美国国家公共电台 NPR Burning Biomass Is A Complicated Climate Calculation（在线收听）

DAVID GREENE, HOST:

World leaders are gathering at a U.N. climate summit in Madrid this week to talk about how to reduce greenhouse emissions. In the search for alternatives to fossil fuel, some countries have now turned to one of the oldest energy sources around - wood. Some are importing it from the United States, calling it clean and renewable. But some environmentalists say this makes no sense. NPR's Dan Charles has the story.

DAN CHARLES, BYLINE: On a soggy field in eastern North Carolina, Jason Tew and his crew of loggers are cutting trees and sorting the logs into piles depending on their size and what kind of wood they are.

JASON TEW: Poplar, sweetgum, there's an elm right there.

CHARLES: Some piles will go into plywood. Some will become puffy absorbent fiber in baby diapers. And then there's the least valuable pile, the small limbs and tops of hardwood trees.

TEW: It's basically a trash. We would've normally have hauled that back out in the woods and just left it.

CHARLES: But now there's a new market for that wood - pellet mills. They've expanded across the southeast over the past decade. They'll take this wood, crush it and press it into little pellets ready for burning as fuel.

TEW: The landowner is getting some value. We're getting some production. It's just an all-around good deal.

CHARLES: Most of these pellets, millions of tons each year, will get shipped to Europe where they're burned in power plants because some European governments are offering financial subsidies to burn these pellets instead of, say, coal. It's supposed to help fight climate change. Here's Seth Ginther, executive director of the industry group that represents wood pellet companies.

SETH GINTHER: The carbon benefits are tremendous.

CHARLES: Burning wood, also called biomass, does release lots of carbon dioxide, the greenhouse gas. But the idea behind the subsidies is you can let forests grow back, and as they do, they'll recapture the carbon dioxide from the air and store it in their branches and roots again. So it's considered renewable, just like wind or solar.

GINTHER: The European Union literally just passed something known as the Renewable Energy Directive II and biomass - sustainable biomass - was unequivocally included as part of what can meet renewable energy goals.

CHARLES: But environmental groups are challenging that decision in court. They say the idea that large-scale wood burning is carbon neutral is based on bad math. And to explain exactly why, Adam Colette from the environmental group Dogwood Alliance takes me to another patch of land in North Carolina, near the town of Williamston.

ADAM COLETTE: I know it doesn't look like much, but we're going to take a little walk.

CHARLES: It's covered with bushes and little trees maybe 10 feet tall.

COLETTE: In the South, we call it a briar patch. But yet on paper, this is a forest.

CHARLES: Four years ago, it really was a forest with big trees. Then it was logged. Some of it went to make wood pellets. So let's count up the carbon emissions accurately, Colette says. When the big trees were cut, they stopped capturing carbon dioxide from the air. That benefit was lost, at least temporarily, and some of the carbon they'd previously stored was released into the air when the wood pellets were burned and as tree roots decomposed. But you won't see any of that in the official calculations of greenhouse emissions, he says.

COLETTE: None of it's ever been counted in any of our, like, emissions counting in the U.S. or in Europe.

CHARLES: That's because the forest eventually will grow back and recapture that lost carbon, but it could take a century for that to happen. Now, Seth Ginther from the U.S. Industrial Pellet Association says his industry should not be blamed for those carbon emissions because wood pellets are not the reason forests are cleared.

GINTHER: These are lands that are being harvested for sawtimber, for housing, for paper and for other things. What we're taking is the byproduct of that.

CHARLES: In fact, though, independent forestry experts say that's not completely true. Their data shows that the wood pellet industry is competing for some of the same wood that might go for making paper or diapers. And it's pushing up prices for that wood. Adam Colette from Dogwood Alliance thinks it's persuading some small landowners to harvest their trees.

COLETTE: You have more knocks on those doors, more telephone calls saying, hey, I'll give you X number of dollars for your trees.

CHARLES: What Colette wants is for officials to knock on those doors with a different message, encouraging landowners to maintain forests, expand them.

COLETTE: Our forests are young; they're degraded. And what that means is that the potential to suck carbon out of the atmosphere of forests in the U.S. South is enormous.

CHARLES: Those forests are some of the best climate solutions we have, he says, if they keep growing. Dan Charles, NPR News.