The 'No.2' bus

I wonder what the proportion of methane to added propane is.

Yes, nice jobbie on the graphics ;-)

What sound does the bell make when you press it to get the bus to stop?

"To power a vehicle, the biogas undergoes "upgrading", where carbon dioxide is removed and propane added"

So it's propane powered, with a bit of digestive methane. Not very Bio at all...

Andy

If I had to guess, I'd say "DUNNNG!!!" :-)

I don't think it's anything like that. Bio-methane has a calorific value of around 36 MJ/m3, while AIUI if you want to inject this into the national gas grid, you have to upgrade its calorific value to 39.5 MJ/m3, to meet appropriate standards. This is done by injecting a little propane (93.3 MJ/m3), around 7% of the mix if my maths is correct. While I doubt that the propane injection is specifically needed for the 'No.2 Bus', I assume that the bulk of the bio-gas from that particular source is for injection into the national gas grid, so they upgrade all of it and the bus only uses a small percentage of that.

...is the correct answer ;-)

You may well be right. I hope you're right. But I am a cynic...

Andy

Is it coincidence that it?s in the home of the Bristol Stool Scale, I wonder?

Or indeed, whether it has anything to do with the source of mysterious 'Bristol Hum' of a few decades ago? Do the buses hum? The stuff that makes the methane certainly does!