- Email: [email protected]
Basic design concept of Closed Ecology Experiment Facilities
Adv. Space Res. Vol. 24, No. 3, pp.343-350, 1999 0 1999COSPAR. Published by Elsevier Science Ltd. All rights reserved
Pergamon
Printed in Great Britain
0273-l 117199$20.00+ 0.00
www.elsevier.nlhcate/asr
PII: SO273-1177(99)00322-l
BASIC DESIGN CONCEPT OF CLOSED ECOLOGY EXPERIMENT FACILITIES Keiji Nitta Institute forE~vironme~tul Sciences I- 7 Ien~m~e, .~buch~,~~~sh~, Aomori 03%32,~~p~n
ABSTRACT In order to study the relationship between the physiological metabolism of living things and the environmental factors such as the atmospheric contents and so on within the closed ecosystem, Closed Ecology Experiment FaGlities (CEEF) were designed and now under construction based on the following concents: (1) In~~dual sealed chamkrs (called modules) for the plant cultivation, animal breeding, human habitation and microbial waste treatment are to be constructed independently to be able to study the metabolic effects of each iiving thing on the environmental factors within closed ecosystem. (2) A chamber for the microbial waste treatment are to be replaced with two systems; wet oxidation reactors and chemical nitrogen fixation reactors. Atmospheric control systems are to be independently attached to each module for stabilizing atmospheric (3) contents in each module. materials having the ~ss~i~ty to absorb oxygen and carbon dioxide are to be (4 Any ~~t~~ion prohibited to use in each module for sust~~g material balance. (9 Facilities have to be developed so that the closed plant and animal experiments can be done independently, as well as integrated experiments with plants and animals through exchanging foods, carbon dioxide, Q 1999 COSPAR. Published by Elsevier Science Ltd. oxygen, condensed water and nutrient solution. INTRODUCTION Closed Ecology Experiment Facilities (CEEF) to be used for various en~o~ental studies such as on radioecology, bio-g~che~cal cycles of materials related to earth’s en~o~ent and on life support systems for fbture space use are now under design and construction at Rokkasho-mura of Aomori in northern part of Japan. The material transfers between living things and their surrounding environment are governed by the physiological metabolism of living things supported with the environmental factors such as temperature, humidity, atmospheric contents, light intensity and so on. And atmospheric contents can be easily affected by the physiological metabolism of living things within the closed sphere if the volume is not very large. In order to clarify material circulation within the ecosystem, it is preferable to separate the biological components having dif%rent c~~e~ics, such as the plants, animals and microbes, and to isolate them within different closed spheres and to measure the material circulation quantities between each isolated sphere. The concept of such artificial ecosystems originally comes Tom space cabin systems having only human beings (crew) as the biological component, but this concept seems to become very useful to study the effects of environmental factors on the behavior of various living thins and also the effects of living things on the environmental factors through material circulation. Design concepts of CEEF are based on above consideration for multi-purpose utilization through the measurements of material circulation. In this paper, the brief history of earths environment is explained with perspectives of earth environmental problems. The CEEF design philosophy is also discussed with the comparison of the results of Biosphere II closure expe~ent. BRIEF HISTORY OF EARTH It is now considered that our universe was formed from Big Bang about 15 billion years ago, and our solar system appeared about 4.5 billion years ago. The present atmosphere of earth is quite unique compared with other planets in our solar system. Earth’s atmosphere contains mostly oxygen and nitrogen, with relatively few carbon dioxide compared with Venus and Mars, and the average temperature on the surface of earth is 343
344
K. Nitta
suitable for keeping our living things. On the other hand, temperature on Venus and Mars are too high and low to sustain living things respectively. On a geologic time scale, earth’s atmosphere having much of oxygen is fairly unstable and seems difficult to be sustained. As well known, oxygen concentration on earth was very low in the initial phase as well as Venus and Mars, but it had gradually increased and reached to present value about 400 million years ago, and then stabilized with the functions of various living things. It can be said; the present earth’s environment had been developed and be maintained by living things /l/. Material Cvclincron Earth /2/. The reasons why earth’s environment has being continuously sustained for about 400 million years are not fully understood, and now our earth’s environment looks like to become destroyed by artificial materials released into our environment by human itself. A~osphe~~ compositions are obviously governed by several, material cycles such as hydrologic, bio-geochemical cycles, and the climatic process between the lithosphere, hydrosphere, cryosphere, atmosphere, and biosphere. The lithosphere (Solid Earth), including the crust, mantle, and core, is the biggest subsystem of earth with 5.976 X 102’gof mass. The hydrosphere exists on the surface of lithosphere as oceans, lakes, and rivers, and its average depth and mass are about 3.8 km and 