Pyrolisis bakes forest slash to produce biochar, or charcoal, and bio-oil, a low grade fuel. The process retains about half the wood’s original carbon load. Photo courtesy U.S. Forest Service
On the west side of the Cascade Range in southern Oregon, U.S. Forest Service researchers on the Umpqua National Forest are trying to come up with a solution to two seemingly disparate environmental challenges: forest health and climate change.
Like other overgrown forests across the country, the stands of Douglas-fir and ponderosa pine around Diamond Lake on the Umpqua underwent a fuels reduction treatment about a decade ago to reduce the risk of a major wildfire or pest outbreak. At the time, there was no marketable timber among the cut slash, so it was gathered into piles and burned.
Such actions are intended to improve forest health. But although burning slash piles gets rid of cut wood and other forest debris—together known as biomass—it also releases carbon once stored in trees and in soil, which then rises into the atmosphere and contributes to global climate change.
Each tree growing in our national forests captures carbon dioxide from the atmosphere and converts it to sugars and oxygen. The process, known as photosynthesis, not only supports tree growth, but by removing carbon from the atmosphere, it helps cancel the effects of the greenhouse gases emitted by our cars, airplanes and fossil-fuel power plants. Just as hybrid fuel vehicles and alternative energy technology can reduce our carbon dioxide emissions, trees and forests can also play a major role in mitigating climate change.
Forests in the United States, both public and private, currently offset between 8 and 16 percent of our fossil fuel emissions. Some researchers and land managers believe that planting trees and processing biofuels derived from wood products could eventually double the amount of carbon stored in forests and forest products.
But faced with a paradox between managing for forest health or for carbon sequestration, the Forest Service is struggling to find its direction. Standard practices that remove trees to improve forest health mean less stored carbon, while leaving trees in place to increase forest carbon means greater fire risks.
On the Umpqua, research soil scientist Debbie Page-Dumroese and her Forest Service colleagues are among those trying to offer guidance through innovation. The Forest Service wants the carbon stored in trees to remain stored, so her group has come up with another way to use biomass that still sequesters some of the carbon. The process employs a portable fast pyrolysis unit—a sort of high-end, steel chemistry set built into a truck trailer—that uses super-hot steel BBs to bake forest slash in an oxygen-free chamber. The unit then condenses the vapors and produces a low-grade fuel called wood bio-oil, which can be used for heat, and biochar, which is charcoal.
Researchers have spread biochar on the forest floor of the Umpqua test site, and they expect its benefits to include accelerated tree growth and nutrient uptake and improved soil moisture and quality. Equally promising, biochar and the other byproducts of the process retain half of the wood’s original carbon load, a major improvement over conventional slash burning, according to Page-Dumroese.
Fast pyrolysis is “one way we can look to mitigate climate change,” she says.
If similar approaches enable the Forest Service to manage for carbon sequestration, the agency would be positioned as a major player in carbon credit markets, just as Congress is debating whether to establish carbon emission limits and regulations. Carbon sequestration projects could even provide the government with a sorely needed cash stream for restoration projects at a time of scarce funds.
But before policymakers start fantasizing about saving the planet—and the forests—by planting more trees and making high-tech charcoal, scientists say managers should focus on shoring up carbon reserves in standing forests.
“I think there’s some real opportunities, and I wouldn’t discount those,” says Richard Birdsey, program manager of the Forest Service’s Northern Global Change Research Program, “but some [management tools] are much more certain than others.”
JUMPSTARTING REFORESTATION
This past summer, two burnt-over sections of California national forests won extreme makeovers—you could call it the ecosystem restoration edition. Forest Service crews planted greenhouse-raised seedlings of Douglas-fir, ponderosa pine, sugar pine and incense cedar trees along the Feather River in the Plumas National Forest in northern California. On the San Bernardino National Forest in the southern part of the state, crews planted a variety of pine and white fir seedlings in the San Jacinto River Basin.
Without the plantings, both of the restoration sites would have had to rely on natural processes for forest regeneration. But the preceding wildfires burned so fiercely that soil quality plummeted and natural seed sources might not have reached them for decades.
