5 ms·
The headline number of 96% (in the original new release) is very misleading. What matters is not the fraction of gaseous carbon that ends up in the fuel (the y
by jlaporte 3y ago
The headline number of 96% (in the original new release) is very misleading.
What matters is not the fraction of gaseous carbon that ends up in the fuel (the yield), it's the energetic efficiency of the process. ie: Nobody will spend 100 Joules of energy to store, say, 1 Joule of energy. The paper says their process has low energy efficiency (low enough they don't seem to want to say the number)[1]:
> ...rather than relying on the CO2(gas) feedstock, bipolar membrane (BPM) electrolyzers with aqueous bicarbonate HCO3−(aq) input were demonstrated (Figure S2b). In principle, the energy-intensive CO2 regeneration process could be circumvented. In practice, however, the BPM induces a large overpotential, causing *low energy efficiency*, and it still suffers from CO2 escape, low FE, low yield, and low operation lifetime. [** emphasis added]
[1] https://www.cell.com/cell-reports-physical-science/fulltext/S2666-3864(23)00485-X https://www.cell.com/cell-reports-physical-science/fulltext/...
- pokstad 3y agoWell not no-one. Maybe if you are on a spaceship and need to replenish your carbon-fuel-cell with your fusion reactor and can’t waste any carbon.
- diroussel 3y agoThat pretty much is the definition of no-one.
- nabakin 3y agoThere have been a few suspect title changes on HN as of late but this would be a good one.
- silisili 3y agoIs it feasible/possible to knowingly do that, and still 'win'? That is, power the process with nuclear or some renewable, not necessarily as a way to get fuel, but a way to get carbon out of the air?
- nomel 3y agoThis seems like far in the future, where the direct use of the nuclear wouldn't prevent more CO2 from being introduced into the atmosphere, than could be removed.
- skaushik92 3y agoAlso, it could be wherever nuclear wouldn’t be permissible otherwise (e.g floating in the middle of the Pacific Ocean extracting CO2 from the atmosphere, away from populations that don’t want it nearby)
- cogman10 3y agoYup, said another way, this would only really make sense if we are producing more energy than we can reasonably use and need to sink it somewhere. However, there are so many sinks for energy that I just doubt CO2 will be a priority any time soon. Desalination, for example, will almost certainly end up being a huge energy sink as the world gets hotter.
- frankus 3y agoI have to wonder if at some point rich eccentrics will start installing CO2 scrubbers in their houses to bring the indoor concentration below 400 ppm.
- Qwertious 3y agoBoth carbon-capture and mass energy-storage are already fairly cheap if the energy is free and you don't care about efficiency. The problem is that free energy is a fantasy for the foreseeable future and thus an energy-inefficient process is a nearly useless process.
- whatever1 3y agoExactly. You need a lot of energy to upgrade CO2 to something with higher enthalpy (fuel). Not sure why so much money has been spent on these thermodynamic dead ends.
- deleted 3y ago[deleted]
- scythe 3y agoThe use case for all of these CO2 reduction methods that seems particularly interesting is if you capture the CO2 inevitably produced as a byproduct of cement production and then convert it into useful plastics. You avoid air capture and you get something that's good for more than just burning.
- cogman10 3y agoWe have so much plastic, I almost wonder if it would be easy enough to burn it, capture the CO2, and convert that into new plastic.
- westurner 3y agohttps://news.ycombinator.com/item?id=37886975 https://news.ycombinator.com/item?id=37886975 : > "Synthesis of Clean Hydrogen Gas [and Graphene] from Waste Plastic at Zero Net Cost" (2023) https://onlinelibrary.wiley.com/doi/10.1002/adma.202306763 https://onlinelibrary.wiley.com/doi/10.1002/adma.202306763
- dharma1 3y agoScalable CCU at source in cement production would be great at getting the 8% or so of global emissions related to cement production down somewhat. Other ways of tackling cement production related emissions are less CO2 producing alternatives to clinker, and even reusing old concrete panels in new construction. There are many rational, viable paths to address this, and other CO2 emission sources - but as long as CO2 emissions don’t have a cost associated, incentives to research, scale and push alternatives forward are lower than to keep doing what we’re doing
- cogman10 3y agoYup. The problem we have is CO2 is mixed into the atmosphere at ~420 ppm. Isolating just the CO2 and concentrating it enough for these processes to work is one of the major energy sinks. This is compounded by the fact that the energy it takes to turn CO2 back into fuel can never be less than the energy released by the fuel.
- elcritch 3y ago> This is compounded by the fact that the energy it takes to turn CO2 back into fuel can never be less than the energy released by the fuel. That doesn’t seem right. Most fossil fuels have multiple CH3 complexes. Even without pulling up the enthalpy of combustion of the molecules, I’d still wager that the 3-H’s combing with O2’s will produce more than the balance of re-capturing the C’s.
- Tcepsa 3y agoThat would violate the conservation of energy. Put simply: The energy that is released from those CH3 complexes has to be put back into them to make them be CH3 complexes again. Otherwise you could, for example, heat your house by burning the same bit of fuel over and over again (using some of the energy released by the combustion to recapture the carbon and rebind it to the hydrogen molecules and leaving the rest as heat to enjoy all through the winter). Alternately, you could generate a tremendous amount of electricity by the same method. Sadly, thermodynamics says, "No."
- elcritch 3y agoAh my mistake. I misread and was thinking in regards to just doing the CO2 capture portion of generating fuel. Yes making new fuel from captured CO2 will take as much or more energy than released from burning it.
- Tcepsa 3y agoOh, yes that makes more sense (I don't know whether it's correct or not, but it is far more plausible!)
- olliej 3y agoThanks for the summary - the headline alone made me immediately question “what is the energy requirement of this” and if they’re unwilling to include it I assume it’s pretty abysmal.
- westurner 3y agoI added the 96% to the title here on HN intentionally, because it says here in the abstract "We convert highly concentrated bicarbonate solution to solid formate fuel with a yield (carbon efficiency) of greater than 96%" Neither MIT Press nor the ScholarlyArticle authors asked or paid me to modify the headline to cite the carbon efficiency. This capability is arguably better than everything else we do for energy; it is 96% carbon efficient. Other stats for comparison of such methods are proposed herein?