Wood waste is being tested U.S. coal-fired power plants, as utilities look to cut carbon dioxide output quickly to meet likely restrictions on CO² by the Environmental Protection Agency.

Generating power - an approach that has already caught on in Europe. 

Minnesota Power has added wood to the mix in its coal fired plants in an effort to convert to one-third renewable fuel. Its M.L. Hibbard Renewable Energy Center in West Duluth, which uses waste wood as a fuel source, is among 200 U.S. coal-fired power plants that have tested a coal-wood mix.

Because wood is cheaper than coal, "We're finding an emissions improvement benefit and an economic benefit," Allan Rudeck, VP strategy and planning, told the Wall St. Journal. The use of wood also allows the ash produced to be used as a soil nutrient on area farmlands, reducing landfill.

Minnesota Power says its Rapids Energy Center is averaging 80% woody biomass fuel, providing Blandin Paper Company with steam, compressed air and electrical energy. Wood waste material from the paper mill and local forest product companies is burned with coal in two high pressure boilers to produce steam. The ash generated is used as a soil nutrient on area farmlands and as agricultural feed pads. 

But a number of utilities using raw wood waste report challenges feeding non-uniformly sized wood chucnks and unreliable wood waste supply volumes - perhaps explaining the popularity of processed wood pellet biofuel in Europe.

  Environmental groups also pose challenges. Wood pellet manufacturers, members of the U.S. Industrial Pellet Association (USIPA) and other members of a group called "Bridging with Biomass" coalition, sponsored a study to counter concerns that U.S. forests would be depleted if wood fuel caught on in a big way.

The production of wood pellets for European power plants has become big business in the last two years, with the world's largest pellets plants built by German power companies in Georgia and Texas. Another large wood pellet plant is run by Viridis, in Nova Scotia. And German Pellets gmbh has opened mega pellet plants in Urania, LA and Woodville, TX to supply power plants in Germany, as utilities their ween themselves from nuclear power