Hardwood fuel is a win-win idea

May 29, 2007

This op-ed appeared May 27 in the Tallahassee Democrat.

By: Francis E. “Jack” Putz
Francis E. “Jack” Putz is a professor of botany at the University of Florida.

Environmentalists whine a lot. I whine mostly about biodiversity loss, global warming and mismanagement of ecosystems. As an environmental scientist, I whine with copious data, stultifying statistics and assumed authority. Even friends get tired of my harping and ask for solutions, not more details about the problems.

Admitting that no environmental solutions are perfect and few are truly novel, I can offer one that seems both good and new. Adoption of this cost-effective solution would reduce the risk and severity of wildfires while enhancing biodiversity protection and reducing emissions of greenhouse gases.

In a recent study published in Restoration Ecology, Brian Condon and I showed that these goals can be approached by restoring the natural structure of pine savannas and woodlands of the Southeast. Given that only 2 percent of these once extensive and hyper-diverse ecosystems still exist, anything we can do to save what remains is worth considering.

The linkage between biodiversity, climate change and wildfire control emerges from the fact that most of our region historically supported open-canopied pine savannas, not forests. Most of the extraordinary biodiversity in these savannas is lost when broadleaved trees are allowed to invade and close the canopy.

Hardwoods invade when fires are suppressed. Shade from these fire-sensitive invaders kills the hundreds of species of understory herbs that historically fueled the low intensity fires that burned through every year or two. Hardwood domination also leads to the demise of gopher tortoises, fox squirrels, red cockaded woodpeckers, and many more species of concern.

After dense forests are allowed to replace open savannas and woodlands, the fires that are inevitably ignited burn hot – very hot. Decades of fire suppression results in dangerous accumulations of fuel, fires that are too intense to stop, and lots of losses, financial and otherwise.

What Brian and I found was that, by selling the invasive hardwoods to the highest bidders, the costs of pine savanna restoration are greatly reduced or even made profitable. Unfortunately, the hardwood market isn’t so good, so most of the invasive hardwood biomass in the 13 restoration projects we studied was sold for fuel chips. The fuel chips are burned in place of fossil fuels to generate electricity.

Generating electricity by burning wood instead of coal or petroleum products still puts carbon dioxide into the atmosphere, but tree carbon is new carbon, not the stuff that accumulated for hundreds of millions of years. Also, chipping of invasive trees requires no mountains to be leveled or wars to be fought. Better to reduce our energy use, but if we want power, better biomass than fossil carbon, negawatts instead of megawatts.

The amount of biomass available for electricity generation varies with the extent of hardwood invasion. In our study sites, the average acre supplied about 20 tons of fuel. Diesel fuel is burned in harvesting and transporting hardwood fuel chips, but the carbon benefit-to-cost ratio is about 100-to-1.

Compare this with the 2-to-1 or even 1-to-1 ratio for corn ethanol, and it’s clear why we are so excited about the prospects of restoring our way to carbon neutrality.

Clearing out invasive hardwoods does not immediately result in savanna restoration, but it is the first big step in the right direction. Given that we’ve already lost 98 percent of the natural pine savannas of the Southeast, taking this step is really important for all the biodiversity we have lost, from fox squirrels and gopher tortoises to squirrel bananas and gopher apples.

Thinning stands will not stop wildfires, but it will certainly make the fires that occur easier to stop. And using invasive hardwoods for fuel won’t stop global warming and the attendant sea level rise, but it will help.