Environmental and Energy
Paul Voosen, E&E reporter
AACHEN, Germany -- Scientists here in the academic heart of Germany's
coal-mining region are readying what they say is a disruptive model for
the electric utility industry.
Leave the coal deep underground, they say, and forget the death and
expense that come with mining. Instead, put a drilling hat on.
By baking coal buried thousands of feet underground using controlled
fires and gravity's pressure, they say, previously inaccessible seams
can be shifted into easily extracted gas. The gas, pumped up, will fuel
turbines. And when most of the coal is gone, inject carbon dioxide to
fill the void.
It is a simple concept that could reduce construction costs and
eliminate the need to build the extensive pipelines required for CO2
storage at any large scale, said Tomas Fernandez-Steeger, an assistant
professor at Aachen University's Department of Engineering Geology and
Hydrogeology. "We make space," he said, "before we put something in the
space."
The model combines an environmentally problematic but proven
technology, underground coal gasification, with recent experiments
finding coal seams greedy to trap CO2 but lacking in storage. By
filling the hollows created by underground burning with waste CO2,
companies could potentially create coal-fired power plants for the same
price as current carbon-spewing power stations.
The Aachen project is still theoretical. But it is part of a new wave
of startup companies and scientists who have targeted underground coal
gasification (UCG), a century-old idea, as the budget-minded savior to
curbing greenhouse gas emissions.
In one stroke, advocates say, underground gasification could triple
U.S. coal reserves; put an end to dangerous underground and
environmentally degrading surface mining; and provide an affordable way
to collect CO2 emissions for storage. And it can be done without the
technical mishaps and water contamination that have plagued past
efforts.
The reality is that coal use in the developing world will double over
the next few decades, and with its low costs, UCG holds more promise
for reducing emissions than nearly any other option, said John
Thompson, director of the coal transition program at the Clean Air Task
Force, a nonprofit focused on reducing atmospheric pollution.
"It's a breakthrough on cost with carbon capture and storage," Thompson
said.
One recent estimate has placed the cost of UCG plants with CO2 storage
as equal to those of surface coal-fired plants without any capture
technology. Other estimates have found the synthetic gas UCG produces
cheaper than natural gas, even at current depressed levels.
Simply put, it is "coal energy with a natural gas footprint," said
Julio Friedmann, leader of the carbon management program at the U.S.
Energy Department's Lawrence Livermore National Lab.
China, which has had several recent mining tragedies, has embraced
underground gasification. There, it is known as "coal without mining,"
Thompson said.
One large-scale project is producing synthetic gas out of Inner
Mongolia's coal seams. Australia is also operating a large UCG pilot,
and more projects are in the pipeline in Asia. Fitfully, UCG is also
returning to the United States, where it was intensely studied after
the 1970s oil crisis. An Alaskan company, CIRI, has begun the process
of building a 100-megawatt UCG plant in the Cook Inlet. The proposal,
which would use its CO2 for enhanced oil recovery, is undergoing
environmental review.
UCG's profile, should the first projects go smoothly, will rise soon,
Thompson said. "If you couple [UCG] with CCS, it is a very, very
attractive way of getting energy out of coal," he said, while also
allowing the world "to make deep, deep reductions in CO2 by the
midcentury."
A 'controllable' problem
Like the rise of unconventional natural gas, underground gasification
has seen its viability increase in recent years thanks to the leaps
made in drilling technology.
Typical underground coal gasification, top, substitutes rock and column
pressure for expensive man-made reactors. The Aachen proposal would add
a second stage to this system, pumping CO2 back into the gasified coal
seams for storage. Graphic courtesy of CO2Sinus.
Unlike previous efforts, which often focused on coal seams in the
drinking water table -- to sometimes disastrous results -- newer UCG
projects would burn coal 2,000 yards underground or more, far removed
from groundwater supplies. Such coal would never be accessible in
today's mining conditions.
For example, rich deposits of hard coal sit several kilometers
underneath Germany's northern reaches, said Rafig Azzam, the leader of
the Aachen project and a hydrogeology professor. "It wouldn't be
appropriate for normal mining," he said. "But with the drilling
techniques we have now, you can reach that."
And down there, Azzam said, "You have much more coal there than we have
ever mined before."
Underground gasification works remarkably similarly to gasification
reactors, the expensive equipment expected to be at the heart of
next-generation coal plants. But rather than using glossy metal
chambers to create the pressure needed to transmute coal into gas, UCG
substitutes rock, gravity and well-injected oxygen.
Gasification projects rely on two wells, one to carry oxygen down to
the seam and the other to evacuate synthetic gas, which flows through
permeable coal. Since seams are often stacked, the synthetic gas well
can serve multiple deposits, said Thomas Kempka, a scientist at the
German Research Center for Geosciences who collaborates with the Aachen
team.
The importance of site selection cannot be stressed enough, Thompson
said.
"The big challenge with this environmentally is groundwater damage,"
Thompson said. "But if a site is located below the potable water
supply, you really eliminate a lot of the problems that existed in the
1970s."
Those problems were not insignificant. Two UCG projects decades ago in
Wyoming resulted in large amounts of organic contaminants --
carcinogens like benzene -- entering the groundwater. One shallow
project was poorly operated and its site badly chosen, and the other
had drilling problems, according to a report written by Friedmann.
These past environmental problems are sure to haunt UCG, especially in
Europe or the United States. UCG is, after all, burning coal.
