The truth about… Carbon Capture and Storage

Carbon capture and storage could recover up to 90% of the carbon dioxide produced from burning fossil fuels in power stations and industrial facilities, then lock it up deep underground. As such, CCS is increasingly regarded as one of the most promising technological solutions to curb emissions and salvage our climate.

But environmental groups are still unconvinced. Greenpeace dubs CCS a “dangerous gamble” that “risks locking the world into an energy future [coal] that fails to save the climate.”

Over a decade away from full commercial rollout, it is too late for CCS, says a Greenpeace spokesman. “The emissions trajectory over the next seven years is critical. But there is no role that CCS can play in this,” he says.

CCS, say opponents, diverts attention away from demand reduction and renewable energy; it provides a smokescreen to deliver new coal plants; it is risky, it wastes energy, the technology is hugely expensive and it carries significant liability risks.


What and where is CCS?


CCS is a three-step process, including the capture of CO₂ from power plants, industrial sources, and natural gas wells; transportation, usually via pipelines, to the storage site; and storage in deep saline formations, depleted oil or gas fields, unmineable coal seams, and enhanced oil recovery (EOR) sites.

The different processes needed to capture and store CO₂ have been around for years and used, on a smaller scale, for example in the manufacture of fertilisers and within the oil and gas sector.

But the processes, until recently, hadn’t been brought together on a large enough scale to cope with the emissions from a typical power plant. The Vattenfall Schwarze Pumpe in Germany is the world’s first full-chain CCS operation attached to a power plant, but its “oxyfuel” technology, which uses pure oxygen to burn coal for CO₂ capture, is still in the test phase and the pilot plant works on a very small scale.


A diversion from renewables?


This is not a long-term solution or an alternative to renewable energy, says Stuart Haszeldine, professor of sedimentary geology at University of Edinburgh.
But it is, he adds, the best short-term option [for up to 40 years] for reducing CO₂ with existing knowledge and equipment.

“You can build any amount of renewable technology or nuclear power you want, but it will not prevent the CO₂ emissions from the power stations already in use, being built and planned,” he says.


Is CCS a smokescreen for new coal-fired power stations?


Power companies are certainly not waiting for CCS before going ahead with plans for new coal-fired stations.

There are more than six coal plants awaiting planning permission in the UK by companies including E.ON, Scottish Power, Scottish and Southern Energy and RWE npower. The applications for these either do not propose CCS, or propose to capture only a small amount of CO₂ emissions.

Instead, companies have offered to make the power stations “CCS ready”. But this is no more than a pledge to leave enough space to build a CCS plant at a later date.

E.ON’s planning application for its new 1,600MW coal plant at Kingsnorth in Kent is not based on it being a CCS plant. It has, however, applied separately to become one of the four bidders for the UK government’s CCS demonstration project.

If its Kingsnorth site wins the funding to demonstrate CCS, the technology will not be in operation until 2014. A full-scale demonstration would not get going until 2018 says an E.ON spokesperson. Even then, it will only capture up to 25% of the plant’s CO₂ emissions.

But while E.ON gains credibility for its role in CCS demonstration, says Greenpeace, it will have managed to burn CO₂ almost unabated from when it is due to open in 2012.


What are the risks of transporting CO₂?


The risks of transporting CO₂ are low, says Edinburgh university’s Haszeldine. CO₂ is not flammable which means there’s no chance of a burning explosion as there is with natural gas.

There is already an established pipeline network in the United States that ships CO₂ for enhanced oil recovery (EOR), where CO₂ is injected into oil reservoirs to extract more oil. The track record on this network shows about a tenth of the number of accidents compared to the number on natural gas pipelines, says Haszeldine.

The main risk with CO₂ transportation is that a pipe carrying pressurised CO₂ bursts, creating the Joule-Thomson Effect. This means the pressurised CO₂ cools and solidifies, causing potential damage to pipes and creating a CO₂ “snow” of ice missiles. “The effect is instantaneous,” says Haszeldine.

CO₂ is also an asphyxiate. One case, often quoted to illustrate the potential dangers of CO₂, was the leakage at Lake Nyos, Cameroon in 1986. Following a volcanic eruption, large quantities of CO2 that had accumulated on the bottom of the lake were suddenly released, suffocating 1,700 people.

