Intergovernmental Panel on Climate Change and Carbon Capture and Storage

This article is part of the Global Energy Monitor coverage of "clean coal."

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Carbon Capture and Storage Carbon Capture and Storage projects which have been abandoned Clean Coal Clean Coal Marketing Campaign Clean Coal Technology Clean coal - quotable quotes

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The Intergovernmental Panel on Climate Change and Carbon Capture and Storage has endorsed Carbon Capture and Storage (CCS) as one of the potential technologies to reduce the impact of greenhouse gas emissions on the global climate.

CCS & the IPCC's First Assessment Report 1990

In its first Assessment Report the IPCC flagged "CO2 separation and geological and marine disposal" as one of three options to pursue "removal, recirculation or fixation" of greenhouse gas emissions from the energy sector.

It also flagged a 'long term' strategy for individual countries as being "enhancing natural and man-made means to sequester greenhouse gases" from the energy sector.

Aside from this, the main focus on reducing emissions from the energy sector was on improving energy efficiency, developing fuel substitution, co-generation and possible economic instruments to promote pollution reduction. They also flagged the need to develop "non-fossil and low greenhouse emission energy sources".

The closest the report came to mentioning CCS was a statement that, as a part of a long-term strategy, policymakers should "encourage the development of new technologies to limit, reduce, or fix greenhouse gas emissions associated with economic and energy activities." However, in the short-term strategy section the focus of "limit, reduce, or fix greenhouse gas emissions" was on "methane emissions from landfills, coal mines and other sources."

CCS and the IPCC's Second Assessment Report 1995

In its Second Assessment Report the IPCC flagged in the executive summary that one option for achieving "greenhouse gas reductions in the use of fossil fuels" was "decarbonization of flue gases and fuels and carbon dioxide storage (e.g., removal and storage of CO2 from the use of fossil fuel feedstocks to make hydrogen-rich fuels)."

Later on in the report the IPCC stated "the removal and storage of CO2 from fossil fuel power-station stack gases is feasible, but reduces the conversion efficiency and significantly increases the production cost of electricity. Another approach to decarbonization uses fossil fuel feedstocks to make hydrogen-rich fuels. Both approaches generate a byproduct stream of CO2 that could be stored, for example, in depleted natural gas fields. The future availability of conversion technologies such as fuel cells that can efficiently use hydrogen would increase the relative attractiveness of the latter approach. For some longer term CO2 storage options, the costs, environmental effects and efficacy of such options remain largely unknown."

In the Working Group report, the IPCC stated that "in the longer term, decarbonization would allow continued large-scale use of fossil fuels. Here, decarbonization implies utilizarion of the energy in carbon with greatly reduced CO2 emissions. This can be done practically only in large-scale energy conversion facilities. It is logical, therefore, to begin decarbonization efforts in large fossil fuel-burning power starions, which at present account for a quarter of total CO2 emissions from fossil fuels. Either CO2 can be captured from flue gases or carbon-containing fuels can be converted to low-carbon, hydrogen-rich fuels before utilizing them."

However, the working group noted that "If deep CO2 emission reductions are desired, it would be necessary to extend the effort beyond power generation. This is problematic, however, because most fuels used directly are consumed in small-scale conversion systems in which decarbonization is not practical. This problem might be solved by converting the fossil fuel to a low-carbon, hydrogen-rich fuel or to a carbon-free fuel (essentially hydrogen) and CO2 in a centralized facility, followed by removal of the CO2 and distribution of the low-carbon or carbon-free fuel to the consumer."

The working group noted that while carbon storage was being investigated in a number of countries for use with power stations, it had initial impetus for the technology "the desire for an inexpensive, readily available source of CO2 to use in enhanced oil recovery (EOR)." The working group noted that three plants were built for EOR based on gas-fired plants and another based on coal for the production of soda ash.

The working group cautioned that the adoption of the technology would incur a significant energy and cost penalty. It calculated that a typical 600 megawatt coal-fired generating unit would drop from 41% to 30% "if the CO2 emission is reduced from 230 gC/kWh [grams of carbon per kilowatt-hour] to about 30 gC/kWh in the modified plant. It estimated that the costs of electricity production would "increase by about 80%, which is equivalent to $150/t С avoided." A gas plant modified to cut emissions from 110 gC/kWh to about 20 gC/kWh would cause the plant efficiency to drop from 52% to 45% with the cost of electricity increased by approximately 50% or $210/t С avoided. (The references cited papers published between 1992 and 1995.)

