Researchers propose solar methanol island using ocean CO₂ | Hacker News Reader

Researchers propose solar methanol island using ocean CO₂

arstechnica.com

64 pointsDoreenMichele63 comments

100meter^2 x 170,000 solar panel units (to replace long-haul transportation fuel) would be a 1700km^2 square, 41km per side. That's a bit smaller than Fiji and more compact. If you add 50% for methanol manufacture it's almost up to the area of Haiti.

So the oceans have plenty of room for it anyway.

> electrifying trucks .. has proved intractable in the near-term,

Really?

See https://logisticsmgepsupv.wordpress.com/2019/06/01/supermark..., https://www.libertyplugins.com/blog/2019/06/07/byd-electric-..., http://mechcrunch.com/2019/05/10/rigterink-logistics-group-t...

I don't claim they are perfect but it does seem not to be intractable.

There's already a highly efficient solar-powered process for extracting carbon dioxide from seawater called "growing seaweed."

It would be far more efficient simply to collect seaweed from the ocean and put it through fermentation and dry distillation processes to produce ethanol and other fuel products. No new technology breakthroughs required.

I do believe there is work being done on this. That said, removing carbon from the oceans, burning it and releasing it back into the atmosphere feels a little bit counterproductive to me.

At least it will slowdown oceans acidification until people find how to give enough power to the planes without liquid fuel.

In this particular idea I don't like the ship - it will pollute the ocean while transferring the fuel.

I ear a lot of talk about airplane pollution, is it actually a significant contribution?

About 2% of CO2 emissions, according to this:

https://www.atag.org/facts-figures.html

Doesn't matter. Point is: while we need airplanes, we need to power them. While we can't power them using "green" sources of power, we should use liquid fuels. And while we need them, this idea (topic-starter) sounds reasonable.

>removing carbon from the oceans, burning it and releasing it back into the atmosphere feels a little bit counterproductive to me

That's the plan in the OP, isn't it?

Not really as it will stop increase of carbon dioxide. Ocean carbon dioxide also comes from the atmosphere a system where carbon dioxide is just recycled through the atmosphere and oceans system will mean we won't be adding more carbon in the system. That is the current problem the world is producing more and more carbon each year first we need to stop the growth at least reversing it can come once we stop increasing it.

I've been thinking about this particular one a lot, and I think the difference is that it still displaces carbon that would have come from the ground otherwise. Plus in a magical future where energy is cheap and no fossil fuels are used at all, the methanol can be easily used to synthesize many useful chemicals.

And it also doesn't litter the oceans with broken solar panels, since a hurricane will probably destroy these islands.

It would be cool if they could dive to a safe depth to wait out storms and then emerge against once the storm's over

There are no hurricanes on the equator, mind.

Growing anything is not "highly efficient". I doubt the efficiency of sunlight => chemical energy of methanol using seaweed would be higher than 1%.

This is the terrible downside of biomass energy: the enormous areas that are needed because the efficiency is so low.

Efficient or not, seaweed is already growing in the enormous area of the oceans and washing up on beaches worldwide. All that needs to be done is go get it.

How do you turn seaweed into liquid fuel efficiently?

Fermentation and dry distillation.

Seaweed contains a lot of cellulose and starch, just like land-based plants. It can be processed with acids or enzymes to convert these into sugars, just as is done to convert corn starch into corn syrup. The sugary byproduct can be fermented to produce ethanol.

Dry distillation is heating biomass without oxygen. It produces a range of gaseous and liquid fuel byproducts, plus charcoal. Solar heat can of course be used.

I imagine this idea works, but to compare some orders of magnitude... solar cells may have efficiencies of 15%. 70% for electrolysis, unclear for desalination (depends on how pure it has to be), unclear for methanol production but probably >50%... maybe you get 3% net in the product?

It's not amazing, but special engineered algae in perfect environments do what, 10% to biomass in a miracle situation? Isn't a major energy input to dry distillation the drying part, especially in this case? And the energy lost during fermentation is more yes?

Maybe they are in the same range, but I think my bet would be on the solar system over a system requiring collecting algae from the open ocean.

The actual efficiency of algae growth is irrelevant in this case, because we're not paying for the sunlight and there's an excess of seaweed available free for the picking up.

Measures of the theoretical efficiency of solar panels generally don't include the costs of manufacture and maintenance. Until panels become a really cheap and disposable commodity, land-based customers will always be able to outbid someone who wants to put them on the ocean, because of lower maintenance costs.

Solar energy is perfect for dry distillation. It's free.

