Towards a Biosphere to Create and Monitor Environmental Conditions

Furthermore, this paper discusses the construction of a table-top experimental design and measuring devices used to quantify the oxygen levels and other environmental variables, such a

Rosa M Munoz1 and Matthew S Garcia2,

Colorado State University-Pueblo, Pueblo, CO 81001, USA

Brandon M Martinez3

Colorado State University-Pueblo, Pueblo, CO 81001, USA

This research project for the spring 2005 semester is to design and construct a closed

ecological system in which plant life and possible insect life may be self-sustained The main

goal, however, is to demonstrate the creation of oxygen gas by utilizing the plant Arabidopsis

Thaliana This project will succeed by utilizing different fields of knowledge including

Engineering, Chemistry and Biology The biosphere will be self-sustaining, will contain one

uniform environment, and will contain only a few plants Furthermore, this paper discusses

the construction of a table-top experimental design and measuring devices used to quantify

the oxygen levels and other environmental variables, such as relative humidity, temperature

and light intensity The system will be completely enclosed from its beginning to its

conclusion This paper will report on our initial findings and the underlying scientific

principles of creating a biosphere It is a contribution for further research in providing

oxygen needed for survival of future outposts on other planets/moons in space.

I Introduction

rom the time of its discovery, Mars has been a topic of major interest to mankind Following the Moon, the Red Planet has attracted more spacecraftthan any other object in the solar system, despite the tremendous challenge

of visiting and observing it Therefore major challenges are visitation, exploration and colonization

F

Mars has an average temperature of –60 oC and the atmosphere contains 95 percent CO2, indicating that direct habitation is almost impossible Therefore, other means of colonizing Mars are being explored, such as the establishment of permanent bases on it – and the creation of an artificial biosphere necessary for human life

Biospheres are meant to be life-sustaining and self-sufficient This means they have to be capable of recycling food, water and air Although they are similar, a biosphere is not a greenhouse A greenhouse provides an ideal growing area for plants, and efficiently nourishes them; however, it is not entirely impervious Conversely, the biosphere is designed to sustain possible human, animal and plant life and once initial conditions are set, they can not be altered Also, a greenhouse can be opened at any time and allows therefore matter exchange On contrary the biosphere is sealed from its onset from all external influences except light Efforts are currently being made to build and observe biospheres and one of the most successful so far has been Biosphere 2 located in Arizona However, it has encountered major challenges in air recycling as far as the depletion of oxygen and overall increase in toxic gases

The objective of the project is to build and observe a tabletop (scaled) biosphere to observe the increase in oxygen content Since it has been proven that the absence of humans has little effect on the air cycle, the microbes in the soil would fully complete the air cycle by producing carbon dioxide To accomplish this task, oxygen, humidity, temperature, and light intensity will be measured The results produced by this experiment may advance the desire

of man to eventually inhabit Mars

1 Undergraduate student, Department of Engineering, 2100 Bonforte Blvd., Pueblo, CO 81001

2Undergraduate student, Department of Biology , 2100 Bonforte Blvd., Pueblo, CO 81001

3 Undergraduate student, Department of Engineering, 2100 Bonforte Blvd., Pueblo, CO 81001

II Literature Review

In this section of the paper a summery of different biosphere experiments is given It shall introduce the reader to previous attempts of biosphere creation and give and give an overview of problems and difficulties in the construction process

A Earth Applications of Closed Ecological Systems: Relevance to the Development of Sustainability in our Global Biosphere 1

Nelson and his coauthors realize the importance of Earth’s environmental ecosystem, and they point out directly that Earth’s natural resources are being depleted by our own fault They recommend that mankind start changing the way they view their home The scientists recognize, however, that some of Earth’s inhabitants appreciate what it provides to them, and that the citizens of this world are too accustomed to having unlimited resources provided to them Therefore, they will not know how to adjust when those resources are depleted or in short supply Nelson et

al recommend that society starts recycling, conserving, and sustaining the resources that they embrace; for the resources may be in limited supply in the future These researchers urge society to recycle industrial by- and end products so that there is less pollution and contamination in our atmosphere and propose an increase of reliance on renewable natural resources such as the light from the sun By developing an understanding of how the Earth operates, further research into methods of life-sustaining modules will be conducted; so that if Earth is ever without its natural resources indispensable to life, civilization may continue elsewhere

Given is a basic overview of the many biosphere experiments that have been conducted over the past fifty years, beginning with the microcosm or miniaturized ecosystem They state, that this is the ideal tool for understanding how an enclosed biosphere of a larger magnitude would operate It was originally created as a teaching instrument for the classroom, when it soon became evident that it could be used for more advanced research The only requirement necessary for the survival of these ecosystems is that they maintain a certain level of energy input from the sun or artificial lights Such models are useful in drawing conclusions about the behaviors and patterns found in Earth’s natural ecosystem

