I always imagined this as a future basic genetic modification with a gene trigger: before starvation sets in your cells would manufacture a bunch of chloroplasts and turn your skin green, to give you a chance with water and sunlight to get some more run way on survival. Then if your calorie levels rise the chloroplasts get re-absorbed.
The problem is that this process would likely use more energy than you could ever hope to gain from photosynthesis, even assuming it could be as efficient as in algae.
In his 1976 essay on (or against) genetic engineering [1] Erwin Chargaff wrote "But screams and empty promises fill the air: Don't you want cheap insulin? (...) And how about a green man synthesizing his nourishment: 10 minutes in the sun for breakfast, 30 minutes for lunch, and 1 hour for dinner?" Nice to see that scientists are actually trying.
It also comes up at least once in John Varley sci fi books. People can get themselves turned into space-floating plants and just sort of hang around saturn. I can't remember if they get genetically modified to photosynthesize or they wear a suit that does it.
Insulin today is produced cheaply in genetically modified microbes, this is the technology that Chargaff is alluding to, which was first succesful 2 years after his letter, in 1978.
For instance you could imagine wearing an LED suit that exposes you to a lot of light. You need 100W for your basal metabolism, if photosynthesis were 10% efficient you'd be dealing with 900W of waste heat which is a lot, real-life efficiency would be worse than that.
You're thinking entirely replacing our energy source. What about just boosting it passively. Imagine if energy requirements for every human were decreased by 2%
Probably not dolable on planetary scale but ii imagine it'd help in space, esp if combined with some other mods like fiximg the vitamin c gene to remove scurvy. If we could use light to suppliment our metabolism it'd mean fewer physical resources to bring alon.
per day though. I think others are right that it has applications in space. going with the butter example, 5 people on a year long mission is almost 11kg you don't have to bring up to space.
on an environmental perspective, if applied to everyone, its almost half a quadrillion kJ removed a year, plus supply chain logistics, waste, packaging,
I still think its probably a ridiculous pipedream, but even pipedreams are meant to be dreamt.
It's still $55k, that could be used somewhere else! Assuming the $5k/kg cost of getting something into LEO. Actual cost is even higher because more delta V is required to get off LEO.
How come chlorophyll photosynthesis isn't more efficient? 6% for plants, 20% for (ordinary) solar panels. Don't plants have to outcompete other plants? Then there's red algae, which inhabit dark places like caves and the ocean, and they're apparently way more efficient. Is it somehow not advantageous to a tree to photosynthesize efficiently?
I think efficiency of plants, but that's measure from light to sugar that is a good long term storage material. Solar panels get 20% but you get electricity that is difficult to store.
I think you linked an article about red algae. I took a look and I think they are counting the efficiency in a strange way to claim "almost 100%". Probably almost 100% in the first step of capturing the energy, not in the complete process to transform it into something useful. (And probably using only monochrome light, but I can't understand the details)
Oh, I removed that link because it was talking about efficiency of light transmission to reaction centers, or something like that, i.e. only the start of the process. And you're quite right, I wasn't even looking at the whole process myself, I'd need to consider a solar-powered carbon-fixing, uh, plant. As in industrial plant.
The terrestrial plants use only a small part of the spectrum, because the available light is frequently too abundant for them, which was even more true at the beginning of their evolution, when there were no forests providing shadows.
For terrestrial plants, it is usually a more important problem to not be overwhelmed by too much energy captured from light, than to capture more.
This is why the green plants dominate on continents, because they reflect a good part of the light, instead of absorbing it, so they are not destroyed by excessive light.
On the other hand, in the oceans the green algae are a minority in comparison with diatoms, brown algae and other kinds of algae that absorb much larger fractions of the solar light, because they can use only the less intense light that remains after passing through water.
On the bottoms of waters there are many places where there are combined algal and bacterial mats that act like a multijunction photovoltaic cell, i.e. there are multiple layers of different algae and bacteria, e.g. diatoms, blue-green algae (cyanobacteria), purple non-oxygenic phototrophic bacteria and green non-oxygenic phototrophic bacteria, so that each layer absorbs a different part of the solar light spectrum, resulting in almost complete absorption through all layers.
