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Background to the report

IPCC's Third Assessment Report stated 'there is new and stronger evidence that most of the warming observed over the past 50 years is attributable to human activities'. It went on to point out that 'human influences will continue to change atmospheric composition throughout the 21st century' (IPCC, 2001c). Carbon dioxide (CO2) is the greenhouse gas that makes the largest contribution from human activities. It is released into the atmosphere by: the combustion of fossil fuels such as coal, oil or natural gas, and renewable fuels like biomass; by the burning of, for example, forests during land clearance; and from certain industrial and resource extraction processes. As a result 'emissions of CO2 due to fossil fuel burning are virtually certain to be the dominant influence on the trends in atmospheric CO2 concentration during the 21st century' and 'global average temperatures and sea level are projected to rise under all ... scenarios' (IPCC, 2001c).

The UN Framework Convention on Climate Change (UNFCCC), which has been ratified by 189 nations and has now gone into force, asserts that the world should achieve an atmospheric concentration of greenhouse gases (GHGs) that would prevent 'dangerous anthropogenic interference with the climate system' (UNFCCC, 1992), although the specific level of atmospheric concentrations has not yet been quantified. Technological options for reducing anthropogenic emissions1 of CO2 include (1) reducing the use of fossil fuels (2) substituting less carbon-intensive fossil fuels for more carbon-intensive fuels (3) replacing fossil fuel technologies with near-zero-carbon alternatives and (4) enhancing the absorption of atmospheric CO2 by natural systems. In this report, the Intergovernmental Panel on Climate Change (IPCC) explores an additional option: Carbon dioxide Capture and Storage (CCS)2. This report will analyze the current state of knowledge in order to understand the technical, economic and policy dimensions of this climate change mitigation option and make it possible to consider it in context with other options.

1.1.1 What is CO2 capture and s torage?

CO2 capture and storage involves capturing the CO2 arising from the combustion of fossil fuels, as in power generation, or from the preparation of fossil fuels, as in natural-gas processing.

It can also be applied to the combustion of biomass-based fuels and in certain industrial processes, such as the production of hydrogen, ammonia, iron and steel, or cement. Capturing CO2 involves separating the CO2 from some other gases3. The CO2 must then be transported to a storage site where it will be

1 In this report, the term 'emissions' is taken to refer to emissions from anthropogenic, rather than natural, sources.

2 CO2 capture and storage is sometimes referred to as carbon sequestration. In this report, the term 'sequestration' is reserved for the enhancement of natural sinks of CO2, a mitigation option which is not examined in this report but in IPCC 2000b.

3 For example, in the flue gas stream of a power plant, the other gases are mainly nitrogen and water vapour.

stored away from the atmosphere for a very long time (IPCC, 2001a). In order to have a significant effect on atmospheric concentrations of CO2, storage reservoirs would have to be large relative to annual emissions.

1.1.2 Why a special report on CO2 capture and storage?

The capture and storage of carbon dioxide is a technically feasible method of making deep reductions in CO2 emissions from sources such as those mentioned above. Although it can be implemented mainly by applying known technology developed for other purposes, its potential role in tackling climate change was not recognized as early as some other mitigation options. Indeed, the topic received little attention in IPCC's Second and Third Assessment Reports (IPCC 1996a, 2001b) - the latter contained a three-page review of technological progress, and an overview of costs and the environmental risks of applying such technology. In recent years, the technical literature on this field has expanded rapidly. Recognizing the need for a broad approach to assessing mitigation options, the potential importance of issues relating to CO2 capture and storage and the extensive literature on other options (due to their longer history), IPCC decided to undertake a thorough assessment of CO2 capture and storage. For these reasons it was thought appropriate to prepare a Special Report on the subject. This would constitute a source of information of comparable nature to the information available on other, more established mitigation options. In response to the invitation from the 7th Conference of the Parties to the UNFCCC in Marrakech4, the IPCC plenary meeting in April 2002 decided to launch work on CO2 capture and storage.

1.1.3 Preparations for this report

In preparation for this work, the 2002 Plenary decided that IPCC should arrange a Workshop under the auspices of Working Group III, with inputs from Working Groups I and II, to recommend how to proceed. This workshop took place in Regina, Canada, in November 2002 (IPCC, 2002). Three options were considered at the workshop: the production of a Technical Report, a Special Report, or the postponement of any action until the Fourth Assessment Report. After extensive discussion, the Workshop decided to advise IPCC to produce a Special Report on CO2 capture and storage. At IPCC's Plenary Meeting in February 2003, the Panel acknowledged the importance of issues relating to CO2 capture and storage and decided that a Special Report would be the most appropriate way of assessing the technical, scientific and socio-economic implications of capturing anthropogenic CO2 and storing it in natural reservoirs. The Panel duly gave approval for work to begin on such a report with 2005 as the target date for publication.

