The Biosphere 2 experiment

Integration of biosphere and technosphere in a created environment

Biosphere 2 in the desert of Arizona is still one of the most interesting architecture and environment projects. Bernd Zabel, Technical Coordinator of Biosphere 2 who also lived dome time in the closed environment, describes the complexity of this new bio-electronical and architectural world, which could be the future human habitat.

... the two worlds of man, the biosphere of his inheritance and the technosphere of his creation, are out of balance, indeed, potentially in deep conflict...No problem is insoluble in the creation of a balanced and conserving planet, save humanity itself. Can it reach in time the vision of joint survival? Can its inescapable physical interdependence, the chief new insight of our century, induce that vision? We do not know. We have the duty to hope.

Barbara Ward, 1964

INTRODUCTION

Biosphere 2 was designed to create an environment of a scale small enough to be workable, yet sufficiently complex and diverse to serve as a meaningful laboratory in which to study natural ecosystems of the Earth.

The process of selecting those parts of our world considered to be essential for a miniaturized model - or, more precisely, a module of Earth's biosphere since practicality prohibited even a miniaturized version of every ecosystem, every climate zone or feature found on the planet - intrigued the imagination of scientists, educators, architects, engineers and lay people working on the project as well as many who watched in fascination from the sidelines. The source of that fascination lay, I believe, in the opportunity which Biosphere 2 presented to explore one's relationship to the larger environment in an entirely new way -- from a perspective of interdependence and participation, for example, rather than that of a privileged passenger who lives supposedly removed from -- or at the expense of -- nature. Necessity posed questions like, "How much nature is required to support my life?" and, "What is it that humans give back to nature in the equation?" Before a technology was admitted, it had to pass extensive tests of nontoxicity to the biosphere -- or include whatever additional steps necessary to render harmless its end products. In many ways, because these sorts of questions are at the same time so fundamental and yet so seldom addressed as practical concerns, the exercise of even conceptualizing Biosphere 2 as a human-inhabited biosphere provided the occasion to examine preconceptions of the world and our place in it.

In the initial three years of its existence, Biosphere 2 was a human-inhabited biosphere. The first crew of eight lived for two years inside Biosphere 2 from 1991 to 1993. A second mission, in which I was a crew member, remained sealed inside for about six months in 1994. During that time, with some exceptions, the air, water and food supporting the humans inside was generated and recycled by the ecosystems of which they were a part. As involved as I have long been in agricultural and environmental endeavors -- including managing the construction of Biosphere 2 for over six years from its inception to completion -- no other experience has ever so basically or profoundly demonstrated the inter-relatedness between myself and the nature around me.

Ironically, or perhaps just naturally, human nature has shown itself in the project in more mundane and less noble ways as well. While the more dire (or comic) predictions of conflict did not come about during the human inhabited closures, discord did sometimes occur. The vision and methods which led to the creation of Biosphere 2 were not always appropriate for the management of an ongoing scientific research project. Mistakes were made. The Biosphere 2 environment as initially designed did not perform as expected, for instance, in maintaining atmospheric oxygen levels. Biosphere 2 was the first large scale complex closed ecosystem ever attempted, and it takes a special kind of courage to be first: the courage to risk being wrong. It is not surprising that some parts did not work. To the contrary, it is surprising that so much of it worked that the weak points could be so clearly identified.

Moreover, none of those shortcomings has proved fatal. The superlative faculty of the Lamont-Doherty Earth Observatory of Columbia University has stepped in to provide the needed ongoing scientific management. Design adaptations of Biosphere 2 continue to be made, and the Biosphere 2 facility itself is sound and diverse enough to support an entirely new set of environmental experiments. While human-inhabited closure experiments are not now being conducted or planned, I am hopeful that they will resume some time in the future - if not in Biosphere 2, then in environments capable of so closely linking the fates and the experience of humanity and nature.

BIOSPHERE 2 SYSTEM OVERVIEW

Biosphere 2 covers a footprint of 1.6 Hectare and encloses a 204,000 Cubic Meter volume (including the two lungs, or variable volume chambers) within its virtually airtight outer structure. Five natural and two human-made biomes are included: tropical rainforest, savannah, marsh, marine, desert, intensive agriculture and human habitat. The atmosphere is generally continuous throughout Biosphere 2.