The second system discussed, was the small laboratory flasks containing microbes, alga and occasionally small brine shrimp These ecosystems are relatively contained within a flask with volumes ranging between 100 ml to 5 l They also require a minimum amount of light necessary to grow and adequate temperatures under which to subsist These small systems have been known to survive for extended periods of time, and a few of them have lasted for several decades

The third closed ecological system is the NASA CELSS (Closed Ecological Life-Support System) The scientists

of this experiment discovered new ways of suppressing phytorespiration, and methods of maximizing the space within their structure The CELSS researchers are most recently conducting experiments on the recycling of human and plant waste

The fourth biosphere experiment was that of the Bios-3 based out of Siberia It was the first to create a plant growing system that was located above the ground Also, the experiment was able to sustain human occupation for 4-6 months They were able to recycle the air from the plants and the water produced by the system Human interaction with the biosphere was essential to its success and that the inhabitants were active in the decision-making

of the system The only component that the Bios-3 scientist lacked was that the soil they used contained microbes that were eventually harmful to the plants and that it aided in the production of harmful trace gases that could have eventually been detrimental to the health of the human occupants

Biosphere 2 was the fifth enclosed ecological system that was discussed by these Nelson and his co-authors They stated that the system was so effective because of the numerous biomes that had been established within the system and that each individual biome was essential for the success of the others Included within Biosphere 2 were five ecological systems including that of the rainforest, desert, savannah, ocean and wetland, and it was designed so that the systems were dependent upon one another According to the Nelson et al., a definite connection between this biosphere and Earth is evident; however, they believe that if humans were to construct such a structure on another planet such as Mars, it would not be successful because the environmental conditions are unlike Earth’s

Finally, these scientists give some ideas for further research into soil conditions necessary for plant growth and maturation They believe that by simply modifying the soil by exposure to various microorganisms before the plants are deposited, it may prevent or at least reduce the production of trace gases produced overall Also, other phenomena such as a decrease in oxygen production or in a decrease in the atmospheric pressure may result

B Development and Research Program for a Soil-based Bioregenerative Agricultural System to Feed a Four Person Crew at Mars Base 2

Silverstone and his colleagues suggested a plan for an establishment they call Mars on Earth, which is a

simulation of a life-support system for four people, and which they hope will eventually be built on the Red Planet However, this paper is not intended to give the overall layout of what the compound should look like or how it should be designed, for it only deals with the question of its agricultural sustainability

In this paper, a framework is given for the humans intending to live on Mars e.g., giving a menu for a nutritional and palatable diet Included in this Martian diet are ten plants comprised of wheat, rice, pinto beans and soybeans; each plant selected because of its heartiness, easy harvest and provision of necessary vitamins and minerals essential for a healthy human life However, the scientists realize that they do not have an exact replica of the type of soil that they would have from the surface of the Red Planet; therefore, they know that whatever results they may have from their experiments here on Earth will be distinctly different and skewed They believe that further research is needed

in the area of Mars soil cultivation, and in the area of nutrient circulation, which is essential for a plentiful harvest They know that the ideal soil compilation is only possible through further deliberation and experimentation

Ideas for the recyclable materials such as human waste and the recirculation of the oxygen produced within the system are also provided The researchers envision an agricultural system that is communitive between the system of water and air They believe that they can design a system that could be operated not only when the two systems behave simultaneously, but also as distinctly separate and independent systems as well, as in the case of impairment Silverstone et al state that their enclosed agricultural system would operate most efficiently when it is totally enclosed with relatively little or no interference by outside influences However, they believe that the system would not be harmed in any way by energy, information or material exchanges

Since the purpose of the agricultural system is to provide food for those living inside the space capsule on the planet Mars; the engineers and scientists recommend two basic ideas for its roof, which will be the primary light source for the plants The first idea is to utilize a roof that is partially transparent instead and the second is to utilize the sunlight by a fiber-optic roof These are both alternatives to using a totally opaque roof, which may be detrimental to the plants and to the human inhabitants inside These two roof ideas allow for the perfect medium of sunlight essential for plant photosynthesis and growth

C Beachworld 3 , Ecosphere 4

These biospheres are sealed enclosures “containing plants and animals in perfect balance within an aquatic environment.”5 They include animal life such as small snails, crustecea, and small borne animals The water-based biospheres are sun driven which helps the plants in their production of oxygen and nourishment through photosynthesis Animals consume the oxygen, and give off the by-product carbon dioxide and other nutrients that the plants need During the night the animals consume the oxygen while no oxygen is being created The Beachworld was created in 1993 by a “space station engineer and two of the original Biosphere 2 crew members”6 (Ms Jane Poynter and Mr Taber MacCallum) The Ecosphere was developed by scientists a NASA’s Jet Propulsion Laboratory NASA was “researching self-contained communities for space explorers to live in during long-term space flights.”7 The two scientists working on this project were Dr Joe Hanson and Dr Clair Folsome