I can get on board with solar thermal for distillation and other heat inputs to chemical reactions. But collecting algae isn't free.

Past experience with pond algae growth is that the drying part is indeed extremely expensive (using solar). But if you throw it into a gasifier I like it a lot better since it doesn't need to be as dry, so I guess fermentation might be similar although you need cellulosic ethanol tech to work better first. Still didn't break even against solar at the time though (a decade past), and solar has gotten way better.

Maybe the algae tech has improved commensurately, but the tech for biomass handling is much more mature so I'd be a bit surprised if the rate of improvement wasn't much different.

The silliest proposal I ever had to write was for why it made sense to take electricity from a power plant, "free hydrogen" and make chemicals. It was so strange, just use the fuel as a precursor to make the chemicals directly instead of burning it...

Edit: I said as much in the proposal. We did not win.

It's true that collecting algae requires effort to collect and transport. But my ultimate point is that the total energy and resource costs of directly converting seaweed to fuel would be far lower than in OP's proposal. Just as in your power plant anecdote. And you achieve the same goal of removing CO2 from the ocean.

Drying pond algae with solar heat is tricky because you can't concentrate the sunlight too much or you get ash instead of dry algae. But with dry distillation the objective is to pyrolize the input, so you can efficiently use concentrated sunlight.

>you need cellulosic ethanol tech to work better first. Still didn't break even against solar

My proposal isn't competing with solar electricity (which doesn't remove CO2 from the ocean), but with OP's proposal to use solar electricity to produce methanol from CO2 extracted from seawater.

Biological processes are usually much less efficient than industrial processes, so it would be hard to believe that your proposal is better without lots of evidence. If we relied on legumes for nitrogen fertilization of agricultural soil, we would starve.

This sounds like a brilliant idea. Instead of off-shore wind farms, off-shore solar power generation. Convert the electrical energy into chemical one (methanol) and ship it to the consumers. No need for huge upfront investments (those huge wind turbines must cost a pretty penny), or for large underwater cables to carry electricity inland. These floating solar panels could be deployed far away from maritime sea lines, like in the middle of the Pacific. Plenty of sun. No problem with sandstorms, like for solar farms in deserts. If a hurricane is forecasted, you pack up and move away. No need to buy the land from owners who want to hold out for a better price. What's not to like?

> What's not to like?

Salt. Salt makes operating things in the seas an absolute maintenance nightmare.

Oh, yesss. Also, bird poop. Seriously - it is already a problem for solar cells on unmanned offshore oil and gas platforms.

If this was completely without any obstacles, it would have been brought to market about 50 years ago. There are obstacles for sure, but they don't sound insurmountable to me.

Salt. Salt is a problem for anything that floats on the ocean. Plenty of things do that, it's not such a deal breaker.

Bird poop. You need to either be close to some islands, or in the middle of some migration line. In the Pacific ocean there are millions of square miles that don't qualify for either of that.

Barnacles, mollusks, etc. Maybe you can get away with some special paints, or with periodic cleanup. Mauybe you need to coat the bottom of the floating structure with some film of pesticide-infused plastic. I don't know. But I'm willing to give this idea a chance to succeed. What are the alternatives? Floating nuclear power plants?

>What are the alternatives?

This is exactly the right question.

Assuming that the goal is a reduction in atmospheric CO2, there are many alternatives that are at least an order of magnitude more cost-effective. Of those, more land based wind and solar plants are for now the best. The cost of land generally is almost negligibly small - about 0.4% of total for a recent project I looked at. Admittedly, this was in Australia, but given that solar power stations cost circa $0.5 million per hectare in equipment and installation, land (rural land of course) would need to be pretty expensive before it became a significant factor.

Algal slime, barnacles and mollusks too. Actually, the slime might be useful in methanol production. It grows amazingly fast.

Also, they talk about methanol production, but if they are already going through the work of desalination, it would probably make sense to have an integrated processing facility to also extract products that are already commercially extracted from seawater (bromine and manganese)

Perhaps it’s feasible that other trace elements in seawater, e.g. gold, uranium, etc. could also be economically extracted...

Not to mention all the pure oxygen you get out of electrolysis. It seems this system would produce a lot of potentially useful byproducts that could have a big effect on ROI calculations.

I could only see this working in a safe harbor or a port. The ocean is not a serene place for a floating platform unless the platform is elevated above potential water lines such as a wind turbine or offshore oil rig.

