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Wed 8 Oct 2008 04:00 AM

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Clean coal

Technology enabling carbon capture may release unrealised potential in coal.

Technology enabling carbon capture may release unrealised potential in coal.

September saw the launch of the world's first complete demonstration of carbon capture and storage (CCS) technology at a coal-fired power station in Germany.

This as yet unproven technology on a commercial scale is important, as it holds out the prospect of enabling coal - a reliable fossil fuel with significant global reserves - to continue to be used, yet at the same time offers the prospect of removing its ‘dirty' image.

Calling for a “global energy technology revolution”, the IEA said a virtual decarbonisation of the power sector was needed.

Clean coal technology would represent a major step forward in helping reduce global carbon dioxide (CO2) emissions, as coal remains a dominant source of electricity generation in many parts of the world, and particularly in developing economies like China and India.

The new demonstration project is being run by Swedish utility Vattenfall alongside the 1600 megawatt (MW) Schwarze Pumpe power plant in north Germany.

The experiment will capture up to 100 000 tonnes (t) of CO2 per year, compress it and then bury it 3000 metres (m) below the surface of the depleted Altmark gas field, some 200km from the site. The €70 million project has an output of around 12MW and 30MW of thermal power, enough to power around 1000 homes.

CCS is seen as a potential solution to the projected increased use of coal in power stations and could, scientists estimate, capture as much as 90% of a plant's carbon emissions.

Although each element of the capture, transportation and storage process has been proven and is in use, a full system has not yet been demonstrated, hence the importance of the Vattenfall project and others now being planned.

The technology remains expensive but its advocates argue that as more projects are demonstrated then experience will remove some of the costs relating to uncertainty about how the full cycle will work.

Others note that even though expensive, any costs are far outweighed by the potential benefits to the environment as coal still accounts for 40-50% of worldwide power generation.

Twenty percent

The International Energy Agency (IEA) said in a report in June 2008 that CCS could account for 20% of the achievable global greenhouse gas emissions reductions by 2050.

Calling for a "global energy technology revolution", the IEA said a virtual decarbonisation of the power sector was needed, meaning on average each year between 2010 and 2050 35 coal- and 20 gas-fired power plants would have to be fitted with CCS technology at a cost of US $1.5 billion each.

Achieving CCS' full potential would, the agency said, require the resolution of the questions on the availability of sufficient geological formations for captured CO2.

Costs and technology issues have meant many generators have been reluctant to invest funds to launch demonstration projects, meaning government intervention will be required to get many off the ground.

In the case of Vattenfall some funding was sourced from the German government and other countries have also adopted this policy.

The EU, which wants up to 12 CCS demonstration projects up and running by 2015, launched in September a call for tender for an external service provider to assist in establishing and running a CCS network.

The contractor will help the European Commission ensure the network allows early-movers to exchange information and experience from large-scale industrial demonstration of the use of CCS technologies and optimise costs.

Vatenfall is also planning a post-combustion pilot plant in Janshwalde in Germany. This 120 MW burning demonstration is expected to become operational around 2013. In France, Alstom is to commission another project of a similar size to Schwarze Pumpe later this year at a power station in Lacq in southern France, in collaboration with Total.

The UK is also planning a government-funded CCS demonstration plant announced in 2006. This will focus on post-combustion technology with a capacity of 400 MW expected to be commissioned in 2014. A decision is due in 2009 following the conclusion of a current government consultation.

The government has already named the four pre-qualified bidders - BP Alternative Energy International, E.ON UK, Peel Power and Scottish Power - and published a consultation on the legal framework of CO2 storage and what should be meant by carbon capture readiness.

Although there has been some criticism for delays to the UK project and also questions about the government's decision to opt for post-combustion technology, the country is well placed as a potential site for CCS as it would be able to store significant amounts of liquefied CO2 in rocks beneath the North Sea.

Scottish Power, which has reportedly identified a potential site, has claimed this could store all of Europe's CO2 emissions for the next 600 years.

Coal generation is currently contentious in the UK with a decision expected imminently by the government on whether to permit E.ON UK to build a new coal-fired plant at its existing Kingsnorth site. This was expected to be sanctioned only if the plant was made CCS-ready.

Environmental groups have been protesting because of speculation the CCS element of the approval will be removed from the planning sanction. Demonstrating generation companies' nervousness about the technology is the UK Association of Electricity Producers, which has warned that making CCS mandatory before it has been demonstrated successfully was "the wrong approach".

The UK Institute of Public Policy Research called this summer for a moratorium on new coal power investment for at least two year saying the EU's goal to cut emissions from the power sector and heavy industry by 21% by 2020 via the EU Emissions Trading Scheme was endangered by proposals for seven new coal plants in the UK, such as that at Kingsnorth and by up to 75 across Europe.

The IPPR said even if only a proportion of these were built, the EU emissions reduction target would only be achievable through widespread deployment of CCS.As the IEA noted above, storage is another part of the technology that has to be addressed although there is existing experience of placing CO2 under the seabed.

The Norwegian Petroleum Directorate this summer began seismic surveys at the country's largest North Sea oil and gas field, Troll, to determine whether CO2 emissions could be stored there.

Troll is touted as one of three possible North Sea locations for storing carbon produced by gas-fired power plants in the coastal cities of Mongstad and Kaarstoe.