0.00 141 X 1027grespectively. The cryosphere consists of northern and southern ice caps, and its mass has not yet accurately estimated. The atmosphere has 21% oxygen, 75% nitrogen, and about 350 ppm of carbon dioxide, and very few of other gases and it’s mass is estimated to be 0.000005 X 1O”‘g, which corresponds to 0.00009% of total mass of earth. The mass of the biosphere covering each sphere has not been accurately estimated, but is considered to be less than atmospheric mass. The earth revolves once around the sun per year and rotates once around its own spinning axis per day. Due to this spinning motion, the General Ocean Circulation (deep and surface water circulation) and General Atmospheric Circulation exists in hydrosphere and in at~sphere respectively. The quantities of material passing through between the hy~osphere and atmosphere are greatly affected by water temperature, chemical compositions in water, and ph~iologi~al activities of aquatic organisms. Flow rates of water between the spheres are complicated and their estimation is difficult with our present knowledge. Hydrologic cycles play an important role for cooling the crust and ocean surfaces. As for the carbon cycle, one of the bio-geochemical cycles, the release and absorption rates from/into the hydrosphere and lithosphere are also difficult to accurately to be estimated. Therefore it seems very useful to study on the relationship between the atmospheric environment in each sphere, and each cycle by using the artificial closed sphere because the knowledge about the hydrologic, bio-geochemical cycles and climatic process are very important to understand the behavior of earth. REQUIREMENTS FOR CEEF As well known, the construction of Biosphere II was finished in 1991 on the high plateau of Arizona desert, and the closure experiment including 8 crew lasted 2 years until Sept. 1993. About 1.5 hectares were covered with sealed glass, and contained the tropical rain forest, tropical Savannah, desert, tidal marsh, ocean, agricultural area, and living quarter. During 2 year’s closure, oxygen fraction of the atmosphere decreased from 21% to 14%. After ending the experiment, the fraction of CaC03 in the concreteswas sampled and analyzed. From these analysis, it was concluded that large quantity of oxygen was used by the bacteria in the soil, and produced carbon oxide reacted with CaOH to produce CaC03 in concretes, and thus much of carbon dioxide and oxygen were removed from the system. Therefore any materials being able to absorb carbon dioxide and/or oxygen such as concrete are to be prohibited to use in CEEF /3/. Isolation of Living Things for Metabolic Measurements The earth’s biosphere is a huge, complicated system in which 3 types of living things, namely plants, animals (including human) and microbes interact each other through food chain and/or network. Plants consume carbon dioxide and various kinds of minerals, and produce oxygen and biomass. Animals consume oxygen and edible biomass, and release carbon dioxide and excrements. Microbes consume oxygen, and produce carbon dioxide, and decompose inedible biomass and excrements. Usually, these types of living things exist together in same place. Therefore, it is very difficult to measure the metabolic material flows between them in natural environment. These material flows vary depending on the growth stage of each type of living things and on the surrounding environment. In order to clarify the effects of each type of living things, it would be
Design Concept of Closed Ecology Facilities
34s
use&l to separate the living territories for each type of living things. However it may be very diflicult to isolate these types of living things in natural environment because it disturbs the natural ecosystem, but it seems to be possible in the small and artificial ecosystem for studying the effects of these material flows on the env~o~ent in this ecosystem. Necessity of Phvsico-Chemical Svstems for Artificial Ecosvstem The volume of the natural biosphere containing atmosphere on earth is extremely large and it takes long time to detect material imbalance. In order to quickly look the effects of material imbalance on atmospheric com~nents, it may be preferable to reduce the atmospheric volume of biosphere, On the contrary, if a reduced volume of atmosphere is applied to the artificial ecosystem, the effects of material imbalance may become extremely sensitive, and become difficult to control the atmospheric contents using only physiological meta~lism of living things. Therefore it becomes essential to regulate the atmosphere contents using physico-chemical devices in small artificial ecosystem. Artificial Waste Treatment Svstem for Nutrient circulation Plant biomass and excrements from animals and human are decomposed by soil microbes in natural en~ronment; therefore it is also diflicult to isolate the microbes from plants and animals in nature. But it becomes possible using bioreactors or physico-chemical reactors instead of soil microbes to simulate the natural environment. In order to find the suitable method to decompose the biomass, feces, and urine, the performance ~h~acte~stics and developmental status about bioreactor, wet oxidation reactor, superc~tical wet oxidation reactor and incineration reactor had been surveyed, and the wet oxidation reactor was selected as the most suitable method in present stage. However, in wet oxidation reactor, some parts of nitrogen components, included in the