In Nashville, Tenn., this past August, about 5,000 revelers in neon chaps, gothic chains and kaleidoscopic crop tops descended on Bicentennial Park for an electronic music festival. They gyrated to pulsating sets by British DJ Chris Lake and the electronic duo Snakehips. They watched choreographed light shows and got massages in a healers’ village.

And when they raised their arms in the air, many of them flashed a green wristband, signifying a commitment to partying in a way that was carbon neutral.

Billed as the "greenest festival” in the country, Deep Tropics had no trash cans (though there were plenty of recycling and compost bins), and single-use plastics were banned. Festival organizers said that all the carbon consumed for the two-day event (including the fuel used by all the festivalgoers) will be offset by the planting of some 23,000 trees.