Are ways to perform human control of the carbon in the atmosphere? How do we do it? Is it safe?
- Natural carbon sinks, like forests, are extremely good at keeping and capturing carbon dioxide from the atmosphere
- Taking carbon out of the atmosphere can be done to a small degree, by human means, but it is expensive and difficult
- This cannot be a permanent solution to the carbon emissions problem and is not without risk
If there's too much carbon in the atmosphere, why don't we grab it back out of the atmosphere and put it away somewhere where it won't cause harm? This is precisely what nature does through vegetation. Forests and oceans absorb almost half of the human emissions in this way. So now we ask the question: if nature can do it, can we?
People are now exploring new sinks for carbon dioxide in the atmosphere through a process called Carbon Capture and Storage (CCS). This process does not stop the burning of fossil fuels but captures the carbon dioxide produced at the smokestacks to prevent it from being emitted into the atmosphere.
There are different proposals on what to do with this captured carbon dioxide. Some involve pumping the carbon dioxide gas back into the ground from which the fossil fuels were extracted. Since there would be a large amount of earth between the atmosphere and the geological formations from which the fossil fuels were extracted, it would theoretically take a very long time before any of the carbon dioxide somehow made it to the surface. However, this approach could be expensive, and there is a risk of leakage of carbon dioxide from the underground storage reservoirs.
Other approaches suggest pumping the carbon dioxide into deep ocean waters, instead of deep underground, where it would be isolated for a long period of time. The carbon dioxide in the ocean would be released into the atmosphere over hundreds of years, and the difference in time scale (hundreds of years as opposed to mere days or years) may allow for an adjustment by the environment. The end result, however, is the same as if the carbon dioxide had been directly released into the atmosphere. There is also the side effect of ocean acidification from the added carbon dioxide which will alter, and likely damage, ocean ecosystems.
Carbon storage may look attractive, since it does not require us to change our lifestyles or energy facilities. But carbon storage can only a temporary solution to our carbon emission problems, and it provides a false sense security by diminishing the urgency of low carbon, alternative energy development. In addition, carbon storage has only been demonstrated to work on small scale projects - way too small to have any significant impact on national emissions.
In the meantime, efforts are being made to maintain and rebuild natural carbon sinks, like forests and other wooded lands. Conservation of existing forests not only prevents the release of carbon dioxide stored, it also continues their absorption from the atmosphere. In order to absorb even more carbon dioxide, there are reforestation and afforestation efforts which aim at planting trees in old mine sites, industrial areas, farms, and towns. Each hectare of forest in Canada can absorb up to twenty tonnes of carbon dioxide per year, or the equivalent emissions of about 4 passenger cars. That it to say, a lot of forest is needed for a small benefit.
To learn more about Carbon Capture and Storage technologies, you can visit the interactive lessons provided by the Pacific Institute for Climate Solutions by clicking on the image below and selecting sections 18-23 on the left side panel:
© Physics and Astronomy Outreach Program at the University of British Columbia (2015-12-31)