biomass and wastes, are gasified into nitrogen gas and the residual solution does not contain enough nitrogen components for nourishing plants. Therefore, when the wet oxidation reactor is used, a nitrogen fixation reaction system composed of ammonia and nitrate synthesis units is also required. MultinIicitv fbr Ecolotical Simulation Local ecological systems ~ontain~g predo~nantly plants, or containing mostly human and mi~obial waste treatment systems, are found on earth. In order to be able to study the relatio~hip between material imbalance and environmental change in such special ecosystem, it is preferable to design the special facilities for simulat~g not only such local ecosystems, and also general integrated ecosystem. DESIGN PHILOSOPHY FOR CEEF /4/ Based upon above consideration, a design philosophy for CEEF has been determined as follows: (I) Individual sealed chambers (called modules) for plant cultivation, animal breeding, human habitation and ~crobial waste treatment are to be constructed independently to be able to study the metabolic effects of each living thiig on the environmental factors within closed ecosystem. (2) A chamber for microbial waste treatment are to be replaced with two physico-chemical systems; wet oxidation reactors and chemical nitrogen fixation reactors. (3) Atmospheric control systems are to be independently attached to each module for stabilizing atmospheric contents in each module. (4) Any ~~t~~tion materials having the possibility to absorb oxygen and carbon dioxide are to be prohibited to use in each module for sustaining material balance. (5) Facilities have to be developed so that the closed plant and animal experiments can be done independently, as well as integrated experiments with plants and animals through exchanging foods, carbon dioxide, oxygen, condensed water and nutrient solution. Present Situation and Future Overview on CEEF /5/ Based on the design philosophy mentioned, the methods making material circulation for realizing the independent and integrated experiments were investigated. As a result of these investigations, two types of
346
K. Nitta
material circulation systems to be attached to pl~tation module and animal breeding & habitation module were derived as shown in Fig. 1 and Fig. 2. As shown in the figures, integrated experiments can be easily conducted using pipe lines for transporting the necessary materials, such as foods, condensed water, oxygen gas, nitrogen gas, carbon dioxide gas and nutrient solution. Each material circulation system contains the atmospheric control system, water recovery system, trace contaminant control system, and wet oxidation system for decomposition of inedible biomass or human & animal wastes. In addition to these common systems, material circulation system (I) to be attached to pl~tation module contains biomass separation system for supplying food, nitrogen fixation system and nutrient control system for cultivating plants. On the other hand, material circulation system (II) contains salt recovery system. Detailed designs had been conducted for the plantation module, material circulation systems (I) and (II), animal breeding& habitation module, an utility system including chiller and boiler systems for air-conditioning in each module, and a water purification system in fiscal year 1993. In addition, the plant cultivation building (PCB) for accommodating the plantation module, material circulation system build~g (MCSB I and MCSB II) for acco~odating material circulation systems I and II, cultivation support building (CSB) to be used for plant research, utility building (LIB) for utility system, and experiment control building (ECB) to be used for accommodating animal breeding & habitation module and control room were designed in fiscal year 1993. Based on these designs, PCB, MCSB I, CSB, UB and ECB were constructed in fiscal year 1994. Fig. 3 shows the plane figure ~dicating the size of each building, and Fig. 4 shows the photograph of the total buildings already constructed. In parallel with this construction, 3 plantation modules with artificial light (by high pressure sodium lamp) having 3Om* cultivation area per each, and the minimum parts of material circulation system (I) have been developed and installed in the 1st floor of PCB and in MCSB I respectively in fiscal year 1994. Fig. 5 shows the photograph indicating the inside view of plantation module. In fiscal year 1995, a material circulation system building (MCSB II) was constructed for preparing the installation of material circulation system II. In parallel with this building construction, one plantation module with glass cover for receiving solar light, having 60 m’ cultivation area, and some parts of material circulation system I including at~spheric control system, water recovery system, wet oxidation system, nitrogen fixation system, and nutrient control system were developed and installed in the 2nd floor of PCB and in the 1st floor of MCSB I. Fig. 6 shows the photograph indicating plantation module with glass cover installed in the 2nd floor of PCB, and Fig. 7 shows the photograph of wet oxidation system installed in MCSB I. Animal breeding and habitation module, material circulation system II, and residual parts of material circulation Gee-hydrosphere system I will be developed and installed during next two years (fiscal year 1996-1997). experiment facility is now in design phase, and will be developed and installed during fiscal year 1997-1999.