You might clarify "too abundant", "overwhelmed", and "destroyed".
Elsewhere, somebody told me:
> one must know that chemical reactions with gases are very dependent on the pressure of the gases. Even the direction, that is if it's exothermic or endothermic, depends highly on the pressure. If RuBisCo would be faster the carbon dioxide could not come fast enough onto the site of enzymatic activity and would therefore drop in pressure there.
And
> Generally plants have too much energy for the amount of water and, most important, carbon dioxide, to synthesize sugar.
So the idea I come away with is that CO2 is not abundant enough for the energy (that a differently-made plant could extract from the light) to be useful.
By overwhelmed, I have meant exactly this, i.e. if the terrestrial plants had captured more solar energy, the only effect would have been the accumulation in their cells of free oxygen and of intermediate reduced chemical compounds that could not be used fast enough to synthesize useful substances like carbohydrates, for various reasons, of which the lack of enough captured carbon dioxide is a major reason.
The capture of carbon dioxide can be hampered by the free oxygen produced by capturing solar light, even if the plant cells attempt to separate the cell parts where these incompatible processes occur.
It might be possible to improve the productivity of the plants by improving their ability to capture carbon dioxide, more than by improving their ability to capture light. However I believe that such research directions are misguided. We are already able to capture light very efficiently with non-biological devices and the same is likely to become true for carbon dioxide capture and electrolytic reduction.
What is unlikely to happen any time soon is to find any way for synthesizing complex organic molecules like those needed for food as efficiently as by using living cells.
So the non-biological capture of solar energy and capture and reduction of carbon dioxide and dinitrogen should be combined with biological syntheses in cultivated organisms.
That is a fun question. Like life around hydrothermal vents, but on land. I can't search for answers easily because of course volcanic soil is really fertile anyway, so people have plenty to say about plants that grow around volcanos already, without reference to carbon dioxide.
The solution is not incorporating photovoltaic cells into living plants.
The most efficient way of making food and other complex organic molecules is to make artificial devices that would use solar panels and which would use the energy to capture both carbon dioxide and nitrogen from the air (possibly also water from the air humidity) and which would make ammonia and some very simple organic molecule.
Whatever is produced with solar energy, could be used as food for some genetically modified fungi or other similar organisms (e.g. genetically modified parasitic plants). These genetically modified living organisms would perform all the complex enzymatic syntheses required to make food suitable for humans or any other complex organic substances of interest. Some time in the future it should become possible to create a fungus (or a parasitic plant) capable of growing not only mushrooms, but also bananas, wheat grains, chicken eggs, turkey thighs or whatever else one could want to harvest from such a culture.
So the coupling between solar panels and some culture of living beings should be external, through food.
This has the advantage that the surface would be occupied only by the solar panels and the associated chemical reactors that would store the solar energy into simple organic molecules and ammonia (possibly combined in a simple amino-acid like glycine), while making food could be done e.g. in underground facilities and only when needed and producing only whatever is in demand at a given time.
I always imagined this as a future basic genetic modification with a gene trigger: before starvation sets in your cells would manufacture a bunch of chloroplasts and turn your skin green, to give you a chance with water and sunlight to get some more run way on survival. Then if your calorie levels rise the chloroplasts get re-absorbed.
The problem is that this process would likely use more energy than you could ever hope to gain from photosynthesis, even assuming it could be as efficient as in algae.
In his 1976 essay on (or against) genetic engineering [1] Erwin Chargaff wrote "But screams and empty promises fill the air: Don't you want cheap insulin? (...) And how about a green man synthesizing his nourishment: 10 minutes in the sun for breakfast, 30 minutes for lunch, and 1 hour for dinner?" Nice to see that scientists are actually trying.
[1] https://www.science.org/doi/10.1126/science.11643312
It also comes up at least once in John Varley sci fi books. People can get themselves turned into space-floating plants and just sort of hang around saturn. I can't remember if they get genetically modified to photosynthesize or they wear a suit that does it.
