CO₂ Capture and Storage

2. What sources of CO₂ emissions are suitable for capture and storage?

• 2.1 What are the characteristics of suitable emission sources?
• 2.2 To what extent could future CO₂ emissions be captured?

2.1 What are the characteristics of suitable emission sources?

The source document for this Digest states:

The Gibson coal power plant, a good example of a large stationary source.
Source: John Blair, valleywatch.net 

Global Distribution of large CO2 sources

Possible storage sites

This section describes the major current anthropogenic sources of CO₂ emissions and their relation to potential storage sites. As noted earlier, CO₂ emissions from human activity arise from a number of different sources, mainly from the combustion of fossil fuels used in power generation, transportation, industrial processes, and residential and commercial buildings. CO₂ is also emitted during certain industrial processes like cement manufacture or hydrogen production and during the combustion of biomass. Future emissions are also discussed in this section.

Current CO₂ sources and characteristics

To assess the potential of CCS as an option for reducing global CO₂ emissions, the current global geographical relationship between large stationary CO₂ emission sources and their proximity to potential storage sites has been examined. CO₂ emissions in the residential, commerical and transportation sectors have not been considered in this analysis because these emission sources are individually small and often mobile, and therefore unsuitable for capture and storage. The discussion here also includes an analysis of potential future sources of CO₂ based on several scenarios of future global energy use and emissions over the next century.

Globally, emissions of CO₂ from fossil-fuel use in the year 2000 totalled about 23.5 GtCO₂ yr-1 (6 GtC yr-1). Of this, close to 60% was attributed to large (>0.1 MtCO₂ yr-1) stationary emission sources (see Table TS.2). However, not all of these sources are amenable to CO₂ capture. Although the sources evaluated are distributed throughout the world, the database reveals four particular clusters of emissions: North America (midwest and eastern USA), Europe (northwest region), East Asia (eastern coast of China) and South Asia (Indiansubcontinent). By contrast, large-scale biomass sources are much smaller in number and less globally distributed.

Table TS.2. Worldwide large stationary CO₂ sources

Currently, the vast majority of large emission sources have CO₂ concentrations of less than 15% (in some cases, substantially less). However, a small portion (less than 2%) of the fossil fuel-based industrial sources have CO₂ concentrations in excess of 95%. The high-concentration sources are potential candidates for the early implementation of CCS because only dehydration and compression would be required at the capture stage (see Section 3). An analysis of these high-purity sources that are within 50 km of storage formations and that have the potential to generate revenues (via the use of CO₂ for enhanced hydrocarbon production through ECBM or EOR) indicates that such sources currently emit approximately 360 MtCO₂ per year. Some biomass sources like bioethanol production also generate high-concentration CO₂ sources which could also be used in similar applications.

The distance between an emission location and a storage site can have a significant bearing on whether or not CCS can play a significant role in reducing CO₂ emissions. Figure TS.2a depicts the major CO₂ emission sources (indicated by dots), and Figure TS.2b shows the sedimentary basins with geological storage prospectivity (shown in different shades of grey). In broad terms, these figures indicate that there is potentially good correlation between major sources and prospective sedimentary basins, with many sources lying either directly above, or within reasonable distances (less than 300 km) from areas with potential for geological storage. The basins shown in Figure TS.2b have not been identified or evaluated as suitable storage reservoirs; more detailed geological analysis on a regional level is required to confirm the suitability of these potential storage sites.

Source & ©: IPCC  Carbon Dioxide Capture and Storage: Technical Summary (2005)
2. Sources of CO2, p. 22

2.2 To what extent could future CO₂ emissions be captured?

The source document for this Digest states:

In the IPCC Special Report on Emission Scenarios (SRES), the future emissions of CO₂ are projected on the basis of six illustrative scenarios in which global CO₂ emissions range from 29 to 44 GtCO₂ (8–12 GtC) per year in 2020, and from 23 to 84 GtCO₂ (6–23 GtC) per year in 2050. It is projected that the number of CO₂ emission sources from the electric power and industrial sectors will increase significantly until 2050, mainly in South and East Asia. By contrast, the number of such sources in Europe may decrease slightly. The proportion of sources with high and low CO₂ content will be a function of the size and rate of introduction of plants employing gasification or liquefaction of fossil fuels to produce hydrogen, or other liquid and gaseous products. The greater the number of these plants, the greater the number of sources with high CO₂ concentrations technically suitable for capture.

The projected potential of CO₂ capture associated with the above emission ranges has been estimated at an annual 2.6 to 4.9 GtCO₂ by 2020 (0.7–1.3 GtC) and 4.7 to 37.5 GtCO₂ by 2050 (1.3–10 GtC). These numbers correspond to 9–12%, and 21–45% of global CO₂ emissions in 2020 and 2050, respectively. The emission and capture ranges reflect the inherent uncertainties of scenario and modelling analyses, and the technical limitations of applying CCS. These scenarios only take into account CO₂ capture from fossil fuels, and not from biomass sources. However, emissions from large-scale biomass conversion facilities could also be technically suitable for capture.

The potential development of low-carbon energy carriers is relevant to the future number and size of large, stationary CO₂ sources with high concentrations. Scenarios also suggest that large-scale production of low-carbon energy carriers such as electricity or hydrogen could, within several decades, begin displacing the fossil fuels currently used by small, distributed sources in residential and commercial buildings and in the transportation sector (see Section 8). These energy carriers could be produced from fossil fuels and/or biomass in large plants that would generate large point sources of CO₂ (power plants or plants similar to current plants producing hydrogen from natural gas). These sources would be suitable for CO₂ capture. Such applications of CCS could reduce dispersed CO₂ emissions from transport and from distributed energy supply systems. At present, however, it is difficult to project the likely number, size, or geographical distribution of the sources associated with such developments.

Source & ©: IPCC (WGI)  Intergovernmental Panel on Climate Change IPCC
Carbon Dioxide Capture and Storage: Technical Summary (2005)
2. Sources of CO2, p. 24