What is carbon capture and storage and will it cut emissions?

  • August 2, 2023
  • Posted by: OptimizeIAS Team
  • Category: DPN Topics
No Comments

 

 

What is carbon capture and storage and will it cut emissions?

Subject: Environment

Section: Climate change

WHAT IS CCS?

  • There are two main types of carbon capture and storage.
  • Point-source carbon capture and storage (CCS) which captures CO2 produced at the source, such as a smokestack, while direct air capture (DAC) removes carbon dioxide (CO2) that has already been released into the atmosphere.
  • They are both designed to capture emissions from heavy-emitting sectors, such as oil and gas refining and steel manufacturing, and store them underground off the coast of Britain in depleted oil and gas fields.

Method of carbon capture and storage:

  • Three main methods:
    • Pre-combustion,
    • Post-combustion and
    • Oxyfuel

Pre-combustion:

  • This method is normally applied to coal-gasification combined-cycle power plants.
  • The coal is gasified to produce a synthetic gas made from carbon monoxide and hydrogen. The former is reacted with water to produce CO2, which is captured, and more hydrogen.
  • The hydrogen can be diverted to a turbine where it can be burned to produce electricity. Alternatively, some of this gas can be bled off to feed hydrogen fuel cells for cars.
  • Most suitable for:
    • It could perhaps be used in natural gas stations, where a synthetic gas is first produced by reacting the methane with steam to produce carbon dioxide and hydrogen.
  • Disadvantage:
    • It cannot be retro-fitted to the older pulverized coal power plants that make up much of the world’s installed base of fossil fuel power.

Post-combustion:

In this method, CO2 is separated from the flue gas of the power station by bubbling the gas through an absorber column packed with liquid solvents (such as ammonia).

  • In the most widely used system, once the chemicals in the absorber column become saturated, a stream of superheated steam at around 120OC is passed through it. This releases the trapped CO2, which can then be transported for storage elsewhere.
  • More experimental techniques to scrub CO2 from flue gas without the two-step process include using seawater to absorb the gas and then returning the mixture back to the ocean for long-term storage. But, so far, these methods have proved less efficient and reliable.

Oxyfuel:

  • When coal, oil or natural gas is burned in normal air, CO2 makes up around 3-15% of the waste gas – and separating it out is difficult and energy-intensive.
  • An alternative method is to burn the fuel in pure oxygen.
  • In this environment, virtually all the waste gas will be composed of CO2 and water vapor.
  • The latter can be condensed out while the former can be piped or transported directly to a storage facility.
  • In the oxyfuel system, the challenge is separating large volumes of air into liquid oxygen, gaseous nitrogen, argon and other trace gasses.
  • This process can use up to 15% of the power produced at the station.

HOW DOES IT WORK?

  • Firstly, the CO2 has to be separated from other gasses produced in industrial processes or during power generation.
  • Once captured it has to be compressed and transported to sites for storage often via pipelines. After that, it has to be injected into rock formations underground – typically 1 km (0.62 mile) or more under the ground – for storage for decades.

IS THE TECHNOLOGY PROVEN?

  • CCS has been in operation since the 1970s with more than 200 million tonnes of CO2 captured and storeddeep underground globally.
  • Many projects however have failed to deliver the carbon savings promised.
  • The world’s largest commercial CCS project, Chevron Corp’s (CVX.N) Gorgon project in Australia has struggled to hit capacity.

HOW MANY FACILITIES ARE THERE?

  • According to the Global CCS Institute, 61 facilities were added to the global project pipeline last year, bringing the total to more than 190.
  • Of those, 30 were in operation,11 were under construction and the remainder in various stages of development.

WHAT IS THE DIFFERENCE BETWEEN CCS AND CARBON CAPTURE, UTILISATION AND STORAGE (CCUS)?

  • CCUS – instead of just storing the CO2 – re-uses it in industrial processes such as plastics, concrete or biofuel manufacture.

Expensive technology:

  • CCS technology is expensive and two thirds of lifetime costs are upfront expenditure.
Environment What is carbon capture and storage and will it cut emissions?