CONCLUDING REMARKS Artificial ecosystem being able to be organized by these facilities (CEEF) are quite different from natural systems because all plant species are collected in one place and isolated from all animal species, and microbial species are replaced by physico-chemical decomposition system composed of wet oxidation systems and nitrogen fixation systems. The effects of the plant and animal metabolism on the environmental factors, such as atmospheric contents, can be evaluated through the material circulation measurements between their respective modules and decomposition systems. After establishing the stable artificial ecosystem of animals and plants using these physico-chemical decomposition systems, it seems possible to introduce the necessary amount of microbes conta~ed in soil into pl~tation module or animal breeding & habitation module. Therefore it may be possible to evaluate the behaviors of soil microbes in ecosystem using these facilities. These facilities have the limited capacity to support many crew and therefore can not be used for studying the group dynamics of human psychology, but would be used to check the capability of life support system for space use as the ground test facilities.
347
Design Concept of Closed Ecology Facilities
ANIMAL BREEDING & ~ITAT~N MODULE
URINE MINERAL FECES
FOODS WASTE WASH k’iAlER &
HUMlDiiY
-l-t-t-I
EXCESS WATER
1
ANIMAL BREEDING & HABITATION SYSTEM INTERFACE
Figure I
Material circulation system of Animal Breeding & Habitation Module
PLANTATION MODULE withartificiallightingand naturallighting
k I
1
AIR I
-
02
1 WASlE _Ic
.I.
NZ
I I
I
\G WATER
EXCESS WATER
NUTRIENT
PLANT CULTlVATtON SYSTEM INTERFACE I
Figure 2
Material circulation system of Plantation Module
348
K. Nitta
lJB CULTIVATION SUPPORT BUILDING
UTILITY BUILDING
MCSB I
PCB
MATERIAL CIRCU~TION SYSTEM BUILDING I
PLANT CULTIVATION BUILDING
CR
CORRIDOR
+
vIcsl3 II MATERIAL CIRCU~TI~N SYSTEM BUILDING II _...____.....__.............. ANIMAL BREEDING 8 HABITATION MODULE
GHEB 3,314 1
1,585 1
4,959 1
i GEO-HYDROSPHERE ; ~P~RIMENT ; BUILDING
: ,_......:
1....................................-...~
Figure 3
CORRIDOR
0 5
Plane figure of Closed Ecology Experiment Facilities (CEEF)
Figure 4
Photograph of the total buildings already constructed
2Om
Design Concept of Closed Ecology Facilities
Figure 5
Figure 6
Plantation Module with artificial lighting
~la~tat~~~Module with glass cuver far receiving solar aught
349
K. Nitta
350
Figure 7
Wet Oxidation System
REFERENCES 1) 2) 3) 4)
Keiji Nitta, Living Space-Natura~~i~cial (Japanese), Series of Problems in 21 century, Iwanamishoten (1996). Kei-ichiro Fuwa et al., Earth Environment Hand Book (Japanese), Asakurashoten (1994). J. P. Severinghaus, et al., Oxygen Loss in Biosphere 2, EOS 1994; 75; 33-7 (1994) Keiji Nitta, Earth Environment and Closed Ecology Experiment Facilities, Acta Astronautica Vol. 33, pp 155-165, Pergamon (1994).
