As one of the so-called "greenhouse gases" that are trapping heat within the Earth's atmosphere, carbon dioxide (CO2) is increasingly being viewed as an airborne pollutant and a danger to the environment, although paradoxically it is essential for plant life. Scientists and environmental engineers have for years been considering a number of different ideas for reducing the amount of CO2 in the planet's atmosphere, as well as ideas for offsetting the increased temperatures by deflecting ultraviolet radiation from the sun, should the CO2 levels prove to be irreducible.
However, the main focus now is formulating a workable plan to reduce the amount of carbon dioxide generated in the first place, and also sequester the excess CO2 already in the atmosphere. Carbon dioxide sequestration is performed naturally by all plant life, as well as the world's oceans — and has for billions of years. Yet with our ongoing deforestation and urban sprawl — as well as the limits of the surviving trees to keep up with our growing fleets of automobiles — environmentalists argue that we cannot rely solely upon natural CO2 sequestration, and should consider alternatives.
Along these lines, scientists have designed a "synthetic tree" that traps airborne carbon dioxide. The device looks not like a tree, but more like a large cylinder sitting atop an even larger rectangular box — about the size and shape of a cargo container. Nonetheless, it theoretically would be able to trap about one ton of CO2 per day, which is roughly the amount produced on average by 20 cars, and the amount captured by 1000 trees. The trapped CO2 is compressed and then stored in liquid form, in preparation for sequestration elsewhere. Each synthetic tree would cost an estimated $30,000 to build, mostly for the technology used to remove the CO2 from the sorbent.
The idea was developed by Dr. Klaus S. Lackner, a physicist with the Earth Engineering Center at Columbia University. He has worked on the concept since the late 1990s, and leverages the technology used at coal plants to remove carbon from flue stacks. He has built a model at his company, Global Research Technologies, in Tucson, and hopes to have a working prototype finished within three years.