United States Department of Transportation
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An evaluation of the economics and logistics of animal mortality composting for the Virginia Department of Transportation.
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2015-04-01
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Abstract:Many maintenance facilities of the Virginia Department of Transportation (VDOT) face a decreasing availability of the
conventional methods of animal mortality disposal (i.e., landfills and burial of individual mortalities) and have a need for a viable
alternative. Others are interested in an alternative means of managing mortality that will save time and labor. Recent studies
found that static windrow composting and in-vessel forced aeration composting systems are useful and effective means of
managing animal mortality for VDOT, but more information is needed with regard to their cost and feasibility.
The purpose of this study was to determine the economic value of implementing a composting program for VDOT. A
survey was used to gather general information on animal mortality management from VDOT’s area headquarters (AHQs).
Weekly diaries were also collected from eight AHQs and two VDOT residencies over an 8-month period to gather more detailed
information regarding their means of mortality management. With the use of these maintenance areas as case studies, cost models
were developed that determined the costs or savings incurred from replacing the maintenance area’s current means of disposal
with one of three composting methods: static windrows, a rotary drum, or a forced aeration composting system.
The study found that even the most expensive composting option currently available to VDOT, the forced air system, is
cost-effective when there is sufficient mortality volume. Under the assumptions of the cost models, with regard to the AHQs
evaluated, purchasing and operating the current forced air system and rotary drum can save VDOT up to $54,000 and $36,500,
respectively, within the lifetime of the vessels. Static windrows are always cost-effective when a free carbon source (i.e.,
woodchips from vegetative debris removal) is available. As a general rule with regard to the cost-effectiveness of composting, the
start-up costs of the current forced aeration composting system should not exceed 22 times the operational savings from
composting in the first year and the start-up costs of rotary drum composting should not exceed 14 times the operational savings
from composting in the first year.
To maximize the cost-effectiveness of composting, maintenance area superintendents who plan to use composting for
animal mortality management should try to identify a no-cost carbon source; use finished compost for transportation project
applications in place of purchasing comparable material; seek other maintenance areas with which to share composting facilities;
and consider using static windrows whenever possible, including to supplement vessel composting during periods of high
mortality. In addition, the Virginia Center for Transportation Innovation and Research should pursue the design of a forced air
system with a smaller capacity and lower construction costs than the one presently in use. This would increase the cost-effectiveness of composting for AHQs that do not have a readily available no-cost carbon source; that have smaller mortality
volumes; and/or for which pooling of mortality with other AHQs is infeasible. VDOT can save costs by replacing current
mortality management methods with a composting alternative and adopting supportive business practices.
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