Scientists Discover Efficient Process to Turn CO2 into Ethanol | Hacker News Reader

Scientists Discover Efficient Process to Turn CO2 into Ethanol

popularmechanics.com

93 pointsff_68 comments

>This process has several advantages when compared to other methods of converting CO2 into fuel. The reaction uses common materials like copper and carbon, and it converts the CO2 into ethanol, which is already widely used as a fuel.

>Perhaps most importantly, it works at room temperature, which means that it can be started and stopped easily and with little energy cost. This means that this conversion process could be used as temporary energy storage during a lull in renewable energy generation, smoothing out fluctuations in a renewable energy grid.

Is it too much to ask that a science journal report on science in, like, quantitative terms to support a headline? Specifically: What's the efficiency (or how much energy is required per mole)? Estimated overall costs compared to batteries or grain ethanol? Other available chemical processes for capturing CO2, and their efficiency? Not reported. I have no idea what their arbitrary cut-off for "efficient" is, but if they say they want to make it more efficient, it obviously isn't efficient enough. Actual numbers might help to judge.

The abstract of the article includes :

>Herein we report a common element, nanostructured catalyst for the direct electrochemical conversion of CO2 to ethanol with high Faradaic efficiency (63 % at −1.2 V vs RHE) and high selectivity (84 %) that operates in water and at ambient temperature and pressure.

I am not exactly sure how to understand the 63% efficiency but I assume that this is the rate of conversion from electrical to chemical energy.

However the conclusion of the article mentions that :

>The overpotential (which might be lowered with the proper electrolyte, and by separating the hydrogen production to another catalyst) probably precludes economic viability for this catalyst, but the high selectivity for a 12-electron reaction suggests that nanostructured surfaces with multiple reactive sites in close proximity can yield novel reaction mechanisms.

Which sounds much less optimistic that the article's headline.

So basically: this is nice, but there's no reason yet to think that this could be the way we slurp carbon out of the atmosphere and avert climate catastrophe. Right? Drat.

Well, this would at least be a way to recoup the costs of not releasing the carbon emmissions in the first place.

Well we already have a solution for that. We just need to create massive farms on unused land. Plant enough stuff to feed the world populations of humans with large excess and you're going to also plant enough things to scrub co2 out of the atmosphere.

Just curious, but my understanding is that plants are generally carbon neutral. Any CO2 that is taken in by a plant is eventually broken back down and released after the plant dies and is consumed or allowed to decay. Unless you take a significant amount of that plant matter and contain it so that the carbon can't be re-released, at best you get a static reduction of CO2 directly proportional to the increase in live plant volume.

So, no carbon scrubbing while feeding the world, but you could maybe scrub carbon by taking massive amounts of excess crops and burying/sealing them away. Not sure what the cost/efficiency of that would be.

You are correct: To get a net reduction of atmospheric carbon dioxide, you need to increase total plant mass or prevent plants from decomposing/being eaten.

As far as I know, the majority of net oxygen production happens through algae, because they die and sink to the bottom of the ocean, permanently removing carbon from the carbon cycle.

Popular Mechanics isn't a science journal. It's the dead-tree version of clickbait.

It isn't anymore, at least. It used to have much more informative content. And Popular Science may have been a lightweight science journal at one time, but they've both since lost their way.

Exactly. It's a bullshit mag

In Popular Mechanics? Yeah, I think you might be asking for a bit much there.

Efficiency can't be very good because you need to burn ethanol limiting things to ~20-40%. Ethanol is great because it's stable and portable. So, it's just a question of cost.

From the last paragraph (of the paper): "The overpotential ... probably precludes economic viability for this catalyst..." There's a reason this is published where it is (and not Science or Nature or JACS). Popular Mechanics turned this reasonable research into click bait.

Something that annoys me with these articles is that such processes are usually praised as carbon capture at the same time as it is energy storage. Well yes, but not both at the same time. And I really doubt its effectiveness as energy storage in the first place - why would you burn fossil fuels (with a loss), then gather energy with renewables to capture back the CO2 (with a loss) and then use the energy of the ethanol again (again with a loss)? Just store the energy from the renewables in batteries.

