The coal question remains perhaps the largest and most difficult issue in the clean-tech and energy world. Proponents of, wind, and even tout themselves as cleaner and safer alternatives. Environmental activists and many scientists also warn that "clean coal" technologies will only dupe the public into a false sense of security.
On the other hand, coal use continues to climb, particularly in China. Clean coal technologies, along with carbon capture and sequestration, may be the only practical way to adapt to climate change. The profits, moreover, are potentially massive.
"Clean coal is the biggest opportunity" in clean tech, said Stephan Dolezalek, a partner at VantagePoint Venture Partners earlier this year. "If you can solve that problem, it will be bigger than Google."
What are those opportunities? They are mostly on the drawing board now. Here's a primer on the basics of coal:
Q: How much coal is there?
Approximately 998 billion tons of recoverable coal sits underground, according to a 2006 estimate from the International Energy Agency. The U.S. has the most, with 268 billion tons, followed by Russia (173 billion tons), China (126 billion tons) and India (102 billion tons). The four collectively hold 67 percent of the recoverable reserves.
In 2006, 1,438 U.S. mines produced 1.163 billion short tons of coal, according to the U.S. Department of Energy, a 2.8 percent increase from the year before. A short ton is 2,000 pounds.
A ton of coal, depending on the grade, has as much heat energy (25 million BTUs) as 4.5 barrels of oil (PDF). There are probably only left for human consumption, and not all of it can be recovered. Thus, there's more than twice as much coal out there than oil.
How fast is demand growing?
Steadily, but ominously. Coal accounted for 26 percent of energy consumed in 2004 worldwide, according to the U.S. Energy Information Agency, and will grow to 28 percent by 2030. Total energy consumption, however, will be going up a few percentage points a year, so in that same period of time, coal consumption will rise a whopping 74 percent, form 114.4 quadrillion BTUs to 199 quadrillion BTUs.
India and China will account for 72 percent of the increase, but coal consumption is expected to also rise in Russia, South Africa, and the U.S. The U.S. is something of a wild card. With carbon taxes and more alternative energy, the growth could decline, but coal will still be a big part of the energy profile.
"Ninety percent of the fossil fuel reserves in the U.S., India, and China are in coal, and China and India are not going to move from this fuel in the future," said Jeremy Carl, a research fellow in the program for Energy and Sustainable Development at Stanford University. "They are not going to turn off the lights."
China last year erected 90 gigawatts' worth of coal plants last year alone, Carl noted. That's bigger than the electrical grid of the U.K.
Where does it get used?
Primarily in electrical power plants. In the United States, roughly 1.03 billion tons of the 1.1 billion tons of coal consumed (PDF) in 2006 got gobbled up by power plants. Coal accounted for 49 percent of the electricity generated in the U.S. in 2006, a slight decline from 2005 due in part to warmer temperatures. (Nuclear power was second, with about 20.2 percent, while natural gas clocked in at 18.8 percent. Solar and wind barely account for 2.4 percent.)
How does coal affect pollution?
Coal accounted for 39 percent of carbon dioxide emissions in 2004 (behind oil) but is expected to pass oil for the No. 1 spot in 2010, according to the EIA. Even if the United States were to replace every incandescent bulb in the country with compact fluorescents, the benefits would be eradicated by the carbon dioxide from two coal-fired plants over a year, said Ed Mazria, founder of Architecture 2030. The nonprofit encourages builders, suppliers, and architects to move toward making carbon neutral buildings by 2030.
"The only fossil fuel that can fuel global warming is coal. If you stop coal, you stop global warming. End of story," Mazria said.
Other pollutants include nitrogen compounds, sulfur, aluminum, silicon, and even trace amounts of radioactive materials like uranium. China has banned the use of coal burners in homes in cities like Beijing, but coal pollution remains a large health hazard in the country.
Environmental and health problems include acid rain, polluted water systems, stripped forests, and mining hazards. Deaths attributed to coal range from several hundred to several thousand a year, depending on who does the counting and which respiratory deaths get attributed to coal.
How much does it cost?
In the early '70s, natural gas was a cheaper source for generating electricity, but coal surpassed it in 1976 and has been at the bottom ever since. In 2005, generating a million BTUs from coal cost $1.54, compared with $8.20 for natural gas. Coal prices are rising, but so is the cost of everything else. , which generate electricity with heat from the sun, are approaching the cost of natural gas plants.
What are some ideas for cleaning up coal?
Squeeze out the water: CoalTek, which has received funds from Draper Fisher Jurvetson among others, has come up with a way to remove water, sulfur, chlorine, ash, and mercury out of low-grade coal in coal-fired plants. The process thus removes some pollutants and also makes coal more energy intensive, which leads to less coal burned, in turn leading to lower pollutants, said CEO Chris Poirier. It has a 120,000-ton-a-year facility in Kentucky and has plans to expand.
Stanford's Carl points to another potential benefit of CoakTek's process. It makes coal more uniform, which makes it easier to burn in a wider variety of plants. In turn, this can cut down on the transportation required to get coal to plants that can burn it, an indirect carbon dioxide benefit.
"There are a hundred different types of things that are called coal, and they all can't be burned in the same place," Carl said.
Convert it to natural gas:and EnergyQuest, among others, says it can make coal into natural gas, a cleaner fossil fuel, that sells for around $4 per million BTUs, less than the $7 per million BTUs of today. Carbon dioxide produced during the conversion will get .
