Aquatic food production modules in bioregenerative life support systems based on higher plants.

Most bioregenerative life support systems (BLSS) are based on gravitropic higher plants which exhibit growth and seed generation disturbances in microgravity. Even when used for a lunar or martian base the reduced gravity may induce a decreased productivity in comparison to Earth. Therefore, the implementation of aquatic biomass production modules in higher plant and/or hybrid BLSS may compensate for this and offer, in addition, the possibility to produce animal protein for human nutrition. It was shown on the SLS-89 and SLS-90 space shuttle missions with the C.E.B.A.S.-MINI MODULE that the edible non gravitropic rootless higher aquatic plant Ceratophyllum demeresum exhibits an undisturbed high biomass production rate in space and that the teleost fish species, Xiphophorus helleri, adapts rapidly to space conditions without loss of its normal reproductive functions. Based on these findings a series of ground-based aquatic food production systems were developed which are disposed for utilization in space. These are plant production bioreactors for the species mentioned above and another suitable candidate, the lemnacean (duckweed) species, Wolffia arrhiza. Moreover, combined intensive aquaculture systems with a closed food loop between herbivorous fishes and aquatic and land plants are being developed which may be suitable for integration into a BLSS of higher complexity. Grant numbers: WS50WB9319-3, IVA1216-00588.     

Possible applications of aquatic bioregenerative life support modules for food production in a Martian base.

Water is the essential precondition of life in general and also for the establishment of a Martian base suitable for long duration stays of humans. It is not yet proven if there is indeed a "frozen ocean" under the surface of Mars but if this could be verified it would open innovative aspects for the construction of bioregenerative life support systems (BLSS). In a general concept higher plants will play the predominant role in a Martian BLSS. It is not clear, however, how these will grow and bring seed in reduced gravity and there may be differences in the productivity in comparison to Earth conditions. Therefore, organisms which are already adapted to low gravity conditions, namely non-gravitropic aquatic plants and also aquatic animals may be used to enhance the functionality of the Martian BLSS as a whole. It has been shown already with the so-called C.E.B.A.S. MINIMODULE in the STS-89 and STS-90 spaceshuttle missions that the water plant Ceratophyllum demersum has an undisturbed and high biomass production under space conditions. Moreover, the teleost fish species Xiphophorus helleri adapted easily to the micro-g environment and maintained its normal reproductive functions. Based on this findings a possible scenario is presented in which aquatic plant production modules and combined animal-plant production systems may be used for human food production and water and air regeneration in a Martian base.     

载人深空探测活动中的尿液处理回收技术分析

生物再生生命保障系统(Bioregenerative Life Support System,BLSS)是人类进行深空探测活动,实现长期载人空间飞行必需的关键技术,对于太空的探索开发具有重要意义。在BLSS系统内,航天员尿液废水的处理回收是非常重要的一部分。将尿液中所含有的大量的水分和丰富的营养物质回收用于系统内植物生长所需营养液的配制,既可以保证植物的正常生长,也有助于实现系统内物质的循环利用进而提高BLSS的闭合度。尿液中所含的大量盐分会威胁植物生长,所以需通过一定的技术手段处理尿液废水并回收其中的水分和营养。为了探索适用于BLSS中的尿液处理回收技术,首先分析了几种面向空间站应用的尿液处理技术,如蒸馏技术等;然后基于回收营养物质的需求,分析了面向民用的、发展较为成熟的尿液处理回收技术,如离子交换吸附技术、氨气吹脱技术和鸟粪石沉淀技术,并讨论了这些尿液处理回收技术在BLSS中的应用前景。最后基于BLSS的实际需求,提出了有望用于BLSS中的尿液处理回收技术流程。     

Material balance and diet in bioregenerative life support systems: connection with coefficient of closure.

