Raymo, I think Hank Hill and Al Gore would disagree with you. Propane burns very clean, though it's production, bottling, and distribution probably do cause more environmental concern than a fire that you would likely have burning in camp anyway.
I don't see how it's anything like a motor in any of the aspects discussed in this thread though. Could you elaborate?
I'd also like to thank everyone involved in not being "Captain Obvious" and discussing the vast amount of miles typically driven to get to and from a river trip. None of us are carbon / environment neutral in our sport, but this always seems to get brought up and seems to have little bearing on the debate at hand.
Rich, thanks again for your insight. It brings up plenty of food for thought, as I really hadn't considered the pace of river traffic as a whole on that level. I do disagree that the chances of a ban are minute. The Grand Canyon is an ideal candidate for Wilderness and has been in some stage of the process for decades.
If anyone else would like to see this amazing place receive Wilderness designation, for it truly is a wild place, please look to, and consider joining, River Runners for Wilderness. The website is very informative and might just make you think twice about pulling that starter cord next time.