The floras in the biospheres consist of Lilly-like plants called the Chain of Stars They are one of the smallest plants in the world; however, they provide protection as well as nutrition for the organisms of the biosphere These plants reproduce “vegetatively”, which means that each of the leaves is a separate plant Another plant that provides protection as well as contributes to the oxygen creation is the Hornwort This plant is usually not eaten by the animals because of the bad taste

The biospheres faunas consist of a variety of animals There are many species of snails such as the Ramshorn, Pond and Trumpet snails The snails “graze on algae and the roots of the Chain of Stars and may be seen pruning dead leaves.”8 Some other animals populating the biosphere are Daphnia, Ostracods, and Copepods These animals are near microscopic, but are very important to the food chain and to the housekeeping of the biosphere They filter feed, which means that they “eat microscopic algae and microbes floating in the water or the debris on the bottom [of the biosphere].”9

D Bios-3: Siberian Experiments in Bioregenerative Life Support 10

This report was written and published in October of 1997 The authors of this report specialize in the areas of Biometeorology and Biophysics NASA’s first biosphere project, was started in 1960 but dropped shortly afterwards The most recent NASA project is called CELSS (Closed Ecological Life-Support System) The Russian Space Agency simultaneously developed a program with the primary goal of constructing and operating a

life-sustaining module to be placed on the surface of the Moon or Mars Nowadays, this same space agency has a specialized program called the Advanced Life Support Program, but it still has the same basic goal in mind

Starting the Russian biosphere program, Boris G Kovrov became the chief designer for the Bios-1, which was constructed in 1965 the Siberian city of Krasnoyarsk A few years later, in 1968, the Bios-1 was slightly modified into Bios-2, with the addition of phytotrons (chambers to lift the plants above the ground) For these experiments, plants such as carrots, cucumbers and wheat were grown in the elevated chambers, which aided in the overall production of oxygen for the biosphere Then, in 1972, the Bios-3 was constructed at a cost of about 1 million dollars It is an underground facility which is divided into four sections with dimensions of 14 m x 9 m x 2.5 m Currently, the Bios-3 has three sections that are entirely devoted to the growth and cultivation of the phytotrons The phytotrons use twenty cylindrical, vertical 6 kW xenon lamps each and the power needed to run these lamps is provided by the nearby water power plant A cooling system called the “water jacket” is used to cool the continuously running lamps so that they do not overheat and possibly harm the plants However, the scientists found that plants such as wheat require too much light in order to grow, which may cause an overheating of the growing lamps They feel that crops such as potatoes and tomatoes would develop better with a period where they are not exposed to the lights, which would stimulate a dark or resting period

Salisbury et al added to their enclosed biosphere air tanks for maintenance of air pressure At certain levels where the pressure went above atmospheric pressure, air was automatically pumped into those tanks Consequently, when the outside pressure was above certain tolerances, the tanks pumped air into those chambers in order to equalize it Overall, they had a minimum amount of air leaks with between 0.020%-0.026% lost by volume Air was also circulated throughout the biosphere for the inhabitants and for the plants to be used in the photosynthesis processes The scientists believed that they did not need an overly complicated air purification system, but yet relied

on the natural purification processes done by the plants themselves and also on a catalytic converter; which heated the air to temperature levels between 600°C-652°C

There were collectively three different enclosure experiments conducted inside of the Bios-3 establishment Following each inhabitation, it was found that after many psychological and physical tests, the “crew” was in good health Also, it was found that the amounts and quality of water, air and plants was not decreased at any time These procedures were conducted in the middle of the winter seasons as to minimize the amount of pathogens that could possibly contaminate the experiment

Salisbury and his co-authors give a brief analysis of the Biosphere 2; saying that the only reason that it was unsuccessful thus far is that it had an overall decrease in oxygen concentration, possibly caused by the process of respiration They believe that too much oxygen was used in this process and that the decay of organic matter did not aid in the oxygen production process either They also state that such a large structure could not possibly exist on such a planet as Mars or even on the surface of the Moon These scientists reason that such a lightweight, pressurized structure would be non-existent on the surface that has nearly not air-pressure Therefore, they make their case for their own enclosed ecological system, the Bios-3 They recommended that in order to continue further experimentation with an enclosed ecological system that the addition of a few invertebrate animals or fish would be helpful to the overall system with a minute amount of energy consumption They advocate that further research should be made in the areas of building a lighter and drastically simplified structure

E NASA BioHome 11

Under the CELSS projects, NASA built a BioHome in 1989 which integrated “‘biogenerative’ components for recycling air, water and nutrients from human wastes into a single, integrated habitat” (par.1) The facilities focus was on wastewater treatment with aquatic and semi-aquatic plants that had the ability to process sewage and make excellent compost material for plant food The effectiveness of several plants was measured and

“In the end, the effluent water flowed through an ultraviolet unit to assure complete kill of all micro organisms, especially those pathogenic to humans This water was then suitable for use in toilets and watering plants” (par 6).

