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Launch HN: Prometheus (YC W19) – Remove CO2 from Air and Turn It into Gasoline
1250 points by rmcginnis on May 6, 2019 | hide | past | favorite | 565 comments
Hi HN! I’m Rob, Founder of Prometheus. We’re removing CO2 from the air and turning it gasoline, diesel, and jet fuel. Since we use zero-carbon electricity from sources like solar and wind to make our fuel, there are no net CO2 emissions when you use it.

An article about us came up on HN recently and people seemed interested (https://news.ycombinator.com/item?id=19792412), so we thought it would be good to try to answer some of the questions we saw there and try to dive in some more to any questions that follow!

The only inputs to make the fuel are CO2 and water (both from the air) and electricity. The only outputs are fuel and oxygen. One way to think about it is that making fuel is reverse combustion. The process isn’t super efficient (we expect 50-60% overall efficiency at maturity), but it turns out that doesn’t matter as long as the electricity is zero carbon and low cost. If the cost of our equipment is also low, then we believe we can not only make zero carbon fuel, but actually compete on price with fossil fuel.

We’re not the first to make fuel from the air - in fact Google, Audi, Carbon Engineering, Global Thermostat, Climeworks, and labs at universities and national labs have all done it before us. What no one has been able to do so far is do it at a low enough cost to compete with fossil fuel.

The thing that’s new about what we’re doing is that we have gotten rid of all the thermal processes normally used, and instead use a process that uses only electricity (no natural gas, etc) and does it at room temperature. This is a big deal for both capital cost and for being truly carbon zero. We can use inexpensive materials, which keeps our cost low, and can start up and shut down quickly, which allows us to run intermittently, matching the intermittent nature of many renewable energy sources. We can also only run when the power is at the price we want.

Digging in to some more details, we absorb CO2 and water vapor from the air into an aqueous electrolyte. We then react the CO2 in the water with a copper catalyst to directly make alcohols like ethanol, butanol, propanol, etc. Both of these things have been done by many others and the science is known. Normally at this point one would have to use a thermal process (distillation) to get the fuel out of the water, and this is expensive and makes the economics really hard to get right. We don’t have to do this step thermally though, because we have a carbon nanotube membrane that replaces it, extracting the alcohols from water in a single step at room temperature. This makes a huge difference in cost. The last step is that we up-convert the alcohols to gasoline, diesel, and jet fuel. This last step is also well known and we can actually buy this step from others.

The carbon nanotube membrane that makes this all work is the product of 6 years at my previous startup, Mattershift. I was developing it for desalination and water purification. About 3 years ago I realized it could do this job, but it wasn’t clear that a startup could raise money for such an ambitious effort, especially one linked to a political issue (unfortunately) like climate change. When I saw the YC request for startups in carbon removal, I knew that the timing was right, and I founded Prometheus to do it.

Please let me know if you have more questions or feedback. I’ll do my best to answer any questions, but please excuse if I’m not able to go too far into details like our piping and instrumentation design, or other really specific things we wouldn’t want to help competitors with.


A few questions from a chemistry major

1. why extract from the air when you can just put a device on the smokestack of an existing coal or natural gas plant? The higher CO2 density of the effluent will make things more efficient. 2. Your key innovation isn't the part where you pull CO2 out of the air; it's the nanotube-based reverse osmosis process for separating ethanol from water. This process could just as easily be applied to other fields. For example, bioethanol production similarly requires a very expensive distillation step to extract pure ethanol from the fermentation medium. Making that step more efficient would be much simpler than reinventing the entire supply chain around carbon dioxide extraction and subsequent reduction to ethanol.

> why extract from the air when you can just put a device on the smokestack of an existing coal or natural gas plant?

So you have spare available energy you can use to run the converter, and you also have a demand for energy that you're satisfying using a hydrocarbon powered generator. Why not reduce your hydrocarbon use in the first place, by substituting in the energy you were going to use in the converter? That seems to me to be an awful lot more efficient.

IMHO this technology really comes into it's own when you have available spare renewable energy, and want to find a way to store it in a dense, portable and easily reusable form. I think it's best thought of as a competitor to battery storage, but with the added benefit of extracting atmospheric CO2.

"why extract from the air when you can just put a device on the smokestack of an existing coal or natural gas plant? "

The process uses clean electricity to reverse the CO2. I suspect here we have a timing issue. When the sun shines, the gas plant will be idle, and that's when the spare electricity is available is used to reverse the process.

And the physical position - the gas plant is likely to be where the sun shines less.

As ever we have a storage buffer problem.

That storage buffer problem leads to one possibility. (excuse my english!)

I think there are really two major business cases for Prometheus. One is in earning back carbon offsets (reducing net CO2 production from a polluting source) while producing a valuable byproduct. The other is as a way to ethically and profitably use local excess energy to create that same byproduct.

I think it makes sense for the Prometheus apparatus to be paired with electrical load balancers (aka industrial battery banks) built for renewable energy. Allow me to expand:

1. Renewable sources like solar collect electric energy on an inconsistent basis.

2. Depending on local energy demands (a factory, the neighboring town, etc.), the grid will either use or store the electric energy. Storage for large businesses and nations nowadays occurs through industrial battery banks (i.e. BYD's).

3. Usually, those who use battery capacity battery stored energy can be used before conditions are right for collection again. However, if local energy demands less than can be stored and used in the next collection cycle, that "buffered" energy is wasted.

This is a prime use for that wasted energy. I imagine it only becomes viable at scale. And there is one other issue to address...

Companies like BYD who do national-scale renewable grid storage usually undershoot the amount of battery storage they provide because over-storing is costly (the energy isn't used or is distributed less efficiently and the batteries incur both capital, installation, and maintenance costs).

If Prometheus reaches cost effectiveness, a renewables/storage company could start over-providing energy generation and battery storage and pair it with CO2 factoring to a) reduce costs associated with wasted energy b) earn carbon offsets for large companies and c) create valuable byproducts.

The co2 could be stored underground? I guess that could deal with the timing issue at least?

You're mostly right, in that a timing issue could be resolved through a temporary storage unit, though probably wouldn't have to put it underground.

Likewise, batteries/capacitors/whatever would probably be set up on the electricity. A plant design would seem to want to control the flow rates of both.

Overall, the parent comment's unlikely to be correct in its speculation that the reason for open-air capture is related to timing issues.

You'd have to separate pump and store it, when electricity is expensive.

I suspect the advantage of this system is that is doesn't need pure co2 to work

And if you were storing CO2 I suspect the first question is how do we liquify it. So the advantage fades away.

edit: You'd probably want to store the electricity on-site instead for this. At least if there's no CO2 to consume you can be in the electricity storage business.

We want to replace fossil fuels with renewable fuels, at the largest possible scale, over 300 billion gallons of fuel per year. Point sources of CO2 and biofuels can't scale to this level.

But first you have to cross the valley of death. Elsewhere you refer to having to limit capital spending, wouldn't getting CO2 from a 3rd party instead of building a massive air capture facility do that? Everything I've seen says that its cheaper to capture from a point source than from the atmosphere, why would you make your costs higher than they need to be? You can of course build air capture down the road but I'd guess that you'd want to get off the ground as easily as possible.

Yes, we're actually agnostic on CO2 source. To get to scale we'll need to use CO2 from direct air capture, but we could by the collection from someone else.

I can completely see the logic. If this only works for point sources it may not scale sufficiently to be viable long term. So that capability needs to be proved out early in order to demonstrate it's long term value to investors.

how many point sources do you need to make atmospheric extraction viable? i'm thinking it's like a million

> 1. why extract from the air when you can just put a device on the smokestack of an existing coal or natural gas plant? The higher CO2 density of the effluent will make things more efficient.

That was my big question, too. Asked and got a response here:


But then, why to use solar energy to convert CO2 into fuel when you can convert the solar energy into electricity directly and remove the need for the fossil fuel based power plants?

This question is probably answered literally more than a hundred times in this comments section!

We have a huge fleet of cars, trucks, planes and ships that are all very carbon-positive. We also have a huge amount of existing infrastructure for delivering fuel to these things.

Sure, cars and trucks could go electric, but large airliners probably never can, and it's difficult for ships. But even for cars it will take decades to fully transition to electric. An economically viable, carbon neutral fuel that could be brought to market and scaled up quickly would be a huge win for the transition. Especially if it's cleaner burning (no/very low sulfur, aromatics etc.).

The unit economics around this are by no means perfect but the BIG point here that should probably be in all caps is that fact that the thermal process is displaced by the use of electricity. We could argue on what is used to generate said electricity, but that is beside the point since this innovation opens up many more possibilities than are stated here. We could also argue about the comparative cost of produced energy vs conventional fossil, but lets not forget that those same arguments were used during the early commercialization of solar energy.

In my opinion, the conversion process should stop at the creation of alcohols which can then be used as additives in E-85 gasoline for example, or in other chemical applications that have a less direct and immediate carbon impact on the environment.

