Here’s a multi­bil­lion-dol­lar ques­tion that could help deter­mine the fate of the glob­al cli­mate: If a tree falls in a forest—and then it’s dri­ven to a mill, where it’s chopped and chipped and com­pressed into wood pel­lets, which are then dri­ven to a port and shipped across the ocean to be burned for elec­tric­i­ty in Euro­pean pow­er plants—does it warm the planet?

Most sci­en­tists and envi­ron­men­tal­ists say yes: By def­i­n­i­tion, clear-cut­ting trees and com­bust­ing their car­bon emits green­house gas­es that heat up the earth. But pol­i­cy­mak­ers in the U.S. Con­gress and gov­ern­ments around the world have declared that no, burn­ing wood for pow­er isn’t a cli­mate threat—it’s actu­al­ly a green cli­mate solu­tion. In Europe, “bio­mass pow­er,” as it’s tech­ni­cal­ly called, is now count­ed and sub­si­dized as zero-emis­sions renew­able ener­gy. As a result, Euro­pean util­i­ties now import tons of wood from U.S. forests every year—and Europe’s sup­pos­ed­ly eco-friend­ly econ­o­my now gen­er­ates more ener­gy from burn­ing wood than from wind and solar combined.

Bio­mass pow­er is a fast-grow­ing $50 bil­lion glob­al indus­try, and it’s not clear whether the cli­mate-con­scious admin­is­tra­tion of Pres­i­dent Joe Biden will try to accel­er­ate it, dis­cour­age it or ignore it. It’s usu­al­ly obvi­ous which ener­gy sources will reduce car­bon emis­sions, even when the pol­i­tics and eco­nom­ics are tricky; every­one agrees that solar and wind are clean­er than coal. But when it comes to pow­er from ground-up trees, there’s still a rag­ing sub­stan­tive debate about whether it’s a for­est-friend­ly, car­bon-neu­tral alter­na­tive to fos­sil fuels, or an envi­ron­men­tal dis­as­ter. Even with­in the Biden admin­is­tra­tion, senior offi­cials have tak­en dif­fer­ent sides of that debate.