POSTED 22 MARCH 2007
Carbon dioxide storage: More than a pipe dream
The notion of slowing global warming by storing carbon dioxide deep underground
may sound far-fetched, but carbon dioxide injection is widely practiced
in tired old oil fields, where the gas pressurizes and forces it toward
the wells. In 1998, Howard Herzog of MIT's Laboratory for Energy and the
Environment estimated (see #4 in the bibliography)
that about 43 million
metric tons of CO2 was injected in the United States each year to enhance
oil recovery. Although experience shows that injection is possible, it's
not clear how much of this carbon dioxide is remaining underground, since
the injections are not aimed at slowing global warming.
Vast quantities of carbon dioxide could be stored around the world, according to early estimates (Gt = gigatons = billion tons). Source: International Energy Agency
Several other projects (either active or planned) should ramp up our knowledge of carbon dioxide injection as an antidote to global warming:
In the North Sea, the Sleipner
project is injecting about 1 million tons of carbon dioxide underground each
year. The gas is a contaminant of natural gas being pumped by the Norwegian national
oil company. A key motive for the injection is to avoid the European Union's
$55 per ton carbon dioxide tax, according to James
Johnson of Lawrence Livermore National Laboratory.
Natural gas is extracted at the Sleipner project. Carbon
dioxide is stripped from the gas and re-injected beneath a cap rock that should
restrain it. Inset: location of the Utsira formation. Slightly
modified graphic
from IPCC
The government of Australia has committed $60 million (Australian) for carbon dioxide capture and storage at the Gorgon project, run by the multinational Chevron, in Western Australia. As at Sleipner, the carbon dioxide is a contaminant in natural gas, which otherwise would be dumped to the air. The carbon dioxide will be injected 2.5 kilometers belowground, in what is expected to be the largest storage effort in the world. The government says Gorgon will cut Australia's annual greenhouse gas pollution by up to 3 million tons, but it's more likely to reduce the increase caused by the new gas wells at Gorgon.
The Fairview project in Queensland, Australia, has just obtained government money to pump carbon dioxide into a deep coal mine, where it will liberate methane gas. The methane will be burned to generate electricity, and carbon dioxide from the exhaust will be pumped into the mine to release more methane.
FutureGen, a U.S. government alliance including several coal-industry giants, aims to spend $1 billion for a demonstration coal plant that will produce 275 million watts of electricity (enough for 150,000 homes), and store the carbon dioxide underground. More than three years after FutureGen was announced, a site remains to be chosen. The plant is scheduled to come on line by 2012, nine years after its announcement.
Carbon storage also played a starring role the TXU buyout drama. The giant Texas utility had been planning to build 11 giant new coal-fired electric generators. The buyers, eager to defuse environmentalist opposition, worked with two environmental groups and have agreed to scrap eight of the planned plants, and to fit two more for carbon capture. "Carbon capture technology is a critical ingredient in the global warming solution, and something that any firm planning coal investments needs to embrace," said Natural Resources Defense Council President Frances Beinecke in a March 7 press release. The buyers have also agreed to promote energy efficiency to TXU's customers, and to support caps on carbon dioxide emissions.
A combination of many mitigation measures may slow or reverse
greenhouse gas pollution, depending on how much it costs to release carbon dioxide
directly to the air. If taxes or carbon-caps raise the cost of emissions (right
panel), pollution will be lower. Slightly modified
graph from IPCC
Did you notice that the list of large-scale carbon storage projects includes precisely zero large electric generators that are now capturing and storing carbon dioxide? And even if and when all the projected plants work as expected, they will store a minuscule fraction of total CO2 pollution.
If we inject billions of tons of carbon dioxide into the ground, will it stay there?
