Understanding CCS
What is CCS, how does it work and why is it important?

Frequently Asked Questions

What is climate change?

The Earth’s leading scientists have warned that the planet’s climate is changing, namely due to increased amount of greenhouse gases in the atmosphere.

To avoid catastrophic climate consequences, current emissions should be cut by 50-80 per cent in a relatively short amount of time, the Intergovernmental Panel on Climate Change (IPCC) has warned. Such a reduction will prevent the global mean temperature from rising by more than 2.0 to 2.4°C, the threshold at which climate change becomes severe according to the IPCC.

Greenhouse gases are produced by human activities, such as:

  • burning fossil fuels, such as coal, oil or gas;
  • using energy generated by burning fossil fuels;
  • certain farming activities, including raising cattle and sheep and using fertilisers;
  • clearing land, including logging;
  • the breakdown of food and plant wastes and sewerage; and
  • some industrial processes, such as making cement and aluminium.

Since industrialisation, carbon dioxide levels in the atmosphere have risen sharply, increasingly global temperatures.

Impacts of this change in climate include increases in global average air and ocean temperature, widespread melting of snow and ice and rising global sea levels. Climate change can also impact on atmospheric and ocean circulation, which influences rainfall and wind patterns. Many recent natural disasters, such as wildfires in Russia and severe flooding in Pakistan during mid-2010, are attributed to climate change.


How does CCS address climate change?

At the same time as Earth is warming up due to rising greenhouse gas emissions, world energy demand is projected to grow by more than 40 per cent over the next two decades. This magnifies the urgency of needing to curb emissions of carbon dioxide (CO2), a leading greenhouse gas.

Electricity sourced from fossil fuels accounts for more than 40 per cent of the world’s energy-related CO2 emissions. A further 25 per cent comes from large-scale industrial processes such as iron and steel production, cement making, natural gas processing and petroleum refining.

CCS technologies are the only available tool for reducing such emissions from existing sources. In fact, CCS can reduce emissions from power plants and factories to almost zero. According to the IEA, some 20 per cent of the total greenhouse gas emission reductions necessary between now and 2050 can be achieved through CCS, if the world manages to get some 3,000 projects off the ground over the next four decades. The Global CCS Institute works towards that goal.


How does CCS work?

Carbon capture and geological storage (CCS) – also known as CO2 sequestration – is a process whereby CO2 is captured from gases produced by the combustion of fossil fuel or industrial processes, compressed, transported and injected into deep geologic formations for permanent storage. Most of the technologies needed to implement CCS are currently available but have not been put together at commercial scale.

There are three generic process routes for capturing CO2 from fossil fuel combustion plants:

  • Post-combustion capture, referring to the separation of CO2 from flue gas (the exhaust from combustion) after fossil fuels are oxidised (burnt) in boilers, furnaces or other industrial apparatus. Flue is scrubbed with a suitable solvent such as an amine solution. The amine-CO2 complex formed is then decomposed by heat to release high purity CO2 and the regenerated amine is recycled to be reused in the capture process.
  • Pre-combustion capture increases the CO2 concentration of the flue stream, requiring smaller equipment size and different solvents with lower regeneration energy requirements. The process involves fuel’s reaction at high pressure with oxygen or steam to produce carbon monoxide (CO) and hydrogen (H2); the CO is reacted with steam in a catalytic shift reactor to produce CO2 and additional H2; the CO2 is then separated, while the hydrogen is used as fuel in a combined cycle plant. Most elements of this technology are already well proven in other industrial processes.
  • In oxy-fuel combustion, the concentration of CO2 in flue gas can be increased by using pure or enriched oxygen (O2) instead of air for combustion, either in a boiler or gas turbine. The O2 would be produced by cryogenic air separation (already used on a large scale industrially), and the CO2-rich flue gas would be recycled to avoid the excessively high flame temperature associated with combustion in pure O2.

