Closed Ecological Systems (CES) are ecosystems that do not exchange matter with any part outside the system. Although the Earth itself clearly fits this definition, the term is most often used to describe much smaller manmade ecosystems. Such systems are scientifically interesting and can potentially serve as a life support system during space flights, at space stations or in submarines. Perhaps confusingly, a closed ecological system is not a closed system in the usual sense, because energy (especially light and heat) is able to enter and leave the system, provided matter does not.

In a closed ecological system, any waste products produced by one species must be used by at least one other species. If the purpose is to maintain a higher life form, such as a mouse or a human, waste products such as carbon dioxide, faeces and urine must eventually be converted into oxygen, water, and food.

A closed ecological system must contain at least one autotrophic organism. While both chemotrophic and phototrophic organisms are plausible, almost all closed ecological systems to date are based on a phototroph such as green algae.

History

List of major closed ecological systems

• Biosphere 2
• MELISSA
• BIOS-1
• BIOS-2
• BIOS-3

Sources

• "Manmade Closed Ecological Systems." I. I. Gitelson, G. M. Lisovsky and R. D. MacElroy. Taylor & Francis (2003) ISBN 0415299985.