User:Milton Beychok/Sandbox

Reducing carbon dioxide emissions from coal-fired power plants

The leading technology for significantly reducing the CO₂ emissions from coal-fired power plants is known as Carbon capture and sequestration (CCS). It involves capturing the CO₂ produced by the combustion of coal and storing it in deep ocean areas or in underground geological structures deep within the Earth's upper crust.

The capture of the CO₂ from the coal combustion flue gases can be accomplished by using absorbents such as amines (see Amine gas treating). The CO₂ is then compressed into a supercritical fluid at about 150 atmospheres (15 MPA), dehydrated and transported to the storage sites for injection into the underground or undersea reservoirs. Compressing the CO₂ into a supercritical fluid greatly increases its density which greatly reduces its volume as compared to transporting and storing the CO₂ as a gas.

Since the current global emissions of carbon dioxide from all energy supply sources is 28 Gt per year, the scale of CO₂ storage required to make a major difference in those emissions is massive. For example, based on a CO₂ emission factor of 1 kg per kWh, 570 coal-fired plants, each producing 1000 MW of electricity, would emit about 5 Gt per year of CO₂ into the atmosphere. Storing 5 Gt per year of CO₂ requires injection of about 65 million barrels per day (about 10 x 10⁶ cubic meters per day) of supercritical CO₂.

Today, and independent of whatever carbon constraints may be chosen, the priority objective with respect to coal should be the successful large-scale demonstration of the technical, economic, and environmental performance of the technologies that make up all of the major components of a large-scale integrated CCS system — capture, transportation and storage. Such demonstrations are a prerequisite for broad deployment at gigatonne scale in response to the adoption of a future carbon mitigation policy, as well as for easing the trade-off between restraining emissions from fossil resource use and meeting the world’s future energy needs

What is needed is to demonstrate an integrated system of capture, transportation, and storage of CO2, at scale. This is a practical goal but requires concerted action to carry out. The integrated demonstration must include a properly instrumented storage site that operates under a regulatory framework which includes site selection, injection and surveillance, and conditions for eventual transfer of liability to the government after a period of good practice is demonstrated. An explicit and rigorous regulatory process that has public and political support is prerequisite for implementation of carbon sequestration on a large scale. This regulatory process must resolve issues associated with the definition of property rights, liability, site licensing and monitoring, ownership, compensation arrangements and other institutional and legal considerations. Regulatory protocols need to be defined for sequestration projects including site selection, injection operation, and eventual transfer of custody to public authorities after a period of successful operation. These issues should be addressed with far more urgency than is evidenced today.