By John Kemp
LONDON May 3 North America has enough
underground capacity in depleted oil and gas fields, uneconomic
coal seams, and saline aquifers to store all its carbon dioxide
emissions for the next 600 years. That is according to the first
comprehensive survey published by the U.S. Department of Energy,
Natural Resources Canada and Mexico's Energy Ministry.
For policymakers in all three countries, underground storage
is essential if North America is to continue to burn its
abundant fossil fuel reserves, especially coal, to meet energy
demand without worsening climate change.
The optimistic message of the new "North American Carbon
Storage Atlas," published on May 1, is that the total carbon
dioxide (CO2) storage capacity of the United States is 1.8-20.4
trillion tonnes, compared with annual emissions of just 3
billion tonnes, enough to last for hundreds if not thousands of
The atlas puts Canada's potential storage at 48-320 billion
tonnes, compared with annual emissions of 219 million, while
Mexico's resource is at least 100 billion tonnes compared with
yearly emissions of 205 million, which is more than ample.
Sedimentary basins containing oil, gas and coal are also the
most suitable for injecting CO2 underground in the form of a
liquid or supercritical fluid (which behaves like a combination
of a gas and a liquid).
The most likely areas for implementing carbon capture and
storage (CCS) projects therefore overlap with states and
provinces that are home to the coal mining and petroleum
industries, which should ease political opposition.
Large-scale CO2 injection is already underway at locations
across the United States and Canada as part of the oil industry.
Pumping CO2 into depleted fields to maintain pressure and
help oil flow through rock formations to the base of wells as
part of enhanced oil recovery (CO2-EOR) programmes is a
well-established process that already accounts for 5 percent of
all U.S. oil production, according to the Department of Energy.
In a flagship project spanning the U.S.-Canadian border,
nearly 3 million tonnes of CO2 are captured each year from a
coal gasification plant in North Dakota and transported by
pipeline to Weyburn in Saskatchewan where they are injected to
boost oil production.
More than 21 million tonnes of CO2 have been injected since
the project at the Weyburn field operated by Cenovus Energy
and a neighbouring one at Midale operated by Apache
Canada started operating in 2000 and 2005 respectively.
Underground storage is therefore feasible. But the atlas
highlights some of the technical challenges that will need to be
overcome to turn it from a niche business into one that captures
and stores millions or even billions of tonnes every year, on a
scale big enough to make a significant difference to regional
According to the atlas, there are 1,811 large stationary
sources emitting over 100,000 tonnes of CO2 per year in the
United States, and another 219 in Canada.
Power plants account for by far the largest share of
emissions from stationary sources (80 percent in the United
States, 45 percent in Canada) but other big emitters include the
oil and gas industry, refiners, ethanol distilleries, cement and
fertiliser manufacturers, and other heavy industries such as
iron and steel.
Chemical plants, ethanol distillers and refiners produce
relatively concentrated CO2 which is easier and more economical
to capture, transport and inject. In contrast, the stream of CO2
from a conventional coal-fired power plant is much more diluted,
making it harder and more expensive to capture, purify and
Policymakers are therefore starting to focus on the
potential for capturing CO2 from industries outside the power
sector. As part of this effort, the U.S. Energy Department is
using stimulus funds to help support three projects expected to
capture a total of 6.5 million tonnes of CO2 per year.
In Texas, Air Products and Chemicals Inc is building
a project that will capture 1 million tonnes of CO2 per year,
starting in November 2012, at its existing steam-methane
reformers at Port Arthur, transporting it via pipeline to oil
and gas fields in the eastern part of the state to support
In Illinois, Archer Daniels Midland is building a
project that will capture 1 million tonnes from an existing
ethanol distillery, beginning in August 2012, and sequester it
in a nearby saline aquifer.
And in the most ambitious project, in Louisiana, Leucadia
Energy plans to capture 4.5 million tonnes of CO2 per year from
a new methanol plant, to be delivered via a 12 mile pipeline and
injected into the West Hastings oil field from April 2014 as
part of an EOR programme.
North of the border, Canada's federal government and
provincial governments "have committed more than $3 billion to
CCS initiatives through a number of federal and provincial
programmes," according to the atlas.
Capturing, transporting and injecting CO2 is expensive, so
policymakers are talking up the commercial value of CO2 and its
usefulness as an input into other industries. The new emphasis
is on carbon capture utilisation and storage (CCUS).
The U.S. Energy Department is focusing research and
development efforts, and subsidies, on "the economic utilization
of captured CO2 for commercial purposes .. By putting the
captured CO2 to use, CCUS provides an additional business and
market case for companies or organizations to pursue the
environmental benefits of CCS" according to an announcement on
The biggest near-term opportunity is an expansion of CO2-EOR
programmes. The Energy Department estimates EOR has the
potential to add an extra 60 billion barrels to recoverable U.S.
oil resources, tripling proven reserves.
In the longer term, researchers are examining CO2 injection
to boost the production of coal-bed methane (CBM). CO2 is
preferentially adsorbed onto the surface of coal, displacing
methane. CO2 injections could therefore boost natural gas
production from coal seams in a technology dubbed "enhanced coal
bed methane" (ECBM).
The biggest uncertainties, however, surround the size of
suitable underground formations for storage. CO2 is toxic in
fairly low concentrations (8-15 percent) so no one wants it to
escape. Fugitive emissions would also negate the climate change
benefits of CCS. Formations therefore need to be picked
Fortunately, injecting CO2 into depleted oil and gas fields
is relatively well understood, though no one has tried to do it
on anything like the required scale. Hydrocarbons were safely
locked away in these fields for millions of years so the CO2
should be sequestered securely.
But depleted oil and gas fields account for only a small
share of the total storage capacity identified in North America.
In the United States, for example, depleted fields account for
124 billion tonnes of CO2 storage capacity (7 percent of the
total). Unmineable coal seams could sequester another 60-118
billion tonnes (3-7 percent).
The big prize is sequestering CO2 in saline aquifers. The
United States could potentially trap 1.6-20.1 trillion tonnes of
CO2 in aquifers buried at least 800 metres below ground level,
safely below the drinking water table. Saline aquifers account
for more than 85 percent of the country's carbon sequestration
capacity according to the atlas.
However, there is much more uncertainty about trapping CO2
in brine. Because they have been less important economically,
saline formations are not as well mapped. Less is known about
how CO2 might flow through them. It would be essential that any
aquifer is overlain by a regionally extensive cap rock with no
Despite the caveats, the atlas does a useful job showing
just how much CO2 could be locked up underground, potentially
extending North America's oil and gas resources by decades and
limiting the impact on the greenhouse effect. But it will only
work if technology for separating CO2 from power plant exhausts
can be perfected and the right financial incentives are put in