Condensation from the air conditioner and dehumidifier supplied drinking water

F Biosphere 2 engineering design 12

Biosphere 2 is 180,000 m3 closed ecological system with “16,000 m2 of laminated glass mounted on a space frame structure” (sec 2, par 6) Despite the size of this biosphere it had an annual air leakage rate of less than 10% per year Dempster describes two methods of measuring leak rates: first, by inserting inert trace gases and measuring their dilution over time, and second by measuring the pressure in the biosphere and then measuring the decrease in inflation of the lungs Both methods of measurement gave similar conclusions The biosphere supported both human

and plant life for about two years The two crews inhabiting the biosphere cultivated their food, recycled their waste, and were able to participate “in scientific conferences and meetings via video during those 2 years” (sec.1, par 3)

A stainless alloy Allegheny Ludlum 6XN was used for the foundation of Biosphere 2 because it does not corrode

when exposed to soil or sea water as does the steel alloy 316 Also, leak detection channels were installed to “locate and repair flaws in the welding before the initial closure” (sec.2, par.6) This liner also allowed for the sealing of necessary utilities such as electricity and communication, and also for the heating and cooling systems of the whole unit

Large lungs regulate the pressure which results from the temperature changes, internal humidity, and external barometric pressures Taking these factors into consideration, without the lungs the structure of the biosphere would

be under an estimated pressure of 90.7 psi, which would exceed the stability tolerances and thus the leak rate would increase Dempster mentions the two expansion chambers or “lungs” and their importance in achieving a leakage rate of 10% per year The lungs are each constructed as a “cylindrical tank with a flexible membrane covering and sealing the top… [and have an expansion capacity of about] 43,000 m3 serving a fixed air volume of about 140,000 m3, or about 30%”(sec 2, par 9) They are enclosed but not air resistant and are operated by blowers to

“neutralize the weight of the membrane by upward suction” (sec 2, par 10)

Researchers in the Biosphere 2 realized that oxygen in the atmosphere of the biosphere was diminishing The

“oxygen concentration declined from normal ambient, 21%, to 14%” (sec 4, par 2) during the first 16 months The researchers did not realize that the exposed concrete and the respiration of organic matter were resulting in an unbalanced equation of the consumption of oxygen and the release of CO2 The equation for basic respiration/photosynthesis resulted in the misconception of the ratio that for every 1 mole of oxygen that is consumed 1 mole of carbon dioxide is produced (inside the biosphere, not taking other factors into consideration) The CO2 was being captured by the 15,800 m2 of exposed concrete; this was demonstrated by equation

“CaO+CO2→CaCO3” which is the carbonation of concrete To resolve this imbalance a “scrubber system was installed enabling the removal of carbon dioxide from the atmosphere” (sec 4, par 3) This system removes the CO2

by “blowing air through a falling ‘rain’ of NaOH solution The scrubber system captured about 98 kmol of the carbon dioxide An electric furnace that was intended for the dissociation of calcium carbonate at high temperature failed due to the malfunction of heating elements in the furnace and the cycle was never completed

Biosphere 2 was constructed in Arizona, due to solar energy as the main energy source The complement energy

is supplied from an outside source Additionally the heat from solar energy is stored Due to the varying temperatures between summer and winter, both cooling systems and heating systems were installed This resulted in

a total of “25 air handlers placed throughout the planted biomes, each capable of moving varying airflow up to 24

m3/s (50,000 cubic feet per minute)” (sec 5, par 4) Half of the air handlers were used for cooling only and the rest were used to cool and reheat This system of air handlers “controls humidity by condensing moisture out of the air and reheating to the desired temperature” (sec 5, par 4) Generators outside the biosphere provided the air handler and other devices with the necessary electrical power The energy cost amounted to 1 million dollars per year Data such as temperature, humidity, light intensity, atmospheric gas concentrations were collected at 15 minute intervals by hundreds of sensors placed throughout the biosphere This was regulated by the “multi-level sensing,

control and data processing system [which] is distributed among many terminals both inside Biosphere 2 and outside

at facilities on the site” (sec 7, par 6) This was considered part of the nerve system of the biosphere; other parts of the nerve system include means of communication and control of equipment Other methods of taking

measurements involved using a tool called the LI-6400 portable photosynthesis system This allowed measurements

of short term responses of leaf photosynthesis under differing concentrations of atmospheric CO2 and light conditions within the rainforest microcosm Using this tool allowed researchers to distinguish a difference in photosynthesis between the plants in the canopy (second highest level of the rainforest) and the plants in the under story (level beneath the canopy)