I also think this innovation has a larger impact if it were used to bring existing generators of emissions closer to being carbon neutral. It also reduces the burden of being cost efficient on Day 1 since the carbon intensity of large emission generators is already a cost they'd be glad to mitigate or get rid of (esp if the process generates a valuable by-product). Imagine power plant stack exhausts channeled through this technology, or if were miniaturized and made a standard part of every fossil fuel combustion engine...we could all be buying gasoline and selling ethanol before you can say Prometheus.

>I also think this innovation has a larger impact if it were used to bring existing generators of emissions closer to being carbon neutral. It also reduces the burden of being cost efficient on Day 1 since the carbon intensity of large emission generators is already a cost they'd be glad to mitigate or get rid of

I can't follow this argument. What exactly are you proposing? His process still has a ~50% efficiency-loss, so even using all energy generated from fossil generators would only mitigate a maximum of 50% emissions (even ignoring all other efficiency losses here). And that obviously would be stupid. That energy is generated for a purpose.

The whole point of his process is to use solar/renewable/carbonfree energy to reverse carbon emissions. It would always be more efficient to just use less electricity/energy in other situations.

In its base form this technology is mining a resource - carbon. Would you rather mine in areas of low or high atmospheric intensity? Would you rather capture it where you fund the whole operation yourself, or where someone else (existing polluters) is willing to pay you to take it out of the air because there is a regulatory cost to them putting said carbon in the air?

Maybe i should have been clearer. I wasn't suggesting using the energy from a fossil plant to power this, but co-locating it to areas where there might be more environmental and cost incentives to do so.

As i said in my earlier post, arguments on cost/efficiency are beside the point. The huge deal here is the use of electricity (of any form including all the advances to come in the future...solar cells in space, nuclear fusion etc), to remove CO2 from the atmosphere. One can now envision a future (regardless of cost or efficiency today) where we can sustainably keep the earth whole.

I imagine the only places you can realistic install this technology is next to hydro dams/large wind farms where you can get very cheap electricity at certain times, and there are likely no hydrocarbon plants in these areas.

I'm not sure it's reasonable to install this in a coal plant and try to source cheap solar from hundreds of miles away to power it (if that were possible, why would the coal plant be active? It can't compete with the energy you're using to scrub it)

So we bleed energy off a hydrocarbon fueled generator system that produces CO2, to power a machine for capturing CO2 to create hydrocarbon fuels. That seems a little pointless.

The advantage of this system is you can use excess renewable energy sources to mitigate hydrocarbon energy generators. If you are running a hydrocarbon powered system, don't use energy to power this capture system at the same time. That's madness. Better to use that energy to reduce your use of hydrocarbons in the first place.

That is not what I was suggesting.

You said:

>Imagine power plant stack exhausts channeled through this technology

What's I'm saying is, if you have spare energy available to power the converter, you're better off reducing the hydrocarbon power plant output and replacing that output with your 'spare' energy supply. Doing so would be dramatically more efficient.

The only case this doesn't apply is if there is no way to substitute your spare available energy for the output of the hydrocarbon plant, but I can't think of such a situation, at industrial scale, off the top of my head.

Ok, I understand where you're coming from, and its a logical argument. However, a lot of fossil generators (esp coal) are baseload plants that stay running for system reliability. They might stay running during off-peak hours when the output is barely needed, just to ensure availability during on-peak hours. In those cases, you can't tweak output to match variable renewable energy output.

Thermal heat is low grade compared to electricity.

If this new process is working at scale, it has huge potential. I just wonder whether this process is covered by a patent or not. Might be a huge risk if not. If so, I wouldn't be surprised when the new process is named after the inventor. Much like the Haber-Bosch process.

Or we could just run engines on alcohol.

Jet fuel has about double the energy density of ethanol. Running planes on ethanol would severely curtail their range.

I'm skeptical, but fascinated by what you're doing.

It sounds like all of the steps of your process are known, except:

1. CO2 fixation uses only electricity - no natural gas or other fossil fuels. It works at room temperature.

2. Distillation of the immediate products (alcohols) is not necessary. A carbon nanotube membrane solves the problem at room temperature through reverse osmosis.


If so, then why target fuels rather than alcohol production directly? Burning gasoline puts the CO2 right back into the atmosphere, which seems like a half measure.

Why not focus on delivering CO2-negative organic feedstocks instead and possibly tap into the carbon credits market?

Edit: another question. How much flexibility/control does your process give over the kinds of alcohols you produce? For example, can you select for long chain alcohols over short? Saturated vs. unsaturated? Cyclic vs acyclic? Aromatic? Mono- vs oligohydroxylated hydrocarbons. Primary, secondary, tertiary? etc.

We could use the alcohols as fuels directly (in flex fuel vehicles), but this wouldn't address the much larger market for gasoline. It's a simple and inexpensive upgrade, so makes sense to do it. We will definitely take advantage of carbon credits, tax incentives, etc too!

If the alcohol upgrade to gasoline makes sense technically and economically for you, why is it not commonly done with (presumably much cheaper and extant in great volume) industrial alcohol today?

Actors are not necessarily as rational as Econ 101 would have us believe. Incomplete information, misinformation and advertisement distort the market. As well as monopolistic practices.

A lot of conspiracy theories are paranoid, but the propaganda machine of the oil industry is very real and managed to incite a lot of economically counter-productive policies.

He said "inexpensive", not "economical". The whole process isn't economical yet. Perhaps conversion is more economical with their particlar sorts of alcohol though.

Understood, although eventually it has to become "economical" or it doesn't fly.

My point was, you can view the alcohols as a feedstock for the gasoline production, and given that, you might just stream in large quantities of already-produced and cheap grain ethanol etc. from Indiana.

It is more likely that polluting methods (net non-zero) will be forced to become uneconomical.

Ethanol mixed fuel is common in a lot of places.

I might have misunderstood your point, but I believe alcohol is commonly used as a fuel in Brazil, where most cars are capable of using it directly.

Organic feedstocks (non-fuel), although smaller isn't exactly a tiny market. Depending on how much control you have over the fixation process you might be able to tap into some high-value alcohol markets. That's the main reason I added the follow-up to the original questions.

In other words, the flow of material would look like:

CO2 -> polymers, drugs, and other useful solid materials

There would be no [product] -> CO2 step at the end. It cuts out the re-release of CO2 and eliminates a dependence on petroleum.

I believe that as long as we have a huge worldwide oil / diesel / gasoline infrastructure in place, from transport to refining to distribution to combustion, it makes a lot of sense to build reasonably-efficient carbon-neutral mechanisms to plug into that infrastructure.

In other words, for the next handful of decades, the worldwide fleet of cars, trucks, generators, boats, etc. are going to be burning carbon that comes from somewhere. Products like this provide a carbon-neutral means of supplying that demand.

It's like working on a huge existing codebase, but at much larger scale, and with geopolitics. People are working on rebuilding it all from scratch, but iterating within the existing infrastructure could also deliver huge wins.

And, if we somehow found ourselves in a world in which carbon-neutral petrochemicals were the norm, well, we can always generate a surplus and sequester that surplus, right?

If I am allowed to daydream freely, a huge fusion reactor with a gasoline pipeline flowing from it, is (in my mind) a beautiful thing.

Ultimately anything we make now with petroleum feedstocks could be made from CO2 mined from the air instead. Gasoline and other transportation fuels is a logical first step, but we don't need to stop there. Agreed!

I think one has to look at this from a business minded point of view. One way of doing that is going for what could be an immense market.

Hi Rob. I'm CTO of a company that generates electricity from waste heat at industrial facilities. Pipeline compressor stations often generate 35MWth+ in waste heat, which we can use at about 20% efficiency to generate electricity.

Many pipeline compressor stations are not anywhere close to distribution lines so just merrily pump this heat up their stack. Especially with new pipelines where companies are battling (legitimate) environmental concerns, there is no reason they would not install your tech, powered by a heat recovery system, on every single proposed compressor station on the line.

We have actually modeled it with negative operating costs (using technology from one of your competitors) and think we could get the pipeline companies or the government (we're in Canada) to pay for it even in the face of bad economics. If your system is a step change in effectiveness from those systems, it could be a game-changer in this market.

Let me know if you'd like to explore this a bit. My email is in my profile.

> Pipeline compressor stations often generate 35MWth+ in waste heat, which we can use at about 20% efficiency to generate electricity.

Can the waste heat be used for distillation instead? To heat up the fuel/water mix to separate the two cleanly?

It would seem to me that the future of "waste heat" is to actually utilize the heat, instead of powering a relatively inefficient heat-engine. Perhaps instead of 20% efficiency, you get closer to 100% efficiency since all you'd be doing is running the fuel-water mix to the heat-source to evaporate the fuel out (I presume anyway, I'm no chemist)

Your instincts are excellent: using heat directly is always and everywhere better than turning it into a fungible commodity like electricity, only to convert that electrical energy to some other form later. (Creating liquid fuel is no different in this regard.)

