7 Juni 2017

Research focuses on reclaiming strip-mine sites for biofuel crop production

Switchgrass can be condensed into fuel pellets for heating and it can be used to make ethanol

Strip mines are so common in rural Pennsylvania that many people are unfazed by the sight of rock-filled piles of dirt and tracts of barren land.

Marvin Hall, a researcher in Penn State’s College of Agricultural Sciences, is not one of those people. To him, all land has value, and his research efforts focus on bringing a highly productive life back to damaged land with a crop that can be used as an alternative fuel source.

“In Pennsylvania, there are hundreds of thousands of acres that have not been reclaimed after strip mining,” said Hall, professor of forage management in the Department of Plant Science. “If we show that land can be highly productive after mining, then maybe we’ll see fewer abandoned strip mines and more grassy fields.”

Hall’s research is taking place on a “reclaimed” strip mine in Clearfield County, near the Centre County borough of Philipsburg. The property had been deep mined about 50 years ago and then strip mined in the mid-2000s. The post-mining remediation of the property with lime, fertilizer and a 10-inch layer of rocky earth did little, if anything, to restore the land. Hall first visited the site in 2008.

“It looked like a moonscape — the ground was filled with rocks and boulders, and the soil had poor water-holding capacity, all common problems after strip mining,” Hall said. “I honestly didn’t know how we were going to get anything to grow on it.”

But he saw promise in one crop — switchgrass. It’s a hardy, deep-rooted perennial grass that’s known for its ability to grow despite poor soil quality, drought or flood. Its deep roots can break through rocky soil layers, improving long-term soil structure. It grows as high as 6 feet, requires little maintenance or fertilizer, and produces crops for up to 20 years. Switchgrass has many environmental and commercial benefits, such as providing shelter and food for wildlife, soil conservation, livestock feed, animal bedding, mulch and landscaping.

Perhaps most important in the strip-mine setting is that switchgrass can serve as a renewable energy source — its biomass can be condensed into fuel pellets for heating, and it also can be used to make ethanol, an alternative to gasoline. It’s a carbon-neutral fuel, meaning what carbon dioxide it releases into the atmosphere as a fuel is reabsorbed and used by plants for growth, and that’s good for the environment. Another advantage is that switchgrass can produce high yields — an acre can yield 7 or 8 tons of dry matter when harvested; one ton can be converted to about 80 gallons of ethanol, according to Hall.

Because there are numerous switchgrass ecotypes, or varieties, determining which ones would survive — and thrive — on strip-mine ground in the region has been the focal point of Hall’s research. To learn more about the soil’s composition and other environmental factors that could affect growth, he worked with colleagues Rick Stehouwer, professor of environmental soil science, and John Carlson, professor of molecular genetics, both of Penn State’s Department of Ecosystem Science and Management.

Stehouwer, who shares an interest in land reclamation, knew the property well as he was conducting experiments there with Hall; Stehouwer’s research focused on the use of agricultural manure and paper-mill sludge to rebuild soil quality and sustainability for the purpose of growing biomass crops — a perfect complement to Hall’s work.

“The soil (at the Philipsburg site) was what we typically find in post-mining areas — very low in nutrients like phosphorus, nitrogen and calcium, low in organic matter and filled with rocks — all factors that make it difficult for plants to grow,” Stehouwer said.

After reviewing test results and his colleagues’ recommendations, Hall connected with researchers from switchgrass breeding programs at Cornell and Rutgers universities and selected 150 ecotypes of seedlings for the first screening crop in 2013. With the help of graduate students, 4,000 seedlings were planted on several plots of the land, with the goal of identifying varieties that fared well and those that didn’t.

Over the next three years — the time it takes for switchgrass to reach maximum yield — Hall and graduate students made regular trips to the site to monitor and document plant growth, soil conditions, insect damage and plant disease. They also focused on weed control, as weeds can be detrimental to seedlings’ first year of root development.

After studying the data and pinpointing 30 switchgrass ecotypes that performed best, the team will plant an additional 1,500 seedlings this summer. At the end of the final, three-year study period, the plan is to narrow the selection to the top five performers for the land conditions and climate, and make seed from these selections available to the public for planting. Hall is pleased with the progress made.

“The differences we found in the productivity of different varieties have been amazing,” he said. “We hope in the not-too-distant future we will be using old coal mines once again to produce our fuel.”

Funding for the research has been provided by NEWBio — the Northeast Woody/Warm-season Bioenergy Consortium — a regional project funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture to promote next-generation bioenergy production in the northeastern United States.

Penn State is the lead institution in the consortium, which also includes Cornell University, SUNY College of Environmental Science and Forestry, West Virginia University, Delaware State University, Ohio State University, Rutgers University, USDA’s Eastern Regional Research Center, and the U.S. Department of Energy’s Oak Ridge National Laboratory and Idaho National Laboratory.

Source: Pennsylvania State University, press release, 2017-05-23.

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