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Mar 11, 2009 04:45 PM | 15
BOSTON (March 11, 2009) -- In most discussions of energy and climate, coal figures prominently as one of the villains. Burning coal is responsible for more than a third of all energy-related U.S. carbon dioxide emissions and 80 percent of those from electricity production. It is also one of the largest contributors of air pollution, acid rain and even toxic environmental mercury. But because coal is so inexpensive and plentiful—at the current rate of domestic demand, the U.S. has enough coal to last for 250 years—nations find it hard to abandon the fuel without risking economic ruin.
The clean-coal technology developed at GreatPoint Energy (with offices in Chicago and Cambridge) might represent a solution to that dilemma, however. CEO Andrew Perlman advanced that argument in his keynote speech here last night at the GoingGreen East conference in Boston. (Here are our previous posts on Going Green East.) GreatPoint Energy was just named overall winner in the GoingGreen East 50 Top Private Companies list, which recognizes exceptional organizations based on clean technology.
(Scientific American is a partner with the AlwaysOn network in presenting the meeting, which is the first East Coast edition of an event held twice before in California.)
Many environmentalists view “clean coal” as a contradiction in terms because of the damage caused by mining and burning it, but GreatPoint Energy’s “hydromethanation” approach might come closest to deserving that description. The key is that it does not burn coal at all: rather, through a three-step catalytic chemical process, it converts coal into natural gas (methane), which burns more cleanly and produces less carbon dioxide than other fossil fuels. Pollutants, including the generated CO2, would be collected for sale or sequestration.
That process is fundamentally different from traditional coal gasification, in which coal reacts with extremely hot, pressurized water and air to yield “syngas,” a flammable mixture of carbon monoxide and hydrogen.
According to Perlman, a single catalyst facilitates all three steps in the hydromethanation process: the steam gasification (which converts the coal feedstock into carbon monoxide and hydrogen gas), the water-gas shift (which turns the carbon monoxide and water into CO2 and hydrogen gas) and the methanation stage (which changes the hydrogen and remaining carbon into methane). All three of these steps can take place in a single reactor vessel, even though the first is highly endothermic (absorbing energy in the form of heat) and the last is highly exothermic (releasing energy in the form of heat); overall, the reaction is thermally neutral, which helps to keep it affordably efficient. The natural gas product contains about 80 percent of the energy in the coal input.
Pollutants in the coal, such as sulfur, ammonia, mercury and other trace metals, can all be scrubbed from the gaseous mixture by conventional technologies, collected and sold as byproducts. Equally important, the CO2 generated can be collected and sequestered efficiently (which is still not the case for CO2 released from burning coal).
Because coalmines are often located near oil fields, building a hydromethanation plant beside a mine could have strategic advantages, Perlman noted. The stream of CO2 byproduct could be sold to oil companies and used to raise the yield from depleted wells. Alternatively, the CO2 might simply be sequestered underground in the oil field.
The GreatPoint Energy team worked for four years to create the hydromethanation process. Amazingly, it might in principle have been discovered two decades ago: Perlman said that Exxon originally identified a catalyst in the 1980s that proved it was possible to crack coal chemically instead of thermally. But that preliminary work had been supported by the Department of Energy, and after the DOE withdrew funding, the work languished until Perlman’s colleagues unearthed it and recommenced development.
GreatPoint Energy has constructed a demonstration plant, the Mayflower Clean Energy Center, in Seekonk, Mass., that has already logged 1,200 hours of online operation. Perlman stated that the company is looking toward commercial production in 2012, with the goal of building, owning and operating its own plants. However, it would be looking to partner with major energy companies in the U.S., Canada, China, India and other key countries.
So, does GreatPoint Energy’s technology prove that clean coal is not necessarily an oxymoron? Mining coal is still environmentally damaging, although according to Perlman, the company is committed to avoiding deals with mining partners engaged in highly destructive practices such as mountaintop removal. And the natural gas produced by the process would eventually be burned and yield CO2—far less CO2 than burning coal for a corresponding amount of energy would release, but still more than solar or wind. But the advantages of finding a better, cleaner way to use coal while even cleaner technologies are still maturing cannot be overstated, this conference makes clear.