The reality is that there's almost never a practical direct use of the heat at the facility where it is created. It is too low quality for the onsite processes. Economizers and Regenerators are two common pieces of equipment that suck out what heat can be used - what's left is too low temperature for whatever they're making onsite.

Sometimes there's an opportunity to broker a deal between two adjacent facilities, where one can use the heat that the other considers waste. But those are rare.

Happy to talk about this until you wished you'd never asked. Feel free to email.

re: waste heat, I've been thinking forever that someone must capture this. I've generally assumed the economics don't work out or no one has cracked it outside of scenarios like regenerative braking. We waste so much energy that we could capture and put back to use.

Regen braking doesn’t use waste heat. It converts mechanical energy back to electrical.

And in so doing, reduces waste heat due to friction, which is likely what the parent commenter meant.

Some say it doubles the lifespan of brake pads.

> We waste so much energy that we could capture and put back to use.

The biggest current waste of energy is residential heating. We take high quality energy in the form of natural gas and fuel oil and use it to produce low quality heat.

Co-gen systems burn fuel to generate electricity and use the waste heat for heating buildings.

Something like 55-60% of the thermal energy created by burning fossil fuels is currently wasted.

It’s kind of ironic that cars and power plants work hard on getting rid of that energy.

Modern power plants work hard at getting every last bit of that energy before it escapes. Current Combined Cycle plants, that generate steam from the exhaust of a gas turbine, are currently getting over 60% efficiency.

One must be a bit careful there. 60% efficiency based on the LOWER heating value of natural gas. That ignores the heat available from condensing the water of combustion. Coal plants typically use the higher heating value when computing efficiency, which does reflect the latent heat of vaporization of that water.

I know ICE engines use turbochargers to "recapture" the energy. Exhaust can be used to power the intake fan, which can increase air-pressure available to the engine's intake.

Turbocharged engined still need a ton of cooling but yes I think they are more efficient overall .

You could certainly do this, using distillation or the thermal processes Carbon Engineering is doing, and it could be worth pursuing, from a business opportunity perspective. We're focused on an implementation that can scale to >300 B gallons per year, so are pursuing an electricity only path.

Thanks. If the scale is lacking, I get it. But to be clear, I’m talking about a series of 10MW electrical power plants each with 95% capacity factor.

Using your number downthread of 60kW/gallon, that translates to about 1.4 million gallons per station per annum - even with dozens of stations per line, a couple of orders of magnitude less than your target opportunity of 300B gallons+.

Would you be willing to expand a bit on your opportunity target of 300B+ gallons/year? My understanding is that the US production of gasoline in 2018 was about 142 billion gallons, so I certainly misunderstand something.

To put this number in perspective: 300B gallons of gasoline is an amount of carbon equivalent to all of the CO2 in the air above all of the earth's land area, up to an altitude of about 80 feet.

If you can pull that off, I'll be impressed; but it seems like a very aggressive target.

It's about half of global annual gasoline consumption. It's going to be hard, but worth it to try.

I don't have anything new to add, other than to say - this is a very well written startup pitch. I'm in awe of how clearly you've laid out the opportunity.

The only thing I have to add here is that a random stranger from the internet is rooting for you. This post sounds awesome and has all the makings of a classic American success story. Good luck!

It's almost surreal reading through the comments in this thread. I'm so used to the internet being a constant wave of negativity and hatred of everyone, especially in recent years.

This thread is such a nice break from that, feels so refreshing. I don't know anything about this process but I hope it works out.

I concur. This is really great news about a great product. I only have supportive feedback and no complaints. It carbon neutral and it’s competitive. It’s one of the pieces to the puzzle solving pollution and GHGs in the atmosphere.

I hope this startup does well and can get this tech widespread across developed and developing countries. It’ll mean we can be carbon efficient with our existing ICE cars.


If you really think the underlying economic problem with electrochemical CO2 to alcohols as fuel is the separation at the end you are in for a world of (economic) hurt. Not that improving the aforementioned separation isn't useful or valuable, its just not the lynch pin.

Take a really hard look at your economics, in particular throughput and capital amortization (which scales proportionally to uptime!). Good comparison industries are chlor-alkali, fuel cell, and water-electrolyzer. Aqueous Cu catalyzed CO2 reduction - even if you are best in class for FY and efficiency and durability - have atrocious current densities, diffusion limited, by the standards of anything considered commercializeable.

The separation itself is not the only thing that makes the economics favorable. It's important that changing the separation makes the process electricity only overall, and this is a big deal. We can run intermittently, allowing low renewable power costs, and since there is no pressure or heat in the system, we can use inexpensive components. When the capex is low, it allows for a lot of other things to not be ideal starting out. Current densities aren't going to be as high as water splitting electrolyzers or aluminum production, for example, but that's ok in this context.

Electricity costs more than heat, as a rule. (electricity = heat at pretty much 100% efficiency)

Intermittent operation blows up CAPEX costs.

There's no heat in the system until you start dumping electricity into the resistive heating of your cells - you won't ever be able to run at scale at room temperature. A gallon of gas per second unit - something nicely sized for intermittent operation at a gas station - would need to vent approximately 120 megawatts of heat.

Current densities are 1-2 OOM lower than water electrolyzer.

Cell CAPEX isn't nearly as catalyst dependent as the daily 'We've invented a replacement for platinum in fuel cells' papers would make you believe. Nafion, balance of hardware, and assembly man-hours are $$$.

I've been where you are (more or less): beware the superficially justifiable assumptions.

It's true that running part of the time is not as good as running continuously, but if the capital is low enough, it's ok to start out running intermittently until we get to the point where we have low cost dedicated power and can have a higher uptime.

We will have to shed heat from the system to the environment, but that can be done passively.

Current densities are likely going to be substantially lower, but our capital costs are also going to be much lower. We don't need to operate at 30 bar for example, nor further compress our product.

Our capital costs aren't magic, they're just good enough in balance with everything else.

Hook to nuclear and hydro electricity and you can get your uptime much higher while remaining carbon free. That should give you a good 2x boost on capex at least.

Building nuclear plants to save on electrolyzer capital cost is not a good idea at all. Penny wise, pound foolish.

Hook to existing plants to help them load follow where intermittent renewables are at high capacity.

If you base yourself in QC you'll have access to cheap and 100% green hydro electricy 24/7.

I hope you are wrong, but realistically I fear you are correct. It is easy to show something works in the lab, hard to make it work in the real world.

How could the math possibly work out on this? If a gallon of gas holds 33.70 kWh of energy, and you can get cheap electricity for $0.1/kWh, you're looking at $3.37/gallon if you have a magical process that converts with 100% efficiency. Even if you hit your efficiency goal, which would be impressive, who is paying $7/gallon for gas? Just buy an electric car. This can only possibly be useful when all of the oil is gone and there is no other alternative, right?

We expect a gallon of gasoline to require approx. 60 kWh of electrical energy. If the price of that electricity is below 5 cents, the economics work. If the price is lower, the efficiency of the conversion could also be lower if that optimized other costs (like capital). Electricity is routinely below 5 cents now at utility scale (wholesale), which is where we will want to be.

60 kWh capacity EV will get you (realisticaly) 200 miles.

A gallon of petrol - 40 miles (realistcally and using UK gallon).

According to Tesla their charging is 92% efficient so reduce that 200 to 184 miles.

Your process is 4.5 times less efficient than just putting that electricity into the EV? Is that right?

If so - and your process is carbon neutral (big if) - what's the point in a future where EVs dominate?

In the long term, electric vehicles may indeed replace ICE cars. That would be awesome. One way to see what we're doing is to make sure the path to that future is good. We can't burn fossil fuels while we wait to replace the existing vehicle fleet with electric cars. By using zero carbon we make sure that we are solving the problem right away.

You might want to focus on jet fuel, since we don't know how to make batteries with sufficient energy density for long range flights and don't know if such energy density will ever become possible.

It might also be worth looking at where airplanes tanker fuel, that is to say, carry more fuel than they need for their current leg because refueling at the next stop would be difficult or expensive. Apparently a lot of that currently happens on short flights to small islands; while I hope Wright Electric and/or the EViation Alice will eventually take over that market, in the short term that's a market that might be willing to pay a bit more for liquid fuel made from air plus local solar panels.

Fuel oil that can be burned in combined cycle power plants in the winter may also be valuable for dealing with seasonal imbalances in demand vs renewable generation that lithium ion batteries can't cost effectively balance.

> what's the point in a future where EVs dominate?

EVs won't dominate some important uses for a long time, e.g. aviation and marine shipping.

4.5 is not so much. Gasoline is very energy dense, stores well (especially synthetic) and transports well. This is great - gas will be around for a long time to come - if we can shift the source of it to something better, I'm all for it.