In the novel Old Man’s War, everyone is a green genetically modified super soldier. To reduce potential calorie intake for the troops.
What about water?
Insulin is already very cheap, the markup in the US is not due to manufacturing costs.
Insulin today is produced cheaply in genetically modified microbes, this is the technology that Chargaff is alluding to, which was first succesful 2 years after his letter, in 1978.
unfortunately to meet animal energy requirements one would need a huge canopy; it'd probably only be feasible outside our gravity well.
The metabolic rate of an animal scales as 0.75 the mass, I guess surface area is about the 0.66 power of mass so I guess it gets more favorable when you get smaller but not by a lot. See https://book.bionumbers.org/how-does-metabolic-rate-scale-wi...
Note thermal efficiency is a problem too.
For instance you could imagine wearing an LED suit that exposes you to a lot of light. You need 100W for your basal metabolism, if photosynthesis were 10% efficient you'd be dealing with 900W of waste heat which is a lot, real-life efficiency would be worse than that.
Maybe you could combine it with some kind of hibernation to drastically reduce metabolism?
You're thinking entirely replacing our energy source. What about just boosting it passively. Imagine if energy requirements for every human were decreased by 2%
Probably not dolable on planetary scale but ii imagine it'd help in space, esp if combined with some other mods like fiximg the vitamin c gene to remove scurvy. If we could use light to suppliment our metabolism it'd mean fewer physical resources to bring alon.
> fixing the vitamin c gene to remove scurvy
There's other possible fixes too. For starters, Vitamin D?
> Imagine if energy requirements for every human were decreased by 2%
Taking the spherical human to require 8400 kJ/day, we're talking ~170 kJ replacement, or:
Not sure that all that biohacking would be worth the single extra smear/swig/bite?per day though. I think others are right that it has applications in space. going with the butter example, 5 people on a year long mission is almost 11kg you don't have to bring up to space.
on an environmental perspective, if applied to everyone, its almost half a quadrillion kJ removed a year, plus supply chain logistics, waste, packaging,
I still think its probably a ridiculous pipedream, but even pipedreams are meant to be dreamt.
11kg is nothing...
It's still $55k, that could be used somewhere else! Assuming the $5k/kg cost of getting something into LEO. Actual cost is even higher because more delta V is required to get off LEO.
That's not a marginal cost, it's some amortized cost.
Maybe this would be enough to get people onto more lean meats, and a reduction of cattle industry? (Is that worth biohacking for?)
> Taking the spherical human ...
Otherwise known as an American? ;)
Relevant what-if-xkcd https://what-if.xkcd.com/17/
How come chlorophyll photosynthesis isn't more efficient? 6% for plants, 20% for (ordinary) solar panels. Don't plants have to outcompete other plants? Then there's red algae, which inhabit dark places like caves and the ocean, and they're apparently way more efficient. Is it somehow not advantageous to a tree to photosynthesize efficiently?
I think efficiency of plants, but that's measure from light to sugar that is a good long term storage material. Solar panels get 20% but you get electricity that is difficult to store.
Some plants have slightly better efficiency https://en.wikipedia.org/wiki/C4_carbon_fixation but not too much.
I think you linked an article about red algae. I took a look and I think they are counting the efficiency in a strange way to claim "almost 100%". Probably almost 100% in the first step of capturing the energy, not in the complete process to transform it into something useful. (And probably using only monochrome light, but I can't understand the details)
Oh, I removed that link because it was talking about efficiency of light transmission to reaction centers, or something like that, i.e. only the start of the process. And you're quite right, I wasn't even looking at the whole process myself, I'd need to consider a solar-powered carbon-fixing, uh, plant. As in industrial plant.
I agree.
plants only use part of the spectrum. Likely they have hit some local or maybe even global maximum that would be hard to evolve past. See https://en.wikipedia.org/wiki/Photosynthetic_efficiency
The terrestrial plants use only a small part of the spectrum, because the available light is frequently too abundant for them, which was even more true at the beginning of their evolution, when there were no forests providing shadows.