Each of these processes involves the separation of CO2 from a gas stream. There are five main technologies available for doing this, with the choice depending on the state (i.e. concentration, pressure, volume) of the CO2 to be captured: (i) chemical solvent scrubbing; (ii) physical solvent scrubbing; (iii) adsorption/desorption; (iv) membrane separation; and (v) cryogenic separation.


What is geological storage?

Over the long-term, CO2 can be stored in a number of geological formations such as depleted oil reservoirs, depleted natural gas fields, deep saline aquifers and unmineable coal seams. Together these are estimated to have a global storage capacity of 1000-10,000 Gt CO2 according to the IPCC. With current world energy-related emissions of about 27Gt CO2 per year, this means that there is sufficient storage capacity around the world, enabling CCS to play a major role in emissions abatement.

Most of the world’s carbon is held in geological formations, and is either locked in minerals or hydrocarbons, or dissolves in seawater. Naturally occurring CO2 is frequently found with petroleum accumulations, having been trapped either separately, or together with hydrocarbons, for millions of years.

Of the geological formations that can be used to store CO2, three are most promising, as described below.

  • Based on current knowledge, deep saline formations provide the largest potential volumes for geological storage of CO2. These brine-filled sedimentary reservoir rocks (e.g. sandstones) are found in sedimentary basins and provinces around the world, although their quality and capacity to store CO2 varies depending on their geological characteristics. To be suitable for storage, saline formations need be (i) sufficiently porous and permeable to allow large volumes of CO2 to be injected in a supercritical state; and (ii) overlain by an impermeable cap rock, or seal, to prevent CO2 migration into overlying fresh water aquifers, other formations, or the atmosphere.
  • Depleted oil and gas reservoirs generally have similar properties to saline formations – e.g. they feature a permeable rock formation (reservoir) and an impermeable cap rock (seal). Conversion of depleted oil and gas fields for CO2 storage should be possible as the fields approach the end of economic production. There is high certainty in the integrity of the reservoirs with respect to CO2 storage, as they have held oil and gas for millions of years.
  • Coal beds below economic mining depth could be used to store CO2. Carbon dioxide injected into unmineable coal beds may react and be absorbed by the coal, providing permanent storage as long as the coal is not mined or otherwise disturbed.

CO2 can also be injected into declining oil fields to increase oil recovery.

Other geological CO2 storage options include injection into: (i) basalt; (ii) oil shale; (iii) salt caverns and cavities; (iv) geothermal reservoirs; (v) lignite seams; or (vi) methano-genesis in coal seams or saline formations.


Is it safe to put CO2 underground?

A strong body of research — and years of industry experience — indicate that CO2 can be stored safely and securely. For well-selected, designed and managed geological storage sites, IPCC estimates that CO2 could be trapped for millions of years and although some leakage occurs upwards through the soil, well selected stores are likely to retain more than 99 per cent of the injected CO2 over 1000 years.

Storage locations need to be reviewed to ensure that the CO2  can be stored underground without any potentially harmful leakage. Geological formations considered for storage are carefully selected and assessed by geologists over a number of years prior to commercial use. Formations suitable for storage have layers of porous rock deep underground that are “capped” by a layer or multiple layers of non-porous rock above them. Once injected, the liquid CO2 tends to be buoyant and will flow upward until it encounters a barrier of non-porous rock, which can trap the CO2 and prevent or control leaks into the atmosphere.

Many geologic formations have naturally stored CO2 and other gases and fluids for millions of years. The oil and gas industry, for instance, have more than 50 years of experience in sequestering CO2, providing a good basis for choosing the best sites and avoiding leakage. Advances in three-dimensional geophysical surveying techniques and mathematically based modelling and imaging of underground reservoirs are helpful, as are commercial practices for CO2 injection to enhance oil recovery. There is now also a growing body of direct CO2 monitoring experience from relatively large CO2 sequestration demonstration projects in Canada, Norway and Algeria as well as smaller, testing sites in Europe, the United States and Australia.