Pergamon
Printed in Great Britain
0273-l 117199$20.00+ 0.00
www.elsevier.nlhcate/asr
PII: SO273-1177(99)00322-l
BASIC DESIGN CONCEPT OF CLOSED ECOLOGY EXPERIMENT FACILITIES Keiji Nitta Institute forE~vironme~tul Sciences I- 7 Ien~m~e, .~buch~,~~~sh~, Aomori 03%32,~~p~n
ABSTRACT In order to study the relationship between the physiological metabolism of living things and the environmental factors such as the atmospheric contents and so on within the closed ecosystem, Closed Ecology Experiment FaGlities (CEEF) were designed and now under construction based on the following concents: (1) In~~dual sealed chamkrs (called modules) for the plant cultivation, animal breeding, human habitation and microbial waste treatment are to be constructed independently to be able to study the metabolic effects of each iiving thing on the environmental factors within closed ecosystem. (2) A chamber for the microbial waste treatment are to be replaced with two systems; wet oxidation reactors and chemical nitrogen fixation reactors. Atmospheric control systems are to be independently attached to each module for stabilizing atmospheric (3) contents in each module. materials having the ~ss~i~ty to absorb oxygen and carbon dioxide are to be (4 Any ~~t~~ion prohibited to use in each module for sust~~g material balance. (9 Facilities have to be developed so that the closed plant and animal experiments can be done independently, as well as integrated experiments with plants and animals through exchanging foods, carbon dioxide, Q 1999 COSPAR. Published by Elsevier Science Ltd. oxygen, condensed water and nutrient solution. INTRODUCTION Closed Ecology Experiment Facilities (CEEF) to be used for various en~o~ental studies such as on radioecology, bio-g~che~cal cycles of materials related to earth’s en~o~ent and on life support systems for fbture space use are now under design and construction at Rokkasho-mura of Aomori in northern part of Japan. The material transfers between living things and their surrounding environment are governed by the physiological metabolism of living things supported with the environmental factors such as temperature, humidity, atmospheric contents, light intensity and so on. And atmospheric contents can be easily affected by the physiological metabolism of living things within the closed sphere if the volume is not very large. In order to clarify material circulation within the ecosystem, it is preferable to separate the biological components having dif%rent c~~e~ics, such as the plants, animals and microbes, and to isolate them within different closed spheres and to measure the material circulation quantities between each isolated sphere. The concept of such artificial ecosystems originally comes Tom space cabin systems having only human beings (crew) as the biological component, but this concept seems to become very useful to study the effects of environmental factors on the behavior of various living thins and also the effects of living things on the environmental factors through material circulation. Design concepts of CEEF are based on above consideration for multi-purpose utilization through the measurements of material circulation. In this paper, the brief history of earths environment is explained with perspectives of earth environmental problems. The CEEF design philosophy is also discussed with the comparison of the results of Biosphere II closure expe~ent. BRIEF HISTORY OF EARTH It is now considered that our universe was formed from Big Bang about 15 billion years ago, and our solar system appeared about 4.5 billion years ago. The present atmosphere of earth is quite unique compared with other planets in our solar system. Earth’s atmosphere contains mostly oxygen and nitrogen, with relatively few carbon dioxide compared with Venus and Mars, and the average temperature on the surface of earth is 343
344
K. Nitta
suitable for keeping our living things. On the other hand, temperature on Venus and Mars are too high and low to sustain living things respectively. On a geologic time scale, earth’s atmosphere having much of oxygen is fairly unstable and seems difficult to be sustained. As well known, oxygen concentration on earth was very low in the initial phase as well as Venus and Mars, but it had gradually increased and reached to present value about 400 million years ago, and then stabilized with the functions of various living things. It can be said; the present earth’s environment had been developed and be maintained by living things /l/. Material Cvclincron Earth /2/. The reasons why earth’s environment has being continuously sustained for about 400 million years are not fully understood, and now our earth’s environment looks like to become destroyed by artificial materials released into our environment by human itself. A~osphe~~ compositions are obviously governed by several, material cycles such as hydrologic, bio-geochemical cycles, and the climatic process between the lithosphere, hydrosphere, cryosphere, atmosphere, and biosphere. The lithosphere (Solid Earth), including the crust, mantle, and core, is the biggest subsystem of earth with 5.976 X 102’gof mass. The hydrosphere exists on the surface of lithosphere as oceans, lakes, and rivers, and its average depth and mass are about 3.8 km and 0.00 141 X 1027grespectively. The cryosphere consists of northern and southern ice caps, and its mass has not yet accurately estimated. The