Conversion technologies tend to "leak" energy--not all of the potential energy that's originally in coal gets turned into electricity, but some analysts who have studied the process say it has promise, particularly as natural gas prices rise.
The company has built a small demo plant in Iowa and has raised more than $100 million to build larger factories. The first will go up in Somerset, Mass.
The federal government, meanwhile, will put $1.5 billion into the FutureGen project, which hopes to build a pollution-free coal plant that will produce power via gasification and hydrogen, and sequester the carbon dioxide on site. The prototype won't be ready, however, for at least another six years.
Better boilers: You don't hear much about Fuel-Tech, but it's come up with an interesting niche (reflected in a fourfold rise in the stock price since 2005). It specializes in boilers, chemicals, and other industrial products that cut down on the amount of nitrogen dioxide, sulfur trioxide, carbon dioxide, and other pollutants that get produced in coal burning. The NOxOut process can cut nitrogen oxides by 25 percent to 50 percent; more than 450 companies have installed it.
Coal to liquids: It could be called the ol' Hans and Franz process. Franz Fischer and Hans Tropsch in the 1920s coined a way to turn coal into a liquid. First the coal is converted to a synthetic gas (basically, the gasification equation for making natural gas) and then converted to a liquid. The high cost of the process, however, has typically made it interesting to people who couldn't get petroleum. The Third Reich used it in World War II to fuel their tanks, and South Africa cranked up production to avoid apartheid trade barriers.
New catalysts and gasifiers, along with rising gas prices, however, are eroding the price premium. Coal companies have said they can make liquid fuel for around $50 a barrel or less. At the same time, U.S. Sens. Jim Bunning (R-Ky.) and Barack Obama (D-Ill.) are pushing for tax credits. (Syntroleum is trying to use Fischer-Tropsch for animal fat and renewable feedstocks.)
Producing and burning this fuel, however, would result in a massive dose of greenhouse gases. In fact, when the whole process is taken into consideration, liquid fuels derived from coal generate more carbon dioxide than just burning coal itself. If a quarter of the world's coal reserves became liquids, it would increase atmospheric greenhouse gases by 300 parts per million, said Alex Farrell, assistant professor in the energy and resources group at U.C. Berkeley. That would more than double the pre-industrial atmospheric concentrations of greenhouse gases. Even with sequestration, gases would rise by 150 parts per million.
Increasing the amount of oil coming from tar sands--which accounts for 3 million barrels of the 80 million barrels consumed a day--would have a similar effect, he added.
"If we do this, I think we are going to have massive increases in the amount of carbons in the atmosphere," he said. If the costs of sequestration and carbon taxes were added, the economic argument also gets substantially weaker.
The car coal latte: Silverado GreenFuel takes low-grade coal, pulverizes it and cooks it under pressure with water until it develops a waxy coating. The waxy coal particles are then reunited with carbon-infused water removed at an earlier part of the process to make a liquid fuel. The end result is a liquid fuel that would sell for $15 a barrel, if it were oil, the company claims.
Silverado has signed a memorandum of understanding with the state of Mississippi to build a $26 million demonstration plant capable of producing the equivalent of about 111,000 barrels of its "Green Fuel" a year. (Roughly 2.5 barrels of Green Fuel equal a barrel of oil.) The plant is due to open in three years.
"Coal is 200 years of dirty. The proof will be in the pudding," said CEO Gary Anselmo. But it's also unproven on a big scale.
Researchers at Louisiana State University, meanwhile, are trying to develop catalysts and processes that would allow energy companies to convert coal into a mix of carbon monoxide and hydrogen, and then convert those gases into ethanol.
What about carbon capture?
Since coal can't disappear overnight, several start-ups and industrial giants have gravitated toward ideas for storing carbon dioxide and other pollutants that come from it. is building a facility in Sugarland, Texas, that will capture the emissions equal to a 125-megawatt generator. The company has developed a process called Electro-Catalytic Oxidation that filters out nitric oxide, sulfur dioxide, mercury, and fine particles from smokestacks. The remaining carbon dioxide is captured by an ammonia-based solution, which is later recovered.
Then there is Skyonic, which has come up with an industrial process called SkyMine that captures 90 percent of the . The baking soda can then be used as a safe material for landfills or sold to industrial buyers.
"It is cleaner than food-grade (baking soda)," said Joe David Jones, Skyonic's CEO.
The big issue for these companies will be cost--capture systems like this will likely cost tens to hundreds of millions--and how difficult it will be to retrofit existing facilities to accommodate this stuff.
How good is carbon capture and sequestration?
No one knows. Ideas range from putting gases into empty, underground chambers and ringing it with (plans are being sketched out for trials in North Africa) to pumping it into porous rock formations (where it will bind with rock) or .
The goal of the Southeast Regional Carbon Sequestration Partnership (SECARB), funded by the National Energy Technology Laboratory of the Department of Energy, is to study carbon-dioxide injection and storage capacity of the Tuscaloosa-Woodbine geologic system that stretches from Texas to Florida. The region has the potential to store more than
Beginning in the fall, SECARB scientists will start to inject a million tons of carbon dioxide a year into a brine reservoir near Natchez, Miss. The large scale of the projects raises questions, though. What about soil contamination, leakage, or earthquakes?
Meanwhile, the clock is ticking.
"We haven't invested in deep research or spent much money in testing out the scenarios. There are a lot of uncertainties," said
"Without carbon capture and sequestration, we are all toast," Lin added.