Batteries might be more expensive than storing energy in liquid fuels. They have a limited number of charge cycles after all, whereas a vat of Ethanol can be refilled forever. There is also a large number of motors available that can burn Ethanol, but a significantly smaller number of electric vehicles.

1.) electric vehicles are also vastly simpler mechanically, so what you gain with energy storage efficiency in gasoline tanks you loose with their complex motors.

2.) if cheap energy density is the problem they want to solve, then this process at least needs to be compared to using the land to grow plants in order to turn them into ethanol fuel. So a comparison like "wind farm under average conditions + ethanol farming" vs. "wind farm under average conditions + solar under average conditions + CO2 to ethanol process" --> how many Joules of kinetic energy can you produce per square kilometer of land, given the fuel/electricity is used in the currently most efficient motors/batteries?

Many people dislike growing plants for Ethanol production because they compete for arable land that can be used to produce food. Solar and wind farms can be built in places where agriculture is not viable.

well, at the end it's just sunlight, carbon, nitrogen, water, a few minerals and a bunch of chemical reactions. I'm pretty sure you could find a biological process to put anywhere that's also viable for solar farms, including open water. In fact, haven't there been a bunch of papers using algae?

Growing plants for fuel by itself is not a problem. Core issue is that the collective intelligence of us as species does not appear to be higher than yeast.

One idea goes like this: We use nuclear or renewables to power a process to capture extant CO2 to be used as fuel, which turns it back to CO2, which will be recaptures, so run-away processes are reigned in. (I can tell by your comment that you get this.)

Here's the kicker: the energy density of liquid fuels is super-hard to beat. Batteries (and super-capacitors) are getting better, but relatively speaking, on a whole bunch of dimensions, it doesn't get much easier economically, technically or infrastructurally than burning some hydrocarbon. Hopefully sulfur and mercury free.

Tieing "the energy of the future" with "the infrastructure of today" is a very attractive concept that draws a lot of funding from a lot of folks. And researchers, in labs, are working on things that have various limitations of their own, such as "well, gosh, how do you make a copper-iridim-mesh-alloy-hydromister in volume?"

Energy density is great, but for most current usecases I'd argue it's not really necessary. It's neither needed in your home (lots of space to put batteries, is connected to a power line), nor for your daily commute, nor for agriculture, nor for heavy industry (even better power lines), nor for long distance land based transport (trains are just as good and can be electrified easily) which covers the largest energy consumers right there. It is very useful for long distance individual travel by car (so, get a Chevy Volt instead of a Tesla) as well as airplanes, rockets and ocean shipping. If we'd just use the remaining fossil fuel for those purposes it would be pretty easy to be carbon negative.

80/20 rule and all that, I agree. I'm originally from a ranch in Wyoming 65m+ from the nearest grocery store, and those use-cases (ag, distance) are burned into my gut. It makes for some bad intuitive generalized conclusions on this topic from time-to-time.

no sweat, it's a pleasure to communicate with people who are able to think systematically and who can do an actual discussion rather than just shouting from rooftops.

Please, don't mistake me - I'm still opinionated. I just got tired of yelling on the Internet. :-)

On this topic, though, in this context: no need to yell. You make a good point.

I will say that it is devilishly hard. Liquid fuels have some impressive characteristics, that make them an easy "go-to" for almost 100% of our heavy portable-power use-cases, and economic alternatives for those use-cases must almost be developed one-at-a-time. I'm an engineer, not a policy constructivist, so somebody saying "tax it" to bring alternatives to economic parity is vaguely unsatisfying to me.

The economics of it are the main reason why I think batteries are the only way forward we have with current technology. We desperately need a solution that is not only carbon neutral, but cheaper than gasoline power at the same time, using a cost-of-ownership kind of calculation.

If Tesla can deliver on making the required batteries as cheap for the usecases outlined above, it is the most promising way of solving an important part of the very near future crisis of unpaid negative externalities we've been causing in our fossil fuel based economy. Neither fuel cells nor bio fuel (both ways to get back higher energy density) can do this, because both can never beat the economics of fossil fuel when you run the numbers, especially in our post shallow water fracking world.

