Carbon Capture & Storage

When fossil fuels such as coal, oil and natural gas are combusted, they emit carbon dioxide (CO₂). To prevent this CO₂ from entering the atmosphere and contributing to climate change, the CO₂ can be captured at the power station. The captured CO₂ can then be stored safely and permanently in deep underground geological structures, or by other physical, chemical or biological means. 

Carbon capture and storage is not a new technology. It is a proven set of technologies. The process can be broken down into three separate parts. First, capture: CO₂ emissions are separated (‘captured’) from the stream of gases released from the combustion of fossil fuels. Second, transport: the separated CO₂ is compressed to a liquid-like state so that it can be transported, via pipeline or truck, to a suitable underground geological structure. And third, storage: the compressed CO₂ is injected deep underground where it will remain, safely, permanently, and well-monitored, in a process known as geosequestration.

The individual components have been demonstrated by the oil and gas industry for decades. The challenge is combining these three steps to form a ‘fully integrated’ system that can be applied on a commercial scale to emission sources like the thousands of fossil-fuel power plants around the world. Built in to new power stations or bolted on to existing ones, the potential for reducing greenhouse gas emissions is significant.

There is no single technology available today that will enable global greenhouse gas emissions from energy production to be stabilised and reduced to the levels scientists say are needed to avoid the worst effects of climate change. A portfolio of technologies will be required and CCS will make up a vital component of this portfolio.

However, the International Energy Agency (IEA) estimate that carbon capture and storage could account for almost 20% of emission reductions needed by 2050 to stabilise atmospheric CO₂ at 450 ppm (parts per million). Reaching this ambitious goal will require dramatically increased global investment in research, development and deployment of CCS technology.

This process removes the CO₂ from fossil fuels like coal before it’s burnt for fuel by converting it into a gas consisting of carbon monoxide and hydrogen. The carbon monoxide is reacted with water to produce hydrogen and CO₂ – the CO₂ is then captured, reducing greenhouse gas emissions.

In a conventional coal-fired power plant, coal is burnt directly to provide the energy for electricity generation and CO₂ is released as a by-product. Some CCS technologies aim to capture this CO₂ after the fuel is combusted. Pre-combustion capture differs because it removes CO₂ before combustion. 

This is how. Coal is made up primarily of carbon and hydrogen. Using a process called Integrated Gasification Combined Cycle (IGCC) technology, the carbon can be removed. This is accomplished not by burning, but by reacting the coal with air or oxygen to produce a synthetic gas that consists of hydrogen, CO₂ and carbon monoxide. The hydrogen gas is then separated. Combusting hydrogen produces only water vapour as a by-product. The carbon monoxide is further reacted to form more CO₂ and hydrogen. The CO₂ is removed (captured) and is ready for transport and geological storage. The technology is capable of removing 90% of the CO₂ emissions generated from coal.

This technology has yet to be demonstrated for electricity generation but has been applied to other industrial processes such as fertiliser manufacture and hydrogen production. There are several projects worldwide aiming to build power plants utilising this advanced technology to produce near-zero emission electricity from coal, including the ZeroGen and Wandoan projects here in Australia.

Excitingly, pre-combustion carbon capture not only has the potential to enable low-emissions coal-based power generation. It also provides a pathway to a future hydrogen economy. The hydrogen produced during this process can be burned to drive a turbine and generate electricity, or used to feed fuel cells for cars.

Post-combustion carbon dioxide (CO₂) capture involves separating CO₂ from the gas stream produced after coal or other fossil fuels are burnt (combusted) for electricity. With many examples of the technology already in action, it’s the most well-developed capture process, capable of removing up to 90% of emitted CO₂.

The most commonly used process for post-combustion CO₂ capture is made possible by chemicals called amines. A CO₂-rich gas stream, such as a power plant’s flue gas, is bubbled through an amine solution. The amines bind to the CO₂ as it passes through the solution but allow the other gases to continue through the flue.

The CO₂-saturated amine solution is then removed and heated to release the captured CO₂, which is then ready for transport and carbon storage. The amines themselves can be recycled and re-used.

Post-combustion capture is the most developed of the CCS technologies. The Sleipner project in Norway, an offshore natural gas production platform operated by Norway’s Statoil, has been capturing and storing more than one million tonnes of CO₂ per year since 1996 using an amine technology. The captured CO₂ has been successfully stored under the seabed below the North Sea.