G Technical review of the Laboratory Biosphere closed ecological system facility 13

The Laboratory Biosphere began its first operation in May of 2002 Dempster and his colleagues state that it was

successful in growing soybean crops from seed to harvest in 94 days

The experimental setup is a 3.68 m x 3.65 m with two planting beds that measure 1.26 m x 2.13 m x 0.30 m; which provide for a total of 5.37 m2 of planting space This chamber was able to “enhance air tightness of the system [by using a] large SaranTM plastic bag called the ‘lung’… [which was]… 9 m3 or roughly 27% of the fixed volume of the main chamber” (sec 1.2, par 1) The lung was stored in a separated building and was connected with 7 m of 3

in PVC pipe This lung was also a means of controlling pressure differentials due to changing temperatures from the outside The daily leakage is calculated to be approximately 0.5% – 1% plus about 1% for each time the airlock system is used to allow personal entry into the biosphere This system consists of two airtight doors in which one

door opens and the other remains closed When the first door closes and seals, the second door opens- allowing entry into the chamber The result of having this airlock is the exchange of “about 10% – 15%” of the outside air with the air inside the chamber Exiting the chamber results in a similar exchange of air, eventually returning the chamber to the equilibrium it experienced before entry

The water was 100% recycled by evapotranspiration, which is provided by the moisture released into the air by the planting beds This is controlled by air handlers which extract moisture and control humidity The air handlers cool the air so that it condenses and collects into a tray beneath each handler and then drains into a “tipping bucket rain gauge, which measures the amount” (sec 6, par 1) of water collected This water is then pumped, by a diaphragm, through the irrigation system that was set for each of the planting beds and the water flow is controlled

by a solenoid valve The air handlers are also involved in environmental control; they re-circulate the air about every

25 seconds, sweeping from one end of the chamber to the other Thus, the ability of the air handler to extract moisture and control humidity by cooling the air helps maintain a suitable environment for plant life

In order to acquire data and control the system thirty-eight sensors dedicated to “monitoring conditions inside the chamber and an additional 22 to the status of support systems outside the chamber” (sec 7, par 1) were used Twenty of the thirty-eight sensors

“measure operational conditions of the air handlers The remaining 18 sensors report temperatures, humidity, water levels, water pressure, total dissolved solids, soil moisture and carbon dioxide and oxygen concentrations in the air” (sec.

7, par 1).

The measurements are recorded every fifteen minutes and are scanned for values that may be out of range so that they can be converted to other formats The measurement of CO2 is important to the growth of plants from seeds to maturity, thus it needs to be regulated CO2 must be injected into the chamber, but as the plants loose leaves or die, causing decomposition and soil respiration CO2 is released Thus, the amount of CO2 injected into the chamber at the beginning may vary throughout the experiment

III Environmental Measurements and Experimental Design

This section of the paper discusses the measurements taken to observe the aerial conditions of the Biosphere Observation eXperiment (BOX) over time Following the explanation of the measurements, the design of the BOX

and devices needed to observe it are described

A Environmental Measurements

Temperature, relative humidity, light intensity and oxygen content are measured in order to observe the biosphere’s aerial environment As Kim and Portis14 show, temperature plays an important role for the rate of photosynthesis Since the temperature is not actively controlled, measuring the temperature is an important variable from which to draw conclusions in the creation of oxygen “Relative humidity indicates the ‘relative’ fraction of water vapor in a volume of air to how much water vapor that air would contain at saturation at the same temperature and pressure.”15 Eamus and Shanahan16 showed in their study that humidity has an impact on the rate of

photosynthesis Since the BOX has no environmental regulation regarding the humidity level, the measurement of

relative humidity is also essential for the observation of oxygen creation Light is the energy resource for the photosynthesis The light spectrum and its intensity is kept constant in the experimental biosphere Nevertheless, a measurement is taken to show differences between the night and day phases

B Experimental Design

The experimental design of the BOX is relatively simple The size of the closed ecological system was the first

decision made As mentioned in the literature review, different sizes are documented for experimental closed ecological systems Differences existed also between water-based and soil-based biospheres When considering the size of the closed ecological system the following points need to be taken into account The size of the closed ecological system has tremendous influence on its leakage rate The difficulty of sealing off a system completely from gas and liquid exchange is positively correlated with the size of the system Therefore, it can be concluded that the smaller the system the easier and more likely it is to completely seal the system The objective of our closed ecological system is to observe the change in oxygen content of the enclosed air This aerial environmental characteristic is

“quantified with instruments that provide numbers With these numbers we can compare the environment under investigation with a predetermined standard and then seek improvement … We can also evaluate changes in environment over time.” 17