There is a big caveat however: It won't do any good if we continue to demolish the clean electric energy we got from nuclear and replace it with fossil fuels. Clean energy in total actually slowed down if not reversed because of recent nuclear scares. That includes Germany btw., often cited for their solar/wind efforts, but this was hardly able to replace the nuclear plants they're closing at the same time. This ist the stuff where I'm getting angry at the world... it's like a frog in a slowly boiling pot throwing out his supply of ice cubes because it scared him.

I wonder if it would be useful to harvest excess CO2 from the atmosphere. That way, you're using the existing CO2 as a fuel source.

Am I missing the sarcasm tag?

I don't get the point of this. We already have a self propagating machine that can turn carbon dioxide into a useful carbon substrate that is stable over long time periods, and is a thoroughly proven carbon sequestration technology. It's called a tree.

I do agree wholeheartedly, but the problem with trees is that they die and then they rot releasing all that carbon back into the atmosphere. It's a good start though! It be awesome if we had some sort of technology that sequestered carbon (where it be in the form of CO2 or wood chips, and sorted that carbon in a solid form effectively indefinitely. for trees to be a permanent solution, we would have to convert 50% of the land we use agriculturally to woodlands and and then better utilize the remaining land for food production. /shrug

This is a problem with 'organic' sequestration. However, trees are relatively long lived and take a long time to fully decay. Suitably harvested and treated wood also lasts a long time. Young growing trees sequester the most carbon, so you could have a cycle of logging older trees and replanting shrubs to maximise the sequestration. Some types of bamboo grow incredibly fast, as much as 90cm a day.

I did some back of the envelope calculations. It would take something like 240 billion extra trees to return us to pre-industrial carbon dioxide levels. This sounds like a lot, but it certainly isn't physically impossible. The Amazon has 400 billion trees. Finding suitable land mass for this purpose is an issue. But trees are remarkable, they grow in many inhospitable places. Mangroves for example survive in very difficult conditions with salt water and changing tides. So there is not necessarily an overlap with arable land. There are always more ambitious things you can try, like GMO trees that can grow in the desert, or giant floating forests in the Pacific

Also, if we could stop deforesting the Amazon currently, that would be a good start

The co2 released by a dead tree is captured again by the next tree. So don't look at single trees but at whole forests.

Which means less atmospheric carbon that we actually want to scrub gets captured by that 'next tree'...

Charcoal?

The main question is whether there's a carbon sequestration process which can be industrialized so that it's more effective than planting trees.

Not sure we want to start competing with trees -- what if we get better than them at it? Do trees start dying for lack of CO2?

If we could process enough CO2 to reverse current inputs(i.e. the equivalent of hundreds of billions of tree growth) we could possibly think about scaling up the process to remove all the CO2 from our atmosphere as fast as we can. But we won't run out of CO2 unless we take all the ethanol we're producing with the CO2 and store it, instead of generating energy from it via combustion.

It's not like we couldn't stop if the CO2 levels dropped too far.

Just like we are able to stop now, as the CO2 levels are life-threateningly high, right?

Plants capture about 1% of the incoming sunlight energy into chemical energy. We might be able to come up with a process that is more efficient.

But would the process scale? If it requires substantial amounts of rare earth minerals or very energy intensive manufacturing it will still be unworkable.

>The catalyst’s novelty lies in its nanoscale structure, consisting of copper nanoparticles embedded in carbon spikes. This nano-texturing approach avoids the use of expensive or rare metals such as platinum that limit the economic viability of many catalysts.

How about large scale production of the catalyst? Do we have any idea of how to produce efficiently a "nanoscale structure consisting of copper nanoparticles embedded in carbon spikes" in large quantities?

No idea about this material in specific but a lot of nanoscale stuff is manufactured using photo lithography, basically the same way we make micro conductors since it's a process we understand well and we can scale (just ask Intel.)

