Flue gases spewing from coal-fired power plants account for nearly half of global CO2 emissions.Ira Block / Getty Images
Feature
11 Feb 2016

Can we bury the carbon dioxide problem?

Carbon capture and storage could be a game-changer. Elizabeth Finkel and Belinda Smith report.

Flue gases spewing from coal-fired power plants account for nearly half of global CO2 emissions.Ira Block / Getty Images

Mention “carbon capture and storage” in polite company and you’re likely to be pounced on. Expressions change to snarly. Then a force of logic takes over. It’s absurdly expensive, it can never be rolled out en masse, storing massive amounts of CO2 below ground sounds risky. And it’s too late. Wind and solar have left it in the dust. The clear unassailable death knell, say the critics, is that even the fossil fuel industry, the biggest beneficiary, hasn’t embraced the technology.

It’s hard to find a friend for carbon capture and storage (CCS). Regulators and governments – though eager to subsidise solar or wind power – offer no such encouragement to capture carbon. Last November, the UK government – a one-time champion – stuck in the knife by cancelling a billion-pound fund earmarked for rolling out CCS.

That’s the tough reality for the chemists, geologists and engineers developing CCS for the past 20 years. When they began they were tarred as collaborators of the fossil fuel empire or as Don Quixotes chasing an impossible dream. Now their ugly duckling technology is ready to fly. And it’s having a very tough time spreading its wings.

But that may be changing. The lead-up to the Paris climate talks last year produced many roadmaps designed to steer the planet away from the cliff of 2°C of warming. In each one, nestled among the windmills and solar farms, was the ugly duckling. Take it out of the equation and the costs of meeting the 2°C target would be more than double – and likely impossible.

Besides, as most of the roadmaps pointed out, even without coal or gas-fired power stations, industrial processes including steel and cement manufacturing generate 15% of CO2 emissions. Many also pointed out that we may need to call on CCS once we go over the safety limit. Combusting biomass, rather than coal, in a CCS power station could create ‘negative’ emissions.

In report after report, fossil fuel industry groups and green non-government organisations supported CCS. “CCS could deliver 13% of the cumulative emissions reductions needed by 2050 to limit the global increase in temperature to 2°C,” declared The International Energy Agency, a support group for energy-producing nations with a commitment to sustainable solutions.

“CCS plays a vital role as part of an economically sustainable route to meet climate mitigation goals with the 2050 timeframe,” said Miguel Arias Cañete, the EU Commissioner for Energy and Climate Action.

Even a coalition of climate NGOs with impeccably green credentials released a report titled Closing the Gap on Climate: Why CCS is a Vital Part of the Solution.

At the very least, Paris seems to have made CCS a respectable topic. Is it possible CCS will take flight at last?

Paris seems to have made CCS a respectable topic. Will it take flight at last?

CCS is not new. Its first adherent was the natural gas industry where CO2 is often found mixed with methane, mostly from ancient organic matter but also some from volcanic origins. Concentrations of CO2 can be as high as 50% or more and must be filtered out to maintain gas quality.

Companies had been pumping gas out of the European North West Shelf for decades and venting waste CO2 into the atmosphere. Then in 1991, Norway was one of the first countries to put a price on CO2 emissions.

That led to the Sleipner Project. In 1996 energy company Statoil initiated the world’s first CCS project, pumping separated CO2 back into the undersea sandstone beds it came from. “They did the sums and decided it was cheaper to put the stuff in the ground,” explains geologist Peter Cook.

British born Cook is Australia’s elder statesman of CCS. Patient and pedagogical, he has an indefatigable enthusiasm for explaining the maligned technology. He first encountered Sleipner as director of the British geological survey in the mid-1990s. Could this technology be the answer to all fossil fuel emissions?

“It was clear to me we really needed to look at this more closely,” Cook says.

His chance came in 1998 when he was offered the job of directing the Australian Petroleum Cooperative Research Centre. Cook managed to convince the board to start a program looking at the feasibility of geologically storing CO2.