Bioregenerative life support systems (BLSS) with different coefficients of closure are considered. The 66.2% coefficient of closure achieved in "BIOS-3" facility experiments has been taken as a base value. The increase in coefficient of closure up to 72.6-93.0% is planned due to use of soil-like substrate (SLS) and concentrating of urine. Food values were estimated both in a base variant ("BIOS-3"), and with increases in the coefficient of closure. It is shown that food requirements will be more fully satisfied by internal crop production with an increase in the coefficient of closure of the BLSS. Changes of massflow rates on an 'input-output' and inside BLSS are considered. Equations of synthesis and degradation of organic substances in BLSS were examined using a stoichiometric model. The paper shows that at incomplete closure of BLSS containing SLS there is a problem of nitrogen balancing. To compensate for the removal of nitrogen from the system in urine and feces, it is necessary to introduce food and a nitrogen-containing additive.     

BLSS: A contribution to future life support

For extended duration missions in space the supply of basic life-supporting ingredients represents a formidable logistics problem. Storage volume and launch weight of water, oxygen and food in a conventional non-regenerable life support system are directly proportional to the crew size and the length of the mission. In view of spacecraft payload limitations this will require that the carbon, or food, recycling loop, the third and final part in the life support system, be closed to further reduce logistics cost. This will be practical only if advanced life support systems can be developed in which metabolic waste products are regenerated and food is produced.

Biological Life Support Systems (BLSS) satisfy the space station environmental control functions and close the food cycle. A Biological Life Support System has to be a balanced ecological system, biotechnical in nature and consisting of some combination of human beings, animals, plants and microorganisms integrated with mechanical and physico-chemical hardware.

Numerous scientific space experiments have been delineated in recent years, the results of which are applicable to the support of BLSS concepts. Furthermore ecological life support systems have become subject to intensified studies and experiments both in the U.S. and the U.S.S.R. The Japanese have also conducted detailed preliminary studies.

Dornier System has in recent years undertaken an effort to define requirements and concepts and to analyse the feasibility of BLSS for space applications. Analyses of the BLSS energy-mass relation have been performed, and the possibilities to influence it to achieve advantages for the BLSS (compared with physico-chemical systems) have been determined. The major problem areas which need immediate attention have been defined, and a programme for the development of BLSS has been proposed.     

Accumulation and effect of volatile organic compounds in closed life support systems.

Bioregenerative life support systems (BLSS) being considered for long duration space missions will operate with limited resupply and utilize biological systems to revitalize the atmosphere, purify water, and produce food. The presence of man-made materials, plant and microbial communities, and human activities will result in the production of volatile organic compounds (VOCs). A database of VOC production from potential BLSS crops is being developed by the Breadboard Project at Kennedy Space Center. Most research to date has focused on the development of air revitalization systems that minimize the concentration of atmospheric contaminants in a closed environment. Similar approaches are being pursued in the design of atmospheric revitalization systems in bioregenerative life support systems. in a BLSS one must consider the effect of VOC concentration on the performance of plants being used for water and atmospheric purification processes. In addition to phytotoxic responses, the impact of removing biogenic compounds from the atmosphere on BLSS function needs to be assessed. This paper provides a synopsis of criteria for setting exposure limits, gives an overview of existing information, and discusses production of biogenic compounds from plants grown in the Biomass Production Chamber at Kennedy Space Center.     

Use of halophytic plants for recycling NaCl in human liquid waste in a bioregenerative life support system