But the risk of something like this happening as a result of CCS is nil, says Haszeldine. “As far as I know it’s totally impossible to move a bubble of CO₂ that size through porous rock.” And if there is a leak from a CO₂ pipes or store, he says, “as long as you don’t lie down and breathe deeply on the floor above, then you would be OK.”


The risks of storage


“Given that depleted natural gas reservoirs have safely held gas for a few million years, it’s likely they’ll be able to hold CO₂ that is injected back in for a few more,” says Ian Phillips, director at CO₂DeepStore, a carbon transportation and storage company based in Aberdeen, Scotland.

The UK has vast quantities of depleted gas stores offshore in the North Sea, enough for around 40 years of total UK CO₂ emissions.

Worldwide, salt-water aquifers offer around 10 times more storage space than depleted gas and oil fields, says Haszeldine. They are also easy to find both on and offshore, so will have greater application for countries with fewer oil and gas fields, like India and China. .

But he adds that less is known about the geology of these sites, in terms of their accessibility and availability, and that more research is needed.


Waste of energy?


There are three main technologies for CCS capture (see Facts 1, below), but the UK government decided to limit the competition for its demonstration project to one: post-combustion technology using amines. The CO₂ passes through an amine solvent that absorbs it. A change in temperature and/or pressure then releases the CO₂ for storage.

The benefit of post-combustion technology is that it can be retrofitted onto existing power plants, so it could potentially have huge application worldwide.

But as CO₂DeepStore’s Phillips says, amine is “horribly energy inefficient”, consuming about 20% of the power from the power station (that would have been used to create electricity) just to capture the CO₂. “It’s a huge cost and a huge energy penalty,” he says.

The efficiency of a new supercritical power plant (such as being planned at Kingsnorth) is reduced from 43% to 34% with CCS, as outlined in the UK House of Commons Environmental Audit Committee’s Carbon Capture and Storage Report from July. This would equate to a 16% increase in coal use.

New solvents are under development to reduce these penalties to 10%. And new post-combustion approaches, where CO₂ is separated through membranes with other absorption methods, are still under development. “That sort of development is years away,” says Phillips.

Pre-combustion and oxyfuel approaches, such as the process used by Vattenfall in Germany, to capture CO₂ are “relatively more elegant and efficient”, says Haszeldine. This is because the carbon capture is an integral part of the process rather than bolted on the back-end.

As Haszeldine points out, there are two or three developers interested in building gasification – or pre-combustion – power plants in the UK, but given the competition is limited to post-combustion, they cannot take part.

“It seems to me the rest of the world [that has open competition for technology] is moving faster, and we are bogged down in this slow, bureaucratic evaluation process,” he says.

Or as a spokesperson for E.ON puts it: “There are far too many people putting barriers in the way for this development. There should be targets that will allow technologies to develop, not conditions that hamper progress.”


How to pay for CCS?


But no matter which technology is chosen, the major obstacle to get CCS going comes down to the massive costs of the first demonstration projects. It is essential that government comes up with a funding mechanism that makes CCS viable for the first movers in the industry (see Facts 2, below).

One proposal is to provide additional emissions allowances on the EU Emissions Trading Scheme for CCS schemes, so operators can effectively make more money by burying rather than releasing carbon. The European Parliament’s Environment Committee voted in October to ring fence 500 million spare emissions allowances, normally reserved for new entrants into the EU ETS scheme, as a financing measure for CCS demonstration plants.


Capturing carbon from existing coal plants will therefore cost €60-€90 (£47-£71) per tonne of CO₂ abated, according to McKinsey


This will provide a funding mechanism for the 12 European demonstration plants that have been proposed. The value will depend on the price of CO₂ when the gas is eventually buried underground, but it could exceed €10 billion (£8 billion) – which could mean more windfall profits for energy companies on the EU ETS.

Alternative incentives include a tax on CO₂ emissions (such as being used by the Norwegian government), or direct government subsidy, such as being offered by the UK government as part of the competition to build the first UK CCS scheme by 2014.

Government intervention could also come in the form of a limit on CO₂ emissions from power stations. The EU’s Environment Committee has voted to back an emissions limit of 500 grams of CO₂ per kilowatt-hour on all new power plants built after 2015, which would mean all new coal-fired power plants would have to be built with CCS. The UK Conservative Party also backed the suggestion that power stations should have a maximum emissions limit this summer.


