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Monday, November 1, 2010

Carbon Capture – Natural vs. Artificial

By: Ramona Madhosingh-Hector, Urban Sustainability Agent

Geoengineering or climate engineering is an engineering concept that focuses on the deliberate manipulation of the environment to counteract global warming due to greenhouse gas emissions. Geoengineering is currently being applied to carbon capture in the environment in an effort to mitigate climate change impacts.

It is a known biological fact that plants and trees remove carbon dioxide from the atmosphere through photosynthesis. The process of photosynthesis uses carbon dioxide and releases oxygen thereby reducing the damaging effects of CO2 in the atmosphere. Is it possible to create a piece of “equipment” that can function like a natural tree?

Recent science has shown that “50% of global carbon dioxide emissions are emitted from non stationary and dispersed sources with… 20% from the transportation sector…” (IME, Institution of Mechanical Engineers 2009). If an artificial tree can duplicate a natural process, then it is possible to reduce carbon emissions on a global scale provided of course, that the trees are mass produced and well distributed.

An artificial tree can operate in 3 phases – capture, removal and storage. In phase one, the “tree” traps carbon dioxide using a filter chamber that absorbs the CO2. The filter chamber and material mimic the functioning of the leaves. In phase two, the CO2 is removed from the filter and released by a cleaning process. Finally, the carbon dioxide can be transported, stored and secured according to the principles for conventional carbon capture and storage.

Some of the obvious advantages of the artificial tree include portability – it can be placed anywhere. With some tweaking of existing technology, the artificial tree can surpass a natural tree in its ability to capture and release the CO2. The obvious disadvantage with an artificial tree is its cost of production and relative energy consumption in the removal and storage process for CO2.

Despite these limitations, imagine the possibility of urban highways and forests with artificial trees that may each remove up to 1 ton of CO2 per day, the equivalent of 20 vehicles in the U.S.

For some perspective on the natural versus artificial argument, consider the regenerative capacity of the natural tree, the limitation imposed by type and location of urban forests, and the energy used to produce organic compounds in the photosynthetic process. An artificial tree can be:

  • manufactured to specific carbon capture standards so there is no need to wait 100 years to see its carbon capture potential

  • can be placed anywhere

  • there is no need to use energy to produce organic compounds like sugars to “feed” the tree

This type of commercial scale carbon sequestration strategy is already occurring in countries like Canada and Norway. Here in the United States, the U.S. Department of Energy is conducting research on using the technology.

Institution of Mechanical Engineers (IME), United Kingdom
Geo-engineering options
Department of Energy
National Academy of Sciences


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