There will be something like tar production in the seams, though it
will likely stay isolated, Fernandez-Steeger said. "We are concerned
about pollution," he said.
Modeling pollution paths is the group's main activity, though nearly
everyone, including U.S. EPA, who has researched UCG has found
pollution to be a "controllable" problem, he added. Whether the public
agrees remains to be seen.
Soviet made, American refined
Prior to this recent surge in interest, underground gasification has
truly had a pilgrim's progress across the world, taking more than 100
years to develop into the latest, greatest hope for coal.
The Soviet Union adopted UCG after World War II, seeing it as a way to
free the worker from the burdens of mining. Despite a successful
program, work was abandoned in the 1970s, perhaps due to the discovery
of Siberian natural gas.
Still, the Soviet legacy looms, and a Soviet-era UCG plant, recently
purchased by an Australian energy company, operates to this day in
Uzbekistan.
The United States built off Soviet research during the 1970s oil
crisis, drilling 33 pilot projects by the late 1980s, when plummeting
energy prices killed the research. Belgium and Spain then hosted
projects proving deep coal could be gasified in a safe way.
But there were problems, said Henk Pagnier, a Dutch geologist who
worked on the Belgian project. "The whole issue was how do you control
the fire underground?" he said "And how do you control your gas
quality? Both are not so easy, I can tell you."
Geologists thought they would need a decade or two to get it right,
Pagnier added. But those issues have been solved, Kempka said.
Thanks to advances that originated in the United States, no oxygen can
reach the coal without human intervention, he said. "You have total
control," he said. "Otherwise the process wouldn't work."
The need for maintaining pressure is one reason gasified coal seams
could make ideal CO2 storage sites, Kempka said. UCG requires
impermeable rock to overhang target coal seams -- the same type of
formations necessary for trapping carbon dioxide in more accepted
geological formations like sandstone. "Everything has to be tight," he
said. "You need the perfect sealing caprock, otherwise you can't hold
this pressure."
Burning pores
At first, it seems counterintuitive that coal would hold CO2. But it
was a project led by Pagnier, the Dutch geologist, that inspired the
Aachen group.
Working in Poland several years ago, Pagnier injected CO2 into a coal
seam deep underground. The coal swelled out of eagerness to trap the
gas, halting injection. Coal, it seemed, had a strong affinity for
holding CO2, though little room to do it.
The central idea of the Aachen group, which requires further study, is
that UCG turns the coal left behind into the rough equivalent of
activated carbon, riddled with a vast network of internal pores.
For example, 1 gram of activated carbon contains close to the surface
area of a basketball court. The amount of space created in the coal,
and its propensity to hold CO2, would mean that most seams could hold
all of the CO2 emissions they would have otherwise emitted, Azzam said,
with the coal moving from 2 percent to 30 percent porosity.
[29]Cap rock thickness-[30][photo_ccsp4_01.jpg]
The Aachen scientists would use UCG for the rich, hard coal seams that
sit nearly 2 kilometers beneath areas of northern Germany like
Muenster. Graphic courtesy of CO2Sinus.
There is a great amount of variability in these projections -- the
projections could fall short -- but more certainty is not possible yet,
Kempka said. "Just a pilot is not enough to get all this data," he
said. "We need a really large-scale operation, which right now is not
available."
The upshot of coal-seam storage, rather than the aquifer storage likely
to be pursued by UCG projects in the immediate future, would be having
source and sink at one point, Azzam said. No pipelines to build, he
said. "These types of expenses," he said, "we don't have."
While the Aachen system could be desirable in the long term, it
requires far more research on how CO2 will behave among the gasified
coal and neighboring rocks. The heat, collapse and chemical reactions
that accompany gasfication change coal seams, and real-world tests have
not been conducted on how CO2 might behave in such an environment.
Costs
For the CO2 tests to happen, more UCG projects will have to get under
way. And in the end it is the price of UCG, even when combined with
carbon capture and storage, that will have any success driving the
technology.
One recent estimate from a Canadian firm, Ergo Exergy Technologies
Inc., put the price of developing a UCG plant with CCS below the cost
of a standard coal-fired plant that made no attempts to curb emissions.
That estimate may not hold, but most estimates agree that UCG can be
competitive with natural gas for power generation, even at current
deflated prices, according to Lawrence Livermore's Friedmann.
Investors who have balked at the price of CCS coal-fired plants, which
will cost more than $1 billion in their earliest incarnations, could
find the modular costs of UCG -- say, several hundred million dollars
-- easier to swallow, Thompson added.
"The advantage of this is it [requires] much lower capital," he said.
"You don't have the mining, so you eliminate that part of the supply
chain. You don't have the surface gasifier. ... Basically, you have a
much lower capital cost."
The United States, with the harsh divides between oil and gas firms and
coal miners, is in some ways poorly suited as a launching point for
UCG, Thompson said.
Few domestic firms have expressed interest, though the British oil
company BP PLC has partnered with the Lawrence Livermore National Lab
to develop the technology ([31]Greenwire, July 16, 2007). Much will
depend on the success of CIRI's Alaska project and efforts in Australia
and Canada, Thompson said.
The Energy Department could really usher the technology along by
independently monitoring the cavities created at the CIRI project and
elsewhere for contaminates, to assuage the fears of early adopters, he
added.
"We need to exercise caution in these first sites," Thompson said. "But
this is a potential game changer."
- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
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