“These areas aren’t going to come back [naturally] anytime in our lives,” says Bill Possiel, president of the National Forest Foundation, a Missoula, Montana-based nonprofit group that supports the Forest Service. Without human help, Possiel says scrub growth would eventually overtake the forest and alter its wildlife value. On the San Bernardino, habitat for bald eagles, the endangered southwestern willow flycatcher and several sensitive amphibians would be lost. The trees also protect water quality in the river basin—and they store carbon in their limbs and roots.
Planting native seedlings jumpstarts the reforestation, Possiel says, but restoration can cost thousands of dollars an acre. “There are millions of acres across the national forests in need of restoration that we don’t have the money for,” he says.
Money for the two California projects came through the National Forest Foundation’s Carbon Capital Fund. The fund is a voluntary program that receives contributions from individuals and corporations choosing to offset their own output of carbon and greenhouse gases.
Congress has waffled over regulations to monitor and limit carbon emissions. But some entities that emit greenhouse gases have begun to either reduce their releases or pay into programs, like the Carbon Capital campaign.
An early 2008 demonstration project funded the replanting of a burnt section of the Custer National Forest in eastern Montana. Possiel says his organization would like to establish and monitor similar pilot projects across the country over the next three years.
So far, the Forest Service hasn’t jumped into issuing contractual carbon offset credits that could be traded under a market, such as the Chicago Climate Exchange (see “Green Economy”).
Environmentalists say that’s a good thing. Ann Ingerson, a Vermont-based economist with the Wilderness Society, says long-term contracts to sequester carbon could lead to troubling outcomes over time, especially if they conflict with other management objectives such as ecosystem health, recreation and timber production.
“That’s our question with long-term contracts for carbon,” Ingerson says. “Do you want the public lands to be tied up?”
Under a sequestration agreement, managers might not be able to eliminate invasive species because they are capturing carbon, and biomass removal would conflict with carbon storage goals. Sequestration could also clash with management for endangered species; wildlife, fish and plants may require thinning treatments to improve or create habitat, but carbon contracts would prevent those measures from being taken.
“I think it’s appropriate that the national forests are moving slowly,” Ingerson adds.
NO EASY SOLUTIONS
Reforestation of burned or other disturbed sites represents the low-hanging fruit of forest carbon sequestration. Whether managers should even pursue other practices remains at the heart of the debate over forests and carbon.
For instance, applying fertilizers, plowing and blading the soil, and planting genetically modified species could speed new tree growth and build carbon reserves quickly. But fertilizer introduces nitrogen pollution and runoff, site preparation is expensive and planting trees that alter the ecosystem would run into opposition inside and outside of the Forest Service.
Managers could also increase stores of carbon by implementing longer forest rotations or less intensive harvests in timber stands. That might sound good to opponents of logging on national forests, but the strategy may be a stopgap answer that comes with high risks, says Mike Ryan, a forest ecologist at the Forest Service’s Rocky Mountain Research Station in Fort Collins, Colorado, who has been conducting forest carbon research for two decades.
Harvesting less timber in the United States could mean we just cut more somewhere else in the world, Ryan says. The management scheme could also lead the agency back to the problem it faces in dry, overstocked forests. “The more carbon on the landscape, the more risk you have,” Ryan says, referring to the increased probability of insect outbreaks and fires in some stands.
Researchers have also looked into whether wood products and biofuels can help reduce the loss of stored carbon, while also allowing for forestry operations. Some advocates have pushed for more manufacturing of wood products to store carbon after trees are felled. Others wonder whether converting biomass to biofuels for power plants and other fuel uses can help minimize carbon loss from logging.
But Ingerson, of the Wilderness Society, says that any forest treatment introduces variability into an ecosystem, and carbon loss is an inevitable part of that chain of events, even if the biomass is used as biofuel or material for wood products. In an April 2009 report she concludes, “Taking the entire lifecycle of these products into account, it becomes clear that an increased use of wood fuels and lumber will have very little net effect on climate change. To the contrary, the impact is as likely to be negative as positive.”
