The Obama administration recently announced the start of the Advanced Research Projects Agency -- Energy. This agency is patterned after the Defense Advanced Research Projects Agency (DARPA) that brought us such innovations as the internet. ARPA-E's assignment is not run of the mill R&D but "technological advances in high-risk areas that industry is not likely to pursue independently." ARPA-E is looking to make major leaps forward in technology by undertaking high-risk concepts with potentially high payoff.

ARPA-E issued a funding notice on April 27, 2009 to provide an initial $150 million in stimulus bill funding for research projects, with another $250 million coming later. ARPA-E estimates that most awards will be in the range of $2 million to $5 million. Applicants were asked to submit only an 8-page "concept paper" to outline the technical concept by June 10, 2009. Applicants that make the first cut will be asked to submit final applications.

A project that is fits ARPA-E's high-risk, high-reward criteria is a catalyst that converts carbon monoxide to carbon and oxygen. Carbon dioxide (CO2) is the primary green house gas. One problem with CO2 is that it is a stable compound. Once CO2 is generated, it is difficult to convert it back into carbon and oxygen. There may be ways to convert CO2 back into carbon and oxygen, but that doesn't seem like a very promising avenue of research, not even for ARPA-E.

A more promising compound is carbon monoxide (CO). Carbon monoxide does not appear to be as stable as CO2. Catalysts have been developed to convert carbon monoxide into CO2 -- that is one of the functions of the catalytic converter on cars. Rather than converting carbon monoxide into CO2, the question is whether a catalyst can be developed that will convert carbon monoxide into carbon and oxygen. The ability to convert carbon monoxide into CO2 using a catalyst gives promise to the possibility of converting carbon monoxide into carbon and oxygen using a catalyst.

Carbon monoxide is also promising because it is one of the products of gasification of carbon fuels and water. In a gasifier, water and carbon are converted into hydrogen and carbon monoxide. The resultant mixture of hydrogen and carbon monoxide is called syngas. The chemical reaction is shown in Equation 1 below. The carbon can come from coal, natural gas, oil, wood, municipal waste, crop wastes, or other sources abundant in carbon.

The proposal here is to split the carbon monoxide back into carbon and oxygen. This process is shown in Equation 2. The carbon would be re-used in the reaction. Hydrogen (H2) is produced and is sent to the power plant for power generation or used for transportation. The oxygen (O) shown in Equation 2 would quickly convert to the more stable O2 form and could also be used for power generation.

It may be necessary to take the syngas out of the gasifier and separate the hydrogen and carbon monoxide. The catalytic reaction converting carbon monoxide back into carbon and oxygen would take place in a vessel separate from the gasifier. The carbon would be fed back into the gasifier to continue the process.

An ideal catalyst would be able to work within the gasifier, however. The carbon monoxide would be converted almost instantly and continuously back into carbon and oxygen. This also means that water would be continuously converted into hydrogen and carbon monoxide in the gasifier. Another possible advantage of working in the gasifier is that the elevated temperature and pressure of the gasifier might make it easier to accomplish the catalytic reaction converting carbon monoxide back to carbon and oxygen. Trying to accomplish this catalytic reaction at room temperature may be impossible, but doing it in a gasifier at a temperature of several hundred degrees may be an entirely different story.

Reusing carbon through the catalytic reaction means that the fuel for this type of power plant is water. Hydrogen is split out of water using carbon. If the carbon can be re-used, then water becomes the primary fuel.

