TREATING DISEASED GREEN WASTE AT COMPOSTING SITES
Pat Paswater

RECENTLY, the California Integrated Waste Management Board (CIWMB) partnered with Matteo Garbelotto at the University of California, Berkeley (UC Berkeley) and commercial composters to research the composting of Sudden Oak Death (SOD) host material. Recognizing the importance of protecting markets for recycled content products established by local jurisdictions and lessening the impact of SOD regulation on composting operations within the 12-county area subject to SOD regulations, the CIWMB has allocated $50,000 towards this effort. Research data generated during the last 18 months is being compiled to show that the composting process kills the newly identified pathogen, Phytophthora ramorum.

One regulatory concern focuses on the risk of spreading the pathogen in green material from the 12-county regulated area to other California counties. Since it is difficult to determine the plant species of commingled trimmings, green material is subject to regulatory scrutiny even if there is no host material present. Currently, no regulated or restricted material within the quarantine area can be moved without a permit issued by CDFA. Technically, this means green material originating within an infested county cannot be composted, landfilled or burned for energy either outside or within the quarantine area unless permits are obtained. Few permits have been issued to date, but municipal green material continues to be collected, moved and processed with the knowledge of the observant regulatory authorities operating in the quarantined twelve-county area.

The state quarantine for P. ramorum has created concern within the collection and transportation infrastructure of curbside-collected organic materials throughout northern California. In 2003, when the state and the federal quarantines for P. ramorum will harmonize, CIWMB staff anticipates that many organics recycling businesses may be negatively impacted in the following counties: Alameda, Contra Costa, Humboldt, Marin, Mendocino, Monterey, Napa, San Mateo, Santa Clara, Santa Cruz, Solano, and Sonoma.

As discussed in the accompanying article, the UC Berkeley field research results from aerated static pile and windrow composting trials indicates that SOD contamination in green material presents little or no risk for spreading the pathogen if the product is composted and protected from exposure to additional P. ramorum inoculum. Research documentation will be submitted to state and federal regulatory staff for consideration of composting as an alternative treatment for SOD in early 2003. If composting is approved as an alternative treatment, CIWMB-permitted composting operations could provide another option for removal of high hazard diseased trees. These operations also could reduce the amount of SOD inoculum present in the regulated area.

At the very least, regulatory approval of SOD host material treatment by the time-temperature process of composting would provide some relief to local jurisdictions in the 12-county regulated area. This would also apply to the CIWMB-permitted operations producing compost and composted-mulch products. For a current list of the quarantined counties, the variety of SOD hosts, and the numerous articles regulated, please visit the California Department of Food and Agriculture’s Web site at http:// pi.cdfa.ca.gov/pqm/manual/455.htm.

Pat Paswater is a composting specialist in the Organics and Resource Efficiency Branch at the California Integrated Waste Management Board in Sacramento, California.