The purpose of this work was to develop technology for recycling NaCl containing in human liquid waste as intrasystem matter in a bioregenerative life support system (BLSS). The circulation of Na⁺ and Cl⁻ excreted in urine is achieved by inclusion of halophytes, i.e. plants that naturally inhabit salt-rich soils and accumulate NaCl in their organs. A model of Na⁺ and Cl⁻ recycling in a BLSS was designed, based on the NaCl turnover in the human–urine–nutrient solution–halophytic plant–human cycle. The study consisted of (i) selecting a halophyte suitable for inclusion in a BLSS, and (ii) determining growth conditions supporting maximal Na⁺ and Cl⁻ accumulation in the shoots of the halophyte growing in a nutrient solution simulating mineralized urine. For the selected halophytic plant, Salicornia europaea, growth rate under optimal conditions, biomass production and quantities of Na⁺ and Cl⁻ absorbed were determined. Characteristics of a plant production conveyor consisting of S.europaea at various ages, and allowing continuity of Na⁺ and Cl⁻ turnover, were estimated. It was shown that closure of the NaCl cycle in a BLSS can be attained if the daily ration of fresh Salicornia biomass for a BLSS inhabitant is approximately 360 g.     

Mass balances for a biological life support system simulation model.

Design decisions to aid the development of future space-based biological life support systems (BLSS) can be made with simulation models. Here we develop the biochemical stoichiometry for 1) protein, carbohydrate, fat, fiber, and lignin production in the edible and inedible parts of plants; 2) food consumption and production of organic solids in urine, feces, and wash water by the humans; and 3) operation of the waste processor. Flux values for all components are derived for a steady-state system with wheat as the sole food source. The large-scale dynamics of a materially-closed (BLSS) computer model is described in a companion paper. An extension of this methodology can explore multi-food systems and more complex biochemical dynamics while maintaining whole-system closure as a focus.     

Spaceflight hardware for conducting plant growth experiments in space: the early years 1960-2000.

The best strategy for supporting long-duration space missions is believed to be bioregenerative life support systems (BLSS). An integral part of a BLSS is a chamber supporting the growth of higher plants that would provide food, water, and atmosphere regeneration for the human crew. Such a chamber will have to be a complete plant growth system, capable of providing lighting, water, and nutrients to plants in microgravity. Other capabilities include temperature, humidity, and atmospheric gas composition controls. Many spaceflight experiments to date have utilized incomplete growth systems (typically having a hydration system but lacking lighting) to study tropic and metabolic changes in germinating seedlings and young plants. American, European, and Russian scientists have also developed a number of small complete plant growth systems for use in spaceflight research. Currently we are entering a new era of experimentation and hardware development as a result of long-term spaceflight opportunities available on the International Space Station. This is already impacting development of plant growth hardware. To take full advantage of these new opportunities and construct innovative systems, we must understand the results of past spaceflight experiments and the basic capabilities of the diverse plant growth systems that were used to conduct these experiments. The objective of this paper is to describe the most influential pieces of plant growth hardware that have been used for the purpose of conducting scientific experiments during the first 40 years of research.     

Soybean cultivar selection for Bioregenerative Life Support Systems (BLSS) – Theoretical selection

The development of plant-based Bioregenerative Life Support Systems (BLSS) is a requirement for the realization of long-duration exploratory-class manned missions in so far as they help fulfilling astronauts’ needs including nutritional demands, air regeneration and psychological support.     

Chlorella vulgaris culture as a regulator of CO2 in a bioregenerative life support system

It is the primary task for a bioregenerative life support system (BLSS) to maintain the stable concentrations of CO₂ and O₂. However, these concentrations could fluctuate based on various factors, such as the imbalance between respiration/assimilation quotients of the heterotrophic and autotrophic components. They can even be out of balance through catastrophic failure of higher plants in the emergency conditions. In this study, the feasibility of using unicellular Chlorella vulgaris of typically rapid growth as both “compensatory system” and “regulator” to control the balance of CO₂ and O₂ was analyzed in a closed ecosystem. For this purpose, a small closed ecosystem called integrative experimental system (IES) was established in our laboratory where we have been conducting multi-biological life support system experiments (MLSSE). The IES consists of a closed integrative cultivating system (CICS) and a plate photo-bioreactor. Four volunteers participated in the study for gas exchange by periodical breathing through a tube connected with the CICS. The plate photo-bioreactor was used to cultivate C. vulgaris. Results showed that the culture of C. vulgaris could be used in a situation of catastrophic failure of higher plant under the emergencies. And the productivity could recover itself to the original state in 3 to 5 days to protect the system till the higher plant was renewed. Besides, C. vulgaris could grow well and the productivity could be affected by the light intensity which could help to keep the balance of CO₂ and O₂ in the IES efficiently. Thus, C. vulgaris could be included in the design of a BLSS as a “compensatory system” in the emergency contingency and a “regulator” during the normal maintenance.     