1. Airplanes and boats will still need gas for a while 2. We’ll need to suck carbon out of the atmosphere anyway. So a process like this will be necessary, even if in the end the product needn’t be turned back into gasoline. This will be costly, but it’s the price we pay for all of the fuel we burn currently.

Aircraft and cargo ships simply can't use batteries.

Ah, that certainly explains it. I'm still highly skeptical of how widespread this will ever be, since electric cars will become even more compelling as electricity costs decrease, but you've convinced me to not dismiss this completely as impractical. Thanks for the context.

Batteries still are the main issue with electric cars. The range, charging time and battery life are getting better but still don't match hydrocarbons.

It's just a great storage mechanism.

Storage is also a big issue when it comes to renewables. You could take in carbon in areas with lots of sun and ship the fuel to areas not well suited for solar generation.

This really would be a game changer for lowing the net carbon output.

This also means you could solve one of the big problems in the power grid, peak generation. Use the extra capacity during off peak hours to generate fuel that is later used to fire up power stations to supply peak demand.

But liquids fuels like ethanol are used for MANY more things than just transport – plus the cost of fossil fuels can only go up on any reasonable timeline.

Intermittent renewable energy like wind also drives cost really low sometimes. This could be an alternative to grid-based storage of electricity. Comparison of capital cost and loss and value of the byproduct would be interesting.

No the economics does not work, if you include the "externalities" of that gallon of gas. You are continually creating waste heat and carbon emissions, while using naive reasoning based on Gas Buddy prices.

Solar is already down to $0.065/kWh for industrial applications [1]. That's $3.90/gallon at today's prices, and solar prices continue to fall.

The DOE's 2020 targets came three years ahead of schedule. Their 2030 target is $0.04/kWh [2], which would work out to $2.40/gallon. Mix in the fact that a bunch of countries (and US states) have implemented carbon taxes and you've got yourself a good long term investment.

[1] http://solarcellcentral.com/cost_page.html [2] https://www.energy.gov/eere/solar/articles/2020-utility-scal...

Do those figures include gas taxes? Don't those make up a large part of the price at the pump?

In the US, gas taxes are low (I think I pay 15 cents per gallon tax on a total of $2.50 per gallon).

Taxes are low as here in the US (a) many people hate taxes and (b) with such a low population density, commerce is very reliant on road vehicles. So raising taxes has an outsized impact on commerce.

California has higher gas taxes. Our gas is currently about $3.70 a gallon where I live.

$4.29 for premium yesterday in oakland.

About that in parts of Seattle as well. Which is low given a few year rolling average. We should expect gasoline prices to rise, and fast. So anything that starts to look into economically viable options at $7-10/gallon is worth checking into now in a startup phase.

There have been 15 year solar power purchase agreements signed already for $0.025/kWh [1].

Assuming they get to 50% efficiency, that's $1.69/gallon.

Sounds crazy low, but I hope it's true.

[1] https://www.utilitydive.com/news/texas-muni-signs-cheap-sola...

Yes, and that's just until now. Anyone want to bet that we've hit rock bottom in terms of prices, efficiencies, and economies of scale? Or are we going to see another 10x? 0.17$/gallon. 20x?, 0.09$/gallon (rounding up because I'm lazy).

My view is that is more a question of when than if and that the point where it stops mattering relative to the comparison to fossil fuels depending on your point may already be quite near or even in the past.

Some places are still getting expensive solar, some places are bidding at 0.025/kwh. It doesn't really matter. What matters is what the bids will be ten years or so from now, which is when realistically this could start becoming operational at a meaningful scale.

It's 2019. Ramping up production for something like this takes some time. A decade can fly by for a startup like this. Doing the math with 2019 prices and efficiencies means you get a very conservative view of what would be possible now with today's level of technology at today's scale.

However, an investor needs to look a decade ahead. Or longer and assign some probabilities to likely outcomes. The outcome where there's no progress whatsoever in making clean energy tech better in the next ten years seems unlikely. So, betting on < 1$/gallon as a feasible goal in 1-2 decades seems like a reasonable bet. If the rest of the technology works as advertised (room temperature synthesis and extraction of alcohols) and the technology can be scaled at reasonable cost, that ought to be basically a money printing machine. The lower that price drops, the better. As long as oil remains the primary source, you can pocket the difference as profit.

At industrial scales, you can buy electricity much cheaper than $0.1/kWh if you locate your facility in the right place. For example, hydroelectric power near a large dam can cost as little as $0.02 to $0.05/kWh.

I believe they’re looking for very cheap electric rates. Excess wind or solar power the grid doesn’t want could certainly be cheap. Or college dorms.

> who is paying $7/gallon for gas?

Today's price for standard gasoline here in the Netherlands is 1.83 EUR/litre, which is currently equivalent to 7.75 USD/gallon.

It would not make sense today, but in 10 to 15 years, with climate regulations, having a carbon neutral jet fuel might start making a lot of sense.

Yup. We could tax extraction rather than fuel purchase. (or only tax fuels that are extracted rather than captured, or tax the latter less, or..)

I expect I'll see new battery powered aircraft before I see today's aircraft powered by kerosene synthesized from water and carbon dioxide in the air. And we'll probably see more rail/car before then since the massive cost increase on airline tickets from this will destroy the industry.

As the other reply pointed out, without a huge(like 5x) improvement in energy density (specific energy, actually) of batteries, this is physically impossible. Even with improvements, it would still be inefficient as batteries don't lose mass as they are used up - airliners can't even land with full fuel, they have to use it up, or dump it in an emergency situation.

Using a process like this would essentially make the fuel simply a much better battery for airplanes than our batteries today.

There is a good chance we will make jet fuel in the next 2-3 years. There appears to be a lot of demand for it. We're starting with gasoline because it's a much bigger market / impact, but it's not that hard to make jet fuel too.

And if synthesizing jet fuel turns out to be viable, I could easily see governments 10–20 years from now requiring airlines to use it, the way they are for automobiles.

Battery powered aircrafts would require huge jumps in electrical storage. There are no signs of them becoming a reality any time soon. Not to mention the complete replacement of old planes is going to be very very slow.

I don't understand your rail/car replacing flying argument. There are no signs that flying is going to get so expensive that people would rather pay for it with so much of their time.

>> who is paying $7/gallon for gas

A lot of people in the world. And Americans would pay close to that without subsidies + rising gas prices.

In the UK, a gallon of Petrol is currently about $7.97 (about £1.20/litre).

who is paying $7/gallon for gas?

In the UK, people pay approx $6 per gallon for gasoline.


If you change that chart to USD and Gallons you'll find this around the cost of gasoline in New Zealand.

For comparison, in Sydney, Australia, as of this morning, basic unleaded 91 octane fuel is about AUD 1.35 / litre at best. Which is USD 0.94 at today's exchange rate. Just under USD 4 / US gallon.

Of that, AUD 0.41 is federal fuel excise, and AUD 0.12 is GST.

Don't forget that UK Gallons are not the same as US Gallons 1 Imperial Gallon = 1.2 US Gallons

In France current prices are around 7$/gallon (1.6€/L)

$7/gallon is the approximate price in Scandinavia. It's not a completely alien price.

In Quebec our electricity can be lower than 0.05$ CAD/kWh (3.28¢/kWh based on the Rate L [1]). Our courrent lowest price is 1.384$ CAD/L. So considering that 1L would be 8.9 kWh. So all it would need is an efficiency of 33% to be profitable with an electricity cost of 0.05$ CAD/kWh. That's excluding any tax incentive to do so or any deal made with HydroQuebec to use excess power.

[1] http://www.hydroquebec.com/business/customer-space/rates/rat...

> Just buy an electric car.

China’s EV goal is 20% of new vehicle sales by 2025. That is to say, 80% of sales in 2025 will still be gas. (So will the 100 million gas vehicles sold in China between now and then). We are a long ways away from not needing this tech.

Don't skate to where the puck is, skate to where the puck is going to be.

Electric cars can't compete against gasoline cars until the price hits about $6/gallon. And considering that crude prices are relatively low, but gas in CA is almost $4/gallon in the Bay Area, it doesn't take much time for normal rates to hit $6/gallon in the next 10 years or so.

At that price, it becomes more economic and that's the time frame probably what they're targeting as well.

What? They compete today with significantly lower fuel cost. You see 100+ mpge on every electric car I know of today, you're looking at half-1/3 the per mile cost in an electric car. That more than makes up for the higher upfront cost over the lifetime of the vehicle, with cars you can go buy right now, today.

And that doesn't even take into account the superior UX.

I don't know why you got down voted on this. My experience of EV vs ICE (sometimes in the same vehicle - daily driving in a Prius plug-in) agrees entirely with your comment: the lovely EV experience of linear, quiet acceleration is so pleasant compared to driving a petrol car, even an automatic. And my Prius in EV mode isn't even a that great an electric experience compared to that of an i3 or 2018 Leaf.

