Mushroom growers who weathered the industry shakeout of the 1980s have expanded production, usually without adding new acreage. In addition, once-rural mushroom operations are now surrounded by suburbs and housing developments. The composting process for mushroom substrate, in which huge piles of animal manures, hay, and other organic materials are watered and blended for three weeks until microbes have decomposed the mixture, creates odors. In some cases, these odors cause disputes or even inspire restrictive local ordinances that make it difficult for farmers to do business.

Plant pathologist David Beyer explains the science behind producing mushrooms to students at Penn State's Mushroom Test Demonstration Facility.

To find an answer for mushroom compost odor problems, Penn State's mushroom faculty did not suggest high-cost, high-technology solutions. Instead, they went on a trip. Plant pathologist David Beyer, agricultural engineer Paul Walker, several graduate students, and four representatives from the mushroom industry toured mushroom growing facilities in Canada, Ireland, England, Italy, Belgium, and the Netherlands to find out how international growers do things. "Europe had to deal with odor and production issues much earlier than Pennsylvania growers," Beyer explains. "The technology and engineering applications for reducing composting odors have been developing in Europe for about 10 years. That meant we didn't have to start from scratch."

Currently, Beyer, Walker, and agricultural engineers Paul Heinemann and Robert Graves are collaborating on the construction and design of two aerated compost horizontal silos at the University's Mushroom Test Demonstration Facility. Unpleasant odors are generated within compost piles if the mixture is not turned regularly or is improperly managed. The aerated silos reduce composting odors by forcing air into the compost mix. "When pockets of material within the pile become deprived of oxygen, the substrate will encourage growth of microbes that make odors," Heinemann says.

Aerated compost silos use air jets embedded into the floor to introduce oxygen within the substrate mixture, and solid walls ensure homogeneous distribution of air throughout the structure. Hy-tech Compost built an aerated silo in July 1998. The company's managers can monitor and adjust temperature, airflow, and odor within the structure from a central computer. Needham says composting takes from 9 to 12 days, compared to 16 to 21 days for traditional methods. Eventually, the silo system will allow Hy-tech to bring its entire composting operation indoors.

Heinemann and graduate student Sarah Labance are testing whether air should flow continuously through the compost silo or be turned on and off as decomposition demands. In addition, Labance is testing several microporous membranes to discover which types most effectively absorb or prevent odor compounds from escaping and how they affect heat and moisture loss from the compost piles. The membranes allow smaller gaseous molecules, such as oxygen, water vapor, and carbon dioxide, to pass through the membrane while preventing larger odor-laden molecules from escaping.

The development of new mushroom marketing opportunities and the search for solutions to problems plaguing the mushroom industry has most Chester County growers singing Penn State's praises. "We all would like to see Penn State's research move a little faster," Needham says. "But we recognize that the University is not working just for the mushroom industry." In an age where universities are concerned with reaching out to new audiences, many researchers involved with the project regard the Mushroom Industry Farmer-Based Applied Research program as a model for outreach. "It has energized all of the mushroom research faculty," Stewart says. "There has been a significant increase in student enrollment, we're attracting postdoctoral researchers and visiting scientists, and we are able to recruit outstanding graduate students." Stewart says the College will continue to collaborate with the mushroom industry to target new research areas, including marketing and product development. "The University and the mushroom industry continue to set long-range goals as equal partners. It's an almost perfect illustration for applying the land-grant system to solve major threats to an industry."

-- John Wall

Faculty referenced in this article are Robert Beelman, professor of food science; David Beyer, assistant professor of plant pathology; Jon Chorover, assistant professor of environmental soil chemistry; Richard Fox, professor of soil science; Paul Heinemann, professor of agricultural engineering; Charles Heuser, associate professor of horticultural physiology; Jay Holcomb, professor of floriculture; Peter Romaine, associate professor of plant pathology; Daniel Royse, professor of plant pathology; Elwin Stewart, professor and head of plant pathology; Paul Walker, professor of agricultural engineering; and Paul Wuest, professor of plant pathology. Research is funded by the Pennsylvania Department of Agriculture, the Mushroom Industry Farmer-Based Applied Research program, the Center for Excellence in Mushroom Products, the Ben Franklin/American Mushroom Institute Products Committee, and the Mushroom Endowment Fund.