Some may doubt that water is a realistic fuel for power plants. Water is already being used for fuel in power plants. Water is a significant part of the fuel used in the syngas of existing IGCC plants, as shown in the IGCC reaction in Equation 1. Water would be almost the entire fuel for IGCC plants that have carbon capture and sequestration. Carbon from coal is not the fuel for IGCC plants that have carbon capture and sequestration. The entire carbon stream is stripped out and never enters the power generation module. Hydrogen is the only fuel that would enter the power generation module (assuming 100% carbon capture). The purpose of the carbon (coal) in an IGCC plant that has carbon capture and sequestration is to hydrogen out of water (again, assuming 100% carbon capture). GE says that water would contribute about 85% of the total hydrogen in a coal-fired IGCC plant and the other 15% would come from the hydrogen in coal. The IGCC manufacturers maintain the fiction that coal is the fuel because power-plant people are more comfortable with coal-fired power plants than with water-fueled power plants. The manufacturers even report heat rates (fuel burn rates) for coal usage, even though coal would never enter the power generation module. It just turns out that the amount of carbon required to split hydrogen out of water in a once through process is about the same amount as would be required if the carbon were burned directly. Coal-fired IGCC power plants with carbon capture and storage are called "clean coal" plants. Clean coal plants are fueled with water.

The existing IGCC approach can be thought of as once-through carbon usage for converting water into hydrogen and carbon monoxide (syngas). The proposal here is to develop a catalyst so that the carbon can be used over and over again rather than only once. Rather than bring millions of tons of coal and producing millions of tons of CO2, it would certainly seem better to try to re-use the carbon. A catalyst would enable the carbon to be re-used.

The only fuel for this system would be water. But this does not mean that the generation costs would be "too cheap to meter," as once was expected of nuclear power. Like nuclear, there would be substantial capital costs. Gasifiers are expensive. The combined cycle power module is also expensive. The plant may also need a module to separate hydrogen and carbon monoxide and a module for the catalytic reaction to convert carbon monoxide back into carbon and oxygen (unless the ideal catalyst could be developed and the catalytic reaction took place in the gasifier).

Gasifier capital costs are probably the second most important factor in determining the economic viability of this approach, after developing a catalyst. If a gasifier costs less than about $1,000 per kilowatt of installed capacity, then this process would likely be highly economic. Gasifiers could be widely added to existing plants and used in new power plants. If gasifiers cost $2,000 to $3,000 per kilowatt of installed capacity, however, then this approach will likely be adopted only slowly and with significant government prodding.

Reduced capital costs for the gasifiers might be possible if gasifier modules were built overseas and shipped to the U.S., which is an approach that has been used to reduce capital costs for many power plant components. These gasifiers would be limited in size due to shipping restrictions. Power plants with barge access might have advantages over plants that had only rail or highway access due to the ability to obtain larger gasifiers with less expensive transportation costs. Multiple gasifiers may be required for larger power plants. Multiple modular gasifiers would be beneficial, however, in that they would increase reliability as one gasifier going down would not take the entire plant down. Multiple gasifiers could also increase capacity factor by incorporating a spare gasifier. Then an individual gasifier module could be taken out for maintenance and the remaining gasifier modules would keep the power plant running at full capacity.

The carbon monoxide catalyst is likely to be expensive. The initial catalyst charge would add to the initial capital costs of the plant. Some catalyst replacement over time will probably be needed, which would add to operations and maintenance (O&M) costs.

There would probably be some fuel costs associated with this type of power plant. The regeneration of the carbon might not be perfect. Some carbon dioxide is created in the gasifier and some of the carbon might slip past the catalyst and be burned in the power generation module. As a rough guess, a plant like this might use 10% to 20% as much fuel as a regular coal-fired or IGCC power plant (which implies 80% to 90% carbon sequestration).

Thus, new carbon monoxide catalytic regenerative power plants are likely to have electric generation costs of the same order of magnitude as today's new power plants given their capital, O&M and fuel costs. The carbon monoxide catalytic regenerative power plant would implicitly sequester carbon, however, while existing plants would not or would do so only with much additional cost. Thus, re-cycling carbon monoxide back to carbon would be an inexpensive approach to reduce greenhouse gas emissions and address global climate change.

