Question is in the title really; is there a (real or conceivable) biological process (I’m thinking enzymes, bacteria, and photosynthesis-like processes here) that would split water (presumably in the presence of some sort of nutrient) into free hydrogen and oxygen (actually, the organism is allowed to keep the oxygen if it wants).
??
Wouldn’t that be called a gill?
Nope: gills and lungs only extract extra oxygen that is dissolved in the water.
I believe photosynthesis accomplishes the feat in question.
Trinopus
Yep. Certain bacteria and algae produce hydrogen as part of their metabolic process. The metabolize water into hydrogen and oxygen. Some researchers are even using figuring out how to use certain species of algae to make a cheap, unlimited source of hydrogen.
Also: the algae in question accomplish it though the release of an enzyme, hydrogenase, you educated guesser you.
Damn those scientists; I was born too late I tell ya.
What would be really cool (although pretty unlikely) would be if the bacteria can be engineered to produce hydrogen at a rate sufficient to supply an internal combustion engine; fill the tank up with water and off we go!
I’m assuming that the bacteria need more than just water though…
Or can we just synthesise hydrogenase?
Trinopus
I am pretty sure that while photosynthesis does split the water molecules the full process leaves the total amount of water unchanged. The Oxygen released comes from carbon dioxide. Resulting in no production of H2 that Mangetout is interested in.
Well, i dont think it would be especially useful in cars per se but certainly, if we engineering a unicellular creature, to produce hydrogenase in heaping spoonfuls, then put them in huge sugar vats, we might be able to set up a nice hydrogen factory to supply said cars with oxygen.
DOH! with hydrogen. at least i’m padding my post count 
Save the oxygen too. Then you could use it to burn the hydrogen, without extracting any from the environment. You could just let the resulting burnt hydrogen (water) drip back into the tank to start over.
Hey?!
I guess you’d have to feed the bacteria gasoline
Ok, it’s been way too long since my high school chemistry class, but I seem to recall the teacher having a somewhat similar set-up. He used something to seperate the hydrogen and oxygen from water (electric current, maybe?) and collected it in two tubes (hydrogen being lighter than oxygen?), then opened a valve on the hydrogen tube and burned it off, creating, of course, water vapor. I suppose the next step would have been to collect the water vapor, allow it to condense and fall back into the container, and seperate it again. I would think it wouldn’t matter whether you’re directly using the oxygen from the seperator, or just release it into the air and let it replace the oxygen burned by the hydrogen. I think the hard part would be getting the seperating, collection, burning, and condensation to occur at a rate fast enough to sustain the burning.
I suppose if it could be done in a way that made economic sense, somebody would already be doing it.
The problem with the above is that you get exactly the same amount of energy from burning the hydrogen as you used to separate it from the oxygen. Net energy gain = 0. Actually less, since the process of hydrolysis isn’t 100% efficient, and neither is the combustion of hydrogen. Definitely not practical.
On an unrelated tangent, I long for the day when cold fusion of hydrogen into helium works, providing near limitless energy cheaply. Because the byproduct, helium, can be effectively used to provide tourists of the fusion facility with balloons!
Recent discovery: getting algae to produce hydrogen
QED: Well, the net effect will be to turn sunlight into car-motion. The question is, is it more efficient than our current methods?
I recall reading that common rock seaweed (fucus) has flotation bladders that are filled with (mostly) hydrogen. I don’t know the mechanism of how the plant does this, but harvesting seaweed doesn’t seem to be a good way to solve our energy problems.
When I was in high school I thought I had invented exactly what you are talking about. I planned to do it for a science project, until my (super genius) uncle told me he had modified an engine to run on hydrogen created through electricity back in the 60’s. He just used a modified propane carbeurator to get the fuel into the engine. Since it had already been done, i didn’t try to build it, but I imagine creating and storing enough gas under pressure to sustain an engine for any length of time would have been more than a high school kid could have done. My uncle was a self taught engineer and could build anything so it wasn’t that big of a deal to him.
So is there a possiblity some day we are all going to have huge clear-domed tanks of algae in our back yards, steadily producing hydrogen and feeding it into a tank in our garages?
We’d go out driving our car, come back with an empty tank of hydrogen and a full tank of water, dump the water back into the algae tank and fill up on hydrogen again.