Oxy-firing

The working group also passingly mentioned that the option of oxy-firing would produce a flue gas mostly comprising CO2 which could lower the cost of extraction to less than $80 per tonnes of avoided carbon. (The figure referred to a 1994 study).

IGCC

The Working Group stated that an Integrated Gasification Combined Cycle (IGCC) plant would produce emissions of approximately 4 kgC/GJ compared with 24 kgC/GJ for a conventional coal plant. IGCC would have a coal-to-electricity efficiency of about 37% compared to 44% for a conventional plant. "Due to the recovery, the costs of electricity production might increase by 30-40%. The removal costs would then be less than $80/t С avoided," the working group stated.

The group noted that "the least costly way to produce hydrogen often involves the use of natural gas as the feedstock; in the process, a stream of pure CO2 is produced as a byproduct. If this CO2 could be captured and stored in a nearby exhausted natural-gas field, the costs of avoiding the CO2 emissions are estimated to be less than $30/t С [$30 per tonne of carbon]".

Storage of CO2

The working group stated that "because of the small potential for utilization" captured co2 would need to be stored either by underground storage or, they considered, via deep ocean locations. While noting that Enhanced oil Recovery was an option, the working group considered that it had significant limitations given the prevailing oil prices of the time. "EOR using CO2 from power plants might reduce the annual anthropogenic CO2 emissions by about 1%," the working group concluded.

CCS and the IPCC's Third Assessment Report 2001

In its Third Assessment Report the working group stated that:

"substantial reductions in emissions of CO2 from fossil fuel combustion for power generation could be achieved by use of technologies for capture and storage of CO2. These technologies have become much better understood during the past few years, so they can now be seriously considered as mitigation options alongside the more well established options, such as the improvements in fossil fuel systems described ... , and the substitutes for fossil fuels ... Strategies for achieving deep reductions in CO2 emissions will be most robust if they involve all three types of mitigation option."

"...The concentration of CO2 in power station flue gas is between about 4% (for gas turbines) and 14% (for pulverized-coal-fired plant). These low concentrations mean that large volumes of gas have to be handled and powerful solvents have to be used, resulting in high energy consumption for solvent regeneration. Research and development is needed to reduce the energy consumption for solvent regeneration, solvent degradation rates, and costs. Nevertheless, 80%-90% of the CO2 in a flue gas stream could be captured by use of such techniques ... After the CO2 is captured, it would be pressurized for transportation to storage, typically to a pressure of 100 bar. CO2 capture and compression imposes a penalty on thermal efficiency of power generation, which is estimated to be between 8 and 13 percentage points (Audus, 2000). Because of the energy required to capture and compress CO2, the amount of emissions avoided is less than the amount captured. The cost of CO2 capture in power stations is estimated to be approximately US$30-50/t CO2 emissions avoided (US$110-180/tC), equivalent to an increase of about 50% in the cost of electricity generation."

The Working Group also noted that Co2 capture and storage was occurring at the Sleipner project in Norway (1 million tonnes a year), that approximately 33 million tonnes a year was being captured and used "at more than 74 enhanced oil recovery (EOR) projects in the USA" and that at "the Allison unit in New Mexico, USA, (Stevens et al., 1999), over 100,000 tonnes of CO2 has been injected over a three-year period to enhance production of coal bed methane."

The working group stated that:

"If the CO2 is used for enhanced oil recovery (EOR) or enhanced coal bed methane production (ECBM), there is a valuable product (oil or methane, respectively) which would help to offset the cost of CO2 capture and transport. In some EOR or ECBM [Enhanced coal bed methane] projects, the net cost of CO2 capture and storage might be negative. Other ideas for utilizing CO2 to make valuable products have not proved to be as useful as sequestration measures, because of the amount of energy consumed in the process and the relatively insignificant quantities of CO2 which would be used. If no valuable products were produced, the overall cost of CO2 capture and storage would be about US$40-60/t CO2 emissions avoided (150-220/tC). As with most new technologies, there is scope to reduce these costs in the future through technical developments and wider application."

They also concluded that:

"Substantial quantities of CO2 from fossil fuel combustion could be captured in the future and sequestered in natural reservoirs (Williams, 2000). Potentially, this approach could achieve deep reductions in emissions of CO2. Edmonds et al. (2000) have considered various possible strategies to achieve stabilization of CO2 concentrations around 550-750 ppmv. It has been shown that inclusion of the option of capture and storage of CO2 offers significant reduction in overall cost compared with strategies which do not include this option." (The Edmonds study is available online).

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