Petroleum and gas producers wanted to sequester CO2 from oil and gas fields. But Cook also thought about Australia’s dependence on coal. Three quarters of the country’s electricity was produced by burning coal, a third of it brown coal.

The state of Victoria was 90% dependent on brown coal. Its Hazelwood power station in the Latrobe Valley produced among the highest carbon emissions per kilowatt of electricity in the world. Cook’s program, GEODISC (Geological Disposal of CO2), investigated whether Australia had enough suitable rocks for storing CO2. Such rocks are known as saline aquifers. They have a layer cake structure with porous sandy watery slabs that have a great capacity to store CO2, topped by a non-porous mudstone layer to seal it in.

The scheme was not popular: “I was perhaps seen as a caricature of a geologist who would rape and pillage the Earth,” recalls Cook.

Nevertheless, GEODISC produced impressive results. It turns out that Australia has “world class rocks”, he says. The project built so much momentum that in 2003 it became the launch pad for a new cooperative research centre devoted to carbon capture and storage – the CRC for Greenhouse Gas Technologies, or CO2CRC. Cook was appointed director.

Cook, a geologist, had command of the storage technology. But “capture” required a separation chemist. Cook recruited one with a stellar international record. Geoff Stevens’ expertise lay in understanding the behaviour of molecules at interfaces: what will make them jump from one solvent to another? He has separated opium from poppies, cobalt from ores, and as part of a tissue-engineering team, gases across membranes in artificial lung sacs: “It’s all the same basic process.”

So why did Stevens join such an unpopular crew? “I thought I had the skills to have a small influence,” he says.

“I was perhaps seen as a caricature of a geologist who would rape and pillage the earth.”

Whether it’s burning coal in a power station or dealing with natural gas whooshing through an undersea pipeline, the task is the same: you have to separate CO2 from the gaseous mix.

At Sleipner they capture CO2 by binding it to chemicals called amines; it’s neither difficult nor overly expensive. Natural gas spurts out of the ground as if from a fire hose – that high pressure helps drive CO2 capture. But the process is different for the vapours escaping a coal-fired power station. That smoke contains CO2 at atmospheric pressure.

If capturing natural gas emissions is like netting a flock of butterflies, capturing coal emissions is the more difficult task of chasing a lone flutterer.

Various capture methods were tested at the CRC. Some were variations on the amine theme; others employed carbonates. The traps might be attached to the flue gases emerging from the combustion of coal. Collectively this method is called “post-combustion capture”.

A second method increases the efficiency of capture by burning the coal in oxygen and recycled flue gas, a method dubbed “oxycombustion”. The flue gas ends up as a mixture of CO2 and steam. Allowing the steam to cool and condense leaves a stream of CO2 concentrated at around 85-90%.

A third method, “pre-combustion capture” involves capturing carbon before it is burnt. Surprisingly, if coal is baked under steamy conditions at 700°C, it vaporises into syngas: a mixture of carbon monoxide, carbon dioxide and hydrogen. Known as “gasification”, this is a time-honoured technique for producing transportable fuel when oil is in short supply, as it was during World War II when gasified coal became the primary vehicle fuel. When coal is gasified, CO2 is produced at a pressure 20-40 times higher than that in a coal flue, making it more efficient to separate. The hydrogen fuel is then burned in a carbon-emission-free turbine that resembles a jet engine.

Capturing millions of tonnes of CO2 is only the first part of the solution. Fifteen facilities are now capturing CO2. Most are connected to natural gas but others are linked to fertiliser and ethanol production or turning Canadian oil sands bitumen into synthetic crude, as does Shell’s Quest project.

According to the International Energy Agency, these projects capture 27 million tonnes of CO2 per year. But to stay below 2°C this will have to ramp up to 6,000 million tonnes per year by 2050 – contributing one seventh of the total emission savings required, according to the IEA.

That means our planet would have to store billions of tonnes of CO2, safely and forever. Is this possible? Not everyone thought so.