In October 2009, the world’s first pilot demonstration of a fully integrated CCS system to capture CO₂ emissions from a coal-fired power plant began operating in West Virginia. The Mountaineer Plant is owned and run by American Electric Power (AEP) and uses a chilled ammonia post-combustion capture technology developed by Alstom. 

Their technology has already been demonstrated to capture over 90% of the CO₂ emissions from a flue stream and they are confident the technology will be ready for commercial deployment by 2015.

In New South Wales, Delta Electricity in conjunction with the CSIRO has been operating a post-combustion capture pilot demonstration project at Munmorah Power Plant. 

This type of capture technology is already widely used commercially in the natural gas and oil industries to purify methane and refine process streams. The technology is also very similar to technologies used by power plants to remove pollutants like particulates and nitrogen and sulphur oxides.

Whilst post-combustion CO₂ capture is technically available now for coal-based power plants, it has not yet been used commercially for large-scale CO₂ removal. The main challenge facing post-combustion technology development is improving its cost and efficiency. One of its key advantages is that it is well suited to retrofitting to existing plants and so is a suitable technology to apply to the thousands of coal-fired power plants across the world, as well as other industrial sources.

Under this process, fossil fuels are burnt in pure oxygen instead of normal air. Virtually all the gas that’s emitted is composed of CO₂ and water vapour: the vapour is condensed out and the CO₂ is then captured.

Conventional boilers combust coal in air, which consists of 78% nitrogen, 21% oxygen, and trace gases including CO₂. This results in a flue gas stream that’s rich in nitrogen and dilute in CO₂, (around 12 - 15%) making CO₂ capture more challenging. By removing the nitrogen first and combusting the coal in nearly pure oxygen, it produces a much more concentrated stream of CO₂ (around 90%), which allows for much easier CO₂ capture.

Oxyfuel combustion with CO₂ storage is currently in demonstration phase. In 2008, the world’s first pilot project to demonstrate oxyfuel technology at a coal-fired power plant was inaugurated. The Schwarze Pumpe project in western Germany is owned by the European energy company, Vattenfall, and it is successfully demonstrating the capture of CO₂ emissions with a purity of over 99%.

In Biloela, Queensland, a low-emissions oxyfuel demonstration project is being established at the Callide Power Station.

Oxyfuel combustion capture applies a new technology to conventional power plant boilers to capture CO₂ emissions. This has the advantage in that it can be retrofitted (‘bolted on’) to the thousands of power plants already in operation around the world, as well as being applied to new power plants. [PDF] It has the potential to be one of the most cost-effective methods of capturing CO₂ emissions from coal-fired power plants. Research is being carried out to reduce costs and improve efficiency.

Carbon storage refers to the process of safely and permanently storing the CO₂ captured from power plants and industrial processes.

Before CO₂ can be transported it must first be compressed at high pressure into a liquid-like state. The technologies available to transport CO₂ are very similar to those used for many years in the natural gas industry. However, unlike natural gas, CO₂ is essentially a stable and inert substance.

The best way to transport CO₂ depends on the quantity, terrain and transport distance required. Tanker trucks may be used for smaller volumes over short distances. Pipelines are a logical choice for large volumes over short, medium or long overland distances. Thousands of kilometres of CO₂ pipeline are already in existence in the US, and have been safely transporting CO₂ for Enhanced Oil Recovery for many years.

The next step is storage. While there are a number of CO₂ storage options, geological storage or geosequestration offers the greatest potential. This involves safely storing captured, liquefied, and transported CO₂ deep underground. A common misconception is that these storage sites are like vast caves or caverns underground. In fact, they consist of tiny pores within the rock, which act like a sponge to house the liquefied CO₂. These tiny pores add up to a huge volume, with the capacity to store millions of tonnes of CO₂. They are overlain by a non-porous ‘cap’ rock that prevents the CO₂ from escaping.

There are three main categories of geological storage options for CO₂. The first is saline water saturated rocks. These are underground formations of porous rock, such as sandstones, that are saturated with salty (non potable) water and covered by a layer of impermeable cap rock (such as shale or clay), which acts as a seal. Once injected into the formation, the CO₂ dissolves into the saline water in the reservoir rock. CO₂ storage in deep saline formations is expected to take place at depths below 800m. At this depth, the CO₂ will be at high enough pressures to remain in a liquid-like state. Saline formations have the largest storage potential globally and a number of CO₂ storage demonstration projects are proving their effectiveness to maximise storage capacity and containment.

