Turning Carbon Dioxide Into Fuel - Using Solar Power
    By News Staff | April 18th 2007 12:20 PM | 44 comments | Print | E-mail | Track Comments

    Turning a greenhouse gas into a clean energy fuel is the Holy Grail of energy research. UC San Diego chemists have a prototype they think is an important milestone.

    Their device captures energy from the sun, converts it to electrical energy and "splits" carbon dioxide into carbon monoxide (CO) and oxygen.

    Obviously carbon monoxide in and of itself is not great either but millions of pounds of it are used each year to manufacture chemicals including detergents and plastics. It can also be converted into liquid fuel.

    "The technology to convert carbon monoxide into liquid fuel has been around a long time," said Kubiak. "It was invented in Germany in the 1920s. The U.S. was very interested in the technology during the 1970s energy crisis, but when the energy crisis ended people lost interest. Now things have come full circle because rising fuel prices make it economically competitive to convert CO into fuel."

    The device designed by Kubiak and Sathrum to split carbon dioxide utilizes a semiconductor and two thin layers of catalysts. It splits carbon dioxide to generate carbon monoxide and oxygen in a three-step process. The first step is the capture of solar energy photons by the semiconductor. The second step is the conversion of optical energy into electrical energy by the semiconductor. The third step is the deployment of electrical energy to the catalysts. The catalysts convert carbon dioxide to carbon monoxide on one side of the device and to oxygen on the other side.

    Because electrons are passed around in these reactions, a special type of catalyst that can convert electrical energy to chemical energy is required Researchers in Kubiak's laboratory have created a large molecule with three nickel atoms at its heart that has proven to be an effective catalyst for this process.

    Choosing the right semiconductor is also critical to making carbon dioxide splitting practical say the researchers. Semiconductors have bands of energy to which electrons are confined. Sunlight causes the electrons to leap from one band to the next creating an electrical energy potential The energy difference between the bands—the band gap—determines how much solar energy will be absorbed and how much electrical energy is generated.

    Kubiak and Sathrum initially used a silicon semiconductor to test the merits of their device because silicon is well-studied. However, silicon absorbs in the infrared range and the researchers say it is "too wimpy" to supply enough energy. The conversion of sunlight by silicon supplied about half of the energy needed to split carbon dioxide, and the reaction worked if the researchers supplied the other half of the energy needed.

    They are now building the device using a gallium-phosphide semiconductor. It has twice the band gap of silicon and absorbs more energetic visible light. Therefore, they predict that it will absorb the optimal amount of energy from the sun to drive the catalytic splitting of carbon dioxide.

    "This project brings together many scientific puzzle pieces," said Sathrum. "Quite a bit of work has been done on each piece, but it takes more science to mesh them all together. Bringing all the pieces together is the part of the problem we are focused on."

    Source: University of California - San Diego.


    Hmm that's interesting but what is the by product of using the CO as a fuel? If the net carbon emisions are the same as just releasing the CO2 into the atmosphere in the first place then this idea is a complete waste of time.

    In liquid fuel it's burnt so it's not a 1:1 ratio. If you don't burn CO completely global warming is the least of your problems. :-)

    hello sir,
    can you say one thing that "is co causes less global warming compared to co2"

    I don't understand your request.
    No, it's not a waste, it's Martha Stewart-ism. :-)

    If the solar conversion is efficient enough -- i.e., doesn't cost too much energy or money to build and run -- then it's reusing CO2.

    If all else is equal, then you get a 2 for 1 deal. Imagine turning all the pollutants from a coal plant into a fuel efficiently, and then reusing it. So, then, you are actually putting out 1/2 the CO2, if you simply vent it the second time. Ergo, it's really CO2 recycling. Of course, there are a bunch of "if's" in this hypothetical scenario.

    This is essentially artificial photosynthesis. I believe plants and other organisms, will always do it better -- well, at least for the foreseeable future.

    The upside to this is that you should theoretically have a low maintenance system, if there are no chemicals or moving parts (other than fans and the like).

    On the other hand, more promising research comes from the new algae to biofuel techniques:

    This study says increasing biofuels would increase mortality from air pollution.

    So it may help with the global warming issue but it would be a negative impact on air quality, hospital visits, etc.

    You can find a lot of articles here on biofuels, both pro- and con-.

