I am surprised no one has mentioned replacing the adsorption CO2 scrubbers on space craft[1] with something that is powered by electricity. The article claims 130 grams of CO2 removed from the air per kilowatt-hour. Astronauts might expel 40 - 50 grams of CO2 per hour into the air, so 500wHrs of power keeps the air breathable forever? That is a good deal. For reference the ISS has a crew of 6 and has 84 - 120kW of power capacity [2].
The reaction consumes water, which isn't exactly abundant on a space station or space vessel. You can regain the water by burning the alcohol, which can be done in a combustion chamber without reintroducing the CO2 to the air of the habitat. That's a rather exothermic reaction – and I'm guessing that the bionic leaf also generates excess heat – which might be a problem. Space vessels can only cool down by radiating heat, which I gather to be a quite complex problem. Nevertheless, it might be workable for all I know...
You're overcomplicating this hugely. It's much simpler to burn the alcohol within the astronauts, converting it to a small amount of heat, CO2 and happiness.
You missed the key distinction here, ethanol is not the greatest substance, but is relatively safe for animals. Other side chain alcohols metabolize into byproducts like formaldehyde and well, are highly toxic. This whole distinction is the basis for the sale of "denatured alcohol" / "wood alcohol" and its much cheaper price.
"In some countries, sales of alcoholic beverages are heavily taxed. In order to avoid paying beverage taxes on alcohol that is not meant to be consumed, the alcohol must be "denatured", or treated with added chemicals to make it unpalatable."
Ethanol is normal drinking alcohol. You are thinking of methyl alcohol, methanol.
As little as 10 mL of pure methanol, ingested, is metabolized into formic acid, which can cause permanent blindness by destruction of the optic nerve. 30 mL is potentially fatal, although the median lethal dose is typically 100 mL (3.4 fl oz) (i.e. 1–2 mL/kg body weight of pure methanol)..
And on a space station, most of your heat differential is created by active cooling, so recovering that via Peltier elements is a bit… counter productive.
It's actually the complete opposite - space is not "infinitely cold" it's more like "infinitely isolating" - like the perfect giant thermos. Space suits for example have a whole layer of water tubes just to cool down the astronaught, otherwise they will pass out from their own body's temperature.
Some of it probably could be, but the effiency of those processes are low enough that you'd still have a heat problem. Also, recall that the energy originated with the solar panels to start with. It's a very wasteful way of generating electricity compared to the solar panels, so although it might be worth considering to recover some of the energy investment and eliminate a fraction of the heat, the net output of such a process will probably be an order of magnitude lower than the initial energy investment.
A rule of thumb for remembering whether you want to say "power" or "energy".
If you could replace "power" with "horsepower", you're on the right track!
If you could say "gallons of gas" instead of "power", you mean energy!
wHrs is energy (and kind of a dumb unit. Watts is already joules per second, so you're saying (joules/second)*hours. It would make more sense to just say joules.
It does actually. The alcohols are mainly made from the carbon in CO2 and the hydrogen in H2O. Isobutanol is (CH3)2CHCH2OH, and isopropanol is C3H8O. So that's a lot of O left over.
Roughly speaking, energy + CO2 = carbon + oxygen. Left to right is photosynthesis. Right to left is fire.
[edit: do be careful when applying this equation in practice! Often, hitting CO2 with a big hammer just yields CO, or carbon monoxide. It's poisonous!]
Actually nuclear submarines already make their own oxygen with electrolysis so they don't ever need to (nor do they) surface, except to exchange personnel or to load additional food.
Of course, they also need separate CO2 scrubbers to keep the air breathable, which consume a lot of power, use caustic and hazardous chemicals, and make the whole ship smell pretty bad.
An artificial leaf that removed CO2 without these downsides might justify a refit.
This needs the additional information that photosynthesis is incredibly inefficient. It's <5% IIRC, so we already have solar panels almost a magnitude better than what nature did.
(RuBisCO as the protein at the center of the process is also quite strange: it's huge and slow. As in 'this ain't funny any more, start working' slow with about a reaction per second.)
The comparison of photosynthesis vs energy generated by solar panels isn't very good, because it neglects the whole biology of the organism, which is optimized for things other than maximum photosynthetic output. For example, leaves are often targets of herbivory, so a plant might want to make a tradeoff [1] of less efficient photosynthesis for better herbivory defense. Or, it might be too costly to do photosynthesis, which requires the input of carbon dioxide, water, and light. In a very dry & hot environment, to get enough carbon dioxide into the leaf, the leaf will lose water by having its stomata open. Google "leaf economics spectrum" for a quick tutorial (the concept isn't 100% correct but it's a good starting point). Compare the leaves of tropical plants (say a banana palm) to arid plants (mesquite tree).
