Will you save money if you divert materials from your solid waste stream?
It depends on your current system and how you account for various options' costs, according to a study conducted by the Solid Waste Association of North America (SWANA), Silver Spring, Md.
Six solid waste programs were examined: Minneapolis; Palm Beach County, Fla.; Scottsdale, Ariz.; Seattle; Sevierville, Tenn.; and Springfield, Mass. Because of each system's complexities, the study sought general conclusions.
The study warned against determining the relative costs of various programs by comparing the average cost per ton of managing solid waste to the average cost per ton of diversion or recovery programs.
Instead, examine the costs incrementally when you are considering adding or changing a program. Also, managers should project costs for each year in the planning period when calculating the program's long-term impact.
When materials are diverted from the waste stream, see if it can reduce basic collection and disposal expenses, the study recommended. If savings can be realized, then the program's incremental cost can be reduced.
For example, Seattle's residential curbside and yard waste programs' incremental costs are relatively low due to savings in its tonnage-based collection and disposal contracts; each ton diverted saves on collection and disposal.
Other cities may encounter several impediments to achieving these savings, at least in the short term, including routing or equipment constraints, union rules, contract limitations and service level limits.
For example, many communities in Palm Beach County pay for residential solid waste (RSW) collection on a per-household basis. When the residential curbside recycling program was instituted, many of the city-based RSW collection contractual fees were not renegotiated.
Therefore, until the next round of bids, there were no savings in MSW collection costs. Springfield's curbside recycling program's incremental cost also is relatively high, in part because its "put or pay" commitment makes it impossible to realize any disposal cost savings at the waste-to-energy facility.
Fortunately, high incremental costs do not necessarily imply a deficiency in diversion or resource recovery programs, the study found. The lower a community's variable cost per ton for MSW collection and disposal, the more likely that a new diversion or recycling program's incremental cost will be high.
For example, in cities like Scottsdale and Sevierville where collection and landfill costs are low, the incremental cost of any diversion program is expected to be relatively high, no matter how well designed or efficient.
Overall, collection consistently represents the largest percentage of a system's total net costs, ranging from 39 to 62 percent, according to the study (see chart). These costs determine whether the system uses several management options or just a couple.
The study discounted the presumption that processing facility costs dominate, despite the expansion of materials and energy recovery services over the past two decades. The additional energy consumed to collect and process recyclables and yard waste also is relatively nominal. Hauling materials 100 miles one way to markets using transfer trucks requires approximately the same energy necessary to collect and locally process these materials.
At drop-off centers, however, the average energy consumed per ton of recyclables collected was three to five times higher than for curbside recycling, according to an independent two-week survey of Scottsdale residents.
In general, all of the curbside recycling, yard waste, composting, waste-to-energy and mixed waste composting programs analyzed were found to increase the cost of managing MSW. Seattle's curbside program was the only exception.
Finally, landfill disposal costs also are relatively small overall, according to the study. The landfills studied varied in age, size, design and operation.
The studies were jointly sponsored by the American Plastics Council, Washington, D.C., and the U.S. Department of Energy's National Renewable Energy Laboratory, Golden, Colo.
For more information on Integrated Municipal Solid Waste Management: Six Case Studies of System Cost and Energy Use, contact: Charlotte Frola, Dianne DeRoze or Kathleen Kilbane, SWANA, P.O. Box 7219, Silver Spring, Md. 20907-7219. (301) 585-2898. Fax: (301) 589-7068.