    The CO is likely converted into a hydrocarbon fuel source such as methane or longer carbon chains as in gasoline. The premise of this conversion is not at all a waste of time considering that it would create a cyclic system that would use current CO2 levels in the atmosphere to generate fuels and avoid the futher release of CO2 from fossil fuels that are not already in the atmosphere. Basically its like recycling the CO2 over and over without increasing the levels that are in the atmosphere because what you release in combustion of the new fuels is what you've taken out and no more. This coupled with the probability that we would cut down or even eliminate using fossil fuels along with the natural conversion of CO2 into organic matter by plants would lead to a decrease in atmospheric CO2 over time.

    You could use the carbon dioxide to be put back into the device and countinue the procces forever. That way the waste material of the device would be used agian to create more carbon and oxygen. That way only oxygen would be released.

    To solve that you would just use the emisions released from this device for more materials that you put in the device so that the only thing you are releasing into the atmosphere is oxygen .If you wanted to you could also use the heat given off by the reaction to boil water to turn turbines so even more power would be created and that way your are gettting as much power out of the device as you can. The only draw back would be the power you needed to cause that reaction would be close to what it would give.That would be something you wopuld have to check.

    We need some alternative fuel cars! There is a country in south America who does NOT use gas! Why are we soo behind in this technological aspect. The government and major automobiles need to step up more!

    I think alternative energy cars are a great idea - I just don't think taxpayers should subsidize them.

    South America does uses biofuel, a mixture of fossil fuels and ethanol. In theory this is a good idea as the ethanol can be made from the fermentation caused by maize by anaerobic respiration. In practice however large amounts are needed, and farming land in Africa vital for food production is now being converted into plants for biofuels. While this does cut down the amount of fossil fuels needed, it increases starvation in third world countries.

    What makes this a good idea is that when CO₂ is split, it can produces CO and O. This is now possible using a enzyme modified catalyst such as titanium oxide. CO provides 25% more energy than CH₄, Methane on combustion, and CO produces CO₂ when split. This is effectively free energy as the solar radiation needed for this is from the visible bandwith, ie. visible light will cause CO₂ to photodissasociate in the prescence of this catalyst.
    Now all they need to do is sort out out the problem of a total vacuum being needed...

    other ideas

    now i'm no scientist, but and idea came to me and i wasn't sure, so i looked for it on google, but had no luck.

    It was creating something using a catalyst, and when carbon dioxide (CO2) is passed through it, it traps or reacts with the catalyst (possibly benzene) and the remaining substance is oxygen, however i wasn't sure if this could be possible, or what metal/non-metal should be used to allow it to only trap or react withe the carbon, and not the oxyen, because if the catalyst does, (CO) carbon monoxide is likely to be produced.

    If you cand tell me about any faults or improvements to my idea, please could you - its for my yr 11 oral presentation, so any comments would be great, thank you.

    You mean something that takes CO2 in and outputs O2, like a plant?

    Seriously, we're working so hard on this problem, and all we really need to do is plant lots of trees and use the wood they produce. The main downside is that it takes lots of land to get a decent rate of carbon reduction, but that's exactly how nature removed the carbon (and trapped in the earth where it eventually became oil/coal/natural gas) in the first place.

    I wish it was as easy as planting more trees but the rate at which we are consuming energy whether it be from oil, natural gas or coal we are easily out pacing natures CO2 to O2 turnover rate and this will not be countered by planting more forests (although it would be good as well) but rather we need to find alternative fuels or recycle the CO2 that we have already produced.

    To whomever said we just need to plant more trees and use wood as fuel...
    Trees take in Co2 but when they are burnt they produce just as much Co2 as they have taken in in their entire life.

    And I can't see how it would produce methane like oil does
    according to telescope evangelist John Dobson lecture friday night.

    Once the CO2 becomes CO it just heeds to be reduced (have more hydrogen added) in order to become either methanol CH3OH or methane CH4, there are many reagents that can accomplish this as well as catalyst, I'm not sure who may have made the statement that it cannot be done but they likely have not done their homework and are making false claims without scientific knowledge to back them up, reduction reactions are quite common and well known they can be found in any first year organic chemistry text book.

    Methane has 20X the warming effect of CO2. How is that an improvement?

    Why don't you folks just get accounts? All of these anonymous messages make it hard to know who is talking.

