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Comment by meri_dian | Hacker News Reader

>"The hybrid organism, M. thermoacetica-CdS, produces acetic acid from CO2, water and light."

I love bacterial and algal based approaches to fuel generation. Re-purposing nature's own highly advanced (relative to our own state of the art) chemical processing machinery seems an easier path forward than building our own from scratch.

That said, relying on a fuel source that requires CO2 as input seems just as potentially destabilizing to the global carbon cycle as relying on a fuel source that produces CO2 as byproduct.

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We are having an excess of CO2 in the atmosphere right now. Using it to generate useful stuff looks ok to me. Water could be a problem.

If we were to lose all the CO2 in the atmosphere, we will all very quickly die. Plants require it to survive. [1]

The problem with bacteria, is that thanks to exponential growth, and an inability to control them, we can end up in deep, deep trouble. Using them in a controlled fashion that will bring us from 400ppm to 250ppm (but no lower) seems incredibly unlikely. Either they won't be able to make a big difference, or they'll bring us to a level far below habitable.

[1] https://en.wikipedia.org/wiki/Future_of_Earth

Agreed, but in this case no cadmium semiconductors == no super bacteria. They can't build semiconductors, we do, so we control the reaction. Are we really going to use up all CO2, stop photosynthesis and suffocate? I don't believe so. We also keep producing plenty of CO2.

As long as you make sure to burn the fuel and don't store gigatons of it somewhere safe I see no problem.

>That said, relying on a fuel source that requires CO2 as >input seems just as potentially destabilizing to the global >carbon cycle as relying on a fuel source that produces CO2 >as byproduct.

Not really. Using CO2 to generate a fuel which then liberates CO2 when it is consumed ends up being CO2-neutral, which is exactly the way to go.

> That said, relying on a fuel source that requires CO2 as input seems just as potentially destabilizing to the global carbon cycle as relying on a fuel source that produces CO2 as byproduct.

You mean like wood? Burning that fuel releases the same amount of CO2 back into the atmosphere; the end-to-end process is carbon-neutral.

The end to end process of burning coal is also carbon-neutral according to that logic, yet it seems to be causing some trouble.

If you were a resident of Earth at the time where the coal deposits were formed, you'd find our current climate pretty frigid. From your point of view it would just be returning back to normal :)

Time scales are essential here.

Burning wood becomes carbon-neutral only after you grow that amount of wood (and in dry weight).

Just put one gallon in an old oil well for every gallon we burn.

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