(Repeats July 10 column with no changes to text. John Kemp is a
Reuters market analyst. The views expressed are his own)
By John Kemp
LONDON, July 10 Fossil fuels will remain an
indispensable part of the global energy supply for at least the
next 50 years, so a means must be found to burn them without
pumping carbon dioxide into the atmosphere.
According to Martin Wolf, chief economics commentator of the
Financial Times: "(Just) as the civilisation of ancient Rome was
built on slaves, ours is built on fossil fuels. What happened in
the beginning of the 19th century was not an industrial
revolution but an energy revolution. Putting carbon into the
atmosphere is what we do."
But there is no necessary connection between using fossil
fuels and belching CO2 skywards. In future, carbon capture and
storage (CCS) projects could sever the link, enabling fossil
fuels to be burned safely in power plants while storing the
Deploying CCS is essential if the rise in average global
temperatures is to be limited to no more than 2 degrees Celsius
by the middle of the century, according to the International
Energy Agency ("Technology roadmap: carbon capture and storage"
"As long as fossil fuels and carbon-intensive industries
play dominant roles in our economies, carbon capture and storage
will remain a critical greenhouse gas reduction solution," the
agency warned in 2013. "There is no climate-friendly solution in
the long run without CCS."
But progress towards deploying the technology remains
The technology of each of the three components of CCS -
capturing the carbon dioxide emissions, transporting them, and
pumping them underground - is fairly well understood. Each of
them has been applied on a modest scale at various locations
around the world for several decades.
But nowhere have they been applied to capture all the
emissions from a utility-scale, coal-fired power plant. The
first two large-scale power plant CCS projects, in Mississippi
and Saskatchewan, will only become operational later this year.
Both projects will inject captured CO2 into depleted oil
fields near power plants to enhance crude recovery.
Their operational and financial performance will not be
known for several years, but given that both are pioneering,
there will almost certainly be teething problems.
Southern Company's integrated gasification and combined
cycle project at Kemper County in Mississippi is already a
Kemper's projected cost has spiralled from $1.8 billion to
$5.5 billion, making it the most expensive power plant in the
world for its output. Construction costs now top of those for a
similar-sized nuclear power plant.
Financial and operational problems with first-of-a-kind
engineering projects are common. The challenge is to learn from
them and apply the lessons in second and subsequent generations
of the same type of project.
In 2008 to help the new technology, the leaders of the
United States, Japan, Germany, France, the United Kingdom,
Italy, Canada and Russia pledged to "support the launching of 20
large-scale CCS demonstration projects by 2010 ... with a view
to beginning broad deployment of CCS by 2020".
Since then, however, progress has been disappointingly slow.
The target of 20 projects has been missed by a wide margin, and
the timeline for deployment has slipped badly.
COST OF CAPTURING CO2
Transportation and storage of carbon dioxide are fairly
mature technologies, though no one has ever tried to deploy on
the massive scale that would be needed to capture most of the
emissions from the world's coal and gas-fired power plants.
For more than 40 years, carbon dioxide has been injected
into depleted oil and gas fields in the United States, Norway,
Algeria and China to help maintain reservoir pressure and sweep
the remaining hydrocarbons towards producing wells.
The United States already has almost 4,000 miles of
pipelines dedicated to carrying carbon dioxide from gas fields
and industrial facilities to oil fields in Texas and Canada for
such enhanced recovery (EOR) projects. ("Comparing existing
pipeline networks with the potential scale of future U.S. CO2
pipeline networks" Feb 2008).
The tricky part of CCS is capturing the carbon dioxide in
the first place.
CO2 can be separated from other gases using amine or ammonia
scrubbers, which have been around for decades. The problem is
how to do it efficiently.
When fossil fuel power plants burn coal or gas, four-fifths
of the air that passes through them consists of nitrogen, which
plays little part in the combustion process. Just one fifth is
oxygen, which reacts with the hydrogen in fossil fuels to
produce water and the carbon to produce carbon dioxide.
As a result, the exhaust gases from a typical power plant
contain as little as 3 percent CO2 for a gas-fired plant and 15
percent for a coal-fired one. The rest is mostly nitrogen with
some pollutants. To treat all this gas, scrubbers have to be
very large to separate out the small proportion of CO2 from the
much larger amount of nitrogen.
Scrubbers require a lot of energy. A typical scrubber will
have large fans to blow the gas through the unit; pumps for all
the water; a stripping unit to regenerate the chemical solvents;
and a compressor. The entire process is energy intensive,
especially regenerating the solvent by heating it to between 100
and 140 degrees Celsius in the stripping unit.
Capturing the CO2 from a typical coal-fired power plant
would use 25 percent of the total electrical output from the
plant, something known as the "energy penalty". Given that a
typical coal-fired power plant is only about 33-40 percent
efficient anyway, the loss of a quarter of its net power output
is a major barrier to the commercial application of CCS.
"For a modern (high-efficiency) coal-burning power plant,
CO2 capture using an amine-based scrubber increases the cost of
electricity generation by approximately 40-70 percent while
reducing emissions per kilowatt-hour by about 85 percent," the
Intergovernmental Panel on Climate Change warned almost a decade
ago ("IPCC Special Report on Carbon Capture and Storage" 2005).
IMPROVING THE ECONOMICS
Carbon capture projects are focused on making the process
more efficient and less expensive. One set of options centres on
reducing the amount of nitrogen being processed and increasing
the concentration of CO2
One route is gasifying rather than burning the coal, turning
it into hydrogen and carbon monoxide, which are then used to run
a combined cycle of gas and steam turbines. The byproduct of
this process is a concentrated stream of CO2, which is cheaper
Kemper is the leading example of an integrated gasification
and combined cycle power plant with carbon capture.
A big drawback is that gasifiers are expensive to build and
run, as Kemper has illustrated. And integrating the process so
that the gasifier, gas turbine, steam turbine and CO2 capture
unit all work seamlessly is a major challenge. Kemper's ability
to make it all work as planned has yet to be determined.
Another option is to burn the coal or gas in a nearly pure
stream of oxygen, rather than ordinary air, a process known as
oxyfuel or oxycombustion. But that requires an air separation
unit to produce oxygen in the first place, and separation units
require a lot of energy to run.
In Britain, a consortium of Alstom, Drax,
British Oxygen Company (BOC) and National Grid
plan to build an oxycombustion plant in North Yorkshire equipped
with CCS and have secured financial backing from the British
government and the European Union.
In the United States, the Department of Energy is backing
the FutureGen 2.0 project in Illinois, which would also employ
A different approach is to try to make the power plant more
efficient so that the energy penalty accounts for a smaller
fraction of the usable output.
Super-critical and ultra-supercritical coal-fired power
plants can achieve thermal efficiencies of up to 46 percent,
compared with just 33-39 percent for an ordinary plant. If they
can ever be made to work, advanced ultra-supercritical plants
could push efficiency to 50 percent or more.
Coupling carbon capture with a supercritical or
ultra-supercritical coal-fired power plant would make the costs
much less forbidding.
Even so, CCS plants will be expensive to build and run
compared with today's coal-fired power plants.
But the only way to cut the cost is to start building many
more power plants with CCS and learn how to build and operate
them more efficiently.
(editing by Jane Baird)