ICE cars cant compete with convenience of: * not needing to refuel * less maintenance needed * not spewing particulates in air etc (if you care about what you breathe)

* not needing to refuel

no, we're taking Soothing30MinuteRelaxingBreaksAt200MileIntervalsAwesomeHappy™ brought to you by Tesla™ instead

I don't know about you. I've driven the last 5 months / 5,000 miles without using a Supercharger once, except for the first day I took delivery just to try it out.

It's there when I need it for the long road trip. But daily life is effectively refueling-free.

What percentage of round-trips are under 200 miles? NHTS recorded the distance from ~750,000 car trips in 2009 and found the 95th percentile is 30 miles, and the 99th percentile is 70 miles. Somewhere on the order of 1 in 1,000 trips needs a Supercharger stop along the way.

[1] - https://nhts.ornl.gov/vehicle-trips

I go on vacation a few times a year. Renting a car just for that is more expensive than extra cost of fuel. Not to mention most rental cars won't let me use my truck as a truck (putting rock in the back damages the bed, and a trailer is right out - both things I do only a couple times a year but I still own a truck for just those few times).

IF this is as good as they claim I don't see electric cars as worth it as a first car. They are slightly cheaper for an in-town only commuter car, but the downsides of electric cars (expensive battery replacement, limited range without long recharge times) are something that fans hate to acknowledge. Note that I said first car, once you have decided to have a second car electric is probably better.

Battery replacement is not really a factor under any kind of "normal" use. One Tesla owner driving for Tesloop was able to burn out a battery after extensively (exclusively) Supercharging from low charge to 95-100% charge after about 350,000 miles. Maintenance cost over that time was calculated as $0.05/mile. [1]

With V3 Supercharging, you can drop in with your Model 3 at 15% and be at 80% in 24 minutes. In my road trip experience, that's barely enough time for everyone to use the bathroom and pick out a beverage. [2]

[1] - https://www.tesloop.com/blog/2018/7/16/tesloops-tesla-model-...

[2] - https://twitter.com/privater/status/1103567772301193216/phot...

Interesting stats on the battery replacement, but if my family/youth groups/etc. routinely took 20+ minutes for a gas station bio break, there'd be words. Especially if we had to do it every 150 miles (80-15%).

I go both ways on that one. On the one hand I want to get there. On the other hand my doctor wants me to get out and take a 10 minute walk every hour anyway.

Also worth mentioning that 65% of the LR Model 3 is over 200 miles.

So if you are starting the day with 95% charge, and ending the day plugged in at your destination with 15% charge, that means you can travel about 450 miles with just one ~20 minute stop to charge along the way.

How is that not fast enough? The only issue is if you can't plug in at your destination. Maybe in that case you have breakfast near the next Supercharge on your route.

Yes, it is something you might have to think about for a minute. The guidance software will map out Supercharging stops for you.

How long are you waiting in line to get a chance to charge? I've been driving with my friend with a Tesla and he visited 2 places before giving up because the line was too long.

I wouldn’t know, I’ve only gone the one time.

I do expect that they will figure out a reservation system which tracks and queues vehicles en route, like an air traffic controller, to cut down on inefficient ad hoc queueing at the location.

It would be super fun to program such a system, backend and front. Even more so as the cars become increasingly autonomous.

For now at least you can click on the map and see live how many chargers are in use.

Bizarre comment. Being able to quickly refuel is one of the key advantages internal combustion engines have over electrics.

Depending on your assumptions.

For day to day use EV doesn't need trips for gas station to refuel - so you actually save time.

For long trips - yes.

But nobody makes trips to the gas station to refuel. Re-fueling is something that's done on the way at a convenient gas bar, and typically takes only 2–3 minutes.

I’m very skeptical about 2-3 minutes. Maybe if you disregard lost momentum and don’t keep track of your mileage or wait for a receipt or have to go around once or twice to find a spot or...

Because I keep track of my mileage and have to carefully babysit the process (likes to overflow) I’d say I lose at least 10 minutes every time I get gas, and that’s every 130 miles or so.

Well, the speed depends entirely on how fast the pump is. Some are faster than others, but I never have to wait for a spot, and printing a receipt takes 5 seconds. Maybe diesel pumps are faster? I sometimes use the truck pumps at freeway service centres, and it comes out like a firehose.

Only 130 miles? Is that normal? My car can easily go 600 miles on a 15 gallon tank (diesel), but I've had it for so long I don't remember what other cars are like.

Now I'm curious how long it actually takes. Next time I fill up I'll time it.

No, 130 is definitely not normal. Theoretically I can go 200, which itself is pretty terrible, but my fuel pump sensor is shot and I just prefer to play it safe.

This is accurate in my experience. Pay at pump takes ~2.5 minutes for the whole process. I note mileage and reset OBC when I do this - included in the time. I typically buy around 50 L.

But A small Gas station can refuel several cars in that 10 mins

If the ev car companies got their shit together, they could have used swappable battery packs.

You can wait around for 12h to charge, or you can turn in your cores and pay for 100% capacity batts now. And the swap would be quicker than standing around filling up a tank.

But no. Each ev is different and proprietary. The chargers aren't even the same.

I mean the battery technology for EV companies is their special sauce. If they are all the same that takes away their differentiator. I agree it would be better for customers but it's understandable why that isn't something they want to do.

Much like swappable batteries in a smartphone, there are tradeoffs to such a scheme. And an electrical “pump” is vastly simpler to implement than something that would allow swapping out a car-sized battery.


Swapping an EV battery is like swapping an ICE transmission. You can do it if you have a car lift and a scissor jack to drop it.

Sure, but one can argue that a EV could be designed/optimized for faster battery replacement. While it would still need at least a forklift to move the batteries, I believe the time needed for battery swapping could be greatly reduced with a proper design.

I’d much rather have an EV optimized for efficiency, battery endurance, etc. given that battery swaps would only really be useful for long distance road trips.

But you’d still need to have expensive batteries in stock on location, technicians and equipment. I can’t see that ever being done at scale.

Tesla did that for a while. They abandoned the plan. Batteries are big and heavy. It turns out to be far more important that engineers have the ability to fit them around the other parts (suspension...) than the ability to swap a standard battery.

Yep, the batteries are ridiculously heavy and they’re used as structural elements in the car.

So swapping batteries is hard to do, and unnecessary for most drives. Sure, you’d want to be able to swap batteries in five minutes like pumping gas. But who’s going to ship batteries out to the middle of Kansas, build infrastructure, and pay technicians just for people on a road trip who want to swap batteries?

> gas in CA is almost $4/gallon in the Bay Area

And the national average (today) is $2.95, you might as well compare Hawaii and Alaska which are also economic islands.

>it doesn't take much time for normal rates to hit $6/gallon in the next 10 years or so.

The national average 10 years ago was $2.45, which is $2.90 accounting for inflation. The only way gas hits $6 is if we have a second Great Inflation or massive political changes in the United States and abroad.

That's very US centric though. It's already much higher where I live (Vancouver, just minutes from the US border): $1.70 CAD/L ~= $4.80 USD/gal. I don't think $6 is far off at all in many locations.

Gas is currently about 1.56€/liter ($6.6 per gallon) in Finland.

That doesn't make it an economic island by any means. This is simply due to regulations that virtually only affect gas prices.

By that measure, Florida or Oregon would be economic islands due to their anomalous taxes.

This is really cool! I hope that you can rise above the comments of the "this isn't good enough" or "zero carbon or bust" crowd. This type of innovation is what we need to move the needle in a realistic manner and that helps to build on the infrastructure that we already have in place.

I'm excited to see what comes of this in the coming years!

I'm conflicted. This is clearly better than what we have but I was really hoping for a carbon negative future. I hope projects like this are a stepping stone and not a handbrake on progress.

Wouldn’t this help carbon negativity eventually? The world can just pay to sequester fuel produced this way, and bring concentrations down to preindustrial levels.

This does not displace a carbon negative future. And zero minus current emissions is still a negative number.

If it breaks our dependency on fossil fuels then I'm all for it.

Ye on reflection and reading more comments from the founder I'm tentatively positive on this. Localised air pollution from burning of fuels and globally elevated co2 levels are two distinct problems. Solving one is already a big step in the right direction.

Precisely! Replacing all gasoline and diesel engines, if that's even possible, will take decades. We need something other than fossil fuels for them in the mean time.


Would you be willing to share vague details of your roadmap?

Specifically; How many barrels of ready to burn gasoline are you outputting per day in 6 months? 1 year? 3 years?

The fact that the general fuel is going to be sold and re-burned means this is at best carbon neutral, so from a cynical environmentalist point of view, what's the point? This can't help anyone unless you pump the synth-gas into the ground and sequester it, but that isn't VC-backed viable.

If you are using some sort of membrane to pull out distillates without heat, why wouldn't you just sell that to existing petro-chemical companies for their distillation processes? What non-thermal-energy related benefits come with this membrane?

