Interface problems between material recycling systems and plants

Adv. Space Ru. Vol. 12, No.5, pp. (5)1 l—(5)19, 1992 Printed in Great Britain. All rights reserved.

0273.-i 177/92 $15.00 Copyright 0 1991 COSPAR

INTERFACE PROBLEMS BETWEEN MATERIAL RECYCLING SYSTEMS AND PLANTS Keiji Nitta, Mitsuo Oguchi and Koji Otsubo Space TechnologyResearch Group, National AerospaceLaboratory, 7-44-1 Jindaiji-Higashimachi, Chofu, Tokyo 182, Japan

ABSTRACT A most important problem to creating a CELSS system to be used in space, for example,for a Lunar Base or Manned Mars mission, seems to be how to design and operate the various material recycling system to be used on the missions. Recent studies of a Lunar Base habitat have identified examples ofCELSS configurations to be used for the Plant Cultivation Module. Material recycling subsystems to be installed in the Plant Cultivation Modules are proposed to consist of various sub-systems, such as dehumidifier, oxygen separation systems, catalytic wet oxidation systems, nitrogen adjustingsystems, including tanks, and so on. The required performances of such various material recycling subsystems are determined based on precise metabolic data of derived from the various species of plants to be selected and investigated. The plant metabolic data, except that for wheat and potato, has not been fully collected at the present time. Therefore, much additional plant cultivation data is required to determine the performances of each material recycling subsystems introduced in Plant Cultivation Modules. INTRODUCTION A conceptual design study of an enclosed ecological life support system to be used in Lunar Base was conducted in 1989, and the preliminary results of this study had been reported in 8th IAA Man in Space Symposium and the 40th Congress ofIAF./1/, /2!. This study has identified three scenarios as follows: Scenario I;

Initial permanent base, composed of two Habitats and one Power Modules, is to be installed in the first year during the construction phase and after that, this permanent base is to be extended by adding one module every year.

Scenario II;

Initial permanent base, same as in Scenario I, is installed and extended by adding two modules every year.

Scenario III;

Initial base is also same one, and three modules are added every year.

With Scenario I, it is demonstrated that initial crew number of 8 cannot be increased during ten years. However, with Scenarios II and Ill, crew number can easily increase from 8 to 16 during ten years. In Scenarios II, onlyone Experiment Module can be installedduring 10 years and itbecomes very difficult to extend the missions to be conducted in the Lunar Base. Therefore Scenario Ill becomesthe most preferable one. The shape, size and weight ofone module has estimated to be a cylinder 4.5 m~X 15 m, with a mass of of 25 tons. Table I shows the number of each module to be constructed every each year and living density ofcrews in Scenario III. (5)11

K. Nitta er al.

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Table I Third Scenario year Habitat Module

1

2

2

2

Plant Cultivation Module Power Generation Module

1

Living Density(m2!person)

1

4 2

5

8 15

6

7

2

2

2

1

1

8

9

10

2

2

1

1

3

16 30

16 30

16 30

1

Experiment Module CrewNumber

3

8 30

2

1

1

8 30

8 30

8 30

12 30

16 30

The life support systems to be installed in each module should be determined based upon the purpose of each module. Power and experiment Modules are to be used for just working area of crews, and should be equipped with a small subsystem that satisfies the minimum requirement for life support, such as dehumidification, CO 2 elimination, oxygen supply and trace contaminate decomposition, because ordinary life performances such as eating, athletic training, reading, body washing, hand washing and so on, will be carried out in Habitat Modules. Therefore the oxygen supply, water condensation and CO2 elimination are to be done using connecting pipe lines between the Power and Experiment modules and the Habitat module. In Habitat Module, it is matter of course, life support of the crews is to be conducted in conjunction with Plant Cultivation Modules. Therefore, the life support systems to be installed in Habitat and Plant Cultivation Modules should be determined based on the various considerations about development cost, bio-hazard protection, ease ofcontrol, operation cost and so on. METABOLIC DATA ON HUMAN BEINGS AND PLANTS Human metabolism is determined according energy consumption, and 2800 kcal is considered to be a requisite for sustaining the diary life. In order to satisfy such an energy intake, well balanced foods with a mass of about 618 g, water with a mass of about 3077 g, and an oxygen mass of 863 g for respiration are to be taken in, and about 200 g of solid waste, including 91 g water content, 3331 g of water such as sweat, urine, evaporation through respiration and about 1000 g of carbon dioxide are expelled as shown in Fig.1.

