You can get similar heat with propane and people are already converting their vans and machines to run off it solely. Not that I'd be keen on driving a large combustible bomb but it is an option.
we run everything on propane. its only $2.19 per gallon. It works really well, minor power loss vs petrol but not bad. 8000hrs out of a motor vs 5000hrs
also propane is only combustible as a vapor so its actually pretty safe, a belly tank of diesel like a lot of big trucks have is much more dangerous.
CNG would really be the future though, its 0.40c/ gallon here. You can get a fueling station at your home for $8k (if your home has NG service). All of our garbage trucks, and a lot of our city trucks run on CNG.