[1] I use this a teleological shorthand for "the selective environment has weeded out species that happen to fall on the wrong side of the tradeoff."
Exactly. I suppose the energy density of sugar is pretty high. The non-nuclear fuel with the highest volumetric energy density is jet fuel[1] at 37.4 MJ/L. I wonder how the most efficient natural compound (adenosine triphosphate / sugar / etc) compares...
ATP + H20 -> ADP + P produces only 30kJ/mol. A mole of ATP weighs ~500g. You likely get a lot more energy from burning it (the Wikipedia doesn't say), as you do with jet fuel, but that reaction is too hard to reverse to be useful for organisms.
A mole of glucose produces 2800kJ/mol when you burn it. A mole weighs ~180g.
Using http://lmgtfy.com/?q=jet+fuel+density to get a range of 775.0-840.0 g/L for jet fuel, that gives us 37.4MJ/807.5g (taking the average of the jet fuel's mass) against 2.8MJ/180g for glucose.
Scaling the denominator of each to 1kg, that's ~46.3MJ/kg for jet fuel and ~15.6MJ/kg for glucose.
Given how biochemically cheap glucose is to produce compared to jet fuel, I'm surprised it's only off the state-of-the-art by a factor of three.
I believe the trick is that they harvest "95 percent of it from the light they absorb", emphasis added. It's sort of like saying an efficient solar system only loses 5% of the energy absorbed by the solar panels.
Photosynthesis may be quite efficient internally, but it's not very good at capturing all of the available power. It really is 3-6%, where even cheap solar panels can achieve 15-20% or higher these days.
Efficiencies are ~1-3% in most plants, with 5% a possible high. Algae can reach 10% without various artificial stimulation. Given gro-lites and other factors (which tend to defeat the purpose), much higher per-hectare yields have been achieved.
As others note, plants offer many, er, plantly services. They're (usually) self-supporting, have disease, insect, and pest deterrance capabilities, self-transport water and minerals, and arrange for their own replication.
In many cases, a seed in a hole, or even on bare ground, is all the infrastructure you need to start manufacturing a new plant. Constructed infrastructure tends to have higher investment requirements.
I suspect there might well be an evolutionarily balanced tradeoff between "construction cost" and "lifetime energy output" of a plant's photosynthesis machinery - as well as a likely overabundance of available solar energy in terms of what a plant actually can use. (Why build a potentially more complex and fragile photosynthesis pathway that's 50% more efficient, if you can instead just grow twice as much leaf surface area?)
But there are places where plants compete fiercely for small amounts of sunlight, such as in forests (especially tropical rainforests). Doesn't your theory suggest they'd use more efficient systems there?
Don't forget plants get the energy back from making a leaf in a few weeks. Solar panels take considerably longer. Generally plants are optimized to compete with others in their niche and as such it's exponential growth that's most important not total energy capture.
Is it actually tropical rainforests, or temperate, that limit sunlight most? Old-growth PNW forests often have large patches of western hemlocks that produce so much shade that no other tree can grow under it, not even conifers - and unless there's a fire to clear some space out, it can stay that way for centuries.
Selection pressure may well have shifted towards C4 in the future if we hadn't come along and been kind enough to dig up some fossilized carbon and put it back into circulation.
I don't know but my guess is to have more efficient collection/processing may require bigger leaves which may be too heavy or catch more wind damaging branches.
> The device uses solar electricity from a photovoltaic panel to power the chemistry that splits water into oxygen and hydrogen. Microbes within the system then feed on the hydrogen and convert carbon dioxide in the air into alcohol that can be burned as fuel
Only the hydrogen + co2 -> alcohol part uses biological components.
I remember my biology teacher's description of photosynthesis: "If you have a river of gold running through your backyard, you don't care how much of it you splash all over the place when you carry the buckets full back to your house."
The article seems to indicate this is electrically powered, not powered by light. Where's the photosynthesis? First they make electricity, then they crack water into oxygen and hydrogen, then they combine the hydrogen and C02 to make hydrocarbons. If you've got electricity, why make fuel? That's wasteful.
Not only that, but if you read the paper, their system is not sustainable, the components break down pretty fast. Then there is this little detail that IPA is not really a useful fuel. So a lot of PR, but not that much to show for.
And my read from the first version of that "leaf", which isn't a leaf at all, is that the original goal was to go after hydrogen generation, but since the hydrogen economy is not trendy anymore,then have a new twist on it...
