>It sounds slightly less bad than dried horse dung on the streets.

How so? It only releases liquid waste, not solid waste, and it's released into the exhaust stream that's 900F, at a rather low flow rate. Just guessing, I'd say the emissions from this device really don't sound harmful at all, whereas the emissions from the vehicle's engine itself (which probably lacks a catalytic converter since it was 1973) are quite awful. I'm also guessing that the emissions from this thing can't possibly be as bad as the emissions from all the diesel pickups today with their engines modified to "roll coal", which is rather common and completely unregulated.