atmosphere has 21% oxygen, 75% nitrogen, and about 350 ppm of carbon dioxide, and very few of other gases and it’s mass is estimated to be 0.000005 X 1O”‘g, which corresponds to 0.00009% of total mass of earth. The mass of the biosphere covering each sphere has not been accurately estimated, but is considered to be less than atmospheric mass. The earth revolves once around the sun per year and rotates once around its own spinning axis per day. Due to this spinning motion, the General Ocean Circulation (deep and surface water circulation) and General Atmospheric Circulation exists in hydrosphere and in at~sphere respectively. The quantities of material passing through between the hy~osphere and atmosphere are greatly affected by water temperature, chemical compositions in water, and ph~iologi~al activities of aquatic organisms. Flow rates of water between the spheres are complicated and their estimation is difficult with our present knowledge. Hydrologic cycles play an important role for cooling the crust and ocean surfaces. As for the carbon cycle, one of the bio-geochemical cycles, the release and absorption rates from/into the hydrosphere and lithosphere are also difficult to accurately to be estimated. Therefore it seems very useful to study on the relationship between the atmospheric environment in each sphere, and each cycle by using the artificial closed sphere because the knowledge about the hydrologic, bio-geochemical cycles and climatic process are very important to understand the behavior of earth. REQUIREMENTS FOR CEEF As well known, the construction of Biosphere II was finished in 1991 on the high plateau of Arizona desert, and the closure experiment including 8 crew lasted 2 years until Sept. 1993. About 1.5 hectares were covered with sealed glass, and contained the tropical rain forest, tropical Savannah, desert, tidal marsh, ocean, agricultural area, and living quarter. During 2 year’s closure, oxygen fraction of the atmosphere decreased from 21% to 14%. After ending the experiment, the fraction of CaC03 in the concreteswas sampled and analyzed. From these analysis, it was concluded that large quantity of oxygen was used by the bacteria in the soil, and produced carbon oxide reacted with CaOH to produce CaC03 in concretes, and thus much of carbon dioxide and oxygen were removed from the system. Therefore any materials being able to absorb carbon dioxide and/or oxygen such as concrete are to be prohibited to use in CEEF /3/. Isolation of Living Things for Metabolic Measurements The earth’s biosphere is a huge, complicated system in which 3 types of living things, namely plants, animals (including human) and microbes interact each other through food chain and/or network. Plants consume carbon dioxide and various kinds of minerals, and produce oxygen and biomass. Animals consume oxygen and edible biomass, and release carbon dioxide and excrements. Microbes consume oxygen, and produce carbon dioxide, and decompose inedible biomass and excrements. Usually, these types of living things exist together in same place. Therefore, it is very difficult to measure the metabolic material flows between them in natural environment. These material flows vary depending on the growth stage of each type of living things and on the surrounding environment. In order to clarify the effects of each type of living things, it would be
Design Concept of Closed Ecology Facilities
34s
use&l to separate the living territories for each type of living things. However it may be very diflicult to isolate these types of living things in natural environment because it disturbs the natural ecosystem, but it seems to be possible in the small and artificial ecosystem for studying the effects of these material flows on the env~o~ent in this ecosystem. Necessity of Phvsico-Chemical Svstems for Artificial Ecosvstem The volume of the natural biosphere containing atmosphere on earth is extremely large and it takes long time to detect material imbalance. In order to quickly look the effects of material imbalance on atmospheric com~nents, it may be preferable to reduce the atmospheric volume of biosphere, On the contrary, if a reduced volume of atmosphere is applied to the artificial ecosystem, the effects of material imbalance may become extremely sensitive, and become difficult to control the atmospheric contents using only physiological meta~lism of living things. Therefore it becomes essential to regulate the atmosphere contents using physico-chemical devices in small artificial ecosystem. Artificial Waste Treatment Svstem for Nutrient circulation Plant biomass and excrements from animals and human are decomposed by soil microbes in natural en~ronment; therefore it is also diflicult to isolate the microbes from plants and animals in nature. But it becomes possible using bioreactors or physico-chemical reactors instead of soil microbes to simulate the natural environment. In order to find the suitable method to decompose the biomass, feces, and urine, the performance ~h~acte~stics and developmental status about bioreactor, wet oxidation reactor, superc~tical wet oxidation reactor and incineration reactor had been surveyed, and the wet oxidation reactor was selected as the most suitable method in present stage. However, in wet oxidation reactor, some parts of nitrogen components, included in the biomass and wastes, are gasified into nitrogen gas and the residual