Science journal is now more about how many clicks they are getting than the actual quality and novelty of the work.
Seems like solar is more or less a break even, where nuclear /wind/geothermal/hydro are pure wins, which makes sense I suppose. Could you manufacture enough of these to consume 1 kilowatt-hour without generating more CO2 in the process than they would consume in their lifecycle?
That's true, but it's important to remember that the amount of waste produced by nuclear power generation is many, many orders of magnitude smaller than fossil fuels.
Let's say you want to generate 1 megawatt-hour of electricity (roughly enough to power an average American household for a month). With coal power, you get roughly 2,000 pounds of carbon dioxide dumped into the atmosphere. [1] To generate the same amount at a nuclear plant, the waste primarily consists of about 3 grams of spent fuel. [2][3]
(And before anyone jumps on me, I'm not trying to dismiss other renewable options... just trying to put nuclear power in perspective.)
That's probably based upon older reactor designs like everything in the nuclear industry, since regulation had made progress slow-going.
Newer designs, and some others, burn spent fuel. Out of the 3 major nuclear reactor incidents, all were old reactor designs. There are new ones that also cannot meltdown in the common understanding of the term.
Don't forget coal mining releases nuclear radiation, since you are unearthing radioactive minerals. So much so, that you are exposed to more radiation in the vicinity of a coal plant than a nuclear reactor.
Here in South Australia, the government, royal commission and a citizens' jury are looking very seriously at establishing a long-term, highly secure nuclear waste dump. We have a lot of very remote areas in this state, and I believe they're looking at a spot with clay very deep down that can be used to insulate against geological movement. The facility is being planned to survive for thousands of years.
As I understand it, being paid to store nuclear waste is being viewed as an income stream for the state to backup or replace income from mining operations.
I'm always suspicious of things "planned to survive thousands of years". I'll bet politicians in Rome and Sparta big-noted themselves with "projects which'll last thousands of years!" (which they then contracted out to their brother-in-law). So far as I can tell there's not much other than Pyramids which humanity has designed/built that could plausibly claim to have "survived thousands of years", and even those didn't come close to being impregnable enough to be considered "safe" for keeping curious humans away from long half life radioactive trash...
Agreed. And Hammam Essalihine/Aquae Flavianae is a Roman bath which is still in use.
Regarding the Pont du Gard, it's intact "due to the importance of its secondary function, as a toll bridge. For centuries the local lords and bishops were responsible for its upkeep, in exchange for the right to levy tolls on travellers using it to cross the river."
I believe bigiain's point is that the structures needed active upkeep to last thousands of years.
Your point is true about people robbing the masonry, but that's closely related to bigiain's comment about "keeping curious humans away from long half life radioactive trash".
I should add that I believe the plan is to do significant work in sealing compartments so anyone looking to wreak havoc would need to breach the facility, get down a significant distance and then work through a huge amount of concrete or clay or whatever it would be.
I think the supply line from port to the facility would be a softer target and is something the jury and stakeholders would be considering in serious detail.
Oh, great point, I hadn't even considered that. I'm sure creating all those steel/concrete containers isn't the most CO2 friendly activity. AFAIK most plants store onsite so there's no transportation cost at least.
Very cool. I thought it was going to be more 'biological' i.e. less about finding a catalyst, and more about microbes and chlorophyll somehow.
I think technology creates things, sometimes problems, and then newer technology sometimes addresses these problems. I like the concept of all of these CO2 extraction-for-energy technologies that seem to be popping up lately.
Now, let's hope they can scrub some CO2 from the atmosphere, but not too much! After all, the climate models have been proven to be underestimating the rise of temperature, so the models are deemed not reliable for prediction or forecasting.
Take too much CO2 out, and we're in for a Global Winter. Sort of like the old Twilight Zone episode on TV (Ok, I'm old) where a guy is feverish, and in the background the Earth is getting too hot because of the sun getting closer? He then wakes up and it is snowing outside, and just when you think it is fine and dandy, it is the beginning of an Apocalyptic Winter!
It should be noted that almost every previous article referencing "new leaf" ... "more efficient than natural photosynthesis", explains a process of slitting water to it's two atomic components.
The leaf in this article implies a completely different product. Alcohol... It's quite a different track, and promising if true.
A promising side effect would be the removal of CO2 from the atmosphere. Although burning the fuel probably returns it back, so it's only helpful inasmuch as it replaces other sources of fuel.
Alcohol on the ground causes less problems than excessive CO2 in the air, and still better to recycle the problematic CO2 in the air than increase its volume by burning oil from the ground.
