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Z-Best Composting Facility

Z-Best Aerial ViewThe Z-Best Composting Facility (Z-Best) is located in Santa Clara County near the City of Gilroy. Z-Best was opened in 1997 for yard waste composting and now can receive up to an average of 1,500 tpd of green/yard waste. The Z-Best composting permit was revised in 2001 to include up to 600 tpd of “in-vessel” municipal solid waste/food wastes (MSW) composting and currently has an average recycling rate of 78 percent for this MSW composting process.

Yard Trimmings Composting

Yard trimmings arriving at Z-Best are weighed and recorded and off-loaded directly In the composting area. The yard trimmings are loaded into a horizontal grinder, shredded and placed directly into windrows. The windrows are trapezoidal in shape, approximately 20′ wide at the base, 12′ high, and 400′ long.

During the 14-18 week composting period, windrows are monitored daily for temperature and moisture. As required by state law, records are maintained on-site and include daily temperature readings, turnings, and documentation of the fifteen-day pathogen reduction period as required by state law. The windrows are turned 1-2 times per week and watered as needed.

When fully composted, the materials are transported to a screen for final processing and marked as organic compost.

Municipal Solid Waste MSW and Food Waste Composting

In January 2001, Z-Best began its MSW composting program after applying for and obtaining a full solid waste facility permit from the Cal Recycle. Currently, the facility accepts up to 350 tons per day of MSW compostable wastes from commercial establishments and area Cities.

Compost Retention BagsAt the Z-Best facility, all materials are processed in an enclosed 20,000 square foot building to remove non-compostable items. The compostable items are then shredded and transported to the composting area, where they are ejected into a 350-foot long bag that houses all the compostable wastes. PVC pipes are also introduced into the bag and used to aerate the compostable materials.

Retention time in the bags is about four months, at which time the contents are removed, turned and cured prior to screening. The materials are then transported to a screening system that is used to remove any larger materials, which are then disposed. The smaller compostable materials are stockpiled and cured for an additional four weeks before being screened again.

Compost Marketing

Compost TrucksCompost produced from both operations are sent monthly to an independent laboratory to be tested for nutrient value, contamination and pathogen reduction. The organic compost is sold primary to farmers and also goes material yards and landscapers. In 2015 Z-Best sold over 150,000 tons of compost products. The Z-Best Compost is certified by the OMRI as organic approved by the California Department of Food and Agriculture for use on farms, gardens and nurseries.