Building a regulatory regime


The other barrier to progress comes down to building a legal and regulatory framework to govern the use of CCS.

This is a complex process with different legislation required for capture, transportation, storage, as well as laws at the national, European and international level.

Regulation is currently being devised at all levels, but there are many unresolved and conflicting issues surrounding liability. The EU Environment Committee has agreed that liability will pass to the state, but only 50 years after the CO₂ is stored. Industry advocates say this is too long to wait. There is also confusion over whether the regulation will cover CO₂ capture from EOR operations.

The time it takes for operators to gain the necessary permits for new plants is likely to hinder progress. The UK government has set a 2014 deadline for the opening of its first demonstration project. But to meet this, operators would need to have permits by 2012 in order to start construction in time. Giedre Kaminskaite-Salters, senior adviser on climate and clean energy at lawyers Norton Rose, said at a recent seminar on CCS that while meeting this time-frame it not impossible, it is not guaranteed.



Facts 1: CO₂ Capture and storage methods

CCS illustration

Post-combustion

The conventional technology for post-combustion capture, or removing CO₂ from flue gas, is amine scrubbing. CO₂ is captured from flue gases by this chemical absorbent; the amine and CO₂ undergo a chemical reaction to form a rich amine solution; this is then heated to release the pure CO₂ gas. The recovered amine is recycled to the flue-gas contactor.

Pre-combustion

In pre-combustion capture, the hydrocarbon is gasified to produce a synthesis gas made up of primarily of hydrogen and carbon dioxide. The CO₂ is then separated from the hydrogen before the fuel goes into the burner.

Pre-combustion plants or integrated gasification and combined cycle plants already exist worldwide to make natural gas out of things such as coal, in order to avoid other aspects of pollution like sulphur dioxide.

Oxyfuel

In the oxyfuel combustion process, pure oxygen rather than air is charged to the combustion chamber of the power station, producing an exhaust or flue gas of CO₂ and water. A portion of the CO₂ is recycled and mixed with the oxygen to absorb heat and control the reaction temperature.



Facts 2: The economics of CCS

In the demonstration phase, CCS can add 40% to 50% onto the cost of a power plant.

Capturing carbon from existing coal plants will therefore cost €60-€90 (£47-£71) per tonne of CO₂ abated, according to the recent McKinsey report, Carbon Capture & Storage: Assessing the Economics.

The likely price of carbon from 2013 to 2020 through the EU Emissions Trading Scheme (the fundamental mechanism to encourage investment in CCS) will be around €39 (£31) per tonne.

Given this gap between operating costs and the carbon price, first movers in CCS could be out of pocket by as much as €0.5bn-€1.1bn (£0.4bn-£0.87bn) per project, says the McKinsey report.

Filling this gap and making CCS economic will require government intervention.



Facts 3: Existing schemes

The Scottish Centre for Carbon Storage, University of Edinburgh has a map of existing and planned schemes. What follows is based on the centre’s data.

Schwarze Pumpe, Germany. Operated by Vattenfall/Gas de France. This was the first full-chain site and opened in September 2008. Using oxyfuel as a separation technology it plans to inject 100,000 tonnes over three years.

Snøhvit, Barents Sea, Norway. Operated by Statoil and removing CO₂ using amine scrubbers from a natural gas stream. Injecting 700,000 tonnes CO₂ per year.

Sleipner West, Norway. Operated by Statoil Hydro since 1996. Using amine scrubbers to remove CO₂ from natural gas stream. Injecting around 2,800 tonnes CO₂ daily into Utsira Formation. Ten million tonnes of CO₂ has been stored up until now.

In Salah, Algeria. Operated by BP, Sonartrach & Statoil since 2004. CO₂ is removed from natural gas using amine scrubbers and reinjected back into the same gas field. 1.2 million tonnes of CO₂ is injected per year.

K-12B CO2 injection project, North Sea. By Dutch ministry of economic affairs, Gaz de France, Production Nederland BV, and TNO. Operational since 1987 using amine scrubbers.

CO2SINK Ketzin, Germany. A project supported by a consortium of 14 companies and research institutions. Operational since July 2008, injecting 60,000 tons of CO₂ over next two years.