The Pennsylvania mushroom industry, the nation's leading producer of commercial button mushrooms, uses more than 500,000 tons of compost each year. The growth medium is composed of a mixture of straw, hay, and horse and other manures, and is composted before use.
"The compost is used for about two months and then discarded," says Dr. Patrick G. Hatcher, director of Penn State's Center for Environmental Chemistry and Geochemistry and professor of fuel science and geosciences and chemistry. "The spent mushroom substrate must be weathered for two years before it can be reused."
The mushroom industry has identified potential uses for this substrate as a soil amendment or potting media, in mine reclamation and wetland establishment. Other uses may be possible, but not much is known about the weathering of the spent substrate or the leachate that drains from the compost when it is spread over a field to weather.
Hatcher; Dr. C. Peter Romaine, associate professor of plant pathology; Dr. Jon Chorover, assistant professor of environmental soil chemistry; and Dr. Richard H. Fox, professor of soil science, will analyze and characterize the weathering compost over a three-year time span.
This joint College of Agricultural Sciences and College of Earth and Mineral Science project is sponsored by MIFBAR, Mushroom Industry Farmer-Based Applied Research project, a legislative initiative to increase the use of mushroom soil. The research is funded at $186,000 for the first year.
The project will be carried out on farm land owned by Vincent Santucci, operator of Elite Mushrooms in Avondale, Pa. A series of lysimeters -- containers that will catch the liquid that leaches out of the substrate -- were built at the surface, just below the level of the compost and then three feet below that.
The researchers will take water samples from these lysimeters following precipitation events to assess leaching from the piles of spent mushroom substrate. They will also take solid samples from the top, middle and bottom of the weathering compost at three-month intervals. Water and compost samples will be analyzed for both organic and inorganic composition.
"A multitude of methods will allow us to evaluate the trends in carbohydrates, proteins, lignin and other organic species as a function of weathering," says Hatcher.
Other analysis will investigate the soluble salt contents of the compost and the nitrogen content and composition. The leachate collected from the lysimeters will be analyzed for the same organic and inorganic contents.
"When we are done, we should know what is going on in the weathering compost, what is leaching out of the compost and what the final composition of the compost is," says Hatcher. "We will then know how the spent mushroom substrate can best be reused and how to weather it in the best way for both the environment and recycling."
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