For the experimental assessment of oxygen creation through plant growth, measuring the oxygen content, light intensity, relative humidity and temperature were essential data to consider These measurements are taken at certain

Figure 2 Hydrofarm light fixture with

6400 k bulb

points Therefore, it is punctual data which represents only the conditions of the environment around that specific measuring point Consequently, the larger the observation area, the more reading points need to be installed Furthermore, the objective of our closed ecological system was narrowly chosen, mainly focusing on oxygen level observation Creating a larger biospheric model would raise its system complexity Due to the objectives, resources and experimental restraints, this biosphere observation experiment is the size of a table top

After determining the size of the biosphere, the next step was choosing the material for the construction of the biosphere As mentioned above, a biosphere differs from a greenhouse through complete elimination of matter exchange Hence, the boundary to the environment should prevent matter exchange yet admit energy transfer in terms of light and thermal energy Glass possesses these characteristics: low permeability to gases and air, and high permeability for light energy and thermal radiation These characteristics allow the control of temperature and light intensity from the outside of the biosphere For the size of a tabletop biosphere a terrarium provided the ideal size and volume The experimental biosphere has a length of 23.5 in., a width of 11.75 in., and a height of 15.75 in., enclosing a volume of 18.75 gallons The terrarium is joined together with silicon rubber, which has a relatively low permeability for oxygen and other gases

In an airtight, rigid, closed system pressure differences occur and need to be taken into account in its construction There are three reasons for these pressure differences

“As temperature rises and falls, expansion and contraction of the contained gases tend to explode or implode the enclosure Variations of internal humidity are actually variations of the amount of gas contained (water vapor) and likewise contribute to pressure fluctuations Thirdly, variations in external barometric pressure create positive and negative differential pressures between the inside and outside.” 18

Due to the relatively small size of the BOX in comparison to Biosphere 2 and the airflow within the BOX, the humidity does not contribute drastically to pressure differences An increase or decrease in pressure inside the BOX would result in structural instability and higher leakage rate In order to prevent these adverse implications, the BOX

is connected with two gas bags called “lungs” via vinyl tubing A similar method

of pressure balance was used in Biosphere 2 and the Laboratory Biosphere The

gas bags (Qubit systems, G122) made from heat-sealed, gas-impermeable, nylon

polyethylene laminate, when fully inflated have a volume of 30 liters each, which

amounts roughly to about 100 % of the fixed volume of the chamber The initial

inflation of the lungs is roughly 50% of the maximum volume to balance the

positive and negative pressure differences When temperature within the BOX

rises and the air volume expands, excess volume flows through the vinyl tubing

into the lungs and expands them As the temperature decreases, the opposite

result occurs

The sensors for the data collection are combined with a data logger to record

the data and show changes in data levels over time It also gives potential

relations between the variables Due to the relatively small size of the BOX, data

collection takes place at a specific measuring point located at the center of the

BOX The data logger device as seen in Fig 1 (HOBO U12

Temp/RH/Light/External Data Logger, MicroDAQ.com) “is a four-channel data logger that provides temperature, relative humidity, relative indoor light level measurements and accepts one external input .[it] offers 12 bit resolution, high accuracy, 64k memory and direct USB connectivity.”19 The data logger has an internal power supply with a battery life expectancy of a year Having the sensors combined into one unit holds the danger of lower systems reliability in case of a malfunction of the data logger In contrast to the reliability aspect, the data logger unit combines recording and measurement in an inexpensive and

simple way It does not hold the danger of incompatibility between the

sensors and logging device Furthermore, the one-unit solution

provides the possibility of perfect synchronization of measuring the

different variables The oxygen sensor (SO-B0-250, Electrovac) is

connected via cable to the driver and analyzation unit (EDAB-M1,

Electrovac) It measures in a range of 0.1% - 25.0% the oxygen

content and returns a signal back to the analyzation unit, which

converts the signal into an linearized output signal between 0 V–2.5 V

DC The analyzation unit connects with the data logger, which in turn

records and stores the oxygen content In order to record and store the

Figure 1 Hobo U12 Temp/ RH/ Light/ External Data Logger

data for relative humidity, oxygen content, temperature, and light intensity with a 12-bit resolution, the data logger contains 64 Kbytes memory for 43,000 data points

In the natural world light is generated by the sun It is the essential resource for the photosynthesis process to

take place Specific light characteristics play an important role for the photosynthesis rate The BOX is illuminated

with a 125 Watt compact fluorescent grow light, held by a hydrofarm light fixture (ACF Greenhouses) with a length

of 19 in and a width of 13 in, as seen in Fig 2 “The 6400 k bulb is a full spectrum bulb which promotes overall plant growth …Fluorescent grow lights also have better color rendering properties incandescent…and produce much less heat.”20 The light fixture is mounted about 2 inches above the top of the biosphere, leaving an opening for heat deflection