Sally Benson is a calmly spoken Stanford University geologist who studies how CO2 moves through saline aquifers. She is also the director of the Global Climate and Energy Project – a university-industry partnership whose remit includes comparing the performance of various low emissions technologies.

But in the early 2000s she was director of Earth Sciences at the Lawrence Livermore National Laboratory in California, and a CCS sceptic. “I thought that’s the silliest thing I ever heard,” she recalls. She was convinced rocks held enough storage capacity for only 10 to 20 years. Then she started collecting data for a paper and reached a different conclusion: the storage capacity was in excess of 300 years, long enough to be useful until zero emissions technologies take over. She has since become a CCS champion. In 2005, she was a lead author for what remains the definitive report on the technology’s potential: the Intergovernmental Panel for Climate Change Special Report on Carbon Dioxide Capture and Storage. Cook was also an author; both were part of a group that received a Nobel Peace Prize for their efforts.

Cook and Benson belong to a passionate and beleaguered minority who believe CCS is a crucial part of the toolkit to keep the planet safe. But the tool needs testing and the geologists have their work cut out.

Nestled in scenic farmland 40 kilometres east of the coastal town of Warrnambool, Victoria, close to the Great Ocean Road, lies a world-leading research facility – but if you didn’t know it was there, you’d never find it. Only after half a kilometre or so down a bumpy dirt track, past fields of cows lazily chewing cud, do you see the pre-fabricated building that serves as the site office. Nearby, a fenced-off network of pipes pokes out of the ground, at the bottom of which lies 65,000 tonnes of pressurised liquid CO2 more than a kilometre below the surface.

This is the Otway project, the latest incarnation of the CRC, which ended its term in 2014. The CRC is now a wholly incorporated non-profit that also coordinates CCS research and policy across centres such as Melbourne University’s Peter Cook Centre, which inherited most of the CRC’s research.

(An embarrassed Cook says the name of the centre was Rio Tinto’s idea. The mining company is one of the centre’s sponsors along with the State Government. But back to the Otway project.)

“Absolute perfection is required,” says program manager Matthias Raab, gesturing at the engineers flocked around a crane that is carefully feeding an insulated wire down a 1.5-kilometre-long pipe, like a catheter into a patient’s vein.

The pipe terminates at a salt-water impregnated rock layer that has received 65,000 tonnes of CO2 injections. This is the Waarre C aquifer; its vital signs are monitored by sensors on the wire. Meanwhile on the surface, the thumps of ‘seismic’ trucks build a 3-D image of the rock layers from sound wave reverberations. The US has several such “laboratories” says Benson, a project collaborator. But she says “the Otway project is unique in the high quality of scientific information it has generated”. It was designed to obtain data that could be used to test computer models – the sort that Stephan Matthai generates in his University of Melbourne laboratory.

Why the need to develop such detailed information about what CO2 will do underground?

Matthai is a jovial and engaging German geologist who leads the reservoir engineering team at the Peter Cook Centre. The sideways spread of CO2 seen at the Otway project is ideal, he explains. But rock structures vary – as he learnt while working in oil and gas fields. Oil and gas droplets, though packed between sand grains, can flow like a reservoir. Understanding those flow properties are crucial to drilling for oil safely.

Mistakes are costly. In the 1950s, proliferating oil derricks caused Long Beach in California to sink by metres. That’s why oil companies employ geologists to model the subsurface. The same care is required when injecting CO2, says Matthai.

His models will be used to decide where and how to safely inject CO2 in the Gippsland Basin, which holds one of Australia’s richest concentrations of fossil fuels, with oil and gas deposits offshore as well as the Latrobe Valley’s brown coal. The area might be re-coloured green if the CarbonNet project gets off the drawing board. The basin would become a hub for carbon capture from power stations, gas generation and other industries that emit CO2, such as concrete manufacturing. The CO2 would be stored in offshore saline aquifers. In Western Australia a similar scheme is planned: the Collie-South West CO2 Geosequestration Hub.

