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This needs the additional information that photosynthesis is incredibly inefficient. It's <5% IIRC, so we already have solar panels almost a magnitude better th
by matt4077 10y ago
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.)
- jessriedel 10y agoDoes anyone know what the evolutionary bottlenecks/tradeoffs are for more efficient photosynthesis?
- chris_va 10y agoIt is a very very old protein, stuck in local maximum more than anything else.
- jessriedel 10y ago> stuck in local maximum more than anything else What's the argument that this is true, rather than it being better than more efficient proteins on some other metric?
- kibibyte 10y agoPlants in arid environments have evolved a more efficient carbon fixation process -- https://en.wikipedia.org/wiki/C4_carbon_fixation https://en.wikipedia.org/wiki/C4_carbon_fixation -- in response to decreased water in the environment. Despite this, C3 plants still dominate the planet, so somehow selection pressure hasn't shifted strongly towards C4 plants in non-arid environments.
- jessriedel 10y agoAccording to the wikipedia page, C4 is more efficient in water usage, but less efficient than C3 in energy production. https://en.wikipedia.org/wiki/C4_carbon_fixation https://en.wikipedia.org/wiki/C4_carbon_fixation
- kibibyte 10y agoOh makes sense. I somehow read over that sentence.
- gd1 10y agoSelection 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.
- bigiain 10y agoI 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?)
- jessriedel 10y agoBut 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?
- lordnacho 10y agohttps://en.wikipedia.org/wiki/C4_carbon_fixation https://en.wikipedia.org/wiki/C4_carbon_fixation Example of such an evolutionary step. C4 vs C3 photosynthesis.
- jessriedel 10y agoC4 is more efficient in water usage, but less efficient than C3 in energy production
- Retric 10y agoDon'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.
- int_19h 10y agoIs 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.
- dghughes 10y agoI 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. Or maybe trees are just lazy by nature?
- swamy_g 10y agoI 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-photosynthesis-plants-perform-quantum-computation/ http://www.scientificamerican.com/article/when-it-comes-to-p...
- Sharlin 10y agoThat particular stage in the hugely complex reaction pathway is hailed as efficient. The whole thing, considerably less so.
- ignostic 10y agoI 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.
- flogic 10y agoPhotosynthesis is a complex process. That article only covers one step of many.
- matt_wulfeck 10y agobut solar panels don't grow out of dirt and replicate themselves.
- jharger 10y agoYet.
- digi_owl 10y agoAnd the first thing that comes to mind is a gray goo scenario.
- danharaj 10y agoLife is a gray goo scenario.
- pimlottc 10y agoPink goo? Red goo?
- Roboprog 10y agoRed goo? My circulatory system uses a copper based hemoglobin analogue, you insensitive clod :-) (arthropod blood) https://en.wikipedia.org/wiki/Hemocyanin https://en.wikipedia.org/wiki/Hemocyanin
- NoGravitas 10y agoGreen goo and pink goo are the accepted terms, at least according to @cstross.
- chriswarbo 10y ago> but solar panels don't grow out of dirt Neither do leaves, they grow out of the air ;) https://www.youtube.com/watch?v=N1pIYI5JQLE https://www.youtube.com/watch?v=N1pIYI5JQLE
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- Rhinobird 10y agoPhotosynthesis is between 0.1% and 2% efficient. Seems that increasing the efficiency of photosynthesis could lead to another agricultural revolution.
- digi_owl 10y agoDo wonder what knock on effects that may have. Would not surprise me if it makes such plants more susceptible to diseases.
- aaron-santos 10y agoIn fact, increasing the efficiency of photosynthesis is the goal of one such project: c4 rice [1]. [1] - https://c4rice.com/the-science/photosynthetic-pathways/ https://c4rice.com/the-science/photosynthetic-pathways/
- shoyer 10y agoThis is not quite right. Solar panels create an electric current, not fuel. This is a much easier task. When you read that photosynthesis has 1-2% efficiency, that's because they're measuring the efficiency of converting light into sugar.
- winter_blue 10y agoExactly. 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... [1] https://en.wikipedia.org/wiki/Energy_density#Energy_densities_of_common_energy_storage_materials https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...
- dredmorbius 10y agoIt's not the energy density of a fuel that matters so much as its net energy content and conversion efficiency. You'll find lipids compare favourably to jet fuel (kerosene), which is distantly related to plant-generated lipids in the first place.
- adrianN 10y agoATP + 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.
- spaceheeder 10y agoUsing http://lmgtfy.com/?q=jet+fuel+density 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.
- jonchang 10y agoThe 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."
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- Tunabrain 10y agoBut this does use solar panels. > 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.
- dredmorbius 10y agoEfficiencies 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.
- garfieldnate 10y agoI 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."