Lots, and lots, and lots ... of fossil fuels.
63% of total festival emissions come from vehicle travel (people driving RVs from all over, then sitting and waiting in traffic for hours to get in the gates, then waiting in traffic for sometimes up to 8 hours in order to get out), while 27% come from people flying in/out, and only 10% comes from activities on the playa. The total? 100,000 tons of CO2. For a festival of one week.
Seven Circles, a coalition of organizations that includes Extinction Rebellion and Rave Revolution, made some simple demands of the Burning Man Organization, which hosts the annual desert party: "Ban private jets, single-use plastics, unnecessary propane burning, and unlimited generator use per capita at the nine day event in Black Rock City, Nevada."
The ban on private jets seems pretty straightforward.

Not all the Burners are 1% ers, but I'll guess that less than 1% of Burners punch a time clock.