solution does not contain enough nitrogen components for nourishing plants. Therefore, when the wet oxidation reactor is used, a nitrogen fixation reaction system composed of ammonia and nitrate synthesis units is also required. MultinIicitv fbr Ecolotical Simulation Local ecological systems ~ontain~g predo~nantly plants, or containing mostly human and mi~obial waste treatment systems, are found on earth. In order to be able to study the relatio~hip between material imbalance and environmental change in such special ecosystem, it is preferable to design the special facilities for simulat~g not only such local ecosystems, and also general integrated ecosystem. DESIGN PHILOSOPHY FOR CEEF /4/ Based upon above consideration, a design philosophy for CEEF has been determined as follows: (I) Individual sealed chambers (called modules) for plant cultivation, animal breeding, human habitation and ~crobial waste treatment are to be constructed independently to be able to study the metabolic effects of each living thiig on the environmental factors within closed ecosystem. (2) A chamber for microbial waste treatment are to be replaced with two physico-chemical systems; wet oxidation reactors and chemical nitrogen fixation reactors. (3) Atmospheric control systems are to be independently attached to each module for stabilizing atmospheric contents in each module. (4) Any ~~t~~tion materials having the possibility to absorb oxygen and carbon dioxide are to be prohibited to use in each module for sustaining material balance. (5) Facilities have to be developed so that the closed plant and animal experiments can be done independently, as well as integrated experiments with plants and animals through exchanging foods, carbon dioxide, oxygen, condensed water and nutrient solution. Present Situation and Future Overview on CEEF /5/ Based on the design philosophy mentioned, the methods making material circulation for realizing the independent and integrated experiments were investigated. As a result of these investigations, two types of
346
K. Nitta
material circulation systems to be attached to pl~tation module and animal breeding & habitation module were derived as shown in Fig. 1 and Fig. 2. As shown in the figures, integrated experiments can be easily conducted using pipe lines for transporting the necessary materials, such as foods, condensed water, oxygen gas, nitrogen gas, carbon dioxide gas and nutrient solution. Each material circulation system contains the atmospheric control system, water recovery system, trace contaminant control system, and wet oxidation system for decomposition of inedible biomass or human & animal wastes. In addition to these common systems, material circulation system (I) to be attached to pl~tation module contains biomass separation system for supplying food, nitrogen fixation system and nutrient control system for cultivating plants. On the other hand, material circulation system (II) contains salt recovery system. Detailed designs had been conducted for the plantation module, material circulation systems (I) and (II), animal breeding& habitation module, an utility system including chiller and boiler systems for air-conditioning in each module, and a water purification system in fiscal year 1993. In addition, the plant cultivation building (PCB) for accommodating the plantation module, material circulation system build~g (MCSB I and MCSB II) for acco~odating material circulation systems I and II, cultivation support building (CSB) to be used for plant research, utility building (LIB) for utility system, and experiment control building (ECB) to be used for accommodating animal breeding & habitation module and control room were designed in fiscal year 1993. Based on these designs, PCB, MCSB I, CSB, UB and ECB were constructed in fiscal year 1994. Fig. 3 shows the plane figure ~dicating the size of each building, and Fig. 4 shows the photograph of the total buildings already constructed. In parallel with this construction, 3 plantation modules with artificial light (by high pressure sodium lamp) having 3Om* cultivation area per each, and the minimum parts of material circulation system (I) have been developed and installed in the 1st floor of PCB and in MCSB I respectively in fiscal year 1994. Fig. 5 shows the photograph indicating the inside view of plantation module. In fiscal year 1995, a material circulation system building (MCSB II) was constructed for preparing the installation of material circulation system II. In parallel with this building construction, one plantation module with glass cover for receiving solar light, having 60 m’ cultivation area, and some parts of material circulation system I including at~spheric control system, water recovery system, wet oxidation system, nitrogen fixation system, and nutrient control system were developed and installed in the 2nd floor of PCB and in the 1st floor of MCSB I. Fig. 6 shows the photograph indicating plantation module with glass cover installed in the 2nd floor of PCB, and Fig. 7 shows the photograph of wet oxidation system installed in MCSB I. Animal breeding and habitation module, material circulation system II, and residual parts of material circulation Gee-hydrosphere system I will be developed and installed during next two years (fiscal year 1996-1997). experiment facility is now in design phase, and will be developed and installed during fiscal year 1997-1999.
