1.1 The climate change challenge
As the effects of climate change become better understood and human-induced CO2 concentrations in the atmosphere are globally accepted as the major cause, substantial reductions in CO2 emissions from power production and other high CO2 emitting industries will be required to manage the risks of climate change through a greater uptake of near-zero emission technologies.
Monitoring has shown that the amount of CO2 in the atmosphere is increasing, with atmospheric concentrations now approaching 400 ppm (Figure 1) compared to pre-industrial levels of 280 ppm (IPCC 2007a). This elevated level of CO2 concentration enhances the greenhouse effect, leading to global warming. This rise in temperature causes the climate to change, sea levels to rise, and ocean and land environments to be affected.
FIGURE 1 Global CO2 emissions
Source: Conway and Tans (2012), NOAA/ESRL.
During the 20th century, the global average temperature increased by around 0.74°C, with the rate of increase accelerating over the period (IPCC 2007a). The IPCC estimated that by 2100, the increase in global average temperature could range between 1.1–6.4°C depending on the level of(GHG) emissions during this century. More recent estimates suggest that the world is on a path towards the 6°C level, given currently enacted legislation to reduce emissions (IEA 2011a).
A changing climate will inevitably lead to increased vulnerability to, and severity and frequency of, climate events which could lead to an increased risk of disasters occurring such as heat waves, species extinction, rising sea levels, and flood events.
Developing countries are likely to be the most affected by such adverse impacts of climate change, which will mostly be abrupt and irreversible in nature. The Intergovernmental Panel on Climate Change (IPCC) cites a sobering statistic that between 1970 and 2008, 95 per cent of all natural disaster-related deaths occurred in developing countries (IPCC 2012).
Recent analysis suggests that temperature increases and climate change affect not only the level of economic output, but also the rate of economic growth. It has been estimated that, for certain developing countries, a 1°C rise in temperature in a given year reduces economic growth by 1.3 percentage points, on average (Dell et al. 2012). Further, higher temperatures have wide-ranging effects, reducing not only agricultural output but also industrial production and influencing political stability.
When fossil fuels burn, large amounts of CO2 are released into the atmosphere. CO2 is also released from the ground together with natural gas during natural gas production. Industrial processes, such as refining oil, or producing iron, steel, cement, and ammonia, also release large amounts of CO2Other major sources of CO2 include emissions from cars, trucks, ships, and aeroplanes, and emissions from domestic sources – such as heating. In addition, land clearing has reduced the ability of the Earth to absorb excess CO2 as there is less plant life to assist in natural regulation. All of these activities contribute to increasing the concentration of CO2 in the atmosphere.
Energy-related CO2 emissions account for nearly 60 per cent of total global anthropogenic GHG emissions. In 2011, CO2 emissions from the combustion of fossil fuels reached a record 31.6 Gt (IEA 2012a) Primary energy consumption continues to rise (Figure 2) and fossil fuels have provided the major share of the incremental growth over the past decade, accounting for more than 80 per cent of the increase in energy consumption (IEA 2012b).
FIGURE 2 Total primary energy supply and energy-related CO2 emissions
Source: IEA (2012b).
Note: The apparent decline in 2009 reflects reduced energy demand due to the economic recession.
The largest global source of fossil fuel emissions comes from coal-fired power plants, with around 9 Gt of CO2 emitted in 2011. Coal is the most abundant fossil-fuel resource worldwide. Recoverable reserves can be found in 70 countries or more, with sufficient reserves for 150 years of generation at current global consumption rates. Between 2000 and 2009, growth in coal consumption far exceeded the combined increase of all non-fossil energy sources (IEA 2012b). Despite the very strong growth in non-fossil energy generation, its share of total generation has declined.
As climate change is driven by the stock of GHGs in the atmosphere, even if all anthropogenic CO2 emissions were to cease tomorrow, climate change has already begun and effects will still be seen long into the future. The global challenge is to enact policies that result in emissions peaking in the near future and rapidly reducing thereafter (Figure 3). In December 2010, the 16th session of the Conference of the Parties (COP 16) to the UNFCCC approved a non-legally binding commitment to cap global average temperature rises to 2°CA 2°C rise will still result in rising sea levels, and increased frequency of extreme weather events, including increased drought and flooding (Stern 2009). Limiting the increase in the stock of CO2 in the atmosphere to 1000 Gt this century will give a 50 per cent chance of limiting to 2°C (Meinshausen, et al. 2009). Achieving this constraint on carbon emissions requires energy-related CO2 emissions to fall to zero by 2075 (IEA 2012b).