Update (posted March 12, 2009): A commenter below (timjwilson) and a Twitter follower (@brookheart) raise a good question: How much CO2 is released overall through GreatPoint's process, and doesn't hydromethanation yield the same amount of CO2 as burning coal? We don't have specific figures on GreatPoint's process, but even if hydromethanation does yield the same amount of CO2, it still seems to have a big advantage over normal coal combustion. Namely, the CO2 produced during the hydromethanation process is all generated in a closed vessel and easily captured for disposal, whereas there is as yet no commercially practical method of efficiently capturing CO2 from burning coal. So the idea is that the process would release less CO2 than would burning coal and capturing it even by an ideal sequestration technology.
Photo of the inside of the Mayflower Hydromethanation Demonstration Plant, in Somerset, Massachusetts, courtesy GreatPoint Energy
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15 Comments
Add CommentOK, I'm confused. I thought that any carbon-based fuel must produce the same amount of CO2 for the same amount of energy output. After all, doesn't the energy come from the chemical reaction that combines the carbon and oxygen to from CO2? So, how can it matter what form the carbon is in (coal or natural gas)?
Reply | Report Abuse | Link to thisHey tim don't pay any attention to the guy behind the curtiuns. You shouldn't
Reply | Report Abuse | Link to thisconfuse yourself with the facts. Senator Obama er president Obama just signed an earmark er not an earmark for these people of $1.3 billion to make this look even more real.
My question was about chemistry, not politics.
Reply | Report Abuse | Link to thisi think that more CO2 is released PER Energy Unit via traditional coal burning, and more energy is generated via burning methane giving off the same amount of CO2. also, there could be some CO2 produced in traditional coal burning processes that is not intentional (meaning not for the sake of generating heat/energy), while the methane production process utilizes all the Carbon in the coal. just my thoughts--that is a good question--i'd like to hear someone who knows more about this give us a definitive answer, with science to back it up
Reply | Report Abuse | Link to thisI took a look at the website referenced in the article and I think I can at least partially answer my own question. The overall reaction is 2C + 2H20 -> CH4 + CO2 (sorry I can't type subscripts here); they claim that this process doesn't use or release any energy (I'm not enough of a chemist to verify that statement). So, 2 moles of C gives you 1 mole of CH4 to sell, plus 1 mole of CO2 that (hopefully!) goes in the ground at the plant. Burning CH4 yields 810 kJ per mole of CO2 output. Burning coal produces (around) 500 kJ per mole of CO2. So yeah, it's better, but only if the CO2 produced at the plant is sequestered. If it's not, then this process actually yields only 810/2 = 405 kJ per mole of CO2 output, which is worse than burning coal. Note that half the C used is wasted (thrown out), so this depends on coal being cheap!
Reply | Report Abuse | Link to thisI've been wondering about this concept of clean coal for awhile. I think you're on track, Tim, but as you say the only way to characterize this hydromethanation as a clean way to generate energy from coal depends on their ability to sequester CO2, and it's not clear at all how they are able to do that and with what efficiency. I've heard of storing it underground, but I'm no more a fan of that than I am of storing nuclear waste underground. It only makes the process cleaner in the sense that it generates more energy per excess CO2 emissions, but that is not "clean" or "green" technology. Not to mention the suggestion that they sell off CO2 byproduct to oil companies to increase their yield--that's exactly what we don't want. Based on the info in this article I am not impressed, and still believe that "clean coal" is only so much propaganda from our dying fossil fuel industry.
Reply | Report Abuse | Link to thisGood job at answering your own question, Tim. Looks like you paid attention in chem. class. My point is. is this valuable technolagy or is it a con job.
Reply | Report Abuse | Link to thisIt's "valuable" technology to increase output from coal plants. It's a "con" by calling it clean coal. Understand?
Reply | Report Abuse | Link to thisThis is in response to the update sciam posted: GreatPoint's process still requires that the CO2 be separated from the CH4 after the reaction. I don't see why that would be easier than the problem of capturing the CO2 at the output of a coal-burning plant. These seem like similar problems to me... And in response to brookheart: I agree, the "clean coal" buzz is clearly being foisted on us by the coal industry, and I wouldn't want to contribute to that cause. I was just trying to understand if there was any element of truth to the claims in this story. My little analysis (based only on nearly-forgotten H.S. chemistry combined with a few facts gleaned from the web) seems to indicate that there is some truth here -- but also a lot of problems being glossed over. This is probably a better idea than corn ethanol, at any rate! Regarding the practicality of CO2 sequesterization, I don't think anybody knows that for sure because it hasn't been studied enough. Perhaps if Bush hadn't killed the FutureGen project, or if the energy companies would put money into actual research rather than just advertising, then we might have some facts around that question. I definitely agree that renewable energy is the most desirable solution, OTOH at this point we can't dismiss approaches that could potentially cut CO2 output by even a small fraction.
