Methanol vs Ethanol in Biodiesel synthesis:

[Elite Engineer]

When making biodiesel, which alcohol yields a more energy efficient product: methanol or ethanol?

 

-making some at home, and I have a lot of ethanol I can use, however I want the best product I can make.

 

~Thanks,

 

~ee

[Sensei]

See article

http://en.wikipedia.org/wiki/Energy_density

 

Ethanol 30 MJ/kg

Methanol 19.7 MJ/kg

[Enthalpy]

Though, industrial-scale biodiesel uses methanol. Does it react more easily maybe? Or is it cheaper where vegetable oil is available? The effect on viscosity and pour point must be small.

[GM11]

In the UK its methanol, Ethanol attracts a high tax so using it can be a cost issue. To get around the tax you use methanol to denature the ethanol and add bitrex! Bonkers if you ask me seeing as I live in Scotland.
If they dropped the stupidity of tax being the same for bio fuel and dropped the tax on ethanol used for fuel production, then the whiskey industry could distill all year every year and make a sustainable fuel.

[John Cuthber]

The duty paid on ethanol for drinking can be reclaimed from the tax man if you can show that it in't used for humn consumption.

On the other hand, all fuel for road vehicles has to pay fuel duty.

 

The big factor isn't duty, but simple cost. methanol is much cheaper than ethanol.

[GM11]

First you have to have a distilling license in the UK, this is only considered if you distill over 1800 liters a year (I am not 100% sure on that number, but its high). So claiming back tax isnt an option on a small scale set up as it is technically illegal but somewhat complicated!

Ethanol currently costs us £1.20 Ltr without duty. Methanol in an IBC works out much cheaper

Edited October 12, 2015 by GM11

[John Cuthber]

No, you don't need a distillation license to claim back duty; the lab I work in used to do it.

Even if you claim back the tax, ethanol still costs more than methanol; it's a more complicated molecule.

 

None of this matters; ethanol gives a slightly higher energy density, and that's what the OP asks for.

Edited October 12, 2015 by John Cuthber