It would be interesting to see what could be accomplished with alternative fuels. Although, the exhaust from something like rubber is probably not so good for the environment? Best of luck to them, thanks for the response.
Depends on the type and the additives. If natural, then it's probably not all that bad if it burns cleanly. Although I'm guessing it's more likely to be synthetic, which puts you into problems. But then even that has to be taken with a grain of salt. Sulphur Dioxide emissions from vulcanized rubber might actually be beneficial to the environment if it's released in the stratosphere.