The future of these projects is uncertain. They remain unpopular with the public – as Matthai knows from experience. In 2009, he was an advisor to the Austrian government on carbon storage. Hostile media likened it to storing nuclear waste. First the German government gave up on CCS; two years later the Austrians followed suit. “It was really unfortunate,” Matthai says.

The otway project, which has cost some A$60 million over the past decade, is testament that CCS, along with other Australian CCS projects (see map), once enjoyed rosier times.

Benson says from 2004 to 2008, the years before the 2009 Copenhagen Climate Summit, were good for CCS globally: “People believed in the technology. We got government money and good attention. Everyone believed a global carbon policy was imminent so the context was to start planning.”

Australia was a big player. In 2008, then prime minister Kevin Rudd launched the Global Carbon Capture and Storage Institute in Canberra. With seed funding from the Federal Government, its mission was to “accelerate the development of CCS globally”. The official view was that this technology would do more than expiate Australia’s carbon sins. It could also be offered to countries like China who buy Australian coal and are responsible for the lion’s share of global emissions.

Then came the Global Financial Crisis in 2008 and the failure of the Copenhagen Summit to set any emissions targets in 2009. Things turned gloomy for CCS. In these circumstances, who would want to invest in the technology?

Canada’s SaskPower did – partly because they were state-owned and anticipated an imminent carbon tax, but there was another economic rationale. A stream of pure, pressurised CO2 is valuable – worth around US$20-40 a tonne. You can sell it to soft drink manufacturers, to chemical plants to make ammonia or plastics – or to oil companies. Across the US much of the free-flowing oil is long gone from wells. What remains is the viscous dregs. CO2 acts like a detergent and flushes the oil out. SaskPower sells Boundary Dam’s CO2 to the nearby Weyburn oil field, where it should yield an extra 130 million barrels over the next 25 years.

But offsetting the price of CCS by producing more oil does nothing to help its public image.

The prospects for CCS were not helped by the apparent death of King Coal in Europe. In Italy, for instance, coal-fired power stations were turned into museums. But elsewhere there was a renaissance – and for good reason. Manufacturing relocated to developing countries. According to a July 2015 report from the Mercator Research Institute on Global Commons and Climate Change, India, China and other Asian and African nations increased their coal consumption 3.7-fold between 1990 to 2011. Some exploited their own coal; others imported it from countries such as Australia because it was so cheap. India is preparing to provide electricity for nearly 600 million new consumers by 2040 while ramping up its “Make in India” program.

And while coal consumption has slowed in China, which will likely hit peak coal well before its promised date of 2030, it will continue emitting vast amounts of CO2 before then. China and India plan to build more than 1,600 new coal-fired power plants between them by 2030, according to the online Global Coal Plant Tracker.

The future for CCS looked so bleak in 2015 we seriously questioned if it was worth writing about. But the Paris conference may have changed the conversation. The signatories agreed that the world needs to achieve zero emissions by 2050. And even if the entire planet manages to switch to renewables and nuclear energy overnight, we would still be emitting CO2 through industrial processes. For instance in 2012, China’s emissions from cement production alone were twice those produced by Australia’s entire energy sector.

That is why Anna Skarbek, chief of Australian NGO Climate Works, supports CCS. Her organisation produced a roadmap to “decarbonise” Australia by 2050 – part of a 15-country exercise headed by special adviser to the UN secretary general Jeffrey Sachs. All included CCS.

Even so, the CCS costs are daunting. Where will the money come from?

For the moment all eyes are on China. Robin Batterham, a former group chief scientist at mining giant Rio Tinto, and former chief scientist of Australia, is a consultant on various Chinese projects. He predicts the costs will fall as more plants are rolled out: “It’s just a universal law – if you build it at scale you discover tricks. We don’t know the real cost of CCS.”

Batterham says the rapid roll out of China’s new fleet of ultra-supercritical plants is evidence of what’s possible. The plants are designed to scrub air pollutants, not CO2. But they are more efficient than standard coal plants, and reduce CO2 emissions by 30%. “The experience in China is they go ahead and build a large demo plant and many more follow.”

