This one’s about climate change friends. Why can’t we invent a device that’s fitted to combustion engines (sort of like a catalytic converter) that splits carbon dioxide molecules into their component parts - carbon and oxygen? The result could be a carbon-oxygen molecule and then an oxygen atom, or two oxygen atoms and a carbon atom. I flunked college chemistry, so cut me some slack, but seriously, would something like this be possible?
I hated Chemistry. ISTR that carbon bonds very easily to other molecules. If I do remember correctly, it may not be effective. Also, a carbon-oxygen molecule is called carbon monoxide, which isn’t a great thing to have in your breathing area.
It looks like the short answer is: “it can be done, but it’s energy-intensive.”
Unfortunately, it’s a terrible idea. A lot of the energy from combustion comes from combining carbon and oxygen. If you want to split them, you have to put all that energy back. Partially splitting it means pumping out huge quantities of carbon monoxide, which is completely dangerous.
We already have something that does something like that. We call them “plants”.
Notice that the process involves energy inputs (plus water and nutrients). Plants get that energy from sunlight. So yes, it could happen. The question is just how much it costs, how efficient it would be, and basic engineering questions like that.
I think it is generally considered a better idea to reduce the emissions in the first place, rather than try to convert the emissions at the source.
Regards,
Shodan
You know how when you burn gasoline, you get an output of energy, carbon dioxide, and water?
If you had to use the energy output to turn the carbon dioxide into carbon and oxygen, you wouldn’t have any energy left to run your car.
If you wanted something you could burn that wouldn’t produce any CO2, you could burn hydrogen, or if you wanted only a little CO2 you could burn natural gas, CH4. But it’s not energetically feasible to use the energy you get from burning a fuel to reverse the burning. You’d be worse off than you started before you burned the fuel.
If you have a carbon-neutral energy source you can use to split apart the CO2 molecules you’d be better off just using that energy source directly to power whatever it is you want to power.
:smack:
Say… I wonder if I can patent those?
2,2,4-Trimethylpentane has a heat of combustion (LHV) of 44.310 MJ/kg or 5061.5 kJ/mol. Carbon monoxide is 283.24 kJ/mol. But we’d be making 8 CO for every isooctane we burn. So even at perfect efficiency (second law be damned), you’d be giving up 45% of the combustion energy.
Never mind the matter of creating a bunch of CO.
The tyranny of entropy and Gibbs free energy. If we could produce perpetual energy (which this would require) we wouldn’t have the CO2 problem in the first place.
For energy sources like solar it is far more productive to use that energy for our needs directly vs taking the huge energy losses to use those forms to force chemical reactions to a higher energy state.
Liquid fuels have their place, and we may see some economical CO2-reduction (as in chemical reduction, not lessening) in some deep decarbonized future. But not on-vehicle.
The quick & simple answer is that burning hydrocarbons is an exothermic reaction that releases energy through the oxidation of carbon and hydrogen (and other components they may contain), which produces CO2 and/or CO and H2O, respectively (plus additional byproducts like SO2). Splitting the CO2 or CO would require more energy than the original oxidation produced in the first place.
As a side note, from a climate change perspective the H2O is harmless, even though water vapor is technically a greenhouse gas. That’s because the absolute amount of tropospheric water vapor is almost entirely a function of surface and near-surface temperature. Unlike CO2, adding more water directly doesn’t do anything (add enough, and you just get more rain), but rising global temperatures are increasing the atmosphere’s absolute humidity, creating a feedback effect.
Start with this article about carbon dioxide removal:
Sure, but the the goal we need in the long term is zero net carbon. That means we need to deal with all situations where energy is currently used. So how do you power long distance commercial aviation? Or provide massive seasonal energy storage (weeks bitterly cold weather with little sun and little wind). There are lots of possible technologies and one wants to provide the most economic combination. It may well turn out that carbon dioxide removal will turn out to be one of these technologies.
Rather than breaking apart CO2 into its component elements, is it more feasible to make it into another molecule? For example, could we add some hydrogen and end up with sugar and some leftover oxygen?
Again, you invented plants.
The reason why CO2 is such an inert gas is because it’s pretty much in the lowest possible energy state. Converting it to anything else requires energy input.
It may. The thing about large stationary carbon-capture facilities (rather than vehicle-based) is that they can have access to large amounts of clean (or at least cleaner) energy. This experimental plant makes synthetic hydrocarbon fuel from carbon extracted out of the air, which they calculate has a 70% lower carbon footprint than conventional fossil fuels even though some natural gas is involved in producing it. With completely clean energy (solar, wind, hydro, or nuclear) they figure their fuel would be virtually carbon-neutral.
No, it is effectively equally hard.
Maybe if we were willing to cut gas mileage in half to supply the energy.
The carbon would either come out as a fine, lung destroying mist, or we’d have to filter and scrape.
It should be noted that automobiles actually have a device to do exactly the opposite of the OP. One of the reactions catalytic converters catalyze is the oxidation of CO to CO[sub]2[/sub]. The carbon monoxide is going to oxidize in the atmosphere eventually; catalytic converters just speed that process up.
This company is offering “devices” (more like installations) for that. It can be “fitted to combustion engines”, too, albeit not moving ones.
I’m already saving up for the home model when it comes out. Imagine making your own gasoline out of the electricity from your solar panels. Simple and convenient. The tech is a century old. Soon these will be everywhere…
Carbon Engineering is the same company described in the link I posted in #15, although that article is about their own pilot plant in BC. Some of the basic tech may be old, but there’s a lot of innovation involved in making it cost-effective.