Determining Animal Mortality Compost Maturity and Suitability for Road Project Applications for the Virginia Department of Transportation

About the report:

A series of studies on the effectiveness, feasibility, and costs of composting as a means of managing animal mortality removed from roadways has been conducted at the Virginia Center for Transportation Innovation and Research (VCTIR). In these studies, three composting methods were evaluated for use by the Virginia Department of Transportation (VDOT) and found to be effective: static compost windrows, a forced aeration system, and a rotary drum. Successful pilot studies at VDOT maintenance facilities have led to a growing interest in adopting this method of mortality management. As plans for additional composting vessels are underway, final tests are needed in order to develop guidance on composting procedures that generate mature, or finished, compost that is suitable for road project applications.

The purpose of this study was to determine the time and treatment conditions necessary for VDOT compost vessels to generate mature compost and to evaluate the suitability of this compost for potential VDOT applications. Four methods were used to assess compost maturity: temperature monitoring, the Solvita compost maturity test, plant germination and growth tests, and qualitative observations. Tests were conducted on compost generated from the rotary drum and forced aeration system and on compost subsequently transferred to curing areas. The suitability of compost for road project applications was determined by testing compost for a suite of biological, physical, and chemical properties and conducting a demonstration project at a VDOT facility.

Of the compost maturity tests, temperature decline was the most conservative indicator of finished compost. As determined primarily by temperature monitoring and supported by the other maturity tests, compost generated from the forced aeration system and rotary drum should be transferred to curing areas to cure for approximately 8 to 9 weeks. Mature compost generated from these vessels met the U.S. Environmental Protection Agency’s compost specifications for transportation applications. It is recommended that VCTIR and VDOT incorporate the findings of this study into a guidance document for VDOT animal mortality composting.

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