Scientists Recycle CO2 with Sunlight to Make Fuel

An anonymous reader brings us this article from Wired about a new method to produce fuel with the help of concentrated sunlight and carbon dioxide. The process "reverses" combustion, breaking down the CO2 into carbon monoxide, which is then used as a building block for hydrocarbons. Quoting: "The Sandia team envisions a day when CR5s are installed in large numbers at coal-fired power plants. Each of them could reclaim 45 pounds of carbon dioxide from the air daily and produce enough carbon monoxide to make 2.5 gallons of fuel. Coupling the CR5 with CO2 reclamation and sequestration technology, which several scientists already are pursuing, could make liquid hydrocarbons a renewable fuel."

Comments

Doesn't make sense

[SiliconEntity]

It doesn't make sense to me: first you burn coal, which basically creates energy by oxidizing carbon and creating CO2; then you use solar energy to undo that and turn the CO2 back into CO. Wouldn't it make more sense to make electricity directly from the solar energy and not involve the coal at all? Besides which, if the CO is later used as fuel as they say, then eventually you're going to oxidize that anyway and create the same CO2 you would have in the first place. It seems like a very roundabout way to add solar energy into the mix.

Re:Doesn't make sense

[vakuona]

It enables people to not have to change everything overnight. We have a big investment in carbon based fuel processes, so having away to create hydrocarbons which we then burn, and create CO2, then use solar energy to repeat the process means that hydrocarbons are now just an intermediate step, and that we have a dynamic equilibrium, and can forgo the pain of trying to get rid of all our petrol engines and replace them with fuel cell engines. At least, this won't have to be done overnight, and we actually do stop the increase in greenhouse gases, because we recycle them.

If it works, it is a clever solution.

Re:Doesn't make sense

[Znork]

"Wouldn't it make more sense to make electricity directly from the solar energy and not involve the coal at all?"

To some extent, yes. The main problem is that electricity produced needs to be (almost) instantly consumed. Chemical storage of the energy avoids that problem. As such, there are various forms of chemical energy storage, ranging from batteries, through hydrogen, through ammonia to hydrocarbons, all with their own problems and advantages.

With batteries, the main trouble is they store too little and they (comparatively) rapidly break down.

Fuel cells can run on hydrogen or ammonia, with varying success. Hydrogen is a PITA to store, but perhaps ammonia is a simpler compromise.

Or hydrocarbons. Which have the advantage of being easy to store and fairly stable.

The thing about the energy crisis is there is no lack of energy (in fact, global warming is in essense an excess of it, and provides excesses of it in the form of weather). There's just a huge problem of extracting, transporting and, above all, storing that energy so you can use it when and where you need it.

Renewable not!

[bradbury]

So long as any of the carbon in the cycle is coming from sources currently in the ground or oceans (e.g. coal, oil, natural gas, or methane clathrates). I.e. we are harvesting energy by oxidizing previously reduced carbon -- it is NOT RENEWABLE or SUSTAINABLE!

The only cycles which potentially work over the long term are: (a) solar; (b) fusion reactors; (c) breeder reactors; (d) thorium fuel cycle reactors. That is probably in decreasing order of length of time we could sustain our civilization off of those sources (your opinions may differ).

The coal power plant output conversion of CO2 to liquid fuels simply shifts the problem from an CO2 source one can easily sequester (coal plant smokestacks) to one which is much less easy to sequester (automobile exhausts). You have a fundamental problem here which is when are we going to incorporate the cost of "full sustainability" into our energy costs? That means any carbon you put into the atmosphere you pay to take back out of the atmosphere. Ideally you do more than that to reduce atomospheric CO2 levels back to pre-industrial levels [1], i.e. you are taking more CO2 out of the atmosphere than you are putting into it. We are currently very far from being able to do that.

So long as we continue to live off of the reduced carbon sources (stored solar energy harvested by plants hundreds of millions of years ago) and don't fully pay for them we have a real problem.

Robert

1. Or humanity makes a decision to allow the glaciers and icecaps to melt, the sea levels rise a bit, some islands and low lying areas get flooded, weather patterns to change a bit *and* spends the money necessary to mitigate the negative effects of these processes.