Self-restoration of biocomponents as a mean to enhance Biological Life Support Systems reliability.

One of the key problems of long-term space missions is limited service life of units. The only exceptions are biological components of biological Life Support Systems--higher plants or microorganisms. These components are capable of self-restoration: after complete disintegration, they can appear again from seeds or spores. The estimate of failure intensity of BLSS regeneration component includes: a number of self-sustained sections of the regeneration component; permissible boost (how many times can productivity of a component be increased); time required to repair (restore) a component; the crew existence time, when all LSS regeneration components fail; failure rate of one section of a regeneration component. Evaluations show that for hydrogen-oxidizing bacteria and micro-algae very high reliability is achieved even for one or two sections. In the case of higher plants (due to low rate of self-restoration) bio-regenerative module has to be divided into 10 self-sustained sections operating simultaneously. These measures can decrease the probability of catastrophe by a factor of 10(6).     

Effect of salt stress on growth and physiology in amaranth and lettuce: Implications for bioregenerative life support system

Growing plants can be used to clean waste water in bioregenerative life support system (BLSS). However, NaCl contained in the human urine always restricts plant growth and further reduces the degree of mass cycle closure of the system (i.e. salt stress). This work determined the effect of NaCl stress on physiological characteristics of plants for the life support system. Amaranth (Amaranthus tricolor L. var. Huahong) and leaf lettuce (Lactuca sativa L. var. Luoma) were cultivated at nutrient solutions with different NaCl contents (0, 1000, 5000 and 10,000 ppm, respectively) for 10 to 18 days after planted in the Controlled Ecological Life Support System Experimental Facility in China. Results showed that the two plants have different responses to the salt stress. The amaranth showed higher salt-tolerance with NaCl stress. If NaCl content in the solution is below 5000 ppm, the salt stress effect is insignificant on above-ground biomass output, leaf photosynthesis rate, Fv/Fm, photosynthesis pigment contents, activities of antioxidant enzymes, and inducing lipid peroxidation. On the other hand, the lettuce is sensitive to NaCl which significantly decreases those indices of growth and physiology. Notably, the lettuce remains high productivity of edible biomass in low NaCl stress, although its salt-tolerant limitation is lower than amaranth. Therefore, we recommended that amaranth could be cultivated under a higher NaCl stress condition (<5000 ppm) for NaCl recycle while lettuce should be under a lower NaCl stress (<1000 ppm) for water cleaning in future BLSS.     

A conceptual configuration of the lunar base bioregenerative life support system including soil-like substrate for growing plants

The paper presents a conceptual configuration of the lunar base bioregenerative life support system (LBLSS), including soil-like substrate (SLS) for growing plants. SLS makes it possible to combine the processes of plant growth and the utilization of plant waste. Plants are to be grown on SLS on the basis of 20 kg of dry SLS mass or 100 kg of wet SLS mass per square meter. The substrate is to be delivered to the base ready-made as part of the plant growth subsystem. Food for the crew was provided by prestored stock 24% and by plant growing system 76%. Total dry weight of the food is 631 g per day (2800 kcal/day) for one crew member (CM). The list of candidate plants to be grown under lunar BLSS conditions included 14 species: wheat, rice, soybean, peanuts, sweet pepper, carrots, tomatoes, coriander, cole, lettuce, radish, squash, onion and garlic. From the prestored stock the crew consumed canned fish, iodinated salt, sugar, beef sauce and seafood sauce. Our calculations show that to provide one CM with plant food requires the area of 47.5 m². The balance of substance is achieved by the removal dehydrated urine 59 g, feces 31 g, food waste 50 g, SLS 134 g, and also waters 86 g from system and introduction food 236 g, liquid potassium soap 4 g and mineral salts 120 g into system daily. To reduce system setup time the first plants could be sowed and germinated to a certain age on the Earth.     

