2009-02-22

Biogas update

Upon reading into the issue somewhat I have learned that car-gas adaptations typically use liquefied Propane/Butane which, having a boiling point of -0.5 ˚C and -30 ˚C are much easier to store in liquid form than biogas / Methane, which has a boiling point of -160 ˚C. The Propane/Butane mix is also a bit denser as liquids than Methane which is all bad news for any plan to run a car on biogas.

Fortunately however, it turns out that Methane burns hotter and as such gives more energy per kg. The figures, are that Propane/Butane gives off 49,2 to 49,9 (depending on the mix) kJ per gram (or MJ/kg), whereas Methane gives off 54 kJ per gram, obviously more.

To convert these values together with density this means...

As gas Propane/Butane gives off 91,3 to 122 MJ energy per m³, and Methane 38,7 MJ per m³. As a liquid Propane/Butane gives off 25,33 to 29,52 GJ per m³, where Methane gives off 22,41 GJ per m³. So keeping Methane as a gas for fuel on a car wouldn't work out very well, but as a liquid it could work. That being said however, it is true that given that you can find a place for a suitable container on a car, biogas does provide more punch per kg of fuel than gasoline, unlike Propane/Butane.

Having done this little bit of amateur research I find that I don't have a clue about chemistry and will have to find someone who does if I intend to continue this project.

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