An Oregon State University study released in July 2009 also pokes holes in the idea of reducing forest carbon loss through biofuels production. Focusing on the fast-growing forests of the Pacific Northwest, the study found that turning trees thinned during fuel reduction projects into biofuel would fall far short of canceling out carbon losses. Among Sitka spruce stands, it would take 169 years before the forest was sequestering carbon at its present levels.
“It had been thought for some time that if you used biofuel treatments to produce energy, you could offset the carbon emissions from this process,” says Mark Harmon, an Oregon State University forest ecology professor. “If fuel reduction treatments are effective in reducing fire severities…it will come at the cost of long-term carbon storage, even if harvested materials are used as biofuels.”
The biochar experiment in the Umpqua National Forest is another attempt to overcome the carbon loss of fuels treatment and thinning. Page-Dumroese calls the forest biochar project “cutting edge,” because other experiments have been located on croplands.
Project researchers are working through their share of wrinkles. Biochar has a texture like talcum powder and is susceptible to erosion, says Page-Dumroese. Scientists are testing whether they can turn the charcoal into pellets. Other agency staff are studying the economics of using the wood bio-oil as truck fuel during forestry operations.
“I think the Forest Service can use [biochar] as a tool, something to get green energy out of,” Page-Dumroese says, but she has no illusions about its impacts. “Right now, it’s not going to change the way the Forest Service does business.”
UNKNOWNS PERSIST
In January 2009, Forest Service researchers in California submitted a report that offers the first comprehensive assessment of a region’s forest carbon capacity and projections for the next century. Scientists modeled six different management scenarios that are a range of “damned-if-you-do, damned-if-you-don’t” outcomes.
The assessment found that, under current management practices, California’s national forests will emit more carbon than they store by the middle of the twenty-first century because “losses from wildfire, disease and other disturbances will exceed growth.”
The report concluded that managing for high levels of carbon storage would come at the expense of ecosystem management—that national forests would have to become tree farms.
The July 2009 Oregon State University report suggests targeting some forests for carbon sequestration—recognizing that there’s low risk of a catastrophic fire on the west side of the Cascades—while managing more fire-prone areas for forest health. Fast-growing forests of Douglas-fir and Sitka spruce and southeastern forests of loblolly pine are well-suited for carbon sequestration projects. Slow-growing stands of ponderosa pine and subalpine fir in the Rocky Mountains, not so much.
Birdsey, the program manager of the Northern Global Change Research Program, has spent twenty years researching carbon levels and climate change. He helped develop methods and guidelines now used by federal agencies to measure national greenhouse gas emissions.
“It’s possible to double the amount of carbon sequestered in forests per year,” Birdsey insists. One key initiative, he suggests, could be the conversion of marginal cropland to forests, including large tracts of land that were originally cleared of trees during the settlement of the country. A 2004 study from scientists at Duke University concludes that turning one-third of farmlands into forest “plantations” could offset 10 percent of the country’s carbon emissions, equivalent to doubling the fuel efficiency of every car and light truck on American roads.
Doubling forest carbon also means managers need to retain the carbon that is stored in forests now, and protect woodlands threatened by development, he says. Rapidly sprawling metropolises, including Atlanta, Seattle and Washington, D.C., will threaten hundreds of thousands of acres of forests in the next few decades. “Reducing deforestation is the number one thing,” Birdsey says.
Developing forest management strategies with more certain outcomes is a sound idea when it comes to carbon sequestration, especially since the unknown effects of climate change complicate any effort to protect ecosystems and reduce forest-health threats. After all, if warmer temperatures and drier climates set off more wildfires, many plans to store carbon in forests will have been rendered null.
Mike Ryan half jokes about the perfect solution to manage for resilient forests that are healthy and optimally storing carbon. “If you could just thin the areas that you knew were going to burn, it could be carbon-positive,” Ryan says, “but you can’t do it.”
Perhaps researchers should turn their efforts to a biofuel-powered time machine. Demonstration projects, ranging from reforestation to biochar, will continue to draw attention and resources as the Forest Service figures out its policies and priorities. The agency may not have to choose between managing for forest health or carbon sequestration, but if officials and managers are not mindful, they may end up protecting neither.
“The thinking is evolving,” Ryan says, “but there’s no one thing that’s going to solve this issue.”