With Vermont’s new universal recycling law slated to ban landfilling of yard waste by summer 2016, and of food scraps by 2020, composting will soon be required. “And we will likely have a lot more compost in Vermont to spread around,” says Stephanie Hurley, a professor UVM’s Plant and Soil Science Department.

That may be good news for farmers and their tomatoes, but there are risks of water pollution from too much compost applied in the wrong places.

That is why Hurley and her doctoral students, Amanda Cording and Paliza Shrestha, have received a $20,000 grant from the State of Vermont’s Department of Environmental Conservation to study nutrient leaching from compost.

“Those of us who know about compost apply it to our gardens and farms to enhance plant growth because of its nutrient-rich attributes,” Hurley says, “But nutrients, like nitrogen and phosphorus, can also be water-quality pollutants, as in the case with phosphorus in stormwater and agricultural runoff stimulating blue-green algae outbreaks in Lake Champlain each summer.”

Hurley’s lab is working with state researchers to begin identifying what the best applications are for compost, “including circumstances where using compost as a soil amendment are better and worse for other important environmental issues,” she says, “like the treatment of stormwater runoff.” The laboratory, in UVM’s Jeffords Hall, is testing six different compost types, acquired from commercial compost producers in Vermont. Each company uses a different variety of “feed stocks” — ingredients — Hurley says, to produce their compost.

These researchers will be comparing the likelihood of leaching of nutrients from these varying composts under different durations of saturation time. The tests range from ten minutes to ten days, to simulate the types of soil and water chemistry that would arise from a quick rainstorm versus a more significant flood event. This approach “simulates how wet that material will get for conditions like a quick rainstorm versus what we saw with Hurricane Irene, where overbank areas are flooding and sitting flooded for a long time,” Hurley says.

After the soaking, the scientists extract water from the compost samples. “We basically syringe up the water,” says Shrestha, and then measure the soluble nutrients in that water. “This research will help us understand what the best uses of all this new compost are,” Hurley says, “so that we don't have water quality problems as a result of this wonderful material that is being kept out of landfills.”