Using modern wood combustion technology, a well-managed woodlot of only 4 acres can sustainably produce enough firewood to heat a modest-size, energy-efficient home.
Wood, the oldest fuel source known to humans, may be about to experience a renaissance thanks to rising oil and gas costs combined with shrinking bank accounts. Ultra-efficient, ultra-clean advanced wood combustion technology and fast-growing “perpetual” fuel woods can, on the micro level, bring increased home heating security for landowners and, on the macro level, create a regenerative fuel source for electricity generation.
How does fuel wood combat climate change? Wood is often considered “carbon neutral,” because growing it pulls as much carbon dioxide out of the air as is released into the atmosphere when it’s burned. So, unlike gas or oil, it releases no net carbon. It is a closed-loop energy source, simply recirculating the carbon dioxide already within the Earth’s carbon cycle.
An analysis led by Daniel D. Richter, professor of soils and forest ecology at Duke University, proposes we are missing a key strategy in our search for sustainable, cleaner energy solutions. Richter says we need to consider advanced wood combustion, which he defines as “automated, high-efficiency wood-fired energy generation systems with strict air pollution control.”
The analysis was detailed by Richter and a multidisciplinary team of experts in the March 13, 2009 issue of Science magazine, and points out that creating thermal and electrical energy with advanced wood combustion has been growing quickly throughout Europe. “These facilities release remarkably low quantities of air pollutants and have system-wide thermal efficiencies approaching 90 percent,” Richter says. According to the article, the cost of wood fuel is several times cheaper than fossil fuel costs (per unit of energy produced).
The authors of the Science article say the United States is well-suited for sustaining a wood-energy economy. Yet currently, energy from wood provides only about 2 to 3 percent of total U.S. energy consumption. This is about half of the potential annual sustainable wood supply available to us for power generation.
The report also identifies “waste” wood as an untapped asset, estimating that 30 million tons of urban wood per year can be safely burned for energy. For example, the District Energy program in St. Paul, Minn., burns 250,000 tons of waste wood and other biomass per year to provide heating, cooling, and other energy to part of the city.
Although wood supplies just a fraction of today’s national energy use, the sustainable wood supply of the United States could easily produce more than the 3 percent that is supplied by our current hydroelectric sources.
Perpetual Fuel Wood
Sustainable harvests from existing forests could be supplemented with “perpetual fuel wood” (fast-growing, hedge-like trees used in Europe).
“People are talking about biomass plantations, efficient burning and super insulation, but older, more accessible strategies not being talked about involve coppiced and pollarded fuel-wood hedges,” says Ben Falk, founder of Whole Systems Design, a Vermont-based sustainable land development company. Coppicing and pollarding are the practices of harvesting firewood from species that resprout from their base or part way up the trunk, capitalizing on the existing energy of the root structure.
Falk and his team have focused on the massive U.S. interstate highway system as a possible site for these hedges. “There are more than 46,000 miles of underutilized interstate corridor landscape,” he says. “Much of the median and surrounding acreage is mowed, which requires huge quantities of fossil fuel, time and labor, and doesn’t offer any actual yields.”
Falk also finds great promise in the ability of coppicing to sequester carbon dioxide. “Each time you cut back a tree, root dieback releases carbon into the soil. Coppiced systems act as large-scale, solar-powered carbon pumps transporting carbon from the atmosphere into the soil — where it belongs.”
Possibly the most attractive selling point of advanced wood combustion is that it’s more quickly and easily implemented than solar or wind energy systems. A number of U.S. cities and public institutions are already integrating advanced wood combustion into their green energy plans, including the Fuels for Schools program in Vermont and various district energy programs in Idaho, Ohio, and South Carolina.
Wood Fuel for Your Home
The Science article didn’t broach the question of home-scale fuel wood for heat, but Falk is excited about the possibilities. “You can grow a lot of your own food calories almost anywhere in this country,” he says. “But your own heat? It’s difficult, but it can be done.”
The question is, how many acres would you need? According to John Gulland, a wood heat expert and MOTHER EARTH NEWS contributing editor, “In many regions, a healthy, well-managed woodlot can perpetually yield half a cord of wood per acre per year. An average home typically requires about 5 cords per winter, which can be sustainably harvested from about 10 acres. A well-insulated, modest-size home using a high-efficiency woodstove might need only 2 cords, cut from 4 acres, per season.”
Falk says the question is also about what type of renewable heating option folks can afford. “Most people can’t afford to retrofit their home for solar heating. Harvesting local firewood for a high-efficiency stove is a better option in many cases.”
The key to implementing these positive projections for fuel woods is a move toward a more localized energy framework. “Everyone says wood is ‘carbon neutral,’ but if you’re moving massive amounts of heavy material — chipping, cutting, logging, hauling — then it won’t be a carbon neutral process,” Falk says. Most of the European growth has been on the community scale.
The Science article analysis predicts that community-based models will recycle money back into the local economy with new jobs and new sources of income for local landowners.
Richter and his colleagues add that advanced wood combustion systems help communities transition to other renewable energies. And, according to Falk, “While we don’t yet have all the answers needed for large-scale transformation toward regenerative resource use, there are many transitional technologies accessible to us right now. By looking across cultures and regions, we can begin to adapt them to the challenges we face today.”