Foods (618g) Water (3077g) Oxygen (836g)

~

~

Solid Waste (200g)

Water including urine, (3331g) sweat and others ~-

Fig. 1. Human Metabolism (!person X day)

Carbon Dioxide (l000g)

Problems Between Material Recycling Systemsand Plants

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The metabolic quantity of plants is greatly changed during growing stage from germination to harvesting. Averaged quantity of metabolism for obtaining necessary foods (618 g) can be estimatedbased upon photosynthetic system equation originally introduced by Volk and Ruminel as follows, Photosynthesis Edible : 26.127C02 + 22.563H20 + 0.4918NH3 + 0.9628HN03 1.453C4H5ON + 3.190C6H12O6 + 0.07182C16H3202 + 28.531002

Inedible

: 38.903C02+22.520H20+2.713NH3+0.9611HNO3 3.674C4H5ON + 2.6887C6H10O5 +0.8016C10H1102 +42.23602

From these system equations, the averaged metabolic quantity of plants producing the required amount offoods for crew is to be described as shown in Fig.2. CO2 (2861g) Water 2g) (81 NH 3 (55g) HNO3 (121g) Minerals

Edibles(Foods) (618g)

Inedibles (817g) _________

________________________

02 (2265g)

Fig. 2. Averaged Plant Metabolism (/personX day) MATERIAL RECYCLING SYSTEMS TO BE INSTALLED IN HABITAT AND PLANT CULTIVATION MODULES Edible parts of plants and about 1000 g of oxygen shown in the right side of Fig. 2 are to be sent to Habitat Module to support crew life, but inedible parts of plants must be retained in Plant Cultivation Module itself to avoid excess transportation from Plant Cultivation Module to Habitat Module. On the other hand, solid waste, urine and sweat in Fig. 1. containing nitrogen components are produced in the habitat module; these materials are preferably removed as soon as possible to keep a clean environment in Habitat Module, and will be oxidized using a catalytic wet oxidation method. Of special interest is the possibility of using the perspiration, containing sodium chloride and other minerals, produced by the crew; therefore a saltrecoverysystem is to be installed in Habitat Module. As already reported, /3!, organic carbon can be completely decomposed to carbon dioxide, and 95.5% of nitrogen components included in organic materials is changed to gaseous nitrogen during the catalytic wet oxidation reaction. Therefore it is necessary to fix gaseous nitrogen to obtain ammonia and nitrate shown in Fig. 2 These ammonia and nitrate compounds are used as the plant fertilizer. Nitrogen coming from human waste and also from inedible plant of plants is to be used to synthesize ammonia and nitrate. For this reason, a nitrogen fixation system must be installed in Plant Cultivation Module.

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Based upon these considerations, the material recycling systems such as shown in Fig. 3 and 4 and Table II, seem to be required in the Habitat Module and Plant Cultivation Module respectively. When only the Habitat Module is used, without any connection to Plant Cultivation Module, such as in very beginning of Lunar base construction phase, additional water reclamation systems may be needed in the Habitat Module itself. This is to address the possibility the insufficient drinking water might be available otherwise. To install the water reclamation system or not will be determined from results of more detailed analysis about water circulation in whole system. From Plants Cultivation Module

Foods (Edible Parts of Plants)

Air

Human O~,N2

s~ Urine’

~ ~ater’~i

1/cII)

Drinking Water

i

rri~~e

Feces Salt(Sodium Chloride)

_______

~

A

10

6

7

11

12

.1 I.

