A journey into the world where scientists recycle everything to survive in space
Material Circulation
Plant Cultivation
Scientific Research
Space Applications
Imagine living for weeks in an airtight environment where every breath you exhale is recycled into the air that plants need to grow, and the plants, in turn, become the food you eat.
This is not science fiction—it is the groundbreaking reality of the Closed Ecology Experiment Facilities (CEEF) in northern Japan. Since 1994, this ambitious scientific endeavor has been tackling one of humanity's most profound challenges: how to create self-sustaining ecosystems that could support human life in space or on other planets 1 5 .
The CEEF represents one of the world's most advanced test beds for Controlled Ecological Life Support Systems (CELSS). At its heart lies a simple but powerful question: Can we replicate Earth's intricate life-support systems within a closed facility? By perfecting the art of material circulation—where water, air, and waste are continuously recycled—CEEF researchers are paving the way for long-duration space missions and offering valuable insights into managing our own planet's delicate ecological balance 3 .
CELSS (Controlled Ecological Life Support Systems) aim to create regenerative environments where waste products are continuously recycled into resources.
CEEF construction begins in northern Japan
First successful material circulation experiments
Ongoing research for space colonization
The CEEF is a sophisticated complex of interconnected modules where scientists can study how humans, plants, and animals coexist in a closed environment with minimal input from the outside world. Constructed in northern Japan beginning in 1994, the facility was originally designed to study environmental problems, including those related to atomic power industries 1 5 .
The CEEF consists of two major installations:
What makes CEEF extraordinary is its ability to closely monitor and control the flow of materials—carbon, oxygen, water, and nutrients—between these different compartments, creating a miniature version of Earth's ecological cycles 6 .
Plant Experiment Facility
Animal & Human Facility
In a perfectly closed ecological system, nothing enters or leaves—all essential elements for life are continuously recycled. On Earth, our planet's biosphere has maintained this balance for billions of years. The CEEF aims to replicate these processes on a much smaller, human-manageable scale.
The theoretical foundation rests on understanding how carbon, oxygen, and water circulate between humans, animals, and plants:
This elegant symmetry forms the basis for creating sustainable environments where humans could potentially live indefinitely without external supplies—a crucial capability for establishing bases on the Moon or Mars 5 .
Plants
Humans
Animals
Between 2005 and 2007, CEEF researchers achieved a major milestone by conducting the first successful material circulation experiments connecting the plant and animal/human facilities 2 . Let's examine one of these pioneering experiments in detail.
"Eco-nauts" living in the closed environment
Animal participants in the ecosystem
Including rice, wheat, soybeans, and vegetables
In 2005, researchers conducted three separate one-week habitation experiments involving:
The experimental system connected two main facilities:
| Component | Description | Function in Experiment |
|---|---|---|
| Human Inhabitants | 2 eco-nauts | Conduct daily activities, consume oxygen and food, produce CO₂ and waste |
| Animals | 2 Shiba goats | Consume plant biomass, produce CO₂ and waste |
| Crops | 23 species including rice, wheat, vegetables | Produce food, absorb CO₂, generate oxygen |
| Plant Chambers | 3 with electric lighting, 1 with mixed lighting | Controlled environments for crop cultivation |
| Gas Circulation System | Connecting pipes and monitoring equipment | Transfer CO₂ and O₂ between modules |
The researchers established three levels of material circulation:
The experiment focused on Level 1 circulation, with the goal of maintaining CO₂ and O₂ concentrations within ranges suitable for humans, plants, and animals while providing necessary food and feed 6 .