Conceptually, the Earth's planetary biosphere served as a general model or basic functional inventory for the design of Biosphere 2. References to parallels between Biosphere 2 and Earth's biosphere are made because of the usefulness of this approach in organizing a relatively large amount of information within a familiar framework, rather than suggesting a literal correspondence in mechanism between Biosphere 2 and the Earth's biosphere. Some aspects of Earth's biosphere - such as an extensive geology or geosphere - are not represented at all in this constructed biosphere, while other functions may be accomplished by substantially dissimilar means or to a differing extent in Biosphere 2. Indeed, a too-literal interpretation of the intended equivalence between the natural biosphere and Biosphere 2 gives rise to the types of misunderstandings which underlay some earlier controversy about the project. Specifically, the Biosphere 2 apparatus does not represent an attempt to duplicate the Earth's biosphere; it is an attempt to create, test and, if possible, improve upon an environmental research and training laboratory that is as versatile and effective as possible.

Biosphere 2 was designed and built to serve as a materially-closed and durable environmental research apparatus, capable of measuring and maintaining a range of internal environmental conditions, while presenting the most inert and non-toxic possible background "container" for resident life systems. As such, Biosphere 2 represents an array of construction, control and monitoring approaches to the design and operation of environments that are (a) tightly sealed, (b) inhabited by plant and animal species, including humans, sensitive to environmental pollution, and (c) requiring maintenance within a defined margin of operating parameters including temperature, humidity, and air and water quality.

For design and operation purposes, material closure was defined as an atmospheric leakage rate of 10% per year or less, with essentially no exchange of other matter (except intentional and documented import and export of testing samples and needed items). In terms of energy, the system was designed to admit maximum possible sunlight for plant growth, to permit electricity import, and to facilitate heat exchange with the surrounding Earth environment since the location in southern Arizona and greenhouse-type structure made heat gain a primary engineering concern.

BIOSPHERE 2 STRUCTURE AND BOUNDARIES

As a closed system, Biosphere 2's outer structure forms a series of defining boundaries that separate the internal (Biosphere 2) environment from the surrounding external environment. The impermeability of these boundaries is central to Biosphere 2's purpose as a closed system.

Below ground, Biosphere 2 is sealed by stainless steel panels of 1/8 inch thickness, which are welded together to form a continuous liner over the entire poured concrete foundation. Allegheny-Ludlum 6XN stainless steel, tested for resistance to saltwater corrosion, was used for the liner. This liner attaches to the above-ground space frame structure by specially fitted metal plates which are caulked in place to ensure continuity of an airtight barrier between the liner and the glazing.

The above-ground structure of Biosphere 2 is made of steel tubing fitted with high performance glass and steel frames. The spaceframe and glazing materials were designed and produced to specification by Peter Pearce & Associates (Pearce was a student of Buckminster Fuller). The spaceframe consists of steel tubing with aluminum flame coating which is in turn coated with an electrostatically precipitated powdered paint which was fused in an oven. The strut length of each member is roughly 5 feet. A corrosion test was constructed prior to installation. Even so, approximately 50 of the 77,000 spaceframe struts corroded and required replacement or painting repair after approximately five years.

Glazing proved to be the most problematic element of construction. Glass panes are fitted and caulked inside steel frames at the factory, where the glass/frame panels were vacuum tested for air tightness. These panels were then transported to the site, bolted and sealed in place in a two stage process using two different colors (white and gray) of silicon caulk to assist verification that each pane had been double-caulked.

Glass used was double-layered, heat-strengthened glass, with a plastic layer sandwiched between the layers, making the glass resistant to breakage. To date, there have been five cracked glass panels, but the airtight seal was maintained because only one side of the double layer cracked, and the plastic layer remained intact.

A "termite taste test" was conducted to determine whether termites - an intentionally introduced species in Biosphere 2 for cellulose recycling - would eat the caulking. Laboratory filter paper, apparently a favored food for termites, was sandwiched between two glass slides and sealed with the intended caulking. A strip of paper was left protruding from the "sandwich" as bait to lure the termites. The test showed that the termites readily ate the exposed strip of paper but did not eat or chew through the caulking, and consequently died of hunger.

Ironically, the termite species also died out in Biosphere 2, out-competed by an indigenous Arizona greenhouse ant whose common name is "crazy ant" (Latin name "Paratrechina longicornis" ). This small ant species does chew through the caulking, apparently for nesting material. Five leaks caused by the ants have been found thus far; leak detection in this case is simply a matter of following the sinuous trail of ants going in and out of the leak.

