Duke Study Examines Benefits of Sustainable Wood Energy

Time is Right to Rekindle Wood Energy in America, Experts Say

DURHAM, N.C. – Increased use of sustainable wood energy could yield long-term economic, social and environmental benefits in many regions of the United States, according to newly published analysis by a Duke University-led team of experts.

“Wood energy is one of America’s most important renewable fuels. Our forests could sustainably produce at least 368 million dry tons of wood for energy annually, yet it’s really not on the national radar screen when we talk about renewable energy sources,” said Daniel D. Richter, lead author of the study and professor of soils and forest ecology at Duke’s Nicholas School of the Environment. “It’s time to reconsider this.”

An article detailing the benefits of increased U.S. investment in sustainable wood energy, written by Richter and a multi-institutional team of ecologists, engineers, forest conservationists and energy specialists, appears in the “Policy Forum” section of the March 13 issue of the journal Science.

Thanks to improved pollution-control and efficiency technologies developed over the last two decades, small-scale power plants fueled partly or solely by advanced wood combustion (AWC) could be a source of clean, affordable energy for communities, campuses and commercial and industrial complexes, especially in heavily wooded areas of the Northeast, Southeast and West, the experts conclude.

“This is not your grandfather’s smoky wood stove,” Richter said. “These facilities release remarkably low quantities of air pollutants and have system-wide thermal efficiencies approaching 90 percent. And they recycle money back into the local economy, by creating new green-technology jobs, providing new sources of income to local farmers and forest landowners, and even add value to local forests.”

“At a time of rising energy costs, and growing concerns about wildfires, greenhouse gas emissions and over-reliance on foreign oil, wood energy is simply too valuable a resource to waste,” said Lew McCreery of the U.S. Forest Service. “Wood can play a larger role in community, state and regional energy strategies based on high-efficiency distributed energy systems.”

Long considered an important fuel source in Scandinavia, community-based AWC is now widely used in France, Germany and central and eastern Europe, the study’s authors note. More than 1,000 AWC facilities have been constructed in Austria alone over the past two decades. Most are small- to mid-sized facilities, designed to provide heat and power to small towns, portions of cities, industrial complexes and public institutions.

“Some of these communities have combined AWC with solar, wind and biomass energy, and they now export surplus energy back to their national power grids,” said John Karakash, a renewable energy expert at the Durham-based consulting firm Resource Professionals Group.

Wood used to power the plants can come from many sources, notes Kasimir Nemestothy of the Austrian Chamber of Commerce. These include beneficial thinnings of local forests; the removal of diseased or dead trees from city property; or by harvesting excess fuelwood from forests in areas where communities are threatened by wildfires. Wood from construction sites and low-value solid wood products from local mills can also be used. Careful monitoring is needed to assure that these practices enhance rather than deplete the forest ecosystems.

“Harvesting practices must encourage forest restoration and safeguard long-term forest health and productivity,” said Dylan Jenkins of The Nature Conservancy’s Pennsylvania Forest Conservation Program.

In their article, Richter and his team propose three initiatives to spark increased use of AWC in America.

First, in areas with sustainable wood supplies, they say, make AWC an energy system of choice for new construction and renovation. Second, make better use of wood collected by municipalities as organic waste from diseased and storm-damaged trees, and woody debris from construction sites. Third, expand the use of AWC-compatible “district energy systems,” in which heat is supplied from a central source to sites across a campus or community. District heating systems powered by wood are already in use in downtown St. Paul, Minn., at hospitals and public buildings in Akron, Ohio, and on campuses such as Colgate University, the University of South Carolina and the University of Idaho, Richter notes.

“District energy, tied to advanced wood combustion and solar thermal systems like those used in Europe, could be an attractive option for high-density American communities and eco-friendly urban and suburban developments,” he said.

“Europe’s successful use of AWC demonstrates that, with public backing, this is a clean, renewable, affordable energy source could be rapidly implemented in American communities, too. It’s a technology whose time has come.”

It’s important that policymakers recognize AWC as an energy source that is largely carbon neutral and does not add to greenhouse gas emissions, Richter adds. Growing, harvesting and processing the wood releases comparatively small amounts of fossil greenhouse gases, compared with the amount of carbon stored in the wood. And burning the wood recycles carbon dioxide that is already in the biosphere, in contrast to coal, heating oil or natural gas, whose combustion adds more carbon dioxide to the biosphere.

Richter and four of his co-authors were among 14 energy, forestry and business professionals who observed forests and advanced bio-energy sites in Austria on a recent tour organized by The Pennsylvania State University School of Forest Resources and the consulting firm Resource Professionals Group with help from the U.S. Forest Service and Austrian business and public policy leaders.