The poster gave important information in another thread: 60kWh per gallon of gas, aiming for ~5 cents per kWh, ~$3.00 per gallon into distribution channels. That makes it instantly cheaper than petrol in, at minimum, the UK

...the general fuel is going to be sold and re-burned means this is at best carbon neutral, so from a cynical environmentalist point of view, what's the point? This can't help anyone unless you pump the synth-gas into the ground and sequester it...

The status quo today is that we are removing carbon from the ground and putting it into the air. This replaces those fuels that currently come out of the ground. It's still a big win, even if it's technically only carbon neutral.

Even electric vehicles aren't carbon neutral, because they're mostly charged by coal power.

Also: you suggest the synth-gas should be pumped into the ground. What would be the point of converting the carbon dioxide to alcohol to gasoline and spending electricity to do it? At a minimum you could just pump at the alcohol stage.

An EV makes several times the motion from the same energy input.

> Even electric vehicles aren't carbon neutral, because they're mostly charged by coal power.Even electric vehicles aren't carbon neutral, because they're mostly charged by coal power.

Is thus an invalid/irrelevant argument.

I can get excited about jet fuel however, since battery powered planes are considerably less practical than their traditional counter parts with the current technology.

This is a completely accurate comment. Why is it downvoted?

I assume the company is operating in the US. In the US only 27% of electricity is from coal and falling. https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...

And in California (where nearly half of the US's electric vehicles reside--with EVs achieving a nearly 8% market share last year among light vehicles), it's MUCH less than that. There's only a single, tiny 63MW coal co-generation plant in the state, so coal power is less than 1% of California electricity.

> Even electric vehicles aren't carbon neutral, because they're mostly charged by coal power.

Additionally, it's absurd to compare two consumers of electricity, both of which are flexible with respect to time of consumption, and just arbitrarily say one is mostly coal power (which is false) and the other isn't.

We definitely need carbon neutral or even carbon negative industrial processes. I kind of question the logic of going for fuels versus more valuable non-fuel feedstocks, however. A maybe 50% efficient conversion of electricity to alcohols with a typical 20% energy conversion of fuels to mechanical power gives you about an order of magnitude less efficiency than battery-electric.

And if you ARE insistent on making carbon neutral fuels: Makes more sense to focus on things that are super hard to electrify, like long-haul aircraft and transoceanic shipping and maybe heating fuels for the far north (where air source heat pumps lose their effectiveness in January).

But I'm glad an electrochemical process is being developed, here. Electrolysis and related processes are much preferable, IMHO, than the more common thermal processes.

If this process were to only make transoceanic shipping carbon neutral it would be well worth it.

Except fuel oil used in shipping is like $1 per gallon or something similarly low.

That said, for bulk low-quality fuel needs like shipping they could reduce costs by skipping the upcycling stage and just burning the alcohol.

California electricity is only 1% coal. 52% is natural gas and 40% is carbon-free. https://en.wikipedia.org/wiki/Energy_in_California. Most growth is in renewables.

The world is bigger than just California, and I thought that SV startups target "world dominance" by default :)

Most advanced economies are phasing out coal. Worldwide it's less than 30% of power generation.

Also, fuel is fairly transportable. You can produce the fuel wherever renewable electricity is most available, and sell it worldwide. The economics are comparable to aluminum, where a large fraction of the world's supply is produced adjacent to geothermal power stations. https://en.wikipedia.org/wiki/Economy_of_Iceland#Aluminium

>What would be the point of converting the carbon dioxide to alcohol to gasoline and spending electricity to do it? At a minimum you could just pump at the alcohol stage.

Sounds like a great idea! My general point is that zero carbon energy sources like wind and solar are at least mildly zero sum, and creating brand new load on them would likely just result in capacity moving over to other producers like natural gas and coal.

I guess I don't understand why YC is throwing money at this because I'm not confident there's profitability on the horizon, unless they nail down mind bogglingly large scale of production of aviation fuel,

Meanwhile, if San Fran is looking to dump money on (IMO) nebulous and green projects, give me money and I'll plant 100k trees

We'll need a lot more wind and solar, so Prometheus will drive the expansion of these. We'll start out taking intermittent power that's low cost (wind at midnight, for example), but will soon have resources built for us to expand. This will be good for displacing other fossil fuel use (other than transportation), as we will be increasing the availability of renewable power, and also solving the problem of being able to use the excess (we can be seen as a kind of grid storage).

So the plan is to only use excess renewable energy that otherwise wouldn't get produced and consumed? If not wouldn't you be a net carbon generator, as you would be burning fossil fuels and releasing carbon in order to capture a lesser amount of carbon in your process?

What steps are in place to prevent the process from displacing other renewable use? Take the fact that it is less than 100% efficient to store renewable energy as gasoline. Others might make more efficient use of this renewable energy by immediately using it to displace fossil fuels, with no or lower storage losses. Under this scenario Prometheus is again a net carbon generator. (edit: The same dilemma is faced by any other type of storage.)

It strikes me that Prometheus will come into its own if it can guarantee that it doesn't displace more efficient users. This will happen when fossil fuel usage becomes negligible or we (as a society) come up with a sophisticated energy scheduling algorithm that can take account of efficiency.

It comes back to that fact that whilst it is green to replace fossil with renewable energy, it's even greener if we can increase efficiency and avoid consuming that energy in the first place.

Don't get me wrong, correctly used it's a great thing you are doing.

Allocating commodity resources efficiently is what capitalist economies are actually pretty good at.

A couple of scenarios where this is ideal:

1. Located close to intermittent renewable generation that is already hooked up to the grid, especially in places like California where intermittent renewables can already push generation beyond load at peak times and result in near zero or negative prices, this can soak up electricity usefully in a way that displaces other carbon emitting fuel.

2. Deployed along with intermittent renewables in the most optimal places for generation, where connection to the grid is impossible, inefficient, or will simply take time. This can soak up the most efficient possible generation of deployable renewables which would make otherwise uneconomical utility scale deployment viable.

Both of these are scenarios that our capitalist market system should work well to optimize for assuming the electricity->fuel technology reaches suitable efficiency (and not before then).

Wouldn't you have to really be paying above market rates to "drive" the expansion of renewables? Any thoughts about essentially building/running your own renewable power facilities?

Renewable power plants are not reliable producers of power. When they produce power they are the cheapest, so utilities would love to have more - but they need a backup plan for when renewable power isn't running which they have complex management schemes to deal with. Expansion of renewable energy it limited more by the power companies willingness to buy it than by ability to install more (though that is of course an issue as well).

If they can scale their process quickly (not just on-off, but to levels in between) the power company will be happy to give them a substantial discount. They can probably get power for $.03/kwh - windmills are about $.02 for profit so that is plenty of profit to pay for transmission infrastructure. Of course they have to agree to how quickly they can change their production.

This assumes they can turn off completely at 5pm when everyone gets home and jumps in the shower needing hot water. Then go to full production as they go to bed while the wind blows the best. Then drop down overnight. Then scaling up again as the sun comes up. In the late afternoon as the sun is hot they scale down to account for air conditioning. Of course they may as well shut down for maintenance in December (Christmas lights). If they can pull this off renewable energy can scale grow to be much better while taking more power plants offline. That is a big if though.

We will just have to agree to a purchase power agreement (PPA), and others will build the renewable power plants for us. We will be going for very large scale, so will help to drive electricty prices down from where they are now. There is a lot of competition to build renewable power plants.

Not sure how in the last 10 years after the last gas shock that people have forgotten the petroleum is a finite resource that we are going through rapidly. If you read E&P announcements and various P2/P3 reserve estimates of existing resources and measure those against daily global consumption it is pretty alarming. Presuming stable petroleum input prices may not be a reasonable assumption.

If we replace fossil gasoline with renewable gasoline, that reduces CO2 emissions. Our gasoline will be zero carbon, and may actually be certified as slightly negative, as we will not be emitting CO2 from drilling and refining as fossil fuels do. If we replace all liquid fuels now made from oil with fuels made from air mining of CO2, it could reduce emissions by approx. 10 gigatons per year. That is huge.

The membrane will definitely replace distillation in a number of industries, but the most exiting thing to do with it is to replace fossil transportation fuel with renewable fuel.

>If we replace fossil gasoline with renewable gasoline, that reduces CO2 emissions

Nitpick: It will leave carbon emissions unchanged, but may reduce the amount added to the carbon cycle.

What kind of production quantity are you looking at? Small batch aviation fuel for a niche "green" airline? Every semi truck on the road in America? The neighbor kid's go-kart?

You give an "efficiency" of 60ish %, but I don't know how to interpret that. How many megajoules (or kilowatts) are required to produce a gallon of 86 rated gasoline?

We are going for the whole gasoline, jet fuel, and diesel market. The 100% efficient energy content of gasoline is approx. 34 kWh/ gallon. At 60% efficiency in converting renewable electricity to chemical energy, that would be approx. 57 kWh/gal.