Lungs (Variable Volume Pressure Relief System)

Because Biosphere 2 is air tight, two lungs serve as variable volume chambers able to expand or contract in response to temperature changes that affect the air volume within Biosphere 2. Each lung has a capacity of 850,000 cubic feet for a total variable volume capacity of 1.77 million cubic feet, in comparison to Biosphere 2 volume of 5.5 million cubic feet (excluding the lungs).

External Penetrations Pipe Fittings

At various points, the external Biosphere 2 structure is penetrated by piping for broadband, electrical, laboratory sampling, small sample tube or water passage. These penetrations, which constitute potential leakage sites, are sealed with a variety of fittings; electrical and data penetrations are gas-tight and explosion proof.

BIOSPHERE 2 INTERNAL STRUCTURE

Within the external shell, there is substantial internal structure to help provide a diversity of biome environments and micro-environments, to house the technosphere, and to create the interfaces between the technosphere and biosphere. Much of Biosphere 2 is underlaid by a lower basement-level story devoted solely to technosphere systems governing water, air circulation, heating and cooling systems.

Human Habitat

The human habitat is a 2600 square meter five-story structure which represents an urban or city environment with public spaces and some private spaces for each crew member. This biome is the one zone within Biosphere 2 constructed primarily of opaque metal rather than glass panels. It houses offices, analytical laboratory, medical facility, machine and wood shop, communications and environmental monitoring terminals, as well as kitchen and other accommodations for resident researchers.

Although potential "indoor air pollution" from off-gassing of building materials made material selection a primary concern throughout Biosphere 2, the human habitat posed additional problems because of human wall and floor coverings, furnishings, analytical, medical and other equipment. Untreated wool and cotton were selected for fabric applications, including wool panels on the interior of human habitat walls and wool carpeting throughout the human habitat for noise reduction. Because of the low ratio of plants to human occupants in this biome, build-up of CO2 was a concern; therefore, "fresh" air from the Intensive Agriculture was vented through the habitat.

Wilderness Biomes

Topographical variation provided the answer to the concern of biome design consultants for a larger surface area for planting and wider variety of micro-environments within the relatively small square footage available to each biome. High quality and imaginative artificial rockwork (ferro-cement) by the Tucson-based Larsen Company facilitated this process. This rockwork also contributed to establishing a more natural appearing environment with softer aesthetic results.

The rainforest, for example, had a "footprint" area of 2,000 square meter if calculated based upon a single flat plane at ground level. A hollow 50 foot tall mountain was built in the rainforest from a standard concrete slab three-story tower, covered by artificial rock to create cavernous doorway entrances, planting terraces and boxes, and a spiraling pathway up the outside of the mountain. Inside, the hollow mountain provided spiral staircase access from the basement technology zone to each of the stories to reduce foot traffic in planted areas, as well as storage area for tools and supplies used in the wilderness. At the mountain top, misting machines provide high humidity for a cloud forest habitat; a pool drains over the mountain top to form a waterfall. A splash pool catches the waterfall runoff which feeds into a meandering stream. The majority of this water recycles, but a small quantity then courses through part of the adjacent savannah biome.

Differences in elevation were also made possible in sections of the rainforest and desert by eliminating the basement sub-story and instead constructing the biome space as 2 to 6 meter deep planting areas filled with soil. This helped support tall trees and heavy plant structures, as well as allowing topographical "sculpting" for greater natural effect and increased surface area for planting. Architectural design of the external structure - such as the 30 meter height of the rainforest biome structure to house tall canopy trees - was developed to enhance ecosystem requirements as well as aesthetics.

CLIMATE CONTROL, WATER AND ATMOSPHERIC CYCLING SYSTEMS

On Earth, the governance of climate, weather phenomena, atmospheric and water cycling are a function of large scale planetary mechanisms which are not effective on substantially smaller scale systems. In Biosphere 2, technology-based mechanisms perform most functions such as climate, atmospheric maintenance and circulation, and water purification and circulation, and ocean wave production. Even so, recognition of the extent to which resident life systems ("biosphere") can interact with the engineered technological environment ("technosphere") to affect internal atmosphere, climate, water flows and storage, among others, is an essential aspect of the design and operation of closed environmental systems. The terms "biosphere" and "technosphere" are a useful shorthand in conceptualizing and comparing these interactions.