Researchers cultivated 23 crop species in the Plant Module, carefully controlling environmental conditions including light, temperature, and nutrient supply 6
Continuous monitoring of O₂ and CO₂ concentrations in both Plant and Animal/Habitation Modules 6
Daily harvesting of edible crop parts, processing into meals for human inhabitants 6
Preparation of crop residues and inedible biomass as feed for goats 6
Precise measurement of O₂ production rates and CO₂ uptake rates in each plant chamber 6
Comprehensive tracking of carbon flow through the system, including human and animal consumption, carbon assimilation by plants, and gas concentrations 6
The one-week habitation experiments successfully demonstrated the feasibility of connecting biological systems in a closed environment. The key findings included:
| Parameter | Plant Chamber A | Plant Chamber B | Plant Chamber C | Plant Chamber F |
|---|---|---|---|---|
| Average Daily O₂ Production (L/day) | 1,893 | 2,161 | 2,159 | 1,846 |
| Average Daily CO₂ Uptake (L/day) | 1,873 | 2,075 | 2,080 | 1,812 |
| Assimilation Quotient (AQ) | 0.989 | 0.960 | 0.963 | 0.982 |
The data revealed that different plant chambers maintained slightly different but stable assimilation quotients, all close to the theoretical ideal of 1.0 (where CO₂ uptake exactly matches O₂ production in volume) 6 .
| Crop Category | Number of Species | Edible Biomass Production | Inedible Biomass Production |
|---|---|---|---|
| Staple Crops | 4 (rice, wheat, soybeans, peanuts) | 40% of total edible biomass | 60% of total inedible biomass |
| Vegetables | 15 (including komatsuna, cabbage, radish) | 45% of total edible biomass | 55% of total inedible biomass |
| Other | 4 (including sweet potato) | 15% of total edible biomass | 20% of total inedible biomass |
The experiments confirmed that a diverse crop portfolio could provide balanced nutrition for human inhabitants while producing sufficient residue biomass to feed the goats 6 .
Creating and maintaining closed ecological systems requires specialized materials and approaches. Here are some of the key solutions and techniques developed by CEEF researchers:
| Research Solution/Material | Function in Closed Ecosystems |
|---|---|
| Wet Oxidized Solution (WOS) | Processed waste solution used as nutrient source for plant cultivation 1 |
| C-13 Isotope Tracer | Stable carbon isotope used to track carbon transfer through ecosystems 6 |
| Controlled Plant Cultivation Equipment | Enables precise measurement of plant metabolic rates in closed environments 1 |
| Multi-Chamber Plant Modules | Allow sequential cultivation of diverse crops under controlled lighting conditions 6 |
| Physical/Chemical Material Circulation Systems | Manage flow of gases and nutrients between facility modules 2 |
While originally conceived to study environmental transfer of radionuclides (particularly carbon-14) from industrial facilities 6 , CEEF's research has profound implications for multiple fields:
Closed ecological systems are essential for long-duration space missions and potential off-world settlements. As noted in NASA's research on Closed Ecological Systems, they "hold the prospect of permanently establishing life beyond Earth; initially with microbes, plants, and small animals, but ultimately in CESs with humans" .
The CEEF serves as an "Environmental Time Machine" that allows scientists to study ecological processes in unprecedented detail 5 . Understanding material cycles in miniature ecosystems helps us better comprehend and protect our planetary biosphere.
The Closed Ecology Experiment Facilities represent a remarkable achievement in ecological engineering. By demonstrating that humans, animals, and plants can coexist in a carefully managed closed environment—with successful circulation of essential gases, food, and water—CEEF researchers have brought us closer to sustainable life beyond Earth.
As we face growing environmental challenges on our home planet and contemplate extending human presence to the Moon and Mars, the lessons learned from CEEF's material circulation experiments become increasingly valuable. The facility continues to serve as a test bed for developing the regenerative life support systems that may one day sustain human colonies in space while teaching us how to better steward our own planetary life-support system 6 .
In the words of researchers involved in the project, this work moves us step by step toward "circulation of materials including waste"—the final stage in creating truly sustainable closed ecosystems that could support humanity's future among the stars 6 .
CEEF research paves the way for sustainable human habitats beyond Earth, potentially enabling long-term space missions and extraterrestrial settlements.