The decision of the 2002 Plenary Meeting required the report to cover the following issues:

4 This draft decision called on IPCC to prepare a 'technical paper on geological carbon storage technologies'.

• sources of CO2 and technologies for capturing CO2;

• transport of CO2 from capture to storage;

• CO2 storage options;

• geographical potential of the technology;

• possibility of re-using captured CO2 in industrial applications;

• costs and energy efficiency of capturing and storing CO2 in comparison with other large-scale mitigation options;

• implications of large-scale introduction, the environmental impact, as well as risks and risk management during capture, transport and storage;

• permanence and safety of CO2 storage, including methods of monitoring CO2 storage;

• barriers to the implementation of storage, and the modelling of CO2 capture and storage in energy and climate models;

• implications for national and international emission inventories, legal aspects and technology transfer.

This report assesses information on all these topics in order to facilitate discussion of the relative merits of this option and to assist decision-making about whether and how the technology should be used.

1.1.4 Purpose of this introduction

This chapter provides an introduction in three distinct ways: it provides the background and context for the report; it provides an introduction to CCS technology; and it provides a framework for the CCS assessment methods used in later chapters.

Because this report is concerned with the physical capture, transport and storage of CO2, the convention is adopted of using physical quantities (i.e. tonnes) of CO2 rather than quantities of C, as is normal in the general literature on climate change. In order to make possible comparison of the results with other literature, quantities in tonnes of C are given in parenthesis.

1.2 Context for considering CO2 Capture and Storage

1.2.1 Energy consumption and CO2 emissions

CO2 continued an upward trend in the early years of the 21st century (Figures 1.1, 1.2). Fossil fuels are the dominant form of energy utilized in the world (86%), and account for about 75% of current anthropogenic CO2 emissions (IPCC, 2001c). In 2002, 149 Exajoules (Ej) of oil, 91 EJ of natural gas, and 101 EJ of coal were consumed by the world's economies (IEA, 2004). Global primary energy consumption grew at an average rate of 1.4% annually between 1990 and 1995 (1.6% per year between 1995 and 2001); the growth rates were 0.3% per year (0.9%) in the industrial sector, 2.1% per year (2.2%) in the transportation sector, 2.7% per year (2.1%) in the buildings sector, and -2.4% per year (-0.8%) in the agricultural/other sector (IEA, 2003).

Worid primary energy consumption by sector

Worid primary energy consumption by sector

■ Buildings - commercial

□ Buildings - residential

■ Industrial

Figure 1.1 World primary energy use by sector from 1971 to 2001 (IEA, 2003).

■ Buildings - commercial

□ Buildings - residential

■ Industrial

Figure 1.1 World primary energy use by sector from 1971 to 2001 (IEA, 2003).

World CCfe emissions by sector 1971-2001

World CCfe emissions by sector 1971-2001

G Agriculture + other

■ Buildings - commercial

□ Buildings - residential

■ Industrial

Figure 1.2 World CO2 emissions from fossil fuel use by sector, 1971 to 2001 (IEA, 2003).

G Agriculture + other

■ Buildings - commercial

□ Buildings - residential

■ Industrial

Figure 1.2 World CO2 emissions from fossil fuel use by sector, 1971 to 2001 (IEA, 2003).

Average global CO2 emissions5 increased by 1.0% per year between 1990 and 1995 (1.4% between 1995 and 2001), a rate slightly below that of energy consumption in both periods. In individual sectors, there was no increase in emissions from industry between 1990 and 1995 (0.9% per year from 1995 to 2001); there was an increase of 1.7% per year (2.0%) in the transport sector, 2.3% per year (2.0%) in the buildings sector, and a fall of 2.8% per year (1.0%) in the agricultural/other sector (IEA, 2003).

Total emissions from fossil fuel consumption and flaring of natural gas were 24 GtCO2 per year (6.6 GtC per year) in 2001 - industrialized countries were responsible for 47% of energy-related CO2 emissions (not including international bunkers6). The Economies in Transition accounted for 13% of 2001 emissions; emissions from those countries have been declining at an annual rate of 3.3% per year since 1990. Developing countries in the Asia-Pacific region emitted 25% of the global total of CO2; the rest of the developing countries accounted for 13% of the2total (IEA, 2003).

5 There are differences in published estimates of CO2 emissions for many countries, as Marland et al. (1999) have shown using two ostensibly similar sources of energy statistics.

6 Emissions from international bunkers amounted to 780 Mt CO2 (213 MtC) in 2001 (IEA, 2003).

Table 1.1 Sources of CO2 emissions from fossil fuel combustion (2001).

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