Europe is trying really hard to reduce its dependence on oil and coal, by upping the use of solar, wind and trash as energy sources. But not all of the methods that the continent has tried are exactly environmental panaceas.

One of the ways that European countries are trying to reduce their dependence on non-renewable fuels sources is by burning wood. Specifically, a whole lot of wood pellets created from trees harvested in the Southeastern United States. According to the EIA, wood pellet exports doubled between 2012 and 2013, mostly because of demand from European countries who are trying to meet their 20-20-20 goals.

The 20-20-20 targets aim to increase energy efficiency, lower greenhouse gas emissions and increase the amount of renewable energy sources in use. One of the sources classed as renewable is biomass, which includes wood. The problem, as Grist reports, is that a recent report out of the U.K. (the largest importer of U.S. wood pellets) found that, in some scenarios, burning imported wood from North America can produce just as much greenhouse gas as burning fossil fuels. Other scenarios (depending on factors including transportation distance, the land and type of tree used) resulted in lower greenhouse gas emissions. But in all cases, the U.K. report asserts, the energy invested in producing North American wood pellets was greater than the energy invested almost any other fuel source (renewable or otherwise).

There’s also the question of scale. Trees grow at a pretty constant rate, but the demand for biomass fuels is growing, and the difference between those two rates can create problems, as Al Jazeera reports:

“It’s just not as simple as 'the trees will grow back,’” said Norman Christensen, a professor of environmental science and policy at Duke University. “Yes, you are regaining carbon when trees grow back, but when you cut landscapes intensely, you release some degree of carbon to the atmosphere more or less permanently.” Christensen and others say that in the years it takes to grow the trees back, a harvested forest isn’t sequestering nearly as much carbon as it would were trees not cut down.

Burning wood is an appealing option for power companies who are already used to (and have the infrastructure for) burning things for fuel, and sustainable forest management does exis. But cutting down trees, treating them and shipping them across an ocean to be burned seems a bit counter-intuitive for a renewable energy push.