Carbon Capture and Storage

Steve A. Rackley

• Editorial: Butterworth-Heinemann
• Año: 2009
• ISBN:
  9780080951386
• Categoría: Tecnologia e ingegneria
• Categoría: Gestione ambientale

Carbon dioxide capture and storage (CCS) is a technology aimed at reducing greenhouse gas emissions from burning fossil fuels during industrial and energy-related processes. CCS involves the capture, transport and long-term storage of carbon dioxide, usually in geological reservoirs deep underground that would otherwise be released to the atmosphere. Carbon dioxide capture and storage offers important possibilities for making further use of fossil fuels more compatible with climate change mitigation policies. The largest volumes of CO2 could be captured from large point sources such as from power generation, which alone accounts for about 40 per cent of total anthropogenic CO2 emissions. The development of capture technologies in the power generation sector could be particularly important in view of the projected increase in demand for electricity in fast developing countries with enormous coal reserves (IEA 2002a). Although, this prospect is promising, more research is needed to overcome several hurdles such as important costs of capture technology and the match of large capture sources with adequate geological storage sites. The book will provide a comprehensive, detailed but non-specialist overview of the wide range of technologies involved in carbon dioxide capture and sequestration.

• Focuses on technology rather than regulation and cost
• Covers both traditional and cutting edge capture technology
• Contains an abundance of case-studies an worked out examples
• Insight into CSS technical processes

Chapter 1. Introduction

The fossil fuel resources of our planet—estimated at between 4000 and 6000 gigatonnes of carbon (Gt-C)—are the product of biological and geologic processes that have occurred over hundreds of million of years and continue today. The carbon sequestered in these resources over geological time was originally a constituent of the atmosphere of a younger earth—an atmosphere that contained ∼1500 parts per million (ppm) CO₂ at the beginning of the Carboniferous age, 360 million years ago, when the evolution of earth’s first primitive forests began the slow process of biogeological sequestration.

Since the dawn of the industrial age, circa 1750, and particularly since the invention of the internal combustion engine, ∼5% of these resource volumes have been combusted and an estimated 280Gt-C released back into the atmosphere in the form of CO₂. In the same period a further ∼150Gt-C has been released to the atmosphere from soil carbon pools as a result of changes in land use. The atmospheric, terrestrial, and oceanic carbon cycles have dispersed the greater part of these anthropogenic emissions, locking the CO₂ away by dissolution in the oceans and in long-lived carbon pools in soils. During the period since 1750, the CO₂ concentration in the atmosphere has increased from 280ppm to 368ppm in 2000, and ∼388ppm in 2010, the highest level in the past 650,000 years and one that is not likely to have been exceeded in the past 20 million years, where “likely” reflects the Intergovernmental Panel on Climate Change (IPCC) judgment of a 66–90% chance.

This increase in atmospheric CO₂ concentration ([CO₂]) influences the balance of incoming and outgoing energy in the earth-atmosphere system, CO₂ being the most significant anthropogenic greenhouse gas (GHG). In its Fourth Assessment Report (AR4), published in 2007, the IPCC concluded that global average surface temperatures had increased by 0.74 ± 0.18°C over the 20th century (Figure 1.1), and that “most of the observed increase in global average temperatures since the mid-20th century is very likely (>90% probability) due to the observed increase in anthropogenic GHG concentrations.”

Figure 1.1 Variation of the earth’s surface temperature during the 20th century (IPCC data)

Although anthropogenic CO₂ emissions are relatively small compared to the natural carbon fluxes—for example, photosynthetic and soil respiration fluxes, at ∼60Gt-C per year, are 10 times greater than current emissions from fossil fuel combustion—these anthropogenic releases have occurred on a time scale of hundreds rather than hundreds of millions of years. Anthropogenic change has also reduced the effectiveness of certain climate feedback mechanisms; for example, changes in land-use and land-management practices have reduced the ability of soils to build soil carbon inventory in response to higher atmospheric CO₂, while ocean acidification has reduced the capacity of the oceans to take up additional CO₂ from the atmosphere.

The energy consumption of modern economies continues to grow, with some scenarios predicting a doubling of global energy demand between 2010 and 2050. Fossil fuels currently satisfy 85% of global energy demand and fuel a similar proportion of global electricity generation, and their predominance in the global energy mix will continue well into the 21st century, perhaps much longer. In the absence of mitigation, the resulting emissions will lead to further increase in atmospheric [CO₂], causing further warming and inducing many changes in global climate. Even if [CO₂] is stabilized before 2100, the warming and other climate effects are expected to continue for centuries, due to the long time scales associated with climate processes. Climate predictions for a variety of stabilization scenarios suggest warming over a multicentury time scale in the range of 2°C to 9°C, with more recent results favoring the upper half of this range.

Although many uncertainties remain, there is little room for serious doubt that measures to reduce CO₂ emissions are urgently required to minimize long-term climate change. While research and development efforts into low- or zero-carbon alternatives to the use of fossil fuels continues, the urgent need to move toward stabilization of [CO₂] means that measures such as the capture and storage of carbon that would otherwise be emitted can play an important role during the period of transition to low-carbon alternatives.

Within the field of carbon capture and storage (CCS), a diverse range of technologies is currently under research and development and a growing number of demonstration projects have been started or are planned. A few technologies have already reached the deployment stage, where local conditions or project specifics have ...