In order to construct and create the initial conditions of the BOX additional equipment was essential In order to

reach a low leakage rate, the biosphere is closed with an acrylic lid of thickness of about 0.5 in Acrylic is also

known as Polymethylmethacrylate and features a low permeability to gases The gap between biosphere and acrylic

lid is sealed with the specialized sealant (Qubitac sealant, Qubit

systems), which is gas impermeable, “adheres well to glass, rubber

and plastic components of gas analysis systems without bonding to

them permanently… [does not] …produce or consume CO2, O2, H2,

C2H2, or other biologically important gases.”21 The biosphere is tightly

sealed off so that no natural air movements occur In Biosphere 2 and

the Laboratory Biosphere, air handlers were installed to solve this

problem Since the BOX is relatively small in comparison to the other

experimental designs, the BOX is equipped with a solar power driven

fan (GAIAM®) In order to set-up the initial conditions with an

increased CO2 content, CO2 is inserted via CO2 Control Wizard

Injection System (Grow-light) “A closed and confined grow room

does not supply optimum 400-600ppm levels of CO2 By adding CO2

to your grow room your plant's growth should increase by up to

30%.”22 This ensures optimal conditions for the photosynthesis to take

place The unsealed BOX is seen in Fig 3

IV Flora, fauna and internal set-up

This section deals with the internal environment and set-up It explains the reason for the proposed design, describes the plants and life forms include in the BOX

A Internal Environment

The internal environment of this closed life system must be fashioned to accomplish the goal of the overall project, which is to show an increase

of oxygen percentage in the internal

atmosphere To accomplish this goal,

two main aspects of the life inside

must be controlled One is to

maximize the process of

photosynthesis, and the other is to

minimize the process of aerobic

respiration To accomplish the first

goal, optimal photosynthetic

conditions must be provided to the

plants

Optimal photosynthetic conditions

are the aspects of the atmosphere and

the soil that will allow plants to

perform photosynthesis at the fastest

rate possible The formula of

photosynthesis is a complex series of

reactions involving conformational

Figure 4 Photosynthesis I and II

Source: Institute of Chemistry, Faculty of Science, The Hebrew University of Jerusalem, “Photosynthesis - an Ideal Natural Biochemical Process Driven Photochemically,” Fig.1, 20 March 2005

<http://chem.ch.huji.ac.il/~eugeniik/photo_enzymes1.htm>

Figure 3 Unsealed BOX without instrumentation

changes in several protein complexes and can be diagramed as Fig 4, called the z-scheme However complex this reaction seems it can be summarized in Eq (1)

2 2   2

From this summarization it is clear what the three

major aspects of optimal photosynthetic conditions

are; water availability, carbon dioxide availability, and

irradiation from a powerful light source

The optimal light source in nature is the sun, which

gives off the entire spectrum of visible light Through

the use of the various pigments present in the plants,

they can only utilize the red (far right of Fig.5) and the

blue spectra (far left of Fig 5).24 The absorption of

theses spectra of light leaves only the green spectra to

be reflected, giving the plants their green color In

order to provide these spectra to the plants a special

fluorescent grow light with reflector was attached to

the terrarium This light provides the appropriate

wavelengths to make up the absorption spectra of the

plant The light is connected to a timer set up to allow

twelve hours of light and twelve hours of dark

simulating the cycle of day and night

Another factor in creating optimal photosynthetic

conditions is the availability of water in the

atmosphere Oxygen molecules generated from

photosynthesis come from water and not carbon

dioxide.25 This means that for best results the air

should be saturated with water vapor, and accomplishing this is relatively simple By sealing the box and providing

an excessive amount of water, the humidity will rise to 100% naturally by the vapor pressure properties of water The last condition that affects the rate of photosynthesis is the concentration of carbon dioxide in the atmosphere In the photosynthetic reaction, reduction of carbon dioxide to glucose is the final step This anabolic pathway is the driving force of photosynthesis and is the recipient of all the energy built up during the photosynthesis process To help ensure the presence of enough carbon dioxide, a tank containing the aforementioned gas will be connected to the terrarium The use of the tank will allow the creation of an atmosphere with concentrations of carbon dioxide far higher that those in nature, but will not continue to add carbon dioxide after that With these conditions in place, photosynthesis should proceed at an optimal rate, however in order to have an overall increase in oxygen aerobic respiration must be controlled as well

In the past biosphere projects, the major problem was consistently oxygen concentrations and this also poses a potential problem to this project as well The majority of oxygen consumed is put into the process of aerobic respiration, a metabolic process that provides energy for the cells This means that the more organisms that are present in the closed life system, the faster the consumption of oxygen