    Methane may have more of a warming effect however the idea of releasing it into the atmosphere as CH4 would be pointless because that would be the compound's state before combustion meaning once the produced methane is burned to generate electricity or run a vehicle it is then transformed via oxidation (combustion) into water and CO2, which CO2 is once again the beginning of the cycle.

    Honestly there are many ways to produce clean burning fuels (wind, solar, geothermal, tidal) and other ways of producing gas such as methane from landfills or even cow manure but these ideas have been around for a long time and the main reason why they have never been taken seriously is because the oil industry lobbies against the use of alternative fuels so they wont lose their cash cow, some oil is even drilled from publicly owned lands and we still end up paying over 3 bucks a gallon, we wont see a change until Washington is forced to listen to the people and not the influence of the oil industry that takes them on vacations and donates to their campaigns. There is even a concrete skyscraper in Spain that uses mirrors to direct the sunlight that hits the building to stored water in its center for heating and steam generation that then runs a turbine that powers the entire city in which it is located, we have many skyscrapers in America but we don't have one for this more respectable purpose.


    Yup.. the CO2 problem looks like it's almost solved!

    Here's another application of the CO+H synthesis: 

    The production process for BTL starts with grinding and drying of biomass which is then formed into pellets.  Feedstock biomass that may be used in this process include wood, straw, corn, garbage, and sewage-sludge.  The biomass-pellets are diverted into a gas (smouldering gas) and solid fraction (charcoal) in a low temperature gasification process and transformed into a synthetic gas in a second step.  After purification the gas is liquefied in a so called “Fischer–Tropsch” reaction, in which carbon monoxide (CO) and hydrogen (H) react and form carbo-hydrogen chains.

    What's the net energy cost of doing that? I recognize that if the CO2 issue is as critical as we are told today there's more than net energy to think about but it has to be a factor. Even assuming some efficiency gains in the future, is there anything on the horizon makes this a net energy gain?


    I wouldn't ever expect a net energy gain ... however, as a net-reduction system, using solar PV, waste heat (using ThermalPhotoVoltaics) or other co-generation technologies, the balance of actual CO2 could be kept way down, closest to neutral as feasible by cracking the CO2. Whether it be more effective and less costly than CO2 sequestration is is another matter, the idea could be implemented in various ways - all that is needed is energy to crack the CO2 into CO & O2.

    The question is what kind of extra catalytic compounds would be needed, their expense, reuse and/or toxicity (disposal costs). The net energy budget could be kept down using the old WWII tech for certain.

    Whether this particular chain of techniques might be the most feasible or cost-effective might be beside the point, it demonstrates that if we had to start sequestering CO2 coming out of large industrial sources tomorrow, there are inexpensive, tried and tested technologies that are well in the public domain that anyone can implement. 

    net gain or even cost efficiency isn't really the point at the moment

    nothing we are doing is really cost efficient in the begginning as oil gas and food cost sky rocket from research into alternative fuels continues

    so taking co2 and making co and possibly methane may be as expensive as Gas but also take the research cost out of the equasion and also leave a future for more cost effective clean fuels to be created

    the cost of reducing co2 emissions may be a factor but will never equal to the value of life that will be lost if not implemented

    If cost efficiency had not been a factor 'at the moment' we would still be using whale oil, or alcohol. The fact is, any time things like this have been mandated rather than adapted because they were effective, they have flopped.

    Environmentalists and Al Gore insisted ethanol was the proper solution to oil for almost 20 years and then it was mandated, subsidized ... and it's still a flop, but now a really expensive one.

    We won't run out of oil in my lifetime but as the population grows it will become expensive enough that one of these other cost curves crosses it and then we will see change. That does not mean throwing money at one that might not naturally evolve, like we have done with ethanol, is fiscally or scientificially prudent, since that focus would delay other, more worthy projects.

    Hatice Cullingford
    Historically, resource availability in the world (whale oil) or the cost subsidies in the USA (energy) has been the dominant drivers. Let's go back a little to the beginning, the car. Ford envisioned the use of ethanol in his cars. Rockefeller et al thought otherwise, hence the petroleum industry. Subsidies have made a future possible not only in that area but also in nuclear energy, etc. (You have mentioned the ethanol subsidies.) What makes sense is to produce ethanol out of applicable garbage/trash/waste resources instead of letting them produce methane in ever-growing landfills. Savings are more than garbage maintenance but also in water, land, etc. This strategy creates good jobs as well.
    The idea is good but i have some sort of co fule can be used?and again we are using co as fule then what is the end product after burnig the this co fuel?