£1212

“\

I

—

1”

_________

-

~

8

144•

Ti. . .

Nitrogen Oxygen To Plant Cultivation Module Fig. 3. Material Recycling System in Habitat Module

Sediment

Problems Between Material Recycling Systems and Plants

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To Habitat Module

PlantBIO~IASS

Air

__

_

________ Oxygen

02,

2’

~

CO 02

______

4

___2)

2

Foods to Habitat [odule

--

()

~

~-.-

-

Nutrient Solution

~~O2ir~i

Inedible

IL

Carbon f ~m Habitat] lodule )‘

~ ______

~

HNO3_~_ ‘~-‘NH

‘~

iH~

J02

-~Q!)--’(~)

16

21

Water ~Sediment _________________________

CO2,

H2O

N2

From Habitat Module Fig. 4. Material Recycling System in Plant Cultivation Module

Nutrient From Habitat

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K. Nina et al.

Table II. List of subsystems in Habitat and Plant Cultivation Modules Habitat Module Number

Names of Subsystems

Plant Cultivation Module Number

Names of Subsystems

1

CO2 Separator

1

Harvestor

2

Toilet

2

Trace Contaminant Decompose

3 4 5

Trace Contaminant Decompose Dehumidifier Clean Water Tank

3

Edible Separator

4 5

Oxygen Tank Carbon Dioxide Tank

6 7

Urine Tank Pulverizer

6 7

Water Reclamation Nutrient Adjuster

8 9

Waste Water Tank CO2 Tank

10 11

Oxygen Separator Wet Oxidation 1

Dehumidifier Oxygen Separator Oxygen Separator Nutrient Tank I

12 13

Wet Oxidation II CO2 Separator

8 9 10 11 12

14

15 16

13

Ammonia Tank Nitrate Tank

Fertilizer Tank Mineral Recovery System

14 15

Nutrient Tank 11 Diluting Water Tank

Condenser

16

Pulverizer

17 18 19

Oxygen Recovery Oxygen Tank Mineral Water Tank

17 18 19

Dehumidifier Nitrogen Tank Ammonia Synthesizer

20

Water Reclamation Tank

20 21 22 23

Nitrate Synthesizer Water Tank Mixer Wet Oxidation III

24

Carbon Dioxide Separator Electrolysis

25

Carbon dioxide, oxygen concentrations and humidity in Plant Cultivation Module will be regulated using a dehumidifier, an oxygen separation system and a carbon dioxide supply system connected with CO2 tank equipped in Plant Cultivation Module itself. The main sources of nutrient for cultivation are clearly human feces and inedible parts ofplants. All human feces and inedible parts of plants are to be oxidized using two catalytic wet oxidation systems located in Habitat Module and

Plant Cultivation Module respectively. Nutrient solutions coming from each catalytic wet oxidation system contain different concentrations of required various ions except nitrogen, therefore two different tanks are to be installed as nutrient tanks, and in addition, ammonia and nitrate tanks are required to provide nitrogen ions, and in order

to obtain appropriate nutrient concentrations, diluting water tank will be again required as show in Fig. 4. EXPRIMENTAL SMALL CLOSED CHAMBER It is necessary to estimate the flow quantity of materials through the plants by photosynthetic function and respiration in order to determine design parameters of each material recycling subsystem, therefore the metabolic balance of each plant species to be used in CELSS should be

Problems Between Material Recycling Systems and Plants

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determined from experiments. It will take long time until enough data about the various kinds of plants is accumulated, and parallel measurements of each plant using small closed chamber system are preferable to save the time. The first exprimental small closed chamber system in National Aerospace Laboratory has been installed and precise testing is now going under way. This experimental system can be divided to

five subsystems: lighting subsystem, growth box subsystem, air conditioning subsystem, gas measurement subsystem and gas concentration control subsystem. Specified items regarding each subsystems are as follows: (1) Lighting Subsystem Lighting Source Cooling method

: 3 “100w” BOC lamps for giving until to 50k lux to plant leaves : Cooling ventilation for lamps, and water filterto prevent heat radiation.