The second main type of geological storage is depleted oil and gas fields. These have a proven ability to store hydrocarbons over millions of years, demonstrating very good reservoir characteristics.[PDF] CO₂ injection is already widely used in the oil industry for Enhanced Oil Recovery (EOR) from mature oilfields. The third is coal seam storage. This involves injecting CO₂ into deep coal seams no longer able to be mined. There it displaces other gases, such as methane. The displacement effect means that coal seam CO₂ injection could be most effective as part of the commercial production of coal seam methane (also known as coal bed methane), an increasingly important and relatively new energy source.

The geosequestration process mimics a natural geological trapping process. Hydrocarbons such as oil and natural gas have been naturally trapped in porous underground sedimentary rocks for millions of years. Safe long-term carbon storage of CO₂ has been demonstrated by the oil and gas industries for more than 40 years. At the Sleipner offshore natural gas production platform in Norway, every year since 1996 more than one million tonnes of CO₂ has been transported by pipeline and safely stored deep under the seabed.

Of course, the geosequestration process does not end when the CO₂ is successfully stored underground. Sites are carefully monitored, both during and long after the CO₂ is injected underground. Technologies and protocols for monitoring and verification that were originally developed by the oil, gas and waste storage industries are being used to track the CO₂ migration within porous rock formations and ensure that the injected CO₂ remains trapped in their reservoirs.

Current CO₂ storage projects such as the CO2CRC Otway project in Australia are developing and demonstrating sophisticated monitoring and verification techniques to confirm the safety and effectiveness of CO₂ storage, and understand how the CO₂ behaves in the storage site.

Emerging Sequestration 

The underground storage of CO₂ has been successfully undertaken on a commercial scale for decades. New research breakthroughs are opening up the possibility of alternative methods for managing carbon dioxide emissions that treat it as a valuable industrial input.

Like other plant life, algae have the ability to consume and capture CO₂. The use of algae to capture CO₂ emissions is being explored in projects around the world. Basically they involve CO₂ being added to water to create biocarbonates which the algae feed on when exposed to sunlight for photosynthesis. After the algae matures it can be harvested for use in agriculture or burnt as a biofuel.

Carbon mineralisation has the advantage of storing CO₂ by converting it to solid stable minerals, such as limestone, that can be stored without risk of releasing carbon into the atmosphere.

The process of carbon mineralisation is a natural one that occurs over thousands of years, but it can be accelerated by reacting CO₂ at high concentrations with silicate oxide minerals to form magnesium carbonates. 

While the process is easily achieved in the lab, commercial scale carbon mineralisation for storing CO₂ is still at an early stage of development. A planned commercial project in the U.S. using technology from the Skyonic Corporation, involves mineralising CO₂ flue emissions as sodium bicarbonate – baking soda.

The U.S. company Carbon Sciences has developed an enzyme-based technology which it claims could be used to recycle CO₂ emissions into gasoline and other portable fuels. The process uses CO₂ as a source of carbon and water as a source of hydrogen, to produce hydrocarbons, which are the building blocks for fuel. [PDF]

The coal industry knows it plays a role in global warming. To play its role in the solution, the Australian coal industry has committed a billion dollars to accelerating low-emissions coal technologies like carbon capture and storage. 

In 2003 the industry established the COAL21 initiative. It brings together the coal and electric power industries, unions, federal and state governments, and research organisations. The COAL21 National Action Plan adopted in 2004 provided a blueprint for demonstrating the technologies that would allow Australians to continue to use affordable coal-fired electricity in future, but with significantly lower greenhouse gas emissions.

In 2006, the Australian Coal Association member companies established the COAL21 Fund, which has committed over $1 billion to support research, development and demonstration of low-emissions coal technologies. The COAL21 Fund is financed through a voluntary levy on the coal industry that’s unique in the world. This levy is separate from, and additional to, existing initiatives such as the Australian Coal Association Research Program (ACARP).

The aim of the COAL21 Fund is to demonstrate the technical and economic viability of low-emissions coal technology, leading to demonstration at industrial-scale from 2015, and commercial deployment availability from 2020.

