Studying Woody Biomass for Energy Across the U.S.

SRS scientists contribute to special journal issue on bioenergy

by Sarah Farmer, SRS Science Communications
Non-traditional equipment is tested for harvesting small trees as an energy crop. The red attachment is a sheer felling head, and allows the skidsteer to accumulate several small stems at a time. Photo by Dana Mitchell, U.S. Forest Service.

Non-traditional equipment is tested for harvesting small trees as an energy crop. The red attachment is a sheer felling head, and allows the skidsteer to accumulate several small stems at a time. Photo by Dana Mitchell, U.S. Forest Service.

Woody biomass includes stems, small branches, treetops, needles, leaves, and sometimes the roots of trees and shrubs. These materials are byproducts of forest management activities such as thinning, but they can also be a valuable source of bioenergy.

Five U.S. Forest Service Southern Research Station (SRS) scientists – John Stanturf, Emile Gardiner, Leslie Groom, Dana Mitchell and James Perdue – recently contributed to four review articles that were part of a special issue of the journal BioEnergy Research. SRS researchers collaborated on the journal articles with scientists and engineers from a number of universities and other agencies, including the Forest Service Northern Research Station, Pacific Northwest Research Station, and Forest Products Laboratory, as well as the USDA Agricultural Research Service and Natural Resources Conservation Service.

The articles cover all aspects of the bioenergy supply chain – from cultivation in fields or forests, to harvest, to conversion into a final product. Since 2009, Forest Service scientists and engineers have contributed to more than 60 peer-reviewed journal articles about forest operations – a branch of industrial engineering that includes designing, implementing, or improving technologies in the forest sector – and logistics, which includes the harvest, handling, processing, transportation, and storage of woody biomass.

“In practice, operations and logistics blend science, engineering, and management functions to efficiently and effectively meet the needs of customers and society,” says Mitchell, a coauthor of one of the papers. “Forests provide products like biomass, and also help clean the water and air, offer food and shelter to wildlife, and provide opportunities for recreation and other benefits.”

In addition, some tree species, or genotypes within a species, have extra abilities and can help remove chloride, selenium, heavy metals, and other pollutants from former landfill sites, old mine tailings, and other contaminated areas. The process is called phytoremediation, and poplars, willows, and their hybrids are especially effective. These species are also used across the globe to generate bioenergy, and are promising candidates for U.S. bioenergy operations.

Even when grown as bioenergy crops, trees provide valuable ecosystem services. Fast-growing trees such as eucalyptus, pine, and poplar can be grown in plantations and harvested after less than 20 years. “These short-rotation woody crops could be an integral component of regional and national energy portfolios,” says Stanturf, a coauthor of one of the papers. “While they’re growing, they can store carbon, clean the air and water, and improve the soil.”

The renewed interest in biofuels provides an opportunity to use small-diameter trees, which grow thickly in many forests and can represent a fire hazard. In some forests, harvesting small trees to create biofuels will support forest restoration and fire prevention. Currently, forest management contracts to mitigate fire risk cost the Forest Service – and by default, the taxpayer – $500 to $1500 per acre.

Although the ultimate goal is that woody biomass removal is valuable enough to pay for itself, partial success will still extend the fire-risk mitigation budget and allow for more acres to receive need treatments. Forest Service scientists continue to develop new strategies for providing the country with sustainable and cost-effective strategies for growing, harvesting, and using forest biomass.

Read Ecosystem services of woody crop production systems.

Read Environmental technologies of woody crop production systems.

Read Forest operations and woody biomass logistics to improve efficiency, value, and sustainability.

Read A survey of bioenergy research in Forest Service Research and Development.

 

For more information, email John Stanturf jstanturf@fs.fed.us.

Access the latest publications by SRS scientists.

 

Tagged with: , ,
Posted in Biomass and Bioenergy, Forest Operations, Forest Products

Partnership to Better Understand Harvest Methods for Ramps Launched in Michigan

by Patty Matteson, SRS Public Affairs
Jim Chamberlains sets up plots to study the sustainability of ramp harvests in Michigan. Photo courtesy of U.S. Forest Service.

Jim Chamberlain reviews placement of study plots where ramps have been harvested for commercial purposes in northwest Lower Michigan. Photo by Michelle Baumflek.

The U.S. Forest Service Southern Research Station (SRS) and Virginia Tech are partnering with the newly formed Institute for Sustainable Foraging (ISF) based in Traverse City, Michigan, to study ramp harvesting techniques used by private landowners and harvesters in Northern Michigan. This research will be used to better understand harvest methods necessary to ensure sustainability of ramp populations over time.

Native to the hardwood forests of eastern North America, ramps emerge in moist, shady areas of forests in late March or April, when the plant sends up a circle of smooth broad leaves that die back when the overhead trees are fully leafed out. People collect both the leaves and spicy bulb of the plant as a spring tonic and increasingly, as a culinary specialty.

Jim Chamberlain, SRS research forest products technologist, along with Michelle Baumflek, an ethnobotanist and post-doctoral research associate at Virginia Tech, have installed study plots where ramps have been harvested for commercial purposes in northwest Lower Michigan. These sites will be revisited in subsequent years to examine the effects that foraging may have on plant density, size, and other indicators of population health to help determine how they may be sustainably harvested.

The study’s fieldwork will provide scientific data for the ISF, a non-profit established with the support of Tamarack Holdings, a group of businesses, Michigan foragers, botanists and others. These entities all share a common and growing interest in assuring the long-term sustainability of ramps and other foraged goods. “By adding Michigan, researchers are able to add to their ongoing studies a whole different region of the country, where ramps are native and the population is more prolific,” says Brian Bourdages, the program manager at Tamarack Holdings. “Results from the study will help the ISF to better assess their sustainable foraging standards.”