While IGCC plants are normally thought of as coal-fired plants, natural gas becomes a viable fuel for base load operation if catalytic regenerative power plants would use only 10% to 20% as much fuel as a conventional power plant. This means that a large fleet of gasification power plants could be quickly created by adding gasifiers to the existing natural gas-fired combined cycle plants. Adding gasifiers to existing plants would also be much less expensive and involve fewer permitting issues than building new power plants from scratch. Roughly 200,000 MW of natural gas-fired combined cycle power plants were built during the boom period of the late 1990s and early 2000s, which amounts to about 20% of the total installed generation capacity in the U.S. This large fleet of under-utilized natural gas-fired combined cycle plants could be converted to carbon monoxide regenerative plants by adding gasifiers (and, if necessary, carbon monoxide separation and regeneration modules). The fuel cost savings would pay for a substation portion of the gasifier capital costs.

Converting a portion of the fleet of existing natural gas-fired combined cycle plants to catalytic regenerative power plants and operating them in base load duty would displace coal-fired generation and reduce large amounts of CO2 emissions. Over time (say 15 to 20 years), this type of conversion might be able to reduce electricity-related CO2 emissions by over 80%. This is the type of game-changing strategy that ARPA-E is targeting.

While the focus of this analysis has been on power generation (because of the author's background in the power industry), catalytic regeneration could also have a significant impact on transportation. The first way to impact transportation would be to have electric and plug-in hybrid vehicles that would be charged over-night by catalytic regeneration power plants. The second way would be to use catalytic regenerative gasifiers to provide hydrogen for hydrogen-powered vehicles. Corner service stations or fleet operation centers could have a natural-gas-fired gasifier that would provide hydrogen. The hydrogen could initially fuel internal combustion engines pending the eventuality of reasonably-priced fuel cells. It would be even better if hydrogen vehicles were plug-in hybrids in order to minimize the use of hydrogen in the vehicle. There are still issues with hydrogen for transportation, such as fuel tanks, but a way to produce modestly-priced hydrogen is the essential first step that can be addressed if a carbon monoxide catalyst can be developed. In this way, the country could move off of imported oil and reduce greenhouse gas emissions from transportation.

This may not work, or the development of a catalyst to convert carbon monoxide into carbon and oxygen could lead to a disruptive technology. The author is not a researcher on catalysts. Those with catalysts backgrounds are encouraged to propose this type of project to ARPA-E, and ARPA-E is encouraged to pursue research projects to investigate and develop catalysts that could convert carbon monoxide to carbon and oxygen.

The opinions expressed here are solely those of the author and do not reflect the position of any other organization.

COMMENTS:

It wouldn't be a single catalyst, of course; it would have to be a system of enzymes and intermediates that operate together to enable sunlight to drive the reaction. An alternative type of photosynthesis, in effect. But that could be quite interesting. And it isn't too much of a breech for someone to label the system, informally, as "a catalyst for reduction of carbon monoxide" to carbon and oxygen.

Roger Arnold
7.6.09

I see that in 1973, Michael Mentzoni published a paper at http://www.iop.org/EJ/abstract/0022-3727/6/4/314 in the abstract of which he discusses using microwaves at a frequency of 9·361 GHz to separate C from O in carbon monoxide... Certainly not much help initially, as generating the microwaves MUST take more energy than available from the H2 out of the process. If only sunlight could be cheaply down-converted to microwaves (or natural sunlight could do the job of the microwaves?)

Len Gould
7.7.09

Let's look at the overall process from a slightly higher altitude:

2 H2O + energy --> 2 H2 + O2

This is accomplished in any number of ways, and basing it around a process which requires one to turn the H2O into steam, run it through a gasifier, hope for some miracle catalyst or process to reverse the formation of CO back such that the O may be recovered - well, it seems to me that it's a long route to a nearby destination.

How about just taking the sunlight to generate electricity for direct consumption, already available at costs below $3/w (on large scales) - OR - if a transportable fuel is required, make H2 or CH4 (using biocarbon, not fossil carbon). I like the methane route, because we already have all the infrastructure for methane in place.

Richard Vesel
7.7.09

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