Energy Center

The largest energy use in Biosphere 2 is for cooling. The Energy Center situated nearby produces all the electrical power for Biosphere 2. The Energy Center also produces 10-21 deg C cooling tower water (cooled by evaporation), 5-7 deg C chilled water (produced by mechanical chilling), and 70 - 80 deg C hot water (by natural gas boilers).

Water from the Energy Center runs through a piping system, penetrating the Biosphere 2, to the radiators of the 26 air handlers. In each airhandler a 60 HP blower circulates Biosphere 2 air through the radiators. Heating, cooling, or dehumidification can result depending on the control setting which determines the flow through these radiators

Water vapor in the air from plant respiration and evaporation condenses within the air handlers, and the condensate water is collected by a trough and then pumped into rain tanks.

Water Cycling System

The water system - reservoirs, flows, delivery systems, and controls - demonstrates the close interaction of biosphere and technosphere in governing the environment of Biosphere 2.

The main water reservoirs are water storage tanks, surface aquatic systems, soils, atmospheric humidity, and plants and other biota. There are twelve distinct water systems: the ocean, marsh, wilderness fresh water stream, wilderness subsoil drainage, wilderness condensate, Intensive Agriculture Biome (IAB) irrigation, IAB potable water, IAB rice/fish system water, IAB subsoil drainage, human waste water, and emergency firefighting system water. (As built, in general, the IAB and Human Habitat biomes are interconnected but can be separated from the wilderness biomes in terms of water and air.)

Aside from the 250,000 liter salt-water ocean, the largest water reservoir in Biosphere 2 is in the water storage tanks in the technosphere basement. Natural biospheric reservoirs in the environment are also significant. In the rainforest biome, for example, the soil may contain up to 20,000 liters of water.

Though the atmospheric reservoir harbors a relatively small volume of water as water vapor or humidity, it is an extremely active and influential component of the hydrologic cycle. If both the optimum temperature and relative humidity operating parameters are maintained in the rainforest, a range of approximately 90 gallons of water (at 70 F and 75% RH) to 200 gallons of water (at 85 F and 95% RH) would reside in the atmosphere of the biome as water vapor.

Rainforest Operating Manual 1995, Linda S. Leigh.

Major flows between reservoirs are rainfall and irrigation, mist, root uptake, subsoil drainage, transpiration, evaporation, condensation, diffusion, reverse osmosis system, and potable and waste water treatment and storage.

Rainfall and mist are delivered through overhead sprinklers, while irrigation water is delivered by a ground-level sprinkler or drip system. Plants take up some of this rain and irrigation water from the soil; the remainder is percolated down through the soil and collected via drainpipes installed beneath the soil layer; this nutrient-containing drainage water then travels to the primary storage tank in the south lung. Plants transpire some water back into the atmosphere as vapor. Atmospheric water vapor - from transpiration, misting, and evaporation from surface aquatic systems or soils - condenses on (1) windows or (2) coils in the air handlers. In either case, drainage troughs collect condensate and deliver it to condensate tanks. Diffusion refers to the movement of water vapor from biome to biome; this is of importance in terms of maintaining desired humidity levels in the varied ecosystems. Finally, the reverse osmosis system treats water from primary storage to remove dissolved solids before storing the water for future use as rain, mist or irrigation. Condensate water can be used without further treatment as rain, mist or irrigation. Most rain delivery systems have inline sensors to measure the level of dissolved solids in water.

Reverse osmosis water from the IAB and Human Habitat is further treated by UV light and filtration before use as potable water for human and domestic animal consumption.

IAB irrigation and wilderness rain water regimes are computer controlled and monitored. Most water flows and tank levels are automatically measured and data recorded in a database which can be monitored both inside and outside Biosphere 2.

ENVIRONMENTAL MONITORING, CONTROL AND RECORD-KEEPING

Central to the purpose of Biosphere 2 is the ability to accurately monitor environmental conditions such as temperature, humidity, photoactive radiation input, atmospheric gas components and water components. To this end, there are 1,200 sensors in Biosphere 2. Eighty of those are considered "Mission Critical" while the rest are either for research or monitoring purposes. During the manned missions, a so-called "Sniffer System" automatically took air samples every 15 minutes from a different biome and ran them through 13 different atmospheric gas analyzers (for example, Ozone, CO2, N2O [Lachgas]). A daily computer generated print-out reported the high and low levels for the last 24 hours and compared them to safety limits.

Bernd Zabel: Biosphere 2 10