For terrestrial plants, it is usually a more important problem to not be overwhelmed by too much energy captured from light, than to capture more.
This is why the green plants dominate on continents, because they reflect a good part of the light, instead of absorbing it, so they are not destroyed by excessive light.
On the other hand, in the oceans the green algae are a minority in comparison with diatoms, brown algae and other kinds of algae that absorb much larger fractions of the solar light, because they can use only the less intense light that remains after passing through water.
On the bottoms of waters there are many places where there are combined algal and bacterial mats that act like a multijunction photovoltaic cell, i.e. there are multiple layers of different algae and bacteria, e.g. diatoms, blue-green algae (cyanobacteria), purple non-oxygenic phototrophic bacteria and green non-oxygenic phototrophic bacteria, so that each layer absorbs a different part of the solar light spectrum, resulting in almost complete absorption through all layers.
You might clarify "too abundant", "overwhelmed", and "destroyed".
Elsewhere, somebody told me:
> one must know that chemical reactions with gases are very dependent on the pressure of the gases. Even the direction, that is if it's exothermic or endothermic, depends highly on the pressure. If RuBisCo would be faster the carbon dioxide could not come fast enough onto the site of enzymatic activity and would therefore drop in pressure there.
And
> Generally plants have too much energy for the amount of water and, most important, carbon dioxide, to synthesize sugar.
So the idea I come away with is that CO2 is not abundant enough for the energy (that a differently-made plant could extract from the light) to be useful.
That is correct.
By overwhelmed, I have meant exactly this, i.e. if the terrestrial plants had captured more solar energy, the only effect would have been the accumulation in their cells of free oxygen and of intermediate reduced chemical compounds that could not be used fast enough to synthesize useful substances like carbohydrates, for various reasons, of which the lack of enough captured carbon dioxide is a major reason.
The capture of carbon dioxide can be hampered by the free oxygen produced by capturing solar light, even if the plant cells attempt to separate the cell parts where these incompatible processes occur.
It might be possible to improve the productivity of the plants by improving their ability to capture carbon dioxide, more than by improving their ability to capture light. However I believe that such research directions are misguided. We are already able to capture light very efficiently with non-biological devices and the same is likely to become true for carbon dioxide capture and electrolytic reduction.
What is unlikely to happen any time soon is to find any way for synthesizing complex organic molecules like those needed for food as efficiently as by using living cells.
So the non-biological capture of solar energy and capture and reduction of carbon dioxide and dinitrogen should be combined with biological syntheses in cultivated organisms.
Can a plant near a volcano get a boost?
How fast can plants (or gree algae) evolve to absorb the increased CO2 in the air?
That is a fun question. Like life around hydrothermal vents, but on land. I can't search for answers easily because of course volcanic soil is really fertile anyway, so people have plenty to say about plants that grow around volcanos already, without reference to carbon dioxide.
You got me thinking about incorporating silicon-based photosynthesis chemistry into plants. Making that work would be tricky, for sure.
The solution is not incorporating photovoltaic cells into living plants.
The most efficient way of making food and other complex organic molecules is to make artificial devices that would use solar panels and which would use the energy to capture both carbon dioxide and nitrogen from the air (possibly also water from the air humidity) and which would make ammonia and some very simple organic molecule.
Whatever is produced with solar energy, could be used as food for some genetically modified fungi or other similar organisms (e.g. genetically modified parasitic plants). These genetically modified living organisms would perform all the complex enzymatic syntheses required to make food suitable for humans or any other complex organic substances of interest. Some time in the future it should become possible to create a fungus (or a parasitic plant) capable of growing not only mushrooms, but also bananas, wheat grains, chicken eggs, turkey thighs or whatever else one could want to harvest from such a culture.
So the coupling between solar panels and some culture of living beings should be external, through food.
This has the advantage that the surface would be occupied only by the solar panels and the associated chemical reactors that would store the solar energy into simple organic molecules and ammonia (possibly combined in a simple amino-acid like glycine), while making food could be done e.g. in underground facilities and only when needed and producing only whatever is in demand at a given time.
My life for Aiur!