If China decrees a carbon tax in 2017, Stevens is confident the new fleet will be fitted with post-capture techniques: “They are not going to dismantle these investments that will still have decades of life in them.”

Ultimately governments are the ones with the muscle, especially when it comes to new developments such as the Gorgon gas project in northwest Australia. The West Australian government ordered the Chevron, Shell and ExxonMobil consortium to capture CO2. Once up and running, three to four million tonnes of CO2 will be captured and injected into a sandstone formation 2.5 kilometres beneath Barrow Island each year. It will be the largest CCS project in the world.

“As a species I don’t think we have a choice.”

The paris conference was hailed as historic for at last securing commitments from 195 countries to reduce their emissions. But another part of its legacy may be to have made CCS respectable.

Whether it does or not, the scientists who’ve spent the past decade battling against the tide will carry on regardless. “As a species I don’t think we have a choice,” says Stevens.

Cook, a self-confessed “born optimist”, is convinced CCS will be rolled out in the next five years: “If people want to cut emissions yet go on using fossil fuels, we need the technology. There’s a certain logic there I find compelling.”

Benson is optimistic too: “CCS is at the same place solar cells were two decades ago. Look how far we’ve come. CCS dead? It’s not even born yet!”  

A COSTLY EXERCISE

The three CCS methods – pre-combustion, oxycombustion and post-combustion – capture at least 90% of CO2 emissions. For the past decade some 20 pilot plants around the world have been trying to find which method will provide the most bang for their billions of bucks.

Cheapest outlay costs come from retrofitting a plant for post-combustion capture. Canada’s Boundary Dam opened in 2014 and captures a million tonnes of CO2 per year. The capture unit was retrofitted to a 60 year old 140-megawatt plant power plant for around US$1.5 billion. Half a billion was to refurbish the boiler, so the capture cost is close to one billion. With lessons learnt, project director Mike Monea says the next such project would be 30% cheaper. But about 13% of the electricity generated must be used to heat the carbon-capturing recyclable amine solvents to drive off the CO2.

Australia runs a tiny demonstration unit that captures 0.1% of emissions at Hazelwood power station. It uses potassium carbonate rather than amines, a process that is 50% cheaper to run and environmentally friendlier, says Barry Hooper who developed the technology at the CO2CRC and has since spun out the company UNO Technology to develop it. China also has a few demonstration plants, including the Huaneng Gaobeidian Thermal Power Plant in Beijing, which fired up just in time for the 2008 Olympics.

The world’s largest oxycombustion pilot plant was built in Callide, Queensland in collaboration with Japanese partners. The 30-megawatt combustion boiler ran from 2012 to March 2015. Overall a third of the plant’s total power output was used to fuel the process. Researchers are now crunching the data with the aim of getting that load down to 20%. Units can also be retrofitted to an existing power station.

Gasification plants have sprung up in a handful of places around the world. Known as integrated gasification combined cycle (IGCC) plants, they look more like a chemical plant than a power station. After the COis siphoned off, hydrogen is burned in a specially designed furnace. Chemical engineer Ke Liu, former vice president of China’s National Institute of Clean & Low-carbon Energy, points out the IGCC plants are more challenging and expensive to build than traditional combustion plants. China only has one gasification plant: GreenGen, a 500-megawatt plant at Tianjin. Mississippi Power built one at Kemper Country for $6.2 billion – its original price tag was $1.6 billion. The 582-megawatt plant will capture three million tonnes of CO2 per year and is slated to switch on in 2016.

There’s no doubt the cost of capturing carbon dioxide is hugely challenging. But as the Intergovernmental Panel for Climate Change made clear in its 2014 report, the cost of not capturing it is greater. Without CCS, their models show the costs of keeping us below 2°C more than doubles.

Elizabeth Finkel is editor-in-chief of Cosmos.

Belinda Smith is deputy editor of Cosmos.