The power for his inventive steam engine came from the gases that resulted from the decomposition of horse manure.
This worked very well as long as the machine burned the fumes, but when parked for any time, the excess fumes were vented.
... but as automobiles replaced the horse, it became more and more difficult to find fuel[horse manure].
Beemer then turned to pig droppings for fuel.
This worked very well since the pig manure produced more methane, but the venting became so much of a problem that his automobiles were officially and legally banned from the streets in the summer time.