How does Pitkin County's Composting Program Work?


The Composting Process

Compostable organics are monitored at the scale house, customers are directed where to place the material. The organic material, including wood chips, is combined into windrow piles. The windrows are turned on an as needed basis to maintain consistent temperature and aeration. The temperatures of the piles are monitored daily by County staff. USCC standards requires the compost to maintain a temperature of greater than 131 degrees Fahrenheit for period of three days or more, or temperatures greater than 113 degrees Fahrenheit for a period of 14 days or more. Studies have shown this is suitable to kill most pathogens, weed seeds, and break down most herbicides and pesticides.

The composting program follows rigorous operational, monitoring, and sampling protocols.  The County’s composting process follows the standards set forth by the US Composting Council (USCC). In 2013 the County’s Compost program became USCC Standard of Testing Assurance (STA) Certified. To become USCC STA Certified the compost program underwent a rigorous review of our procedures and laboratory sampling. In order to maintain STA Certification the program must be re-certified annually.

There is significant cost involved in processing the organic material into compost. The operational costs of composting include permitting, annual reporting, laboratory sampling, and equipment and labor involved in the operations. In order to make the compost operation viable it is necessary to charge a fee for the incoming material. While the compost program does generate positive revenue for the Landfill, these funds are used to support other non-revenue generating solid waste programs such as recycling, household hazardous waste collection, purchase and maintenance of equipment, and added to our state required post-closure care fund.



Unfortunately, contaminants such as plastic and metals do enter the compost piles. This is a constant challenge for most composting programs across the country. However, the final screening process catches much of this material before the product is ready for sale. Pitkin County’s compost is relatively clean compared to other programs, this can be traced to plastic bag bans the City of Aspen has implemented, as well careful screening of loads at the scale house.

In recent years there have been concerns of the herbicide clopyralid contaminating compost across the country. Clopyralid does not degrade in the composting process, and is capable of injuring certain plants such as beans and tomatoes. Studies have shown clopyralid in compost does not significantly affect the growth of grasses or trees. The County has taken measures to monitor for clopyralid by including the analysis in the sampling process. To date we have not seen detectable quantities of this herbicide. County staff makes available the analytical and temperature monitoring results to anyone who requests them.

The County is stepping up efforts to exclude manufactured wood from the compost process. Customers who have manufactured wood products are directed to dispose the material into the construction and demolition debris pile for landfilling. Brush and non-treated wood is directed to the wood pile for grinding. During the grinding process, the manufactured wood material in the organic wood pile is separated and diverted for disposal in to the landfill. County staff are ramping up efforts to better educate landfill customers on the proper sorting of wood. This will further improve the quality of the compost.