Leakage of CO2 from a well-chosen storage site is highly unlikely. However, if the stored CO2 were to move, it would be a slow process. Migrating CO2 may not reach the Earth’s surface but rather stay trapped in porous rock layers of rock. If slowly seeping CO2 were to reach the surface, it would usually be dissipated by the wind, which is what normally happens to CO2 vented by nature in volcanically active areas.

CO2 is not toxic, flammable or explosive. It can only cause harm if collect in unventilated subgrade structures or topographic depressions can be a concern. If a CO2 storage site were leaking, the project operators would apply methods used to manage fluid movements in oil and gas reservoirs, or leak mitigation technologies.


Is there anything else we can do with captured CO2

Generally speaking, there are three possibilities: (i) store the CO2; (ii) use it as a value-added commodity; or (iii) convert the CO2 to methane, biomass, mineral carbonates, or other substances.

Some of the uses for commodity CO2 result in a portion of the CO2 being sequestered, which is an added benefit. A common example of this is enhanced oil recovery (EOR). In the United States, for example, oil companies currently inject more than 30 million tonnes of CO2 per year in depleting oil formations to enhance the production of crude oil. A portion of this CO2 remains underground.

A similar CO2 use/storage application is the enhancement of methane production from coal seams that are too deep to be mined. Concepts for converting CO2 to other chemicals, especially fuels, are in the very early stages of research.


Where is CCS happening?

As of April 2010, there were more than 320 CCS projects at various stages of development. The vast majority of these projects have been drawn up in recent years, so given that getting a project off the ground takes five to seven years on average, most projects will not be operational for some time yet.

There are eight large-scale projects in operation around the world and a further six under construction.  Three of these projects have recently commenced construction.  Importantly, these include a second power project, Boundary Dam in Canada, and the first project in the United States that will store CO2 in a deep saline formation, the Illinois Industrial Carbon Capture and Sequestration (ICCS) Project.


What are the barriers to CCS?

All the elements of CCS have been tested and proven, however, widespread cost-effective deployment of the technology will occur only if it is commercially available and a supportive national policy framework is in place.

While there are no insurmountable technological, legal, institutional, regulatory or other barriers that prevent CCS from playing a role in reducing emissions, early projects face economic challenges related to climate policy uncertainty, first-of-a-kind technology risks and the current high cost of CCS relative to other technologies.

Most analyses show that it will be difficult for CCS technologies to be widely deployed in the next two decades absent financial incentives that supplement projected carbon prices.

CCS projects will also need to meet regulatory requirements. Long-standing regulatory programs are being adapted in various jurisdictions around the world to meet the circumstances of CCS, but limited experience and institutional capacity may hinder implementation of CCS-specific requirements. Key legal issues, such as long-term liability and property rights, also need resolution.

Climate policy designed to reduce emissions is the most important step for commercial deployment of low-carbon technologies such as CCS, because it will create a stable, long-term framework for private investments. A concerted effort to properly address financial, economic, technological, legal, institutional and social barriers will enable CCS to be a viable climate change mitigation option that can over time play an important role in reducing the overall cost of meeting emissions reduction targets.


What does the Global CCS Institute do?

The Global CCS Institute, funded by the Australian Government, works with organisations and governments to accelerate the broad deployment of commercial CCS and ensure that the technology plays a role in responding to the world’s need for a low carbon energy future. The Institute plays a key role in knowledge sharing across demonstration projects and is working on enabling the regulatory and policy as well as commercial and financial conditions for CCS to be deployed commercially around the world.


Who are the Institute’s Members?

As of 14 May 2013, the Institute’s Membership comprises 374 government, industry, non-government and research organisations from around the world.

View our current list of Members


How can I become a Member?

Membership is available to governments, corporations and organisations who can demonstrate a legitimate interest in the advancement of CCS, where they:

  • have demonstrated that they will make a material contribution to the fulfilment of the objectives of the Institute, or are likely to make such a contribution; and
  • carry on a business or activity where the advancement of CCS is not merely incidental to its core business or activities.

For more details, visit the Membership section.