We have excess energy all the time. Many power plants have fixed, unpredictable (e.g. solar/wind), or slow-changing output. When demand is low, these plants often are often producing excess power.
An even more egregious example is gas flaring. The extraction rate is not totally controllable, so there can be more pressure than the plant can handle. Currently, most plants just burn this gas without generating anything, because it would be prohibitively costly (compared to the return) to transport that electricity.
That's wasted energy, not excess energy. If we're going to invest any resources into doing something productive with it, it will be towards doing something profitable. Who's going to invest a ton of money into infrastructure that doesn't pay anything back?
And I don't see how gas flaring has bearing here. If it's not profitable to capture carbon fuel that's right there, in the form a widely traded energy source - why on earth would it be profitable to burn it, to power a generator, to extract CO2 from the air, to turn it back into carbon fuel? You just end up back where you started. Surely it's easier to simply build a plant that can handle higher pressure surges, and ship the gas as-is. But it's not profitable.
As appealing as that narrative is (just utilize waste electricity, its cheap/free!) a plant (making anything, not just this chemistry) that only runs 50% of the time for e.g. nighttime electricity costs twice as much[0] as one that runs all the time.
To the parent re: efficiency and economics, the supplemental info: https://pubs.acs.org/doi/10.1021/jacs.9b07310 (as a rule, free/open access w/ 90% of the utility of a given paper) has the half cell potential at about 0.6V[1] vs RHE, which puts a whole cell potential at about 2V. So count the electrons to convert CO2 to propanol, take Coulomb's constant to get amps, convert to watts, and do the stoichiometry to get kwh/tonne propanol.
This is all ignoring throughput and CAPEX utilization, which is almost certainly poor (but not unexpected at this stage of research).
It is also worth noting that they are using a 3 dimensional, convoluted electrode (carbon cloth) to support their catalyst which may be responsible for the claimed 'trapping of CO'-effect, rather than their specific catalyst. Notably C3's have been observed before in CO2 reduction from less involved catalysts.
tl;dr Probably not very efficient at all, I'm too lazy to do the math. If it was efficient, it would probably still be wildly uneconomic to make propanol via this route.
[0]per unit of production, revenue
[1]Don't forget to account for side product production, per the supplemental information they are making about 600 moles of H2 per mole of propanol (hard to read the chart).
The fact of that matter is that this is something we have to do, both to undo the effects of climate change, and to ensure energy deposits for posterity in case we fuck it all up.
It's non-negotiable. We have to do it. So the economics of it don't matter. We aren't wasting power. We're paying back a very large debt to the planet that we've been accruing for over a century.
Yes they do and saying they don't only hurts efforts with actual chances to succeed. Money isn't some made up thing, it is man-hours and resources, and spending people on feel-good technology keeps them from doing actual good to help the environment.
No, they don't. This isn't "feel-good technology". We're talking about saving the ecosystem and providing for posterity.
There are no ifs, ands or buts about it, we have to return the energy we borrowed and rebind the carbon in our atmosphere. It doesn't matter if thereisnospork doesn't see the utility in this, it doesn't change reality. So again, the energy is not being wasted. It's being used. Just because there isn't a net 0 expenditure doesn't mean it's a stupid idea, that sounds like a Conservative talking point waiting to happen.
No, we are talking about effective ways to save the ecosystem, and this technology is effective in the same way a unicycle is. It works, but only an idiot would propose investing in unicycles over bicycles or scooters or electric cars (etc.) to green up urban transit. Don't be that idiot.
So energy is only meant to be used for powering our frivolous lifestyles but we aren't allowed to store it for later use while simultaneously fixing our atmosphere? Lol okay.
Gas flaring really needs to be brought under control. As does direct methane leakage. Both of those are tremendous contributors to greenhouse cases from pure waste.
I'm starting to think that the solution might be a "drilling/price moratorium" rather than a direct carbon price. Like OPEC but global.
An even more egregious example is gas flaring. The extraction rate is not totally controllable, so there can be more pressure than the plant can handle. Currently, most plants just burn this gas without generating anything, because it would be prohibitively costly (compared to the return) to transport that electricity.