganism]

Objective. To construct an experimental facility for microorganism waste processing, which will be used to recover plant nutrient liquids from plant inedible biomass essential for growth and development of plants. Method. After technical parameters and performance requirements were defined, plan demonstration, drawing design, fabrication, debug and preliminary plant inedible residue-biodegradation tests of microorganisms were conducted. Result. The temperature, stirring speed and gas-supplying flow of bioreactor of the facility were controlled automatically, as well as the pH and dissolved oxygen concentration were measured automatically and controlled manually, testifying that its performance reached the requirements of predetermined technical indexes. The 15-d test showed that the facility ran smoothly, its above-mentioned parameters could be measured and controlled precisely, and the biodegradation rate of lettuce's inedible biomass approximately attained 90%. Conclusion. The facility holding reasonable technical indexes, smooth and dependable performances, is capable of being utilized to biodegrade plant inedible biomass. It is expected that if the above-mentioned parameter combinations are optimized further, the results should be better.

[Effects of CO2 concentration on growth and development of lettuce in controlled environment]

Objective. To study the tolerance of lettuce to elevated CO2 concentration in Controlled Ecological Life Support System (CELSS). Method. Lettuce was cultivated in the Ground-based Experimental Facility for Higher Plant Cultivation in Space (GEFHPCS), in which many parameters were kept unchanged, while concentration of CO2 was controlled at 5 different levels (2000-10000 micromoles mol-1). During the growing periods, the morphologies of lettuce were observed every day, the replenished amounts of CO2 to GEFHPCS and water to the nutrient fluid box as well as the amounts of condensed water collected from GEFHPCS were all recorded every day. After harvest, the output and photosynthetic rate were calculated and lots of constituents of lettuce were analyzed. Result. The growth of lettuce were relatively ideal when CO2 concentration was at 6000 micromoles mol-1, but an obviously withering appearance was found when CO2 concentration increased 10000 micromoles mol-1, this time the output and quality of lettuce were unsatisfactory. Conclusion. It would be optimal when CO2 concentration is controlled at about 6000 micromoles mol-1 in a lettuce-cultivating chamber.

[Development of a ground-based experimental facility for space cultivation of higher plant]

A ground-based experimental facility was developed for conducting initial ground-based simulation study of Controlled Ecological Life Support System (CELSS). The facility is composed of a main chamber, O2 and CO2 composition control subsystems, plant cultivation subsystem and whole data management subsystem. The growth room, being composed of a inner wall of mirror-face stainless steel, holds a volume of 1.8 m3 and a growing area of 1.2 m2; electronic fluorescent lamps were used as lighting sources and polyvinyl formal was used for root matrixes; the environmental parameters of the growing room such as temperature, relative humidity, O2 concentration, CO2 concentration, lighting period and irradiance intensity and the nutrient parameters such as pH, electrical conductivity, dissolved oxygen concentration, liquid level of nutrient storage tank and flow rate of nutrient were all controlled automatically; all of the above-mentioned parameters can be inspected, collected, stored and printed regularly and dynamically. The results of a combined debugging and preliminary plant cultivation verified that the technical target of the facility had reached its initial design requirements, it can be used to conduct ground-based simulation studies of space cultivation of higher plants.