
New “Leaf” Is More Efficient Than Natural Photosynthesis - jseip
http://www.scientificamerican.com/article/new-bionic-leaf-is-roughly-10-times-more-efficient-than-natural-photosynthesis/?wt.mc=SA_Twitter-Share
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ChuckMcM
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].

[1] Study problem on CO2 removal from NASA --
[https://www.nasa.gov/pdf/519338main_AP_ED_Chem_CO2Removal_St...](https://www.nasa.gov/pdf/519338main_AP_ED_Chem_CO2Removal_Stoich%2012-20-10.pdf)

[2]
[https://www.nasa.gov/mission_pages/station/structure/element...](https://www.nasa.gov/mission_pages/station/structure/elements/solar_arrays.html)

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pavanky
This leaf isn't generating oxygen though. It's generating alcohols. I wonder
what it would take to generate oxygen out of the alcohol.

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dTal
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!]

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matt4077
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.)

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swamy_g
I don't understand. Photosynthesis has been hailed as one of the most
efficient processes by nature.

[http://www.scientificamerican.com/article/when-it-comes-
to-p...](http://www.scientificamerican.com/article/when-it-comes-to-
photosynthesis-plants-perform-quantum-computation/)

~~~
ignostic
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.

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Animats
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.

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dragonwriter
> If you've got electricity, why make fuel?

Because fuel is in lots of cases a better way to store (and transport) energy
to be used later and a different time and potentially place.

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cmccart
This got me thinking: how much CO2 is emitted by different energy sources in
generating 1 kilowatt-hour?

I came across this link: [http://blueskymodel.org/kilowatt-
hour](http://blueskymodel.org/kilowatt-hour)

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?

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sevenless
I don't see any accounting for the cost of storing nuclear waste, long-term.
(Nobody wants to do it; how do you even estimate that?)

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unchocked
It's easy, you take the cost of Yucca mountain depository (which is already
sunk, btw), and amortize that over 10,000 years or so.

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omegaworks
So easy!

Watch how it's done:
[https://www.youtube.com/watch?v=HeVPMzJOFrQ](https://www.youtube.com/watch?v=HeVPMzJOFrQ)

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eggy
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!

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Osiris30
Previous discussions on 'artificial leaves':

[https://hn.algolia.com/?query=artificial+leaf](https://hn.algolia.com/?query=artificial+leaf)

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headShrinker
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.

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mark-r
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.

~~~
azinman2
Better to recycle the existing co2 than remove oil from the ground and put
that into the air.

~~~
Amygaz
You still end-up with a by-product that you need to do something with. In this
case burning it...

~~~
azinman2
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.

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fernly
Found the paper:

[http://science.sciencemag.org/content/352/6290/1210](http://science.sciencemag.org/content/352/6290/1210)

Found a nice quote in the LA Times coverage:

[http://www.latimes.com/science/sciencenow/la-sci-sn-
bionic-l...](http://www.latimes.com/science/sciencenow/la-sci-sn-bionic-leaf-
photosynthesis-20160603-snap-story.html)

“Stay tuned because Pam and I are on a path to do nitrogen fixation in the
same sort of way we’ve just done water splitting,” [Nocera said]

~~~
davidf18
Thank you for finding the article.

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taneq
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.

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sleepychu
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?

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Kurtz79
Might it be this one ?

[http://www.goodreads.com/book/show/8065404-containment](http://www.goodreads.com/book/show/8065404-containment)

(Fifth google result searching "photosynthesis venus novel")

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sleepychu
Yes! Thank you. I'm sure I've searched similar things in the past but maybe I
was too focused on the fact that it was self-published.

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_pmf_
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.

[0]
[https://en.wikipedia.org/wiki/Algae_bioreactor](https://en.wikipedia.org/wiki/Algae_bioreactor)

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lechevalierd3on
I was expecting some crazy analogy between the a Nissan Leaf and natural
photosynthesis.

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mtgx
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.

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frgewut
Does anyone know how does the efficiency of an entire tree compare (i.e a
single leaf reflects some light, which then is absorbed by another leaf)?

I would guess that number should be higher than simple "photosynthesis
efficiency".

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fsiefken
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?

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naasking
Very neat technology for a possibly carbon neutral fossil fuel economy.

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lwis
Does this present any potential improvements to solar panel efficiency?

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sanoy
This is insanely cool.