    There has been research into turning CO into a fuel by way of reduction to an alcohol. Put simply you react it with Hydrogen and you can get methanol or possibly ethanol. However, this requires some catalysis which makes it not so easy to accomplish. There after the resulting alcohol can be combusted as a fuel and as you know if the process is efficient you get CO2 and water as the end product.

    I believe that the use of CO2 as a biofuel could be worthwhile. It would provide a very accessible alternative fuel source, as well as, cut down on our CO2 emissions. If corporations emiting CO2 from smoke stacks and steam vents were to place a CO2 converter over the emissions, then they could use the resulting energy to provide power back to their plant! It may not be a complete replacement, but then again, NO alternative fuel source will be. We will always be forced to rely on multiple sources. However, more attention should be paid to the CO2 Conversion as an alternative fuel source. By the way the use of CO2 would actually IMPROVE air Quality not harm it!

    Pasi Hakkarainen
    Considering the fact, that I've not seen Sun for few weeks, I would not invest on that.
    Well, the south-west states of the U.S. have over 300 sunny days per year. Solar energy might become their most valuable asset once this technology is developed.

    I like the concept you are trying to develop. I am a good chemist and not only can judge the potential of this project but also I could make valuable contributions to it. Please check me out and contact me to discuss what we could accomplish together. You will not be disappointed!

    I actually have an idea very similar to this. However i can't disclose it yet because i have not patented it. mine doesnt use solar power and doesnt emit CO but rather just oxygen. im only 12 years old.

    i too had this idea and had put many questions on yahoo but i didnt even get one right answer for this and if any one can please send me that processss

    it is good idea man iam looking one like this can we use co2 as a fuel for it rather than co because co is that we need a converter but in co2 we dont any instead of burning it we can make that co2 stocked in a bag and use it when we release it the mechanical work has to be conducted.

    i am not sure about the mechanical process but it is my idea i am working on it. i am 25%over
    any one intrested can give suggestions

    it is good idea man iam looking one like this can we use co2 as a fuel for it rather than co because co is that we need a converter but in co2 we dont any instead of burning it we can make that co2 stocked in a bag and use it when we release it the mechanical work has to be conducted.

    i am not sure about the mechanical process but it is my idea i am working on it. i am 25%over
    any one intrested can give suggestions

    You cannot use CO₂ as a fuel. When you burn something you add O. CO₂ can have 4 molecules bonded to it. O takes up 2 so can only have CO₂. The best way is to convert CO₂ into CO using a titanium dioxide catalyst and an enzmye. CO releases more energy than CO₂. What this means is that you are taking a fossil fuel out of the atmosphere using a carbon scrubber, splitting it up, burning it to generate electricty, and producing CO₂, where you started. This means that not as much oil is needed as existing amounts of CO₂ can be used.

    it is very helpful to our earth from the globle woeming. i am very happy
    i hav a dought about what is cost for the conversion and how much yield we get in this conversion?

    My question is:

    If a coal fired power plant can consume 250 - 300 tons of pulverized coal per hour in it's blast furnace, how large of a solar cell array would be required to supply the energy required to split the resulting CO2 into reusable CO?

    Hint: The power output of this sized plant is around 500MWe. The largest photovoltaic plants in the world are producing between 50 and 100MWp.

    You can use the emissions from a car to give something to the device so it can start it's process of splitting carbon dioxide atom. When the splitting starts there will be a great amount of heat given off that could be harnessed to boil water to power a generator to give power to homes, this device, etc. Also when the reaction accurse you can take the by product which is carbon and oxygen and release the oxygen. Then compact the carbon into coal that you could burn to get more carbon dioxide. Also you could capture the heat from that to boil water to power a generator to get energy. Also you could put the emissions from burning the coal bake into the atom splitter to restart the process. Finally before you put the emissions into the splitter you could run the emission smoke into a generator to maximize the power you could get from the splitter device.

    Please comment on my comment so I can refine my conclusion of this device.

    Please use my idea if you want but if you do will you at least give me credit for some of the idea. I would be very grateful for it.Also if this does become a big thing would you cantact me so I could put you down as a refrence for a college application.

    Thi is a great idea, we just have to get people to start using it, if this was put in a car, would the weight or size of the device make it less efficient?