(2) Growth Box Subsystem Box size : 450mm 4~W,l000mmH, transparent acrylic resin Hight Control : Manual control for keeping appropriate illumination Nutrient solution control : Temperature control, nutrient regulator with 5 tanks, oxygen desolver, EC, PH, DO, measurements. (3) Air Conditioning Chamber Subsystem Chamber Size : 1500mm W, 1000 mm L, 1000mm H, acrylic resin Temperature and Humidity Control : Temperature, 10-35°C,humidity, 60-80%RH CO 2 Supply and Concentration Control: From 400 1 CO2 gas mixing tank, controlled with molecular sieves (4) Gas Measurement Subsystem CO2 Measurement: Infrared CO2 gas analyzer, 0-l000ppm Absolute, 0-50ppm Duff. Measurement: To be determined Transpiration Measurement : Differential humiditymeasurement between inlet and outlet

°2

of growth box (5) Gas Concentration Control Subsystem CO2 Concentration Control : Control with molecular sieves 02 Concentration Control : With zirconia oxygen pump.

The system block diagram of whole small closed chamber system is shown in Figs. 5 and Fig. 6. Cultivation experiments about crop plant using this system has been planned, and now testing 02 measurement accuracy in order to determine the sort of 02 sensor to be integrated in this chamber system. CONCLUSION Through the study about Lunar Base Construction, a very clear system image and knowledge of the kinds of material recycling subsystem to be integrated in Habitat Module and Plant Cultivation Module, has been obtained. Every environment control subsystems such as CO2 supply, 02 elimination and appropriate nutrient solution supply, waste water elimination should be controlled based upon the metabolic requirement of all plants inside of the Plant Cultivation Module, nutrient sources are of course very limited in closed system as shown in Fig. 4. Therefore, the plant cultivation experiments in the same limited condition are to be required to obtain useful metabolic balance data for determining control methods regarding material recycling using ground based small growth chamber. Based upon the consideration above, ground based experimental growth chamber system had been designed and has been manufactured, and performance characteristics of this chamber system have been tested, after integrating proper 02 sensor, cultivation experiment using crop seeds will begin in very near future. JASR

12:5—C

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K. Nina et al.

- --

25

Heaterr Cooler

30

~

~

~8

~ 1 T

::m~rB

Growth Box B Temperature, Humid~tySensors (inlet) Temperature, Humidity Sensors (outlet) Circulation Blower Regulating Valve

6 7 8 9 10 ii 12 13 14 15 16

Flowmeter Regulating Valve Regulating Valve Control Valve CO2 Scruber 02 Pump regulating Valve Water FItter BOC Lamps Cooler Filter

_____________________

B

17 18 19 20 21 3

22

24

B

Fig. 5

22 23 24 25 26 27 28 29 30 31

Ion Exchange Filter Regulating Valve Dehumidifier Dehumidifier CO 2 Analyzer On-Off Valve On-O~fValve 02 Analyzer Air Condifioning Unit Nutrient Regulating Systems Drain Tank Water Pump Irreversible Valve Pressure Regulating Ballon CO2 Supply System

System Block Diagram of Growth Chamber System

Fig. 6.

it

L...J

26

2 3 4 5

17

Closed Small Growth Chamber

Problems BetweenMaterial Recycling Systems and Plants

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REFERENCE 1)Keiji Nitta et al, Lunar Base Extension Program and Closed Loop Life Support System, IAA-T-50, 8th IAAMAN in Space Symposium, Sept 29-Oct. 4, 1989, Uzbekistan,USSR. 2)Keiji Nitta et al, Various Problems in Lunar Habitat Construction Scenarios, IAFIIAA-89-572, 40th Congress of IAF, Oct. 7-14, 1989, Malaga, Spain. 3)Mitsuo Oguchi et al, Wet Oxidation Waste Management using Catalyst in CELSS, Proceedings of the XVIth International Symposium on Technology and Sciences pp. 1695-1699.