(CNN) -- In the high-stakes game of climate change, the United States and other countries are betting on the idea that technology can make dirty coal cleaner.
For years if not decades, U.S. efforts to develop big coal-fired power plants that push CO2 emissions into the ground instead of spewing them into the atmosphere have stalled.
The situation has gotten so bad that green-tech experts refer to this period of technological development as the "valley of death" for carbon capture and storage technology, or CCS.
But some CCS advocates say that new investments in the emissions-reducing technology will push it off the drawing boards and into reality.
"If we're going to be able to add carbon capture and storage to our toolbox of ways to address climate change, the time to demonstrate it is right now -- or yesterday, maybe," said Sarah Forbes, a senior associate at the World Resources Institute. "CO2 emissions are continuing to rise, and we're seeing impacts of climate change."
A climate bill passed by the U.S. House of Representatives and up for debate in the Senate would provide research money and incentive for companies to work on the technology.
And President Obama last month announced a $1 billion revamp of the country's flagship CCS research project, a near-zero-emissions coal-fired power plant in Illinois called FutureGen.
It's urgent that both efforts succeed, Forbes said.
CCS is not the silver bullet for fighting climate change, but developing technology to make coal greener is necessary, said Kelly Sims Gallagher, director of energy technology innovation policy at Harvard's Belfer Center for Science and International Affairs.
"I don't think that there's any silver bullet," she said. "I think we're going to need to do a little bit of everything as fast as we can in order to adequately address the climate change threat."
Governments are putting much of their money on clean coal tech, though.
U.S. investment in CCS research, development and deployment is expected to double between fiscal years 2009 and 2010, from $3.6 billion to $7.2 billion, according to a report by Gallagher and colleagues.
Obama's stimulus package put about $14 billion, nearly twice that amount, into energy efficiency and renewable energy.
Supporters of CCS say the technology is essential to the climate change fight.
About half of U.S. power comes from coal, and the process of burning coal for electricity accounts for about 80 percent of the country's CO2 emissions from electricity, according to the Energy Information Administration.
Renewable energy sources like wind and solar -- which, together, account for less than 2 percent of U.S. electricity production -- won't be able to ramp up fast enough to replace coal, said Scott Anderson, a senior policy adviser at the Environmental Defense Fund.
"We're not champions of coal at EDF, but we're realists," he said. "Although we see room for a huge expansion of renewable energy and efficiency, in the near term, we don't think that coal is going away. ... We still have a huge existing base of coal plants that will be around, at a minimum, for a number of decades."
CCS technology would reduce emissions by catching CO2 before it's released into the atmosphere, transporting the emissions to a suitable location for underground storage and then injecting the gas into deep geological formations: either in the pores of rocks or in gaps left by oil and natural gas extraction.
The process is complicated, and the emissions can be captured in several ways.
But the two main pieces of that process -- making coal into gas and storing gas in the ground -- have been proved on small scales, Anderson said.
Still, some have criticized the U.S. government for leaning too far on CCS and dirty coal instead of investing more in renewable energy and energy efficiency.
"CCS is a scam," said Daniel Kessler, a spokesman for Greenpeace, an environmental group. "It's being used as a promise to the American people that we can keep burning coal, the world's dirtiest fuel, in perpetuity."
Every dollar spent on CCS could be invested more wisely in renewable energy, he said, adding that carbon capture and storage technology will not be ready soon enough to address the urgency of the climate change crisis.
There also have been questions raised about the long-term safety of pumping carbon dioxide into the Earth for supposedly permanent storage. And the world will be able to store only a limited amount of CO2 underground, Forbes said.
Another problem with CCS is the price. Currently, the price of storing CO2 underground is far higher than the greenhouse gas' price on markets.
There's also no large-scale demonstration of CCS in the world.
In the United States, many are pinning hopes on FutureGen to change that. The research plant was scrapped by the Bush administration because of its high cost but was revived June 12 by the Obama administration as part of its economic stimulus plan.
The project took a blow in late June, however, when two of its private-sector backers, American Electric Power Co. and Southern Co., withdrew.
Because of delays and cost overruns, the project has earned the nickname "NeverGen."
Forbes, of the World Resources Institute, said FutureGen is essential for the United States to prove to itself and the world that there is hope for tackling climate change with technology.
"I feel like we should build it to show that CCS is possible and attainable," she said, adding, "I worry that we may be fostering a history of planning these showcase projects and never building them, and I think that's a waste of resources."
Meanwhile, other nations are moving ahead.
In China, the similarly named GreenGen plant is expected to be completed before FutureGen. Australia has a project called ZeroGen, and several European countries are working on similar technologies.
Some have described the situation as an arms race. The country first to prove that CCS works may be able to export the technology elsewhere.
But Gallagher, of Harvard, said that what's most interesting about the international situation is how well countries are cooperating on CCS technology.
"To some extent, I can see why it's described as a race," she said, "but on the other hand, I think that [with] climate change, we're at a point where we need to work together."