FIGURE 3 CO2 concentration, temperature and sea level changes after emissions are reduced
Source: IPCC (2001). Note that the vertical axis on this graph is qualitative and separate lines cannot be compared with each other as they relate to different units (changes in CO emissions, CO concentration, temperature, and sea level).
The total costs over time of avoiding the global average temperature rising beyond 2°C is estimated to be around 3–4 per cent of a single year’s value of global economic output (IPCC 2007b, Stern 2008). This would delay the increase in global prosperity by around a year over the medium to long term (Figure 4) The total benefits of managing the risks of climate change are estimated to be well in excess of this cost (Stern 2007).
FIGURE 4 Modest economic impact from taking action
Source: IPCC (2007b).
Reducing GHG emissions requires fundamental changes to society, including the way electricity is generated, industrial systems operate, and how people and goods travel. These changes include developing more renewable energy sources, switching to less carbon-intensive fuels and generally being more energy efficient. These alternative energy generation technologies include solar thermal, biomass, geothermal, wind, and tidal. However, as fossil fuels are expected to continue to be widely used in the coming decades, something must be done to reduce the emissions resulting from their use.
CCS can make an essential contribution to the overall GHG reduction effort by reducing the emission of CO2 from industries and power stations that use fossil fuels (see box). Most of the technologies needed for CCS are already being used extensively in a variety of industries, but are yet to be widely applied to power generation and industry at a commercial scale. There are also industries, such as iron and steel manufacturing, and cement production, where CCS is often the only solution for substantial emission reductions.
WHAT IS CCS?
CCS is the long-term isolation of fossil fuel CO2 emissions from the atmosphere through capturing and storing the CO2 deep in the subsurface of the Earth.
CCS is made up of three key stages.
- Capture: Carbon capture is the separation of CO2 from the other gases produced when fossil fuels are burnt for power generation and when CO2 is produced in other industrial processes.
- Transport: Once separated, the CO2 is compressed and transported to a suitable site for geologic storage.
- Storage: At its storage site, CO2 is injected into deep underground rock formations, often at depths of 1 km or more.
1: Capturing the CO2
Capturing CO2 emissions from industrial processes is easiest at large plants where for example CO2-rich flue gas can be processed at the facility.
The separation of CO2 is already performed in a number of standard industrial processes. For example, in natural gas production, CO2 is separated from the natural gas during processing. Similarly, in industrial plants that produce ammonia or hydrogen, CO2 is removed as part of the process.
As the largest contribution to CO2 emissions is from the burning of fossil fuel, particularly in producing electricity, three main processes are being developed to capture CO2 from power plants that use coal or gas. These are:
- post-combustion capture;
- re-combustion capture; and
- oxyfuel combustion capture.
In other industries, such as in steel mills and cement plants, capture processes have not yet been developed at a large scale, but in each case an existing capture method could be tailored to suit the particular production process. For instance, collection of CO2 from cement plants uses post-combustion capture, and collection from modified steel manufacturing processes uses a type of oxyfuel combustion.
2: Transporting the CO2
Once separated, the CO2 is compressed to make it easier to transport and store. It is then transported to a suitable storage site. Today, CO2 is already being transported by pipeline, by ship, and by road tanker – primarily for use in industry or to recover more oil and gas from oil and gas fields. The scale of transportation required for widespread deployment of CCS is far more significant than at present, and will involve the transportation of CO2 in a dense phase.
3: Storing the CO2
The final stage of the CCS process sees the CO2 injected into deep underground rock formations, often at depths of 1 km or more (Figure 5). At this depth, the temperature and pressure keep the CO2 as a dense fluid. The CO2 slowly moves through the porous rock, filling the tiny spaces known as pore space.
Appropriate storage sites include depleted oil fields, depleted gas fields, or rock formations which contain water with a high level of salinity (saline formations). These storage sites generally have an impermeable rock (also known as a ’seal’ or ‘cap rock’) above them. The seal and other geologic features prevent the CO2 from returning to the surface.
These types of sites have securely contained fluids and gases for millions of years, and with careful selection, they can securely store CO2 for just as long.
Once injected, a range of sensing and monitoring technologies are used to monitor the CO2’s movement and changes within the rock formations. Monitoring, reporting and verification processes are important for the project performance management and to assure the public and regulators that the CO2 is safely stored.
Finding appropriate storage sites requires the collection of a great deal of data, and takes significant time and effort. Many economies around the world have active programs to identify storage sites for CO2, including the US, Canada, China, South Africa,and Europe.
FIGURE 5 Geologic storage options for CO2