Some scientists and analysts are touting carbon capture and storage as a necessary tool for avoiding catastrophic climate change. But critics of the technology regard it as simply another way of perpetuating a reliance on fossil fuels.
For more than 40 years, companies have been drilling for carbon dioxide in southwestern Colorado. Time and geology had conspired to trap an enormous bubble of CO2 that drillers tapped, and a pipeline was built to carry the greenhouse gas all the way to the oil fields of west Texas. When scoured with the CO2, these aged wells gush forth more oil, and much of the CO2 stays permanently trapped in its new home underneath Texas.
More recently, drillers have tapped the Jackson Dome, nearly three miles beneath Jackson, Mississippi, to get at a trapped pocket of CO2 for similar use. It’s called enhanced oil recovery. And now there’s a new source of CO2 coming online in Mississippi — a power plant that burns gasified coal in Kemper County, due to be churning out electricity and captured CO2 by 2015 and sending it via a 60-mile pipeline to oil fields in the southern part of the state.
The Mississippi project uses emissions from burning a fossil fuel to help bring more fossil fuels out of the ground — a less than ideal solution to the problem of climate change. But enhanced oil recovery may prove an important step in making more widely available a technology that could be critical for combating climate change — CO2 capture and storage, or CCS.
As the use of coal continues to grow globally — coal consumption is expected to double from 2000 to 2020 largely due to demand in China and India — some scientists believe the widespread adoption of CCS technology could be key to any hope of limiting global average temperature increase to 2 degrees Celsius, the threshold for avoiding major climate disruption. After all, coal is the dirtiest fossil fuel.
“Fossil fuels aren’t disappearing anytime soon,” says John Thompson, director of the Fossil Fuel Transition Project for the non-profit Clean Air Task Force. “If we’re serious about preventing global warming, we’re going to have to find a way to use those fuels without the carbon going into the atmosphere. It seems inconceivable that we can do that without a significant amount of carbon capture and storage. The question is how do we deploy it in time and in a way that’s cost-effective across many nations?”
The biggest challenge is one of scale, as the potential demand from aging oil fields for CO2 produced from coal-fired power plants is enormous.
Thompson estimates that enhanced oil recovery could ultimately consume 33 billion metric tons of CO2 in total, or the equivalent of all the CO2 pollution from all U.S. power plants for several decades. Thompson and other analysts view such large-scale enhanced oil recovery as an important phase in the deployment of CCS technology while replacements for fossil fuels are developed.
"In the short term, in order to develop the technology, we probably will enable more use of hydrocarbons, which makes environmentally conscious people uncomfortable,” says Chris Jones, a chemical engineer working on CO2 capture at the Georgia Institute of Technology. “But it’s a necessary thing we have to do to get the technology out there and learn how to make it more efficient."
At the same time, CO2 capture and storage is not as simple as locking away carbon deep underground. As Jones notes, the process will perpetuate fossil fuel use and may prove a wash as far as keeping global warming pollution out of the atmosphere. Then there are the risks of human-caused earthquakes as a result of pumping high-pressure liquids underground or accidental releases as all that CO2 finds its way back to the atmosphere.
"Any solution that doesn’t take carbon from the air is, in principle, not sustainable," says physicist Peter Eisenberger of the Lamont-Doherty Earth Observatory at Columbia University, who is working on methods to pull CO2 out of the sky rather than smokestacks. He notes that merely avoiding CO2 pollution is not enough and will create political powerhouses—heirs to the energy companies of today—that will entrench such unsustainable technologies "Why spend so much time and energy and ingenuity coming up with solutions that are not really solutions?” he adds.
But the expansion of enhanced oil recovery remains the main front in an intensifying effort to more broadly adopt CCS technology and reduce its price, which is currently the major impediment to its deployment. The need for CO2 storage goes beyond China and the U.S., the world’s two largest polluters. Worldwide, more than 35 billion metric tons of CO2 are being dumped into the atmosphere annually, almost all from the burning of coal, oil, and natural gas. To restrain global warming to the 2 degree C target, more than 100 CCS projects eliminating 270 million metric tons of CO2 pollution annually would have to be built by 2020, according to the International Energy Agency. But only 60 are currently planned or proposed and just 21 of those are actually built or in operation.
Those include the Kemper facility and other coal-fired power plants, but also a CCS project under construction at an ethanol refinery in Illinois. A group led by Royal Dutch Shell is building technology to capture the CO2 pollution from tar sands operations in Alberta, Canada, and in Saskatchewan, a $1.2 billion project to retrofit a large coal-fired power plant with CCS technology is expected to open later this year. And there are 34 proposed or operating CCS projects outside of North America, the majority in Asia and Australia. But European countries like Germany have rolled back plans to adopt CCS because of public opposition, dropping the number of European projects from 14 planned in 2011 to just five as of 2014, according to the Global CCS Institute.
That might conflict with the European Union’s avowed intention to help combat climate change. The U.N. Intergovernmental Panel on Climate Change suggested earlier this year that carbon capture and storage at power plants could prove a critical part of any serious effort to restrain global warming. "We depend on removing large amounts of CO2 from the atmosphere in order to bring concentrations well below 450 [parts-per-million] in 2100," said Ottmar Edenhofer, an economist at the Potsdam Institute for Climate Impact Research and co-chair of the IPCC’s third working group, which was tasked with figuring out ways to mitigate climate change. Ultimately, he said, keeping a global temperature rise to 2 degrees without any CCS would require phasing out fossil fuels entirely within “the next few decades.”