To date, the COAL21 Fund has made major commitments to active and in-development CCS research projects. This includes up to $300 million for a Queensland Integrated Gasification Combined Cycle (IGCC) project, including $46 million for a pre-feasibility study for the ZeroGen project and $14 million for a pre-feasibility study for the Wandoan Project. COAL21 is contributing $68 million to the Callide Oxyfuel project in Queensland, $50 million for the Delta post combustion capture project in New South Wales, (which will build on the Munmorah PCC project), $20 million for Queensland geosequestration initiatives, and $75 million for a national research program (Australian National Low Emissions Research Limited). The coal industry is also supporting the CO2CRC Otway Project, Australia’s first CO₂ pilot storage project.

These projects will help to demonstrate carbon capture and storage technology, and accelerate deployment and global commercialisation – and have the potential to make a real difference in the fight against climate change.

Carbon capture and storage is recognised globally as an essential component of any realistic global climate change mitigation strategy. Globally, governments have pledged significant support to accelerate its development and reduce the hurdles standing in the way of swift, worldwide deployment.

Here in Australia, the Government is committed to the adoption of low emissions coal technologies. In 2008, the Federal Government established the National Low Emissions Coal Council and a Carbon Storage Taskforce, backed by a $500 million National Low Emissions Coal Fund (NLECF) and more than $1 billion from the industry COAL21 Fund and the states. 

As part of the May 2009 Budget, the Australian government announced the Clean Energy Initiative (CEI) to support the research, development and demonstration of low-emission energy technologies. A key component of the CEI is the Carbon Capture and Storage Flagships program, which will receive in excess of $2 billion over nine years to create two to four full-scale carbon capture and storage demonstration projects in Australia. The CEI will also provide over $2 billion in funding for solar energy and other renewable projects to ensure that the Australian government reaches its target of producing 20% of Australia’s energy from renewable sources by 2020.

In December 2009, the Federal Government selected four Australian CCS projects to receive $120 million to carry out pre-feasibility work as part of the initial stage of the CCS flagships program. In addition, the Australian government will provide $100 million a year for the Global Carbon Capture and Storage institute.

State-based initiatives also represent a collective commitment of over $500 million towards ongoing low-emissions coal technology research. These include: Queensland Clean Coal Council ($300 million);  NSW Clean Coal Council ($100 million); and the Victoria Energy Technology Innovation Strategy ($110 million). 

The United States is a strong supporter of carbon capture and storage. In 2009 President Obama announced $3.4 billion in new funding for projects as part of the American Recovery and Reinvestment Act. The US Department of Energy has allocated this funding to a variety of projects across the country to carry out research and development, as well as funding the large-scale CCS demonstrations. 

In 2010, the President established an Interagency Task Force on Carbon Capture and Storage to speed the development and deployment of clean coal technologies, with the aim of five to ten commercial demonstration projects to be operational by 2016.

Any climate change legislation passed by the US Senate is also expected to include significant support for low-emission coal technologies.

In the United Kingdom, the Government is currently running a carbon capture and storage competition, the winner of which will receive funding to create a commercially operational facility by 2014. The Government also announced the funding of up to four carbon capture and storage projects which will be funded by a levy on electricity suppliers. Furthermore, no new coal-fired power stations over 300 MW will be constructed unless they are carbon capture ready or have CCS fitted to a portion of their flue streams.

The EU has allocated €1.05 billion for six carbon capture and storage projects across Europe to demonstrate a variety of methods and help to commercialise low-carbon technology.

Many other countries, including Canada, Norway, France, South Africa and the UAE, are supporting carbon capture and storage as part of their greenhouse mitigation strategies. 

In 2008, energy ministers from the G8 met in Aomori, Japan, and set a target of launching 20 large-scale CCS demonstration projects globally by 2010 with a view of beginning broad deployment of the technology by 2020. [PDF]

The International Energy Agency (IEA) is tracking the progress made towards this ambitious goal. You can view the progress here. 

In April 2009, Prime Minister Kevin Rudd officially launched the Global Carbon Capture and Storage Institute (GCCSI) in Canberra. It has the support from more than 200 Governments, institutions and corporations from around the world.

The GCCSI is a major initiative with a goal to drive global cooperation in CCS research and development and so accelerate the deployment of such technologies around the world. The Rudd Government will contribute $100 million each year to the GCCSI, which aims to generate investment in CCS technology and deliver the G8’s goal of having 20 large-scale CCS plants in operation by 2020. In July 2009, Kevin Rudd launched the Institute onto the international stage at the G8 summit in L’Aquila 2009 alongside US president Barack Obama and with the support of the G8 world leaders.