Today we are coming to terms with global warming and the ever-growing carbon footprint that humans are making on the environment. We understand now that our existence and our way of life is polluting the earth in ways that have spun out of control, to the point where we are literally warming the earth, and affecting natural weather patterns in a dangerous way. Just as it is human technology that created all of this excess waste in the first place, it is the same inventive spirit that can for now alleviate, and eventually solve the problem.
One solution that scientists are examining all over the world is carbon sequestration, or carbon storage. Global warming is caused by too many greenhouse gases in the atmosphere, as they absorb and emit the sun's radiation, trapping heat. These gases are a necessary part of the earth's atmosphere, because without them our planet would be too cold to inhabit. But because of the sudden increase in carbon emissions over the past century, the concentration of greenhouse gases has increased faster than the earth's environment can naturally keep up with. The belief is that to sequester, or trap and store the excess carbon that nature isn't able to do on its own, will slow down, and possibly reverse the effects of global warming. There are several avenues of carbon sequestration. They are, geologic sequestration, terrestrial sequestration, and oceanic sequestration.
Geologic sequestration, also called geosequestration, is a method of capturing carbon dioxide emissions before they are released into the atmosphere from coal-fired power plants. The carbon is then compressed into a liquid and injected deep within an underground hole. In September of 2008 a coal-fired power plant in Spremberg, Germany was the first to successfully capture and store its carbon emissions. This process is however controversial because it is a difficult, expensive procedure, that would consume nearly as much energy as it would save. Also, there has not been enough research to determine the prolonged safety of storing huge amounts of carbon beneath the earth. To actually capture the carbon is nearly impossible because the gas emitted from the power plants isn't pure; it is diluted with nitrogen gas. Presently, they are trying to capture the carbon with amine absorbers and cryogenic coolers. The price of this process is $150 per ton of carbon, which could cause the cost of electricity to rise from 2.5 cents to 4 cents per kilowatt hour.
Geosequestration also entails storing carbon gas in oil and natural gas reservoirs, coal seams, and saline reservoirs. Energy companies have already been using this method because it makes pumping gas or oil out of very deep reservoirs much more efficient. They simply pump the carbon dioxide down, which pushes the gas or oil up. This is called enhanced oil recovery. The United States alone uses around 32 million tons of carbon a year to do this. The same process is used in difficult to reach coal beds. Also, the potential storage of saline reservoirs makes them a great option, with a capacity of almost 500 billion tons of carbon in the United States. The problem with all geologic sequestration lies in the lack of research. There is not enough proof to say that the carbon won't migrate to the earth's surface, or escape into drinking water supplies.
Terrestrial sequestration involves the natural ecosystem. Both the soil and the roots of plants store carbon, and plants naturally remove carbon from the atmosphere. It is estimated that the entire biosphere absorbs around 2 billion tons of carbon annually, which constitutes one third of all global carbon emissions. So, scientists have realized that if they increase the capacity of the biosphere to absorb carbon, the earth will naturally sequester a huge portion of excess carbon. This entails increasing the area covered by forests, and slowing down human deforestation. This is by far the most cost-effective method of carbon storage, and the safest for the environment. Still, technology is needed to read the specific amounts of carbon in each given ecosystem. This would be pertinent especially with potential carbon emissions trading programs, where states or entities could purchase carbon credits from other states that have low carbon emissions, or high carbon capture rates.
The third form of carbon storage is oceanic sequestration. The ocean is a natural carbon sink. It absorbs carbon on its own to reach an equilibrium with the carbon in the atmosphere, as well as through the photosynthesis of phytoplankton. Scientists believe that they can speed up the process of carbon equilibrium by injecting carbon straight into the ocean through carbon pipelines, leaving it to dissolve. The theory is that because the ocean has much larger capacity for carbon than the atmosphere, that it wouldn't be detrimental. For example, the amount of carbon needed to double the concentration in the atmosphere, would only increase the ocean's concentrations by 2%.
They also believe that by increasing the phytoplankton populations in the ocean, they can increase the ocean's natural process of carbon absorption. Phytoplankton are at the very bottom of the ocean's food chain, so their increase, would potentially increase all marine life. Just like with terrestrial sequestration, the more biomass there is in the ocean, the more carbon that will be absorbed since all life is carbon-based. Scientists have learned that by fertilizing the ocean with iron, an essential nutrient, they can enrich phytoplankton populations.
With all the methods and theories out there about carbon sequestration, the bottom line is that there hasn't been enough research done to make definitive decisions about the best possible solutions to greenhouse gas emissions. There are many avenues that scientists and researchers can take, some more efficient than others. Right now carbon sequestration is still a political issue. One that hasn't been delved into or invested in enough to fully understand. As the global community grows, and our carbon footprint with it, we will hopefully be able to find a solution to our problems. In the meantime, the best, and cheapest way to reduce waste is to not use the energy in the first place.
Sources:
http://www.princeton.edu/~chm333/2002/ fall/co_two/oceans/
http://csite.ornl.gov/
http://www. fossil.energy.gov/programs/sequestration/capture/
htt p://www.fossil.energy.gov/programs/sequestration/geo logic/
http://www.fossil.energy.gov/programs/sequestr ation/terrestrial/