Yet, from 2007 to 2013, global coal consumption increased from 6.4 billion to 7.4 billion metric tons, and coal use continues to rise. Although renewable energy sources like solar and wind are growing rapidly, they are doing so from a very small base and many energy analysts argue that it will be decades before they can supplant fossil fuels. The time and expense of building nuclear power plants — and public opposition — has also hampered that low-carbon technology’s ability to replace coal burning. And biofuels or electric cars remain a long way from supplanting oil for transportation.
The Obama administration hopes to encourage the development of CO2 capture and use or storage. New rules from the Environmental Protection Agency requiring a 30 percent cut in power plant emissions by 2030 may spur development of CCS technologies. Already, NRG Energy has partnered with a Japanese firm to add CO2 capture to a coal-fired power plant near Houston and use a pipeline to send the captured pollution to nearby oilfields. Dubbed Petra Nova, the $1 billion CCS project is the latest in a series of 19 CO2 capture projects underway or proposed in the U.S.
The bulk of such CO2 capture and storage experiments may soon shift to China, the world’s largest emitter of CO2. The Chinese and U.S. governments have a cooperative agreement to develop the technology, including partnerships between Chinese power companies like Huaneng and American corporations such as Summit Power, which is developing a CCS power plant in west Texas. In China, the long-awaited GreenGen power plant in Tianjin is still under construction and will capture CO2 for China’s own efforts at enhanced oil recovery. But going forward, the expense of CCS may make the technology even more unpalatable in a developing country like China, which also has plans to turn coal into liquid fuels — a process that, from a climate perspective, is even worse than burning the dirty rock directly.
The technology to capture CO2 is relatively simple, and has been in use since the 1930s. For example, CO2 can be captured from the smokestacks of coal plants, natural gas plants, and even factories by routing the flue gases through an amine chemical bath, which binds the CO2. The chemical is then heated to release the CO2. The CO2 is pressurized to convert it to a liquid, and the liquid is then pumped via pipeline to an appropriate storage site. Those include underground geological formations, such as sandstones or saline aquifers, but also old oil fields, where the CO2 replaces the oil in small pores in the rock left behind by conventional methods and forces it up to the surface. Six percent of U.S. oil already comes from using enhanced oil recovery, a number that will increase, according to the U.S. Energy Information Administration.
Still, the economic and technological challenges facing CCS are daunting. Much-heralded projects like the CO2 capture and storage demonstration at the Mountaineer Power Plant in West Virginia were abandoned because no one wanted to pay for it. The hardware sits unused next to the hulking power plant’s smokestacks and cooling towers.
The ultimate challenge is that capturing CO2 from a smokestack costs more than simply dumping it into the atmosphere. Analysts say the simplest way to encourage less pollution and more CO2 capture would be to charge for the privilege of emitting CO2 by imposing a tax on carbon emissions. A price on CO2, if high enough, might make capturing the greenhouse gas look cheap.
Even if that policy change happens, the problem of storing all that CO2 remains, including concerns that the CO2 could escape back into the atmosphere or cause earthquakes. In Algeria, a test to store nearly 4 million metric tons of injected CO2 underground was halted after the gas raised the overlying rock and fractured it. Concerns over such induced seismicity or accidental releases of CO2 have blocked CCS plans in Europe, as have concerns over how to ensure the stored CO2 stays put for millennia.
But storing CO2 underground can work, as Norway’s Sleipner project in the North Sea has demonstrated. At Sleipner, which started capturing and storing CO2 in 1996, more than 16 million metric tons of CO2 have been put in an undersea sandstone formation; the project is funded by Norway’s carbon tax. And around the world, the potential storage resource is gargantuan. The U.S. alone has an estimated 4 metric tons of CO2 storage capacity in the form of porous sandstones or saltwater aquifers, according to the U.S. Department of Energy.
Scientists at Columbia’s Lamont-Doherty Earth Observatory and elsewhere are investigating just how vast the storage potential under the ocean could be. David Goldberg, a marine geophysicist at Lamont, proposes that liquid CO2 could be pumped offshore and injected into the ubiquitous basalt formations found off many of the world’s coastlines. When mixed with water, the CO2 leaches metals out of the basalt and forms a carbonate chalk, Goldberg explains.
“The goal of the whole CCS exercise is to take CO2, which is volatile, and put it in solid form where it will stay locked away forever,” he adds. Goldberg has calculated that just one such ridge site that runs the north-south length of the Atlantic Ocean could theoretically store all of humanity’s excess CO2 emissions to date. “The magic of being offshore is that you are away from people and away from property.”
There is also basalt on land. In an experiment in Iceland, more than 80 percent of the injected CO2 interacted with the surrounding basalt and converted to rock in less than a year. A similar experiment in Washington State achieved similar results.
In the end, getting off fossil fuels entirely is the only way to control CO2 pollution. But until that happens, CCS could be vital to stave off catastrophic climate change. "Ultimately, we need a thermostat on this planet," says Klaus Lackner, a Columbia University physicist who is working on pulling the greenhouse gas directly out of the air rather than capturing it from smokestacks. "And we need to control the CO2."
Photo credit: Wikipedia/LeJean Hardin and Jamie Payne derivative work: Jarl Arntzen (talk)/CC BY-SA 3.0