It sounds like this material would have good tolerance for minor imperfections (unlike IC) so yield could be really good.

The problem with this one attempt is the energy input required for it to work. That requires major research on the cathode.

>potentially creating a new technology to help avert climate change

>The reaction turns CO2 into ethanol, which could in turn be used to power generators and vehicles.

I am no scientist, my question is this: wouldn't it be a zero sum game at best? You are taking C02 out of the atmosphere, turning it into fuel, which then is used in C02 emitting engines.

Yes it would. But if we can switch from a losing game to a zero sum game, that could still help prevent more climate change in the future.

Right now, the best solution in most cases is probably renewables and batteries. But this could be a useful solution for something like air travel, where batteries are currently too big and heavy to allow for a good zero-carbon approach.

You can convert ethanol into hydrogen (http://www.sciencedirect.com/science/article/pii/S0360319907...), and use that as an (essentially, almost) emission-free fuel.

A zero sum game would be a huge improvement on the status quo.

>I am no scientist, my question is this: wouldn't it be a zero sum game at best? You are taking CO2 out of the atmosphere, turning it into fuel, which then is used in CO2 emitting engines.

Indeed, it's a losing game, not even zero sum. But it's suitable for some scenarios: absorb the renewable production peaks (broad daylight, wind blowing, massive output from solar panels and wind turbines), now you have a reserve for when production is lower than demand. Bonus, this reserve is not just a battery, you can fuel cars with it. Or fill a lake if you really have a lot. whatever.

Well a zero sum game would be pretty awesome, wouldn't it? ..Free fuel etc.

If it were truly zero sum that could help solve the CO2 increase problem.

But it can be better than that. If you had a zero sum technology that evened out fluctuations in other renewables then you're in the realms of CO2 reduction.

You also may have the possibility of more practical sequestration than CO2 though I can think of a few pitfalls with ethanol lakes, especially around Spring Break time.

Another article with more/better content here: https://www.ornl.gov/news/nano-spike-catalysts-convert-carbo...

> I am no scientist, my question is this: wouldn't it be a zero sum game at best?

Worse than zero sum.

that is why I said at best

We can fill the Aral Sea up with vodka.

Except it also generates CO and methane in nontrivial amount (something like 5-10% apparently), one of which is a highly toxic pollutant and the other is a much worse greenhouse gas than CO2.

Methane can be used as fuel, so can be converted back into energy and CO2.

CO is more troublesome as it is converted into ozone in presence of sunlight and hydroxide ions.

I used to read PopMech in the bathroom, but years ago it fell far below even that modest standard. Today, I wouldn't wipe myself with it.

"By using common materials..." Which ones? In what arrangement? How would it scale to the level of atmospheric scrubbing?

They mention copper and carbon later, but fail to mention if that carbon is in the form of nanotubes, or some more easily mass-manufactured form. If you read this article and come out of it with fewer questions than you did going in, you're doing it wrong.

Is there a way to cheaply store ethanol long term and prevent it from turning back into co2?

Barrels.

"Efficient" here does not imply "economic viability," which the original article suggests is out of reach for this technique.

Should click-baity science articles be flagged on HN? I don't know.

So, basically, we can fight Global Warming and get hammered doing so? Now that's what I call a win-win! (Seriously, though, one could do other things with ethanol besides burning it.)

Could we run this process on Venus for terraforming?

We got moonshine, yes we do!

"Great, now we can go back to using coal!" - said coal industry supporters.

This strikes me as a Hail Mary play by the fossil fuel industry to make us think--for a little more profit for them--that it's okay to burn carbon.

I don't buy it.

There isn't actually anything wrong with burning carbon fuels that are derived from atmospheric carbon - it's a net neutral.

Most people in Tennessee don't care about burning carbon so I don't see why they'd need a "hail mary play".

I'd presume that people in Tennessee may still prefer to burn a carbon-based fuel that does not leave behind a toxic ash slurry [0].

[0] https://en.wikipedia.org/wiki/Kingston_Fossil_Plant_coal_fly... http://www.timesfreepress.com/news/local/story/2015/may/10/r...

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