Seems like France would love to have this technology to replace imported fuels, and the political problems that go with them, with fully-local nuclear-powered hydrocarbon production.

Please think twice about diesel - NOX is a killer. On the other hand, I expect particle emissions to be much lower with your fuel.

Much lower particle emissions is what we expect. Also no benzene, sulfur, or aromatics. Despite diesel's drawbacks, I'd rather offer zero carbon diesel as long as people are still using it.

You are certainly aware of this, but synthetic fuel is perfect for military applications and for backup generators and such, because there is no biofouling or degradation. Also wasn't the USAF testing bio jet fuel? Your product is superior on all technical points and just as good if not better on the environment.

The main thing that's turned me positive on "e-fuels" is that there's such a huge amount of petroleum that's used today in applications where we basically have no other options.

Think stuff like big jets, or container ships. If you sit down and crunch the numbers for any non-carbon energy carrier, you either end up sinking the ship or with a fuel tank twice the size of the cargo.

The problem with e-fuels for jets is that a majority of the climate forcing comes from the high altitude water vapor in the exhaust, not actually the CO2. EDIT: I should point out here you COULD actually make an e-fuel without hydrogen and thus without water vapor as a combustion product. Carbon monoxide, for instance. The energy density is much lower, but it is sufficient. HOWEVER, there are obvious safety concerns with CO fuel that basically makes that a non-starter. Another option is a fuel cell that condenses the water output and stores it for periodic (possibly lower altitude) discharge in liquid form.

But I agree container ships would be a good application of this. Container ships also have pretty high efficiency internal combustion engines (about 50%), meaning there's less advantage in electrification there than for land vehicles which often have 15-25% efficient engines. And it allows low particulates, which is one of the main forcing regulations on shipping powertrains nowadays, without the overhead of cryogenic LNG.

However, container ships use ridiculously cheap bunker fuel instead of highly refined gasoline.

CO2 seems much worse pollutant than water long term, because it stays in the air. Water at high altitudes condenses, reflects some radiation back to space and then falls back down.

At high altitude, the water stays up long enough and has such a huge impact that even its long term averaged impact is greater than the CO2.

Could you give a source for that? My understanding after some search is that effect of high-altitude water is hard to evaluate. I agree that at high altitudes contrails may evaporate and the water then may not fall down... Is it possible that jet exhaust water vapor accumulates in stratosphere? That would be terrible.

It is hard to evaluate, but of course being hard to evaluate does not mean it's not a real thing.

The effect (not counting contrails) is about double the effect of CO2 emissions alone. Including contrails, it may be even higher. There are mitigation strategies to deal with these non-CO2 radiative forcing effects, though it's very complicated.

Good article: https://www.carbonbrief.org/explainer-challenge-tackling-avi...

Thanks. That article refers to paper doi:10.1016/j.atmosenv.2009.04.044


which says

> At pressures greater than 500 hPa (i.e. below roughly 6 km), the forcing [of water vapor] is assumed to be negligible

So flying below 6km would help a lot for impact of water vapor. However, given this was not yet acted upon, IPCC is probably right that

> the effect of water vapour emissions is likely to be a significant, or even the dominant, contributor to their climate forcing.

This is even worse given the projections of aviation expansion. Right now the water does not seem to be a big problem and it could stay that way - water lifetimes even in stratosphere is counted in years, as opposed to centuries for CO2 - but if aviation expands, then it becomes more serious than CO2.

I have been completely unaware of this effect. Could you provide me with a source where I can read up on this?

Plastics! Zero-carbon plastics would be great. Pull CO2 from the air, mix with water and wind/solar elec and product bags, phones etc!

Absolutely. A friend of mine founded a company to produce carbon-net-zero biodegradable plastics. Their seed round went well, and making great progress, and are currently raising a series A. If anyone's interested in learning more, email me steven.buss@gmail.com.

The thought is kind of horrifying, but you could even make it a closed process - send your old phone to the factory, where it's burned to produce the plastics for your new phone.

That would open up a pretty good avenue for "recycling" then, and could possibly reduce waste plastic in the environment

As I learned today in another thread [1], the only problem would be that plastic is usually doped with additional elements that I assume we would somehow have to deal with when burning it.

[1] https://news.ycombinator.com/item?id=19845427

Why is this horrifying? Is there some part of this I'm missing here?

It just feels wrong to burn this stuff as part of an established cycle.

Well, every barrel of their stuff that is burned is one that wasn't sucked from the ground and put into the carbon cycle. So as long as it doesn't depress the price of gas much and cause consumption to increase, I'd take a bit of a less cynical view towards it.

Personally: Carbon negative aims are admirable, but idealistic. Carbon neutrality is in many cases much more feasible and makes a massive impact in an industry that is currently overwhelmingly carbon positive. By argument of historical trends to future trends replacing a carbon positive market with carbon neutrality at the end of the day is removing carbon from the air that would otherwise have ended up there.

> is at best carbon neutral, so from a cynical environmentalist point of view, what's the point?

This doesn't make sense to me? Wouldn't even the most cynical environmentalist agree that carbon neutral is much preferable to carbon positive?

> The fact that the general fuel is going to be sold and re-burned means this is at best carbon neutral, so from a cynical environmentalist point of view, what's the point?

It's meant to replace a carbon-emitting process (burning gasoline made from fossil fuels) with a carbon-neutral process. The replacement process is not carbon-neutral.

It can be seen as an energy storage technology for renewables.

Interesting timing of Derek's Lowe's post on "In the pipeline".[1]

There are government levers (subsidies, tax breaks, carbon use taxes and so on) that can change the economic landscape, but the paper estimates that you’d need electrochemical efficiencies of at least 60% and electricity available at 4 cents/kilowatt-hr or better to make these ideas profitable (with the usual 30-year-amortization assumption about the plants themselves). How close are we? Many of the processes are currently in the 40-50% efficiency range, and need further scale-up work: within sight, but not there yet. And renewable electricity costs vary a great deal by region. The best cases are getting down around that figure, though, and continuing to improve.


Yes, that data is from a recent Science review article: https://science.sciencemag.org/content/364/6438/eaav3506

I think the timing on this effort is right, from a cost of renewable power perspective, as well from a growing consensus that it is very close to being achieved. Hope to prove that soon!

How quickly could you pull CO2 out of the air if you were scaled up to make full use of a typical nuclear reactor for the electricity? If you just stored the output of that process rather than refining it into gasoline, diesel, or jet fuel, how would that product compare in cost to drilled oil in the same state?

My thinking here is that creating gasoline and selling it for immediate use is at best carbon neutral, and at worst delaying the replacement of that gasoline-burning equipment with an all-electric version. But if your focus was on replenishing raw oil reserves for future (hopefully mostly non-burning) use, you'll be removing CO2 from the atmosphere. To do it at significant scale requires a lot of energy, and a nuclear reactor is much better at providing that level of energy than other zero-carbon sources. The trade-off is nuclear waste, but that's much more containable than the waste from non-zero-carbon energy producers for equivalent amounts of energy. Eventually it could be reprocessed to extract more energy from it as well, until the radioactivity is used up.

As a person with a background in Environmental Studies, a c o2 to fuel conversion technology such as this sounds revolutionary! I am most curious about the fundementals.

Can you give us more specifics on the process such as;

1. What is the scale of the operation? Does this process need to be done at a large scale to work out economically? 2. Take a Boeing 737 for example which has a fuel capacity of ~6,875 Gallons. How much would it cost to build a C02 refinery that could produce that much fuel daily?

3. How much does it cost at a small scale? Say you have a miminal viable product that can refine 100 gallons of gasoline per day. What is the cost of that production in USD?

4.How many KWh of electricity would be required to refine 1 gallon of fuel using your current prototype?

I would love to hear / see data your numbers.

Thanks, 01

The smallest scale at which we can operate profitably is probably in the 100,000 gallon/year range, although that could go down over time. We will make modular, mobile systems that don't have to be very big to be profitable. One shipping container will likely be able to do 100,000 gal/yr for example.

The electricity required will be approx. 60 kWh/gallon.

60 kWh is about 200 mi of range in a gen 2 Chevy Volt, while a gallon of gasoline is worth about 40 miles. Just trying to put the efficiency in context using something I'm familiar with.

That shipping container model would be ideal for remote villages in Alaska! Making fuel locally would be so much more energy efficient!

"60kWh/gallon" -- is that gallon of gasoline? Or ethanol? Or CO2?

If you know the figures off-hand (to save me doing the chemistry), how much water and CO2 is required to produce the gallon of output?

Gasoline. Each metric ton of CO2 corresponds to approx. 113 gallons of gasoline. The amount of water is approx. 1:1 by volume.

Very rough calculation:

* 60 kWh / gallon of gasoline * 100,000 gallons / year * = 6 GWh / year * = 3.5 MW solar array (from on-line calculator) * ~ 18,000 m^2 of solar panels (500W, 1.9m * 1.3m) (roughly 3 football fields of solar panels).

