A biodome is a sealed or semi-sealed structure designed to replicate a natural ecosystem under controlled conditions. In scientific terms, it functions as a closed ecological system, where waste from one organism becomes a resource for another, and the only external input is energy from the sun (or artificial lighting). Scientists use biodomes to study how ecosystems behave, test life support technologies for space, and simulate the effects of climate change on specific environments.
How a Biodome Works
The core principle behind a biodome is material recycling. Inside a sealed biodome, plants absorb carbon dioxide and release oxygen. Animals and humans do the reverse. Water evaporates from soil and plant surfaces, condenses on interior walls or in air handling systems, and is collected as freshwater. Wastewater gets filtered through constructed wetlands or biological treatment systems and is reused for irrigation. In a well-functioning biodome, nearly everything circulates in loops rather than being consumed and discarded.
This makes a biodome fundamentally different from a greenhouse or a terrarium. A greenhouse exchanges air freely with the outside and relies on external water and fertilizer. A terrarium might recycle water passively but doesn’t attempt to sustain complex food webs or human inhabitants. A true scientific biodome aims to close all material loops so that the system can sustain itself indefinitely with only light energy coming in from outside.
Biosphere 2: The Landmark Experiment
The most famous biodome experiment is Biosphere 2, a three-acre sealed facility in southern Arizona. It contained miniature versions of several Earth ecosystems under one roof: a tropical rainforest, a savanna, a desert, a mangrove marsh, and even a coral reef ocean. Eight crew members sealed themselves inside on September 26, 1991, and lived there for two years.
The experiment revealed just how difficult it is to keep an artificial biosphere in balance. Carbon dioxide levels were a constant threat, monitored around the clock because even small increases could destabilize plant growth and make the air dangerous to breathe. The crew called CO2 “the tiger of Biosphere 2.” Oxygen posed an even more dramatic problem. It slowly disappeared over 16 months, dropping to about 14 percent, the equivalent of breathing at 15,000 feet of elevation. When a door was briefly opened in January 1993, the crew experienced an immediate physical revival as outside air rushed in.
Food was another challenge. The crew grew their own crops in an intensive agriculture section, but they experienced persistent hunger throughout the two years. Wastewater from the crew’s living quarters and a small animal barn was treated using constructed wetlands, a series of tanks filled with rooted and floating aquatic plants that filtered the water biologically. Over the two-year closure, these 41-square-meter wetlands produced over 1,200 kilograms of harvestable plant material that was used as animal fodder, and the treated water was recycled back to irrigate food crops.
Biosphere 2 was designed as a shakedown mission, a first attempt to find the flaws in a sealed ecosystem. It succeeded at that goal. The fog desert transformed on its own during the experiment, the coral reef nearly collapsed, and maintaining each biome required constant human intervention. But the project generated invaluable data on how closed life support systems actually behave under real conditions.
Building Materials and Structure
Modern biodomes often use a lightweight plastic called ETFE (ethylene tetrafluoroethylene) instead of glass. ETFE is a polymer related to Teflon that can be extruded into thin, transparent film. It transmits more light than glass, including ultraviolet rays that many plants and animals need, while weighing a fraction as much. Panels are typically created by inflating two or more layers of ETFE foil into cushion-shaped cells, which provide insulation while remaining transparent. The material also has a non-stick surface that sheds dirt and rain, reducing maintenance.
The Eden Project in Cornwall, England, is the most visible example. Its iconic domes use tubular steel frames with hexagonal ETFE cladding panels. The Rainforest Biome inside maintains temperatures between 18 and 35°C, hot enough that visitors are advised to dress for tropical weather. Glass would have been far too heavy for structures that large.
Biodomes and Space Exploration
NASA considers closed ecological life support systems one of the critical technologies needed for long-term human presence beyond Earth. A crew on Mars can’t rely on supply shipments for air, water, and food. They need a system that regenerates all three from biological processes, essentially a small biodome.
NASA studies have examined what it would take to replicate something like Biosphere 2 at a lunar outpost. The focus isn’t on copying the exact design, but on understanding what resources and infrastructure a self-sustaining habitat requires. A permanently crewed lunar base at one of the poles has been the leading concept, where a habitat with closed-loop life support could be tested in actual space conditions before a Mars mission.
China has made significant progress in this area. The “Lunar Palace 1” facility in Beijing is a ground-based biodome designed to simulate a lunar base. In its longest trial, the “Lunar Palace 365” mission, eight crew members lived inside for 370 days across three rotating phases, with one group staying for a continuous 200-day stretch. The system achieved 100 percent recycling of oxygen and water, and its plant cultivation fully met the crew’s plant-based food needs. Overall, 98.2 percent of materials essential for human survival were recycled and regenerated. That level of closure represents a major step beyond what Biosphere 2 achieved in the early 1990s.
Climate and Ecosystem Research
Not all biodomes are sealed environments designed for space. Many serve as outdoor or semi-enclosed research tools for studying how ecosystems respond to changing conditions. The SPRUCE experiment in northern Minnesota, for instance, uses biodome-like enclosures in a peatland forest to expose sections of the ecosystem to elevated temperatures and CO2 levels. This lets researchers observe, in real time, how boreal forests and the carbon-rich peat beneath them respond to conditions that climate models project for the coming decades.
This type of research is difficult to do any other way. You can model ecosystem responses on a computer, but models depend on assumptions. A physical enclosure that manipulates real soil, real microbes, and real trees under controlled atmospheric conditions produces data that no simulation can replicate. Biodomes give ecologists something rare in their field: the ability to run experiments on entire ecosystems rather than just individual species or soil samples.
Why Biodomes Matter
The scientific value of a biodome comes down to one idea: isolating a piece of the living world so you can study how its parts interact. Earth’s biosphere is too large and complex to experiment on directly. A biodome shrinks it to a manageable scale where researchers can track every molecule of carbon, every liter of water, and every shift in atmospheric chemistry. The lessons apply in two directions. Looking inward, they reveal how fragile the balance of a living system really is. Looking outward, they provide the engineering foundation for keeping humans alive in places where no biosphere exists at all.