CONCLUDING REMARKS Artificial ecosystem being able to be organized by these facilities (CEEF) are quite different from natural systems because all plant species are collected in one place and isolated from all animal species, and microbial species are replaced by physico-chemical decomposition system composed of wet oxidation systems and nitrogen fixation systems. The effects of the plant and animal metabolism on the environmental factors, such as atmospheric contents, can be evaluated through the material circulation measurements between their respective modules and decomposition systems. After establishing the stable artificial ecosystem of animals and plants using these physico-chemical decomposition systems, it seems possible to introduce the necessary amount of microbes conta~ed in soil into pl~tation module or animal breeding & habitation module. Therefore it may be possible to evaluate the behaviors of soil microbes in ecosystem using these facilities. These facilities have the limited capacity to support many crew and therefore can not be used for studying the group dynamics of human psychology, but would be used to check the capability of life support system for space use as the ground test facilities.
347
Design Concept of Closed Ecology Facilities
ANIMAL BREEDING & ~ITAT~N MODULE
URINE MINERAL FECES
FOODS WASTE WASH k’iAlER &
HUMlDiiY
-l-t-t-I
EXCESS WATER
1
ANIMAL BREEDING & HABITATION SYSTEM INTERFACE
Figure I
Material circulation system of Animal Breeding & Habitation Module
PLANTATION MODULE withartificiallightingand naturallighting
k I
1
AIR I
-
02
1 WASlE _Ic
.I.
NZ
I I
I
\G WATER
EXCESS WATER
NUTRIENT
PLANT CULTlVATtON SYSTEM INTERFACE I
Figure 2
Material circulation system of Plantation Module
348
K. Nitta
lJB CULTIVATION SUPPORT BUILDING
UTILITY BUILDING
MCSB I
PCB
MATERIAL CIRCU~TION SYSTEM BUILDING I
PLANT CULTIVATION BUILDING
CR
CORRIDOR
+
vIcsl3 II MATERIAL CIRCU~TI~N SYSTEM BUILDING II _...____.....__.............. ANIMAL BREEDING 8 HABITATION MODULE
GHEB 3,314 1
1,585 1
4,959 1
i GEO-HYDROSPHERE ; ~P~RIMENT ; BUILDING
: ,_......:
1....................................-...~
Figure 3
CORRIDOR
0 5
Plane figure of Closed Ecology Experiment Facilities (CEEF)
Figure 4
Photograph of the total buildings already constructed
2Om
Design Concept of Closed Ecology Facilities
Figure 5
Figure 6
Plantation Module with artificial lighting
~la~tat~~~Module with glass cuver far receiving solar aught
349
K. Nitta
350
Figure 7
Wet Oxidation System
REFERENCES 1) 2) 3) 4)
Keiji Nitta, Living Space-Natura~~i~cial (Japanese), Series of Problems in 21 century, Iwanamishoten (1996). Kei-ichiro Fuwa et al., Earth Environment Hand Book (Japanese), Asakurashoten (1994). J. P. Severinghaus, et al., Oxygen Loss in Biosphere 2, EOS 1994; 75; 33-7 (1994) Keiji Nitta, Earth Environment and Closed Ecology Experiment Facilities, Acta Astronautica Vol. 33, pp 155-165, Pergamon (1994).