Water Resource Recovery Facility Spotlight - City of Coeur d’Alene’s Coeur d’Green Composting Facility

Resource Recovery in Action: City of Coeur d’Alene’s Coeur d’GreenTM Composting Facility turns municipal biosolids into nutrient-rich soil amendment.

The City of Coeur d’Alene has been a pioneer in the wastewater treatment industry since 1939, when it’s 10,000 residents passed a bond to build one of the first secondary wastewater treatment plants in the Northwest (for a whopping $140,000!). Then, in 1989, the City again demonstrated its pioneering efforts in resource recovery with the construction of a composting facility that converts biosolids from the City’s wastewater treatment facility into a high-quality soil amendment using the aerated static pile composting method. The Class A Exceptional Quality product has been affectionately coined Coeur d’GreenTM compost and is unrestricted for horticultural uses. Since 1989, the composting facility has gone through many upgrades to improve operations and the quality of the end product, including covered wood chip storage, added bays for aerated curing, and upgraded conveying, mixing, and screening equipment. Figure 1 below is a schematic of the current composting process.

Figure 1: Aerated Static Pile Composting Process Schematic

An aerial photo (Figure 2) shows the existing 18-acre facility. As it’s adjacent to residential areas, compost bed biofilters are used for odor control.

Figure 2: Aerial of Compost Facility

Figure 3 shows static compost piles, which must reach temperatures of 131° F for 3 consecutive days and average 113° F for at least 14 days. The compost is then screened to remove the large wood chips, which are recycled several times in the process, and finally placed in an aerated curing pile for an additional 30 days before it is ready for use.

Figure 3: Aerated Static Compost Piles

Currently, the City’s composting facility processes approximately 20 cubic yards (CY) per day of anaerobically digested and dewatered biosolids. Since its beginning, an estimated 100,000 cubic yards of biosolids (equivalent to covering 62 acres with 12 inches of compost) have been converted to Coeur d’GreenTM compost, recycling essential micro-nutrients back into the soils to which it is applied. Coeur d’GreenTM compost is not sold directly to the public by the City but may be obtained from local landscape supply companies.

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