The effects of composting on the nutritional composition of fibrous bio-regenerative life support systems (BLSS) plant waste residues and its impact on the growth of Nile tilapia (Oreochromis niloticus)

Utilization of bio-regenerative life support systems (BLSS) plant waste residues as a nutritional source by Nile tilapia (Oreochromis niloticus) has proven problematic as a result of high concentrations of fibrous compounds in the plant waste residues. Nutritional improvement of plant waste residues by composting with the oyster mushroom (Pleurotus ostreatus), and the effects on growth and nutrient utilization of Nile tilapia fed such residues were evaluated. Five Nile tilapia (mean weight = 70.9 ± 3.1 g) were stocked in triplicate aquaria and fed one of two experimental diets, cowpea (CP) and composted cowpea (CCP), twice daily for a period of 8 weeks. Composting of cowpea residue resulted in reduced concentrations of nitrogen-free extract, hemi-cellulose and trypsin inhibitor activity, though trypsin inhibitor activity remained high. Composting did not reduce crude fiber, lignin, or cellulose concentrations in the diet. No significant differences (P < 0.05) were observed in weight gain, specific growth rate, survival rate, daily consumption, and food conversion ratio between tilapia fed CP and CCP. These results suggest that P. ostreatus is not a suitable candidate for culture in conjunction with the culture of Nile tilapia. Additional work is needed to determine what, if any, benefit can be obtained from incorporating composted residue as feed for Nile tilapia.     

Preliminary characterization of carbon dioxide transfer in a hollow fiber membrane module as a possible solution for gas–liquid transfer in microgravity conditions

In microgravity, one of the major challenge encountered in biological life support systems (BLSS) is the gas–liquid transfer with, for instance, the necessity to provide CO₂ (carbon source, pH control) and to recover the evolved O₂ in photobioreactors used as atmosphere bioregenerative systems.     

A biological method of including mineralized human liquid and solid wastes into the mass exchange of bio-technical life support systems

The main obstacle to using mineralized human solid and liquid wastes as a source of mineral elements for plants cultivated in bio-technical life support systems (BLSS) is that they contain NaCl. The purpose of this study is to determine whether mineralized human wastes can be used to prepare the nutrient solution for long-duration conveyor cultivation of uneven-aged wheat and Salicornia europaea L. plant community. Human solid and liquid wastes were mineralized by the method of “wet incineration” developed by Yu. Kudenko. They served as a basis for preparing the solutions that were used for conveyor-type cultivation of wheat community represented by 5 age groups, planted with a time interval of 14 days. Wheat was cultivated hydroponically on expanded clay particles. To reduce salt content of the nutrient solution, every two weeks, after wheat was harvested, 12 L of solution was removed from the wheat irrigation tank and used for Salicornia europaea cultivation in water culture in a conveyor mode. The Salicornia community was represented by 2 age groups, planted with a time interval of 14 days. As some portion of the nutrient solution used for wheat cultivation was regularly removed, sodium concentration in the wheat irrigation solution did not exceed 400 mg/L, and mineral elements contained in the removed portion were used for Salicornia cultivation. The experiment lasted 4 months. The total wheat biomass productivity averaged 30.1 g · m⁻² · day⁻¹, and the harvest index amounted to 36.8%. The average productivity of Salicornia edible biomass on a dry weight basis was 39.3 g · m⁻² · day⁻¹, and its aboveground mass contained at least 20% of NaCl. Thus, the proposed technology of cultivation of wheat and halophyte plant community enables using mineralized human wastes as a basis for preparing nutrient solutions and including NaCl in the mass exchange of the BLSS; moreover, humans are supplied with additional amounts of leafy vegetables.     