There seems to be something about solar in particular that engenders overly optimistic claims. I've read several breathless stories over a span of decades about next-generation solar panels for instance, and yet we still have the same old ones, albeit manufactured more and more cheaply.
There has to be a science fiction story where the crew urinates on a platinum rich asteroid to generate enough fuel to get them out of some life threatening predicament.
Some of you might wonder how did the engine block resist to such immense detonation inside the combustion chamber. This may not be the answer you were looking for – and most of you might not believe it – but it seems BMW was in fact using seasoned inline 4 cylinder blocks – picked up from several junkyards – for their F1 operations. The interesting part about it was that the blocks were kept out in the cold and urinated upon in order to strengthen their composition.
stross's "accelerando" had a great reference to that:
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Getting back to the history lesson, the prospects for the decade look mostly medical.
A few thousand elderly baby boomers are converging on Tehran for Woodstock Four. Europe is desperately trying to import eastern European nurses and home-care assistants; in Japan, whole agricultural villages lie vacant and decaying, ghost communities sucked dry as cities slurp people in like residential black holes.
A rumor is spreading throughout gated old-age communities in the American Midwest, leaving havoc and riots in its wake: Senescence is caused by a slow virus coded into the mammalian genome that evolution hasn't weeded out, and rich billionaires are sitting on the rights to a vaccine. As usual, Charles Darwin gets more than his fair share of the blame. (Less spectacular but more realistic treatments for old age - telomere reconstruction and hexose-denatured protein reduction - are available in private clinics for those who are willing to surrender their pensions.) Progress is expected to speed up shortly, as the fundamental patents in genomic engineering begin to expire; the Free Chromosome Foundation has already published a manifesto calling for the creation of an intellectual-property-free genome with improved replacements for all commonly defective exons.
Experiments in digitizing and running neural wetware under emulation are well established; some radical libertarians claim that, as the technology matures, death - with its draconian curtailment of property and voting rights - will become the biggest civil rights issue of all.
For a small extra fee, most veterinary insurance policies now cover cloning of pets in the event of their accidental and distressing death. Human cloning, for reasons nobody is very clear on anymore, is still illegal in most developed nations - but very few judiciaries push for mandatory abortion of identical twins.
Some commodities are expensive: the price of crude oil has broken eighty Euros a barrel and is edging inexorably up. Other commodities are cheap: computers, for example. Hobbyists print off weird new processor architectures on their home inkjets; middle-aged folks wipe their backsides with diagnostic paper that can tell how their cholesterol levels are tending.
The latest casualties of the march of technological progress are: the high-street clothes shop, the flushing water closet, the Main Battle Tank, and the first generation of quantum computers. New with the decade are cheap enhanced immune systems, brain implants that hook right into the Chomsky organ and talk to their owners through their own speech centers, and widespread public paranoia about limbic spam. Nanotechnology has shattered into a dozen disjoint disciplines, and skeptics are predicting that it will all peter out before long. Philosophers have ceded qualia to engineers, and the current difficult problem in AI is getting software to experience embarrassment.
Fusion power is still, of course, fifty years away.
Who puts a search box at the absolute bottom of the page? I had no idea that was there, and it took me a few seconds to see it when I was explicitly looking for it.
It seems disingenuous to say this is "more efficient than natural photosynthesis" when it's a bioreactor using photosynthesizing microbes (and thus presumably use the same chlorophyll-based chemistry as natural photosynthesis).
On the other hand, I wonder about the potential for evolution to occur inside reactors like these, essentially self-optimising them over time.
I read science fiction story where they're on a colony on venus where the big problem is "how do we do make artificial photosynthesis? Plants are rubbish." but it was a free self-published novel and I now cannot find it. Anyone else read it?
I cannot fathom why we have large scale, highly efficient meat production facilities (remember: animal rights are only relevant to hippie tree huggers), yet there's virtually no commercial efforts to harness plants. The technology exists [0]; I don't understand what the practical or political problems are. I think small scale plant reactors have the potential of being able to be manufactured very cheaply; maintenance is probably the issue, but I'd like to hear from an expert in the field.
The question is if this is more efficient than just using solar panels + batteries to power something up. My guess is it's not, probably not even close. But perhaps there can be some niche uses for it where this system complexity and lower efficiency still makes more sense than using batteries.
So if you replace standard solar panels with this and you burn the alcohol in an engine each hour, does it produce more or less electricity each hour if we know it's 10x more efficient then natural photosynthesis?
[1] Study problem on CO2 removal from NASA -- https://www.nasa.gov/pdf/519338main_AP_ED_Chem_CO2Removal_St...
[2] https://www.nasa.gov/mission_pages/station/structure/element...