Very interesting. I have long felt that sequestering CO2 is a dead end (I think expecting a compressed gas to stay in an artificial geologic formation is Pollyanna), and so some form of carbon recycling is the long term solution. Beginning with that prejudice, I found the article very interesting.
You properly point out that this is energy intensive. Your readers may be interested in just how much energy can be required to recycle CO2. Using the simplest chemistry, making methanol, CH4O, from CO2 requires some hydrogen atoms, initially probably from natural gas CH4. The heat content of natural gas, methane, is 889 KJ/mol, for methanol it is 726 KJ/mol. That is right, this process LOOSES 123 kilo-joules per mole produced. Starting with H2 the process is much better, but making H2 has its own energy issues. All of that said, society is getting a liquid fuel, some value added, and we recycle some carbon, maybe more value added. My bottom line -- recycling carbon will be an expensive, energy consuming alternative that society may decide we want to pursue; but it will be expensive and energy consuming.
David Dixon
Energy Commentator
Presumably some or a lot of this research is being financed directly by the government (as to Sandia) or by grants to private companies. How adequate in terms of lengthy expertise and highly-acknowledged scholarship in their fields, is the staffing of the scientific and engineering panels that will direct the creation of RFPs, and review responses to RFPs? I think everyone has a real stake in the answers to this question.
Public money and private capital in general are at a premium -- we have to bet them on the absolutely best horses and with the best proportionate odds that can be identified. I suggest this is an area where cooperation and shared information ought to be brought in. A panel and administrator might take two RFP responses, and negotiate with the two companies / institutions for a different divvying up of the investigation or project than was first envisioned. An incentives structure to jointly achieve the "win" desired would, of course, be critical.
Peter Cross
Turning CO2 back into hydrocarbon?
Thermodynamics is a useful method of calculating the energy cost of accomplishing work and anything related. To reverse the oxidation of CO2 will unavoidably require more energy than can be obtained from later re-oxidation of the carbon. To further convert the carbon into hydrocarbons will significantly increase the net deficit of energy. These are inescapable facts. No matter the path of reactions and mechanisms used, the least possible energy loss is significant.
If the "reverse oxidation" is part of a process to capture and utilize solar energy, that is a different story for the solar input may possibly result in a net increase in energy in the fuel. However, it is unlikely to achieve an overall net gain. One MUST consider all the energy required to build and maintain the conversion equipment and capture the solar energy, harvest the reaction products, and then refine/convert those materials into usable fuels. After all, all fossil fuel energy results from capture of solar energy.
Keith E. Bowers
Do the math. If sunlight is the source of the energy used to convert the CO2 back into usable products, and you get 100 percent efficiency in that conversion, it will still take something like 7 square miles of solar energy collectors to handle the output from your 500 megawatt plant, and you will have to figure out what to do with the flue gas produced at night when the sun is not shining. If the actual process used is photosynthesis, which is much less efficient, the figure becomes more like 70 square miles.
And if you propose to use some other source of energy, the question is why not put that energy directly into the grid rather than trying to convert the CO2 from another source?
Jeff Gerken
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