Coal generation is currently contentious in the UK with a decision expected imminently ... on whether to permit ... a new coal-fired plant at its existing Kingsnorth site.

Field operator StatoilHydro has been storing CO2 below the seabed at the Sleipner gas field for over ten years but this is taken from the gas stream at the field. The Johansen formation in which the CO2 could be stored is located below Troll's oil and gas reservoirs, at a depth of approximately 2500m.

Beyond Europe

Away from Europe, other demonstration projects are being launched. In the US the Mountaineer project in West Virginia, due to begin in 2009, is expected to be the first pilot plant to combine all the elements of post-combustion technology.

It will act as a test for a more ambitious plan to capture and store emissions from a coal-fired station in Oklahoma due to be commissioned after 2010. This plans to trap and bury 1.5 million tonnes of CO2 per year. The US Department of Energy has also announced that it will share the cost of CCS projects with private firms.

In Canada, utility Saskatchewan Power is heading a C$1.4 billion project to retrofit part of a power plant and use CCS technology. In August it said it was soliciting project proposals to demonstrate the technology as part of a plan to retrofit one of its six power-generation units at a coal-fired plant. CO2 emissions would be trapped and sent to nearby oil fields to extracting hard to reach oil.

The Middle East is also involved. CCS is attractive for oil- and gas-rich areas because of its potential to enhance oil recovery. In 2007 the UAE launched as part of the Masdar Initiative a plan to deliver a national CCS network.

This states that a fully-developed CCS network could potentially reduce the UAE's CO2 emissions by almost 40%, while increasing oil production by up to 10% and liberating large quantities of natural gas. This would be achieved by separating CO2 from industrial and energy related sources and transporting to oil reservoirs for enhanced oil recovery (EOR).

A feasibility study has been carried out by Canada's SNC Lavalin which has estimated that the UAE network would cost between US$2-$3 billion. It has identified four to six projects with an approximate cost of US$500 million each. If realised this would be the largest single integrated CCS project in the world.

Elsewhere, Australia this year opened its first underground carbon storage facility in the southern state of Victoria. The geo-sequestration plant, the only one in the Southern hemisphere, will capture CO2 from a power station and store it 2km below the surface. It will also be one of the largest pilot projects in the world. The scheme has the support of the Australian government and the country's coal industry.

Still on storage, Royal Dutch Shell is investing in one of the largest CCS projects in the world. It will co-sponsor the final stage of the £80 million Weyburn-Midale CO2 monitoring and storage project in Canada.

Shell and its partners on the project, the IEA and the Petroleum Technology Research Centre, will gather data on underground CO2 storage and hope to produce a "best practice" manual as a guide for similar projects.

China, one of the world's largest coal producers, which builds on average one new coal-fired plant a week, launched its first CCS project in 2007. This is due to begin operations in 2009, under a joint venture partnership, GreenGen, between a group of state-owned enterprises and US firm Peabody Energy.

The US $1 billion, 650 MW plant at Tianjin near Beijing will capture the majority of its emissions for storage underground and the manufacture of by-products for use by nearby chemical companies.

But despite all this activity a lack of public funding, legal and safety concerns continue to undermine the technology's widespread development and this is causing concern because with coal set to remain a major fuel for generation for the foreseeable future, its high level of emissions threaten to undermine global and individual state attempts to meet CO2 reduction targets.

The pressure is particularly on the EU, which has legally binding emissions reduction targets in place for 2020. Generators have, so far, with some exceptions, proved reluctant to take the risk on CCS.

The UK CCS Association has argued that if Europe is to meet its goals, it will have to enforce regulations whereby which CCS plant operators would be granted carbon credits, which they could then sell on for a profit.

CCS has now attracted widespread attention from policymakers and all the rhetoric suggests there is a strong political will to see the technology commercialised.

G8 ministers meeting in Tokyo in July called for an international initiative to develop roadmaps for CCS, and said they wanted to see 20 large-scale demonstration projects launched around the world by 2010 with a view to "broad deployment" by 2020.

For now, it is hard to see how respective governments will not be forced to part fund the technology's developmental stage as CCS remains the best option for coal to remain a reliable, widespread source of power generation yet also offers the chance of making a significant dent in the fuel's contribution to greenhouse gas emissions and global warming.

As Vattenfall Europe chairman Tuomo Hatakka, said at the launch of Schwarze Pumpe: "Coal has a future - but not the CO2 emissions it produces. With our pilot unit we are demonstrating that coal and high-tech do not represent a contradiction."

The three types of CCS technologyPost-combustion capture

CO2 is captured from the exhaust of a combustion process by absorbing it in a suitable solvent. The absorbed CO2 is liberated from the solvent and is compressed for transportation and storage. Other methods for separating CO2 include high-pressure membrane filtration, adsorption/desorption processes and cryogenic separation.

Pre-combustion capture

Solid, liquid or gaseous fuel is first converted to a mixture of hydrogen and CO2 via gasification or reforming. Hydrogen produced may be used for electricity production but also possibly to power cars and heat homes.

Oxy-fuel combustion

In oxy-fuel combustion the oxygen required is separated from air prior to combustion, so producing a more concentrated stream for easier purification. This process promises high efficiency levels and offers major business opportunities. This is the technology being used by Vattenfall at Schwarze Pumpe.

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