Sources of Color

Abstract

Assessing CO2 capture and storage calls for a comprehensive delineation of CO2 sources. The attractiveness of a particular CO2 source for capture depends on its volume, concentration and partial pressure, integrated system aspects, and its proximity to a suitable reservoir. Emissions of CO2 arise from a number of sources, mainly fossil fuel combustion in the power generation, industrial, residential and transport sectors. In the power generation and industrial sectors, many sources have large emission volumes that make them amenable to the addition of CO2 capture technology. Large numbers of small point sources and, in the case of transport, mobile sources characterize the other sectors, making them less amenable for capture at present. Technological changes in the production and nature of transport fuels, however, may eventually allow the capture of CO2 from energy use in this sector. Over 7,500 large CO2 emission sources (above 0.1 MtCO2 yr-1 ) have been identified. These sources are distributed geographically around the world but four clusters of emissions can be observed: in North America (the Midwest and the eastern freeboard of the USA), North West Europe, South East Asia (eastern coast) and Southern Asia (the Indian sub-continent). Projections for the future (up to 2050) indicate that the number of emission sources from the power and industry sectors is likely to increase, predominantly in Southern and South East Asia, while the number of emission sources suitable for capture and storage in regions like Europe may decrease slightly. Comparing the geographical distribution of the emission sources with geological storage opportunities, it can be seen that there is a good match between sources and opportunities. A substantial proportion of the emission sources are either on top of, or within 300 km from, a site with potential for geological storage. Detailed studies are, however, needed to confirm the suitability of such sites for CO2 storage. In the case of ocean storage, related research suggests that only a small proportion of large emission sources will be close to potential ocean storage sites. The majority of the emissions sources have concentrations of CO2 that are typically lower than 15%. However, a small proportion (less than 2%) have concentrations that exceed 95%, making them more suitable for CO2 capture. The high- content sources open up the possibility of lower capture costs compared to low-content sources because only dehydration and compression are required. The future proportion of high- and low-content CO2 sources will largely depend on the rate of introduction of hydrogen, biofuels, and the gasification or liquefaction of fossil fuels, as well as future developments in plant sizes. Technological changes, such as the centralized production of liquid or gaseous energy carriers (e.g., methanol, ethanol or hydrogen) from fossil sources or the centralized production of those energy carriers or electricity from biomass, may allow for CO2 capture and storage. Under these conditions, power generation and industrial emission sources would largely remain unaffected but CO2 emissions from transport and distributed energy-supply systems would be replaced by additional point sources that would be amenable to capture. The CO2 could then be stored either in geological formations or in the oceans. Given the scarcity of data, it is not possible to project the likely numbers of such additional point sources, or their geographical distribution, with confidence (estimates range from 0 to 1,400 GtCO2 (0–380 GtC) for 2050). According to six illustrative SRES scenarios, global CO2 emissions could range from 29.3 to 44.2 GtCO2 (8–12 GtC) in 2020 and from 22.5 to 83.7 GtCO2 (6–23 GtC) in 2050. The technical potential of CO2 capture associated with these emission ranges has been estimated recently at 2.6–4.9 GtCO2 for 2020 (0.7–1.3 GtC) and 4.9–37.5 GtCO2 for 2050 (1.3–10 GtC). These emission and capture ranges reflect the inherent uncertainties of scenario and modelling analyses. However, there is one trend common to all of the six illustrative SRES scenarios: the general increase of future CO2 emissions in the developing countries relative to the industrialized countries.