Reply | Report Abuse | Link to thisIn short, pgtruspace, like brookheart says: it's not "clean" coal, it's really "slightly less filthy coal"... and only if capture & sequesterization actually works, which is a darned big if.
Reply | Report Abuse | Link to thisAnd one more thing. I just noticed that the sciam update says: "So the idea is that the process would release less CO2 than would burning coal and capturing it even by an ideal sequestration technology". This is clearly false. If I could burn coal and ideally sequester all the CO2, then there would be no CO2 produced. The GreatPoint process cannot accomplish that, unless the consumer of the CH4 also sequesters, which doesn't seem to be the idea.
Reply | Report Abuse | Link to thisCO2 that is produced on the "tail pipe" of a normal fossil fuel plant is "polluted" with ~80% N2. The separation costs energy. Alternatively, the oxygen used for the process could be separated from the air before the reactor, but that also costs energy and money. 50/50 CO2/CH4 may be a bit easier to separate.
Reply | Report Abuse | Link to thisI do not see a discussion of a balance for the other pollutants of coal energy (e.g. sulphur, or radioactive elements that are released upon mining and burning coal)
As the CEO of GreatPoint Energy, I think I can help to clarify some of your questions and concerns. Natural gas is the cleanest and lowest carbon commercial fuel in use today. For all intents and purposes it has zero traditional emissions (sulphur, particulates, mercury, etc) and is so clean we burn it in our homes and kitchens without even needing a vent. It also burns extermely efficiently so you generate less CO2 per unit electricty produced. The net result is that burning natural gas in a modern power plant generates about 60% less greenhouse gas emissions than burning coal and almost 100% less of everything else. This is a big deal since coal is a primary cause not only of global warming, but also of mercury buildup in fish, acid rain, NOx, and asthma. A 60% reduction in greenhouse gas emissions is not perfect, but it is significantly better than burning coal, which is how we get half of our power. And unfortunately renewables cannot be built fast enough or on a big enough scale to make this much of a positive impact nearly as quickly. The EIA anticpates that renewables will only account for 13% of power generation by 2030, even at very aggressive buildouts. Also natural gas is far less expensive than renewables, which is not everything but is important. So what do we do with the carbon after we remove it from the coal and how do we do it?
Reply | Report Abuse | Link to thisAs someone pointed out, the carbon has to go somewhere. The problem is that it is extremely expensive and inefficient to remove the carbon after combustion as it is mixed with large amounts of nitrogen and argon. It is also very difficult to remove all pollutants after combustion. Alternatively, removing the carbon and other bad actors before combustion in an unoxidized, closed, and pressurized
environment is well understood and low cost. In fact, we use the same commercial technology that is used to separate CO2, sulphur, etc. from natural gas well-heads today. All of the traditional pollutants are converted in saleable products (elemental sulfur, ammonia, drywall) and the CO2 comes out fully captured and pressurized into a liquid. We intend to build our plants minemouth and most mines are located in places where CO2 can be geologically sequestered or even sold for enhanced oil recovery. In both of these situations the CO2 is monitored to make sure it is not released. CO2 by the way is non-toxic (hence ventless natural gas fireplaces). Again, nothing is perfect, but I have yet to see a better, faster, cheaper plan to reduce pollutants and global warming emissions.
Thank you, Andrew, for this great clarification.
Reply | Report Abuse | Link to thisCan you elaborate on the way your process deals with the pollutants in coal? Can you concentrate and sell the mercury and other heavy metals? How does the sulphur come out?
Some of us here at ACCCE recently attended the National Energy Technology Laboratory (NETL) conference on carbon capture where listened to researchers, academics and government agencies talk about their projects and findings. We got <a href="http://sn.im/ffpzi">an update on the DOEs R&D program</a>, which aims to deploy commercial CO2 capture that grabs 90 percent of CO2; has 90 percent storage permanence; and has less than a 10 percent increase on the cost of electricity. We also interviewed a professor from Notre Dame <a href="
Reply | Report Abuse | Link to thishttp://sn.im/maginn">about his breakthrough absorption technology</a> for post-combustion carbon dioxide capture.
When we arrived, we werent sure what wed hear. But we left town more optimistic than ever that coal can meet the needs of Americas energy future while simultaneously meeting our nations stringent environmental standards. We posted more thoughts on the NETL carbon capture conference (along with some of our interviews) on the ACCCE blog, <a href="
http://sn.im/bplug">Behind the Plug</a>.