I don't know anyone that goes to Burning Man that thinks it's some kind of conservation event. It was started on a beach in SF to mourn the loss of a relationship by a man with a broken heart. Then it got too big and moved to the desert. I think a lot of people have misconceptions about what Burning Man really is. The fact is, it's a lot of things to a lot of people, but one thing it is not is, is fuel efficiency or any kind of conservation.
The fact that it gets cleaned up is only due to the requirement to get a permit for the next year.
In 1997, BM was held on a private property, and the playa there was absolutely trashed, for as far as you could see. Bottles and cans littered everywhere. In the morning after the burn, I saw one woman was going around picking it all up. Others started to join in. It was not pretty. I think we made a dent in cleaning it up, but the trash was everywhere.
Unlike today, where people actually do make an attempt to clean up, but obviously some still do not give a single fuck about it.