Carbon capture and storage

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Carbon is emitted into the atmosphere as carbon dioxide, as a result of burning fuels mainly by are cars and lorries, and non-nuclear power stations - those that burn coal, oil or gas. To prevent build-up of carbon dioxide in the atmosphere, which can cause global warming and ocean acidification, we can capture and store it, using natural storage facilites. Some of the best natural containers are old oil and gas fields, such as those in the North Sea.

Contents

Why should I be aware of this?

  • Human activity causes emission of some 30 billion metric tons of carbon dioxide per year. About half of the greenhouse gas is absorbed by the world's oceans and plants, and the rest lingers in the atmosphere for a century or more, driving up annual CO2 concentrations by around two parts per million (ppm).
  • Concentrations of carbon in the atmosphere have risen from roughly 280 ppm in the 18th century to 386 ppm today, and continue to rise. This has resulted primarily from the widespread burning of fossil fuels. According to the Natural Resources Defense Council (NRDC), the coal-fired power plants built or planned since the turn of the 21st century will emit more carbon dioxide than all human coal-burning since the dawn of the Industrial Age: 660 billion metric tons over the next 25 years versus 524 billion metric tons emitted between 1751 and 2000. [1]

All about carbon capture and storage

Carbon capture and storage, which is also known as sequestration of carbon dioxide, is an important approach for stabilizing atmospheric greenhouse gases—although there are many economic, technical, and legal barriers to its implementation.

There are three types of technology to capture CO2 at a power plant. One, which uses the oxyfuel process, involves burning coal in pure oxygen to produce a CO2-rich emission stream. The second uses various forms of chemistry—in the form of amine or ammonia scrubbers, special membranes or ionic liquids—to pull CO2 out of a more mixed set of exhaust gases. The third is gasification, in which liquid or solid fuels are first turned into synthetic natural gas, the most common being integrated gasification combined cycle (IGCC) technology; CO2 from the conversion of the gas can be siphoned off.

The process

Carbon capture and storage refers to the process of stripping carbon dioxide from fossil fuels before or after they're burnt to produce energy. It is then piped back into the earth to a depth of at least 800 meters -- deep enough for the pressure of the earth to keep it in a liquidized form where it stays for thousands, if not millions, of years.

Such large volumes of carbon emissions can only be stored in depleted oil and gas reservoirs. Alternatives including deep saline aquifers and deep coal seams are also being explored.

Done in small scale

Carbon capture and storage is being done, but only a small scale. Trials are underway in a number of countries including Norway, Algeria and Australia. Last week, Australia's national science agency, the CSIRO, announced plans to test China's first post-combustion capture (PCC) technology at a pilot plant in Beijing.

The problem is that while the different processes needed to capture and store carbon dioxide have been around for years, no one has brought them together on a large enough scale to cope with the volume of emissions from a typical power plant. High cost is also another deterrent.

Fears and opposition

Though most environmental groups agree that global greenhouse gas emissions must be reduced by at least 80 percent below 1990 levels by mid-century, they differ on how that can be achieved. Some prominent groups oppose CCS technology, and prefer renewable resources, such as wind and solar energy as solution.

A fear associated with carbon sequestration is that trapped CO2 might suddenly escape to the surface with deadly consequences, as happened in 1986 at Lake Nyos in Cameroon. That volcanic lake had naturally accumulated two million metric tons of carbon dioxide in its cold depths; one night it spontaneously vented, displacing the oxygenated air, and suffocated more than 1,000 nearby villagers.

Most of the underground vaults would be out at sea, and geologists are confident the C02 won't escape from sites approved for storage.

CopperBytes

  • Carbon dioxide could be captured from power plants or industrial facilities that produce large amounts of carbon dioxide. [2]
  • Technology for CO2 capture from small or mobile emission sources, such as home heating systems or cars, is not sufficiently developed yet.[2]
  • A significant proportion of the CO2 produced by fossil fuel power plants could potentially be captured. [2]
  • By 2050 the amount captured could represent 21 to 45% of all the CO2 emitted by human activities.[2]
  • It is possible to reduce the CO2 emissions from new power plants by about 80 to 90%, but this increases the cost of electricity produced by 35 to 85%. For industrial processes where a relatively pure CO2 stream is produced, the cost per tonne of CO2 captured is lower. [2]

References:

  • A guide to carbon capture and storage
  • How Fast Can Carbon Capture and Storage Fix Climate Change?
  • Carbon capture and storage: how does it work?

Source

  1. Scientific American
  2. 2.0 2.1 2.2 2.3 2.4 CO2 Capture and Storage