Characteristics of the soil-like substrates produced with a novel technique combining aerobic fermentation and earthworm treatment

The soil-like substrate (SLS) technique is key for improving the closure of bioregenerative life support system (BLSS) by recycling the inedible biomass of higher plants. In this study, a novel SLS technique (NSLST) was proposed: aerobic fermentations at 35 °C for 1 day, then 60 °C for 6 days, finally 30 °C for 3 days, followed by earthworm treatment for 70 days. Comparing with the original SLS technique (OSLST), its process cycle was 13 days shorter, and the dry weight loss rate (81.1%) was improved by 24.77%. The cellulose and lignin degradation rates were 96.6% and 94.6%. The concentrations of available N, P and K in mature SLS were respectively 776.1 mg/L, 348.0 mg/L and 7943.0 mg/L. Low CH₄ and NH₃ production was observed, but no accumulation. According to the seed germination test, the SLSs were feasible for plant growth. This investigation will provide a preliminary foundation for BLSS design.     

Potential of salt-accumulating and salt-secreting halophytic plants for recycling sodium chloride in human urine in bioregenerative life support systems

This study addresses the possibility of growing different halophytic plants on mineralized human urine as a way to recycle NaCl from human wastes in a bioregenerative life support system (BLSS). Two halophytic plant species were studied: the salt-accumulating Salicornia europaea and the salt-secreting Limonium gmelinii. During the first two weeks, plants were grown on Knop’s solution, then an average daily amount of urine produced by one human, which had been preliminarily mineralized, was gradually added to the experimental solutions. Nutrient solutions simulating urine mineral composition were gradually added to control solutions. NaCl concentrations in the stock solutions added to the experimental and control solutions were 9 g/L in the first treatment and 20 g/L in the second treatment. The mineralized human urine showed some inhibitory effects on S. europaea and L. gmelinii. The biomass yield of experimental plants was lower than that of control ones. If calculated for the same time period (120 d) and area (1 m²), the amount of sodium chloride taken up by S. europaea plants would be 11.7 times larger than the amount taken up by L. gmelinii plants (486 g/m² vs. 41 g/m²). Thus, S. europaea is the better choice of halophyte for recycling sodium chloride from human wastes in BLSS.     

Tolerance of wheat and lettuce plants grown on human mineralized waste to high temperature stress

The main objective of a life support system for space missions is to supply a crew with food, water and oxygen, and to eliminate their wastes. The ultimate goal is to achieve the highest degree of closure of the system using controlled processes offering a high level of reliability and flexibility. Enhancement of closure of a biological life support system (BLSS) that includes plants relies on increased regeneration of plant waste, and utilization of solid and liquid human wastes. Clearly, the robustness of a BLSS subjected to stress will be substantially determined by the robustness of the plant components of the phototrophic unit. The aim of the present work was to estimate the heat resistance of two plants (wheat and lettuce) grown on human wastes. Human exometabolites mineralized by hydrogen peroxide in an electromagnetic field were used to make a nutrient solution for the plants. We looked for a possible increase in the heat tolerance of the wheat plants using changes in photosynthetically active radiation (PAR) intensity during heat stress. At age 15 days, plants were subjected to a rise in air temperature (from 23 ± 1 °C to 44 ± 1 °С) under different PAR intensities for 4 h. The status of the photosynthetic apparatus of the plants was assessed by external СО₂ gas exchange and fluorescence measurements. The increased irradiance of the plants during the high temperature period demonstrated its protective action for both the photosynthetic apparatus of the leaves and subsequent plant growth and development. The productivity of the plants subjected to temperature changes at 250 W m⁻² of PAR did not differ from that of controls, whereas the productivity of the plants subjected to the same heat stress but in darkness was halved.