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Purpose

According to some, even with increases in energy efficiency and low-carbon fuels usage, carbon sequestration will be necessary to meet greenhouse gas reduction goals. Even those who are optimistic about the penetration of wind, solar, and even nuclear power in the near future will admit that in the immediate future, we are going to have at least some fossil fuel plants, so carbon sequestration will play a role in greening up these power sources. About 1/3 of the US' carbon emissions come from power plants and other large point sources. It has been described as an important technology for the 21st century by the President's Committee of Advisors on Science and Technology (PCAST). Carbon sequestration from plants and large point sources has an advantage over other terrestrial sequestration techniques like agriculture and planting trees because it is less likely for the carbon to be released over time. Trees can be burned or cut, and soil tillage regimes abandoned, but carbon stored as a part of CCS strategies, are less likely to be lost to the atmosphere. Both of these systems affect the levels of other greenhouse gas pollutants in sometimes unpredictable ways, but do have other advantages, such as the ability to generally enhance the quality of soil, water, air, and wildlife habitat, especially the terrestrial storage in the form of plant storage.

Cost

The increased energy requirements of capturing and compressing CO2 significantly raises the operating costs of CCS power plants, in addition to the increased capital costs. CCS would increase the fuel requirement of a plant with CCS by about 25% for coal-fired plant and about 15% for a gas-fired plant. It will increase the costs of energy from a CCS power plant by about 30-60%, depending on the type of plant, cost of fuel, and transport and storage method. On average, geological storage costs $0.50-8.00 per metric ton of CO2 injected. In total, the cost of sequestration is in the range of $100-300 per ton of carbon, although the goal of the US government is that it would cost less than $10 per ton of carbon by 2015. The current price would add 2.5-4 cents/KWh of electricity produced. It is also argued that it is not necessary to use the most advanced, zero emissions system, immediately, allowing some time to lower the cost while using the cheaper, established technologies today. One of the reasons its so expensive for power plants and other large point sources is that CO2 is exhausted with nitrogen, which then needs to be separated out so the carbon can be efficiently stored. In coal-fired plants, CO2 only makes up 10-12% of the exhaust by volume, and in natural gas combined cycle plants, its only 3-6%. As a result, CO2 capture makes up about 3/4 of the cost of the total CCS system, from capture to transport to storage and monitoring. For terrestrial carbon storage, estimates of cost are on the order of $10-50 per metric ton of carbon stored.

Limitations

One of the major concerns with CCS is whether leakage of stored CO2 will negate some of the effects of CCS. As described above, geological storage and mineral storage are highly unlikely to leak, but ocean storage is likely to release 15-70% of stored carbon after 500 years for depths from 1000-3000m. Terrestrial storage is likely to be released if the biomass used to store the carbon is not preserved. CCS for power plants or other large point sources require large amounts of additional energy, increasing resource consumption by about 1/3 and is also very expensive, especially when considering the need to install pipelines, prepare storage sites, and constantly monitor those sites. In addition to the energy required to remove CO2 from the smokestacks, compressing the CO2 to liquid form and injecting it into the ground requires about 20% of the energy produced by burning coal in the first place. There are also only a certain number of reservoirs, so it can not be viewed as the answer, but only a small part of the answer.