What happens to sea life when we restrict the sun over a large area like this? How much microscopic sea life would be killed off in enormous quantities, and would that generate toxicity worse than the CO2 currently being absorbed by the ocean?

These secondary effects are what I’m concerned about as well. Seems this would create a dead zone.

Why not just do this on the shore instead of a floating ship with unmaintainable floating solar islands? I suspect the more realistic scenario though would be to use a huge nuclear power plant to make fuel by pulling CO_2 from the air.

Unless we have costs breakthroughs in nuclear, solar is going to stay cheaper.

I doubt solar is actually cheaper for this process right now.

Last I read Japan still has green plans involving hydrogen. They could just save a step, thereby also conserving energy. In fact, that's an old proposition as an alternative to fossil fuels. Too bad nuclear has enormous public image and political cost problems.

This seems like an old Idea, repackaged with a bit of new technology, i.e. solar panels. Here is a paper from 1984, suggesting methanol production from Ocean Thermal Energy Conversion (OTEC).

https://www.jhuapl.edu/techdigest/views/pdfs/V05_N2_1984/V5_...

What is OTEC? http://www.otecnews.org/what-is-otec/

Disclaimer: I started OTEC News once upon a time.

Wouldn’t it make sense to build these on large lakes and skip the desalination step?

One reason that springs to mind is the shortage of large lakes near the equator. Solar "lily pads" would be much less efficient on the Great Lakes or Lake Baikal, and have seasonal swings of output.

What about the African Great Lakes?

The Great Lakes in Africa are close to the equator.

And they're one group of very few lakes which was the point.

That wouldn't help de-acidify the oceans. But I guess through diffusion it's all connected anyway.

The Mediterranean is connected to the oceans and to the black sea but their salinity is really different, I do not believe diffusion works as easily.

Right but if you take CO2 from the Mediterranean, then it will absorb more from the air, which means the oceans will absorb less from the air.

For what I know, about methanol extraction, it depends of various factors. If we can sacrifice portability, we can just pump salt water to a facility, extract the CO2, and pump it back. What I find novel in this approach is the utilization of seawater for the carbon extraction, but the other steps are known or in active research.

I wonder about the energy payback time or in that case rather the CO2 payback time. The CO2 released through production of silicon is not negligable (in fact for every silicon atom a CO2 molecule is released regardless of the CO2 released during the energy production)

I found an article from 2010 saying that the CO2 breakeven for solar PV was at around the 3-year mark. That article mentioned 225 W panels, the state of the art today is 400W with presumably the same CO2 load to produce. So that would put the payback at more like 2 years. It would get worse again to account for the energy losses in the desalination, CO2 collection and conversion.

Since this CO2 production at a point source it should be easier to capture, and so removed from the equation.

It sounds like quite a concentrated source of CO2.

This is such a novel idea. This is an example of why we need huge investment in this type of thing(idk if you call it green). I would have never thought of something like this, it won't impact the average person's life and it is carbon neutral. If this exact thing won't solve the biggest problem of our lifetime, something like it will.

>…and has an energy storage efficiency of 8% over a 20-year lifetime.

The concept is fun to imagine but these numbers look pretty lousy.

The energy is free, so efficiency is only important for comparison reasons. Is there something better we could be doing with that solar panel output? Solar panels themselves are maybe 22% efficient to begin with so this process cuts the efficiently to about 1/3. Personally, I'm impressed that it's even positive.

I couldn't find anything in the paper how or if the channels are filtered. Microorganisms in the water would be subjected to pretty abnormal conditions while being pumped through the acidic and basic channels, so I hope they do filter the water well?

Interesting idea, I wonder how it can be protected from rough seas?

It says in the article that it would be built in areas of the ocean where break wave heights don’t exceed 7 feet.

But is that just where wave heights rarely exceed 7 feet? It seems like they would still need some kind of safe mode to deal with once per year/once per ten years conditions. Maybe the could fold up.

All the land above sea level between 1'-20' soon (relatively) to be usurped by the measurable volumes of ice being depleted already have lots of pipe and structural (piles and beams) infrastructure protected underground and may could be retrofitted to support the safe mode folding you are suggesting.

SpaceX will be looking for bulk methane and oxygen supply at their offshore Earth-to-Earth transport system within the decade.

These floating fuel production facilities could be nice for ships too - refueling en route means you have to carry less fuel and you run more efficiently.

The most impressive to me, is to read only a single comment worried about the ecological impact and the sustainability

Why not produce artifical steam - aka clouds when the wind is right and make it rain over dry country?

Reply on news.ycombinator.com