Controlling this aspect of life within the biosphere is relatively easy Although the absence of aerobic organisms would although maximum increase of atmospheric oxygen, this should not be the goal Many bacteria that live in soil would not only be very difficult to remove completely, but have unique metabolic pathways that may include the processing of nutrients that would otherwise be unavailable to the plants These bacteria are needed for healthy plant growth and should be the only aerobic organisms present in the terrarium

Once the two metabolic processes have been controlled properly, a few other conditions must be maintained to protect the health of the plants Two such conditions considered: the release of heat from the plant and prevention of decomposing in the roots Without proper release of heat from the plant, the plant body can heat up by one hundred degrees per minute When the temperature of the plant body becomes too high, the internal processes of the plant cells, including photosynthesis, shut down; resulting in the eventual death of the plant The three ways in which a plant releases heat, are transpiration, convection from the wind, and radiation from the leaf surface The first two of these would be almost nonexistent within the enclosure, being as there is no wind in the box and the humidity would

Fi gure 5 Absorption spectra for Arabidopsis

Source: Causes of Color, “Plants”, Ed Michael Douma,

2005, WebExhibits.org, 20 March 2005

<http://webexhibits.org/causesofcolor/7.html>

be at 100% To compensate for this, a small fan will be placed inside the biosphere This fan will be powered by a small solar panel and will circulate the air and in turn cooling the plants

The rotting of roots is the result of soil saturated with water, and no place for the water to go To hinder this, the area of the biosphere was divided into two separate sections

by a piece of acrylic and connected by small holes cut at the

bottom The bottom of both areas was lined with rocks

averaging half an inch in diameter and weighing

approximately six kilograms The area containing the plants

(Fig 6), which measures 11.5 in x 15 in., was lined with four

inches of common potting soil from a gardening store

totaling 2851.26 g in mass The remainder of the total area

contains only rocks and will act as a reservoir for the excess

water The rocks on both sides of the acrylic barrier will

allow the water to drain from the soil to the reservoir To

ensure that drainage occurs in the direction of the empty side,

small wedges were placed under the side opposite of the

reservoir creating a slope that will complete the cycle of

water in the closed system

B Arabidopsis Thaliana

After the terrarium was established the next step was to select the flora and fauna to be transplanted into the

biosphere The flora (plant life) would be solely represented by the plant Arabidopsis thaliana Commonly called

mouse-ear cress, this plant is a member of the family Brassicaceae (mustard family) and is found in forty-two out of fifty states.26 In addition, Arabidopsis thaliana has a rapid life cycle; going from germination to production of

mature seeds in only six weeks.27 It has also been shown that Arabidopsis has no trouble growing in restricted spaces For these reasons Arabidopsis has been made a model plant for cellular and genetic research in plants The

rate at which this plant assimilates CO2 and produces O2 was calculated by Raymon A Donahue, Mary E Poulson and Gerald E Edwards to be 30.2 micromoles per squared meter of plant surface per second in full light.28 This rate

is slightly higher than that of most plants, making Arabidopsis a model organism for this experiment as well.

C Fauna

The fauna (animal life) is to be kept at a minimum to reduce the assimilation of oxygen However, some animals can be beneficial or even essential to healthy plant growth To aid in the production of nutrients from the soil to the plants, the addition of common earth worms was proposed However, the presence of worms has the potential to have both positive and negative effects on this project The beneficial aspect of the earth worms is that they digest organic material in the soil leaving a natural fertilizer that provides essential nutrients to the plants This is not a large necessity for the experiment, considering the amount of nutrients that will already be present in the potting soil In addition to this the process, the worms will assimilate large amounts of oxygen, making the presence of worms detrimental to the overall goal of the project With the exception of the bacteria that will be present in the soil

at the time of planting, there will be no other organisms present in the terrarium By putting these controls on the flora and fauna within the biosphere, the maximum net production of oxygen will be provided

V Conclusion

Through a collaboration of efforts, a successful biosphere has been created Although much has been learned through research and experimentation for this enclosed ecological system, there is still much to discover and alter The results of the experiment have not yet been determined due to the length of time necessary for plant growth and taking a reliable series of data, for the “BOX” has only been in operation for two weeks However, the research accumulated thus far is an important first step in the long journey towards its completion The research team would like to make the following recommendations for further research First, it is essential that more research

be done from a biological perspective in the area of the size of the terrarium An increase in the overall volume would allow for more diverse forms of life to be grown within the biosphere It is possible that one or more species

of plants, as well as smaller animal life forms such as insects could be included Secondly, from an engineering standpoint, further research could be done in the areas of water drainage and circulation as well as in the monitoring

of CO2 It is hoped that the ideas and results that have been made up to this point will provide a strong basis for further research either by Colorado State University – Pueblo students or other research teams

Figure 6 Planting area with stone bed