What is carbon sequestration?
Carbon dioxide levels in the atmosphere can be reduced by withdrawal and segregation.
Carbon sequestration is a term that is used regularly today, but was not heard of before the recent interest in atmospheric carbon dioxide levels. There are sources and sinks of carbon dioxide. Sources produce and release carbon dioxide into the atmosphere. They include burning of fossil fuels, decay of organic materials and respiration from humans and animals. A sink is something that takes carbon dioxide out of the atmosphere and stores it in a liquid or solid form, including oceans, photosynthesis in plants and new carbon sequestration technologies. In a balanced system, the release of carbon dioxide by sources is equivalent to the uptake by sinks. Today, a great deal of excess carbon dioxide is being stored in the atmosphere, which impacts global climate.
One of the biggest sources of carbon dioxide in the atmosphere is the burning of fossil fuels for heat and electricity. Many power plants burn coal and natural gas to generate electricity. Industry uses electricity and heat to manufacture goods. In these cases, the emission of carbon dioxide is highly concentrated, which offers a real opportunity. This concentration allows the capture or removal of carbon dioxide from the exhaust stream. EPA defines the carbon capture and sequestration process in the following way:
- Capture of CO2 from power plants or industrial processes.
- Transport of the captured and compressed CO2 (usually in pipelines).
- Underground injection and geologic sequestration (also referred to as storage) of the CO2 into deep underground rock formations. These formations are often a mile or more beneath the surface and consist of porous rock that holds the CO2. Overlying these formations are impermeable, non-porous layers of rock that trap the CO2 and prevent it from migrating upward.
In addition to this system of engineered carbon capture, the use of carbon dioxide by vegetative plants is natural and occurs without human action, but this process can be affected by the choice of plant species and production systems used. Many perennial plants are especially good at storing carbon in their root systems. Potential energy crops such as switchgrass have been shown to accumulate more carbon in the soil through root growth than would be removed by harvesting the above ground portion of the plant. Reductions in tillage intensity also increase the amount of carbon in the soil since it is not decomposed as quickly as it would be under intensive tillage.
The Long Term Ecological Research project at Michigan State University has included significant efforts in measuring the release of greenhouse gases, including carbon dioxide, to enhance the understanding of systems that may reduce environmental impacts from agriculture and natural systems. Michigan State University Extension is utilizing this work to inform citizens on this topic.