“The research in Michigan will help provide valuable information on how ramps can be grown and harvested sustainably there and in other forests,” says Chamberlain. “I am really excited about this partnership with Virginia Tech and the Institute for Sustainable Foraging and how it will expand our knowledge of ramp conservation and management.”

Baumflek spoke of her excitement at seeing the prolific nature of the ramp patches in Michigan. “In the mountains of North Carolina, where I’ve been doing much of my work, ramps rely on mesic cove habitats, which limits their distribution to smaller, steeper and more confined areas than here in this part of Michigan. It’s amazing to see such large and healthy populations of ramps covering the forest floor.”

“It is also important to acknowledge that our field methodology was adapted from research by SRS research plant ecologist Joan Walker in western North Carolina,” said Baumflek. “Walker has been monitoring ramp patches that are subject to gathering pressure on federal forest land for over 15 years.”

John Munsell, associate professor and forest management extension specialist in Virginia Tech’s Department of Forest Resources and Environmental Conservation, had this observation about the study’s expansion, “This partnership is significant not only for improving ramps harvesting but more generally because of what it achieves among the agencies, industries, and institutions focusing on non-timber forest products. Stakeholder cooperation is necessary to move in a fundamental direction toward sustainability and we are well on our way.”

For more information, email Jim Chamberlain at jchamberlain@fs.fed.us.

Access the latest publications by SRS scientists.

Tagged with: , ,
Posted in Forest Products, Non-Timber Forest Products, Uncategorized, Upland Hardwoods

Turning Trees into Bioenergy: What are the Effects on Soil?

by Sarah Farmer, SRS Science Communications
A crowded loblolly pine plantation in Arkansas is thinned, providing small branches and other woody biomass that can be used to generate electricity. Photo by Andy Scott, U.S. Forest Service.

A crowded loblolly pine plantation in Arkansas is thinned, providing small branches and other woody biomass that can be used to generate electricity. Photo by Andy Scott, U.S. Forest Service.

Timber has been harvested for hundreds of years, but current bioenergy operations use more parts of a tree than ever before; small branches that used to be considered non-merchantable are now often harvested instead of left rotting on the forest floor.

“The increased use of small branches and formerly non-merchantable wood has been linked to changes in energy cycles, short and long-term hydrology, and changes in a number of soil properties,” says Andy Scott, a research soil scientist at the U.S. Forest Service Southern Research Station.

Scott and his co-author Deborah Page-Dumroese, a soil scientist at the Forest Service Rocky Mountain Research Station, recently wrote an overview of the issues around bioenergy and site productivity. Their study was published in the journal BioEnergy Research as part of a special issue on the USDA Regional Biomass Research Centers.

The first coordinated, nationwide research on soil changes after timber harvesting dates back to 1990, when a site on the Palustris Experimental Forest near Alexandria, Louisiana became part of the Long-Term Soil Productivity (LTSP) experiment. Started in 1989, the LTSP has grown into a network of more than 100 field sites in the U.S. and Canada. Although the LTSP was not designed specifically to test the impacts of harvesting biomass, it evaluates soil organic matter and compaction – two issues that are intrinsically linked to biomass harvesting.

In traditional logging operations, only the tree trunks are harvested, and huge piles of branches and other organic matter are left behind to rot and return their nutrients to the forest floor. However, on some of the LTSP sites that Scott and his colleagues reviewed, all aboveground organic matter and nutrients had been removed.

“Most plant nutrients are in the leaves and branches,” says Scott. “Harvesting a whole tree, rather than just the trunk, removes three times as many nutrients from a site.” Losing the nutrients could affect soil’s fertility, as well as its ability to store carbon – and ultimately its ability to produce new trees.

However, in a testament to the resilience of forests, removing all aboveground organic matter and nutrients from LTSP sites did not cause widespread losses in tree productivity. After 10 to 15 years, only the LTSP sites that were extremely infertile to begin with were affected. “However, 15 years is still quite young for managed forests,” says Scott. “Nutrient deficiencies could still occur as the trees mature.”

Harvesting for biomass also increases the amount of traffic on a site. Trucks, tractors, excavators, and other logging machines lumber through a stand, disturbing soil as they go. With each pass, their tires pack soil particles together,  sometimes tightly enough to limit the movement of air, water, and nutrients.

Compaction can reduce microbial activity and root growth, although trees are typically less affected by compaction than shrubs, flowers, grasses, and other vegetation competing to survive. In the LTSP sites, soil compaction had mixed effects on productivity. In heavy clay soils it hindered tree growth, while in sandy soils it actually increased productivity.

Scott and his colleagues also considered the use of products like biochar. Biochar looks like charcoal, and is created through a similar process, but it has a long tradition of use as a soil additive. Indigenous people in the Amazon used it to improve soil for millennia, and scientists have found it benefits soil in gardens and farms. It also stores carbon for long periods of time in a highly stable form. Biochar has not been thoroughly studied in forests, but it could potentially improve soil health and productivity. It could even be produced as a by-product of producing energy with the small branches and other woody residues.

“Biomass harvesting is no panacea,” says Scott. “However, in forests with an overabundance of small-diameter trees, it can help reduce wildfire severity and increase forest health. And with sensible precautions, biomass harvesting will not diminish the soil’s ability to support plant growth.”

Read the full text of the article.

Read more about the role of the Palustris and three other U.S. experimental forests in the LTSP network.

For more information, email Andy Scott at andyscott@fs.fed.us

Access the latest publications by SRS scientists.

Tagged with: , , , ,
Posted in Biomass and Bioenergy, Experimental Forests
Subscribe to our newsletter!
Archives