Not to be flippant; but doesn't that seem like a surprisingly small installation for ~273 gallons a day?

Can you talk a bit about the waste-water left over? Assuming it's non-potable, what does the disposal path look like? How much of such water is there at scale, e.g., water-per gallon of petro-product? Thanks, sounds awsome.

There is no waste. The only inputs are water, CO2, and electricity. The only outputs are fuel and oxygen.

With respect, that answer skirts the question of what happens to the water.

You said you're using the nanotube membrane to separate petro products from the water. What do you do with the water left over? What state is the water in when the process is complete? Potable? In need of treatment by traditional water treatment facilities?

I think you're asking a different question from the one being responded to (and the one being responded to is more obvious to me): I will try to help this conversation by restating the questions, both of you should correct me if I've misread this.

Your question is, in the distillation step, the nanotube membrane separates fuel from water, leaving some amount of water; what happens to that water in the process?

The question that was answered was, what happens to waste water? For which the answer is that there is no water "left over", and so the question of what happens to it is ill-defined because it doesn't exist.

So I guess what is happening is that any water left in the aqueous electrolyte can continue to be used in the process indefinitely, and there is no point at which the water becomes waste water? That all the water collected from the air gets broken up into hydrogen (in the fuel) and oxygen (waste product, sent into the atmosphere) and the amount of water in the aqueous electrolyte doesn't grow?


Thanks for confirming, though what if the ingested air/vapor/carbon mixture has a consistently higher than required water-vapor/co2 ratio? Or is that a non-issue?

If the inputs are truly CO2 and electricity, and 100% gets converted to usable hydrocarbons, then there's no waste water; the catalyst and water remain behind.

Assuming some water is lost due to electrolysis, you can top it off over time.

If the catalyst breaks down, or some undesired reaction limits efficiency (i.e. generation of perioxide or other undesired chemicals that degrade or react with the membrane, electrodes, catalyst, etc) then I think there might be some treatment or maintenance necessary.

However, none of this sounds remotely as bad as the treatment needed in the production of petrochemicals or lithium batteries or recycling.

There is no water left either—you forgot that oxygen is also produced.

I wasn't really sure how much of the o2 generated came from the co2 and how much came from the water. Either way, I don't see "waste water" to be as big an issue as the earlier posts i was replying to did.

The water becomes the fuel. The hydrogen combines with the carbon in CO2 to form hydrocarbons, while the oxygen combines with itself to form molecular oxygen.

I would think so, but the founder says: we have a carbon nanotube membrane that replaces it, extracting the alcohols from water

This implies there is still water there. Maybe it was poor phrasing, and all of the water is consumed, but that isn't what is stated.

If water is an input and not an output, that implies it's consumed, not left over.

Yes, one of the things that gets glossed over many times in this field (I used to do research in artificial photosynthesis) is that water gets consumed to create the fuel, and is released as vapor from every engine's exhaust. So to generate 10 million barrels requires about 10 millions barrels of pure water, per day, to satiate the US.

Yes, water is turned into fuel and oxygen. In most places the water can be obtained from moisture in the air (there is much more water than CO2 in air, and we are already mining the air, so we can get both). In the process the fuel is separated from the water, which remains in the reactor, and is topped off as it is used to make the fuel. No waste water.

Somewhat tangential, but does your crystal ball show when we will start seeing carbon nanotube desalination tech making it into the real world?

His startup was supposed to start shipping it last year...

I would think so, but the founder says: we have a carbon nanotube membrane that replaces it [distillation], extracting the alcohols from water

This implies there is still water there. Maybe it was poor phrasing, and all of the water is consumed, but that isn't what is stated.

I think the water that is still there after distillation will just be used for more distillation, it just hasn't been consumed yet, it isn't a waste product.

What about dust, pollens, etc, from the air? Is there a maintenance requirement to clean filters or something? Does the efficiency of ingesting the water vapour and CO2 decrease over time until maintenance is performed?

We'll want to filter our air, yes. This means replacing filters, etc, which factors into the maintenance costs.

What about the device itself, its lifetime, and the resources used to build it?

We expect a long lifetime (approx. 20 years or more), assuming modest maintenance costs. The capital is actually pretty inexpensive for a room temperature, unpressurized, electricity only system, so this helps mitigate longevity risks.

So, the goal is carbon-neutral gasoline.

Short term, I suppose your target is feel-good gas burning vehicles. Longer term, do you envision this technology being used for clean(er) + carbon neutral municipal power generation, or is the fuel type just wrong for that?

I ask because a stop-gap can easily become permanent, and it'd be unfortunate to continue dumping particulates (pm2.5/10), smog, etc into the air in major cities. One huge benefit of electric vehicles is you can make power where population is scarce, and use it where the population is. You don't get that with burner vehicles.

In the near term, we will remove the damage caused by fossil fuel use. Our fuel will burn much cleaner, so that's also helpful. In the medium to long term, cars will switch to electric, but now we'll have enough time to do that. As that happens, Prometheus will roll out new products made from CO2, like carbon negative building materials, etc. It's important to look not only at the end goal, but also the path!

> cars will switch to electric

Even once cars are all electric, I can’t see gas turbine engines in planes, trains and ships being replaced in a hurry.

And rockets are never going to be electric. I assume you can make RP-1 with this process.

I can imagine hydrocarbons being produced where electricity is cheap and practical, and being shipped to where it is expensive and impractical.

In theory if it was efficient enough, you could even use it to store electricity, (e.g. in the summer) and burn it again in the winter.

> Even once cars are all electric, I can’t see gas turbine engines in planes, trains and ships being replaced in a hurry.

Of course most (non-electric) train engines use Diesel-electric propulsion (https://en.wikipedia.org/wiki/Diesel%E2%80%93electric_transm...). That's mostly because of the flat torque curve of the electric motor. Some ships do too.

I'm not sure why you think that battery-electric train engines or ships aren't going to happen. There is a lot of room for batteries on vehicles like that!

A fun usage of dimensional analysis:

Fuel capacity of a diesel electric locomotive: 6200 gallons

Energy density of diesel fuel: 40kWh/gal

Total energy capacity of full fuel load: 248 megawatt hours

Tesla battery pack weight: 540kg

Tesla energy capacity: 85kWh

Weight of equivalent battery pack for a diesel locomotive:

248 MWh / (85 kWh / 540 kg) = 1575 metric tons

Weight of a diesel locomotive: 196 metric tons

So you'd roughly 10x the weight of a locomotive by trying to make it run on batteries, leaving aside the challenges of actually trying to charge those batteries.

Another fun fact: that locomotive can run flat out at max power for 2.2 days without refueling.

Of course, while it's neither easy, nor cheap, that train does not need to have any batteries in order to run on electricity. Much of the UK's rail network is either electrified or in the process of being electrified.

The side effect of not needing to use energy to haul your energy source around is pretty cool, too.

Why will your fuel burn cleaner? Soot and NOx are fundamental to the combustion process. I guess you have no sulfur, which is worth something.

Gasoline and hydrocarbons in general are mixtures of many different kinds of chemicals, and not 'pure' to some degree (the refinement process purifies to some extent).

If this process produces a specific hydrocarbon or class of hydrocarbon, it is feasible that common byproducts of combustion will not appear with their fuels.

Different molecules burn differently. They might not be able to stop NOx, but they can make a fuel burns cleaner in an engine. We already know how to make those molecules, but it isn't practical to make gasoline that way for normal use (read 3x the price of pump gas)

The perfect is the enemy of the good.

We have a carbon problem now, that is causing real damage now. We shouldn't be turning our noses up at "stopgap" just because it doesn't do everything we can dream of doing.


I do not question the sanity of carbon neutral gasoline. Esp aviation fuel and rockets.

I was suggesting carbon neutral gas plants which can power electric fleets, as a way to also reduce pollution.

My most immediate question (after others you already answered in this thread) is about getting enough CO2.

When you start absorbing CO2 from the air, won't the CO2 in the neighborhood be depleted very quickly? And I'm assuming you can't pump enormous amounts of air either for various reasons (noise, energy usage, other environmental issues). Of course there's wind to bring more CO2, but I'm curious about your computations.

This won't be a limiting factor. It won't be stagnant air, and the diffusion rate for gases is high.

CCS: large amounts of high quality concentrated CO2 from gas fired electricity can be stored underground https://en.m.wikipedia.org/wiki/Carbon_capture_and_storage

And when power prices are low and the gas fired plant is turned off, you have a transmission system right there ready to deliver power.

They're looking at cheap off-peak electricity sources, one of which is excess wind power at night, so they're likely to be operating when the wind is blowing anyway.

(Not that they need it - gas diffusion is fast - but it's a cute synergy.)

Don't you just need to open a window and wait a few seconds to desaturate a room where too many people breathe ?

Doesn't matter, air is a fluid, so diffusion works in your favor.

Yes, but does it work fast enough?

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