PARIS, Jan. 6 -- Carbon dioxide capture and underground storage could constitute as much as half of the global emissions reduction by 2050, according to the International Energy Agency in the book CO2 Capture and Storage. IEA Executive Director Claude Mandil presented the book last month at the United Nations Conference of Parties on Climate Change in Buenos Aires.
The publication describes the challenges for a CO2 capture and storage (CCS) strategy to reach market introduction and achieve its full potential within 30-50 years.
Developing CCS technologies provides the opportunity to continue using fossil fuels such as coal, oil, or natural gas without significant CO2 emissions. In addition, the captured CO2 may be used for enhanced oil and gas recovery, which would offset, at least partially, the high cost of capturing CO2 through additional oil and gas production, IEA stated.
CCS involves three distinct processes: capturing CO2 from the gas streams emitted during electric power production, industrial processes, or fuel processing; transporting the captured CO2 by pipeline or via tanker; and storing CO2 underground in deep salt aquifers, depleted oil and gas reservoirs, or unmineable coal seams.
Since all three of these processes have been used for decades, CCS fits well into the existing technology trajectory of fossil fuel-based energy supply and can be developed by existing energy technology suppliers, IEA contends.
Also, no major adjustments would be required in any energy infrastructure. In principle, CO2 capture can be applied to all fossil fuel and biomass combustion processes, IEA said. But only large point sourcesthose emitting more than 1 million tonnes/year of CO2can achieve the scale economies needed to make CCS a cost-effective strategy.
Sources of CO2
The electric power sector remains the main source for capture potential as it is projected to account for about 80% of the total CO2 emitted in 2050.
The other 20% is evenly split between fuel processing and the industrial sectors. Most of the CO2 is released from coal-fired electric power plants. Emissions from other sources, such as transportation, agriculture, and the service and residential sectors, are too dispersed to make capture viable.
Besides fossil fuel-fired electric power plants, CO2 also can be captured, to a lesser extent, during the production of iron, steel, cement, chemicals, and pulp, as well as from refining, natural gas processing, and synthetic fuel production.
The key issue in CO2 capture is to lower costs to economically practicable levels as the processes are known and do not represent high technological risks.
CO2 can be captured either before or after combustion using a range of existing and emerging technologies. In precombustion, physical absorption of CO2 is the most promising capture option. In postcombustion capture, options include processes based on chemical absorption or oxyfueling (combustion using oxygen separated from air), which generates nearly pure CO2 flue gas.
Chemical and physical absorption are proven technologies. In the longer term, gas separation membranes and other new technologies may be used for precombustion and postcombustion capture. Existing technologies are applied in most CO2 capture projects, but various small-scale pilot plants based on new technologies are in operation around the world.
The only megatonne-scale power plant demonstration is the FutureGen coal-fired advanced power plant in the US planned to start in 2007. Other projects are planned in Canada, Europe, and Australia.
Significant research and development work is also needed to prove the feasibility and integrity of CO2 storage in various reservoirs through long-term monitoring projects. In 2030, the IEA projects that half of the captured CO2 should be used to enhance fossil fuel production or stored in depleted oil and gas reservoirs. By 2050 aquifer storage will dominate.
However, many oil and gas fields are in remote regions, far from sources where CO2 could be captured. So the effort to bring CO2 to the site must be compared to the cost of alternative enhanced oil recovery technologies and conducted on a case-by-case basis.
In all cases where CO2 transport applies, the technology is an established one. But potential pipeline siting constraints and transportation distances of hundreds of kilometers would require a CO2 "backbone" connecting multiple power plants and a number of storage sites to be cost-effective. CO2 transport by ship also is an option.
Currently there are about 100 ongoing and proposed CO2 storage projects. The more noteworthy projects include a commercial-scale project at the Sleipner site in Norway (subsea storage), where about 1 million tonnes/year of CO2 has been stored since 1996 with no leakage so far detected, and the Weyburn project in Canada, where 2 million tonnes/year of CO2 has been stored since 2001.These two projects have sparked many more smaller storage demonstration projects.
IEA insists that sufficient proof of storage integrity and permanence is essential for any credible CCS strategy and for public awareness and acceptance. It is critical to advancing technological understanding, increasing efficiency, and driving down costs. Currently the CCS budget is a little more than $100 million/year.
An increase in funding to $500 million/year for CCS projects is needed in the short term if gigatons of CO2 are to be captured over the next 20-30 years. The current R&D budget trends are not up to this requirement even though a large amount of data gathered through demonstration projects also is needed to set up a suitable legal and regulatory framework to attract financing and gain public acceptance.
Today the costs of capturing and storing CO2 range from $50/tonne to $100/tonne. Costs can be brought down to $25-50/tonne by 2030 through more R&D work. Even if costs are reduced, policy incentives would be needed to stimulate the market interest in CCS technologies. Emissions trading systems would help if prices are high enough to make CCS competitive.
The IEA book suggests that CCS could start on a large scale in IEA member countries from 2015 onwards and that significant emissions reductions18 gigatonnescould be achieved by 2050 with more than a third of global electricity generation equipped with CCS by then. It warns that without CO2 capture and storage 2050 emissions would be 25% higher.