Mixed Waste Processing

As the name indicates, a mixed waste processing (MWP) facility manages unsegregated refuse; it separates some material out to be recycled before the remainder is sent for disposal. Separation can be performed by different methods: (1) manually by handpickers as waste runs across a conveyor, (2) mechanically by automated equipment designed to extract recyclables, or (3) some combination of manual and mechanical means. As an example of technology used in a MWP facility, an automated system may have a large magnetic separator to remove ferrous metal from the waste stream. MWP facilities may sort a range of materials including cans, bottles, and paper; the array of materials recycled varies with the facility. MWP facilities differ from material recovery facilities (MRFs) in that they accept commingled garbage; MRFs accept "clean" recyclables already segregated from the rest of the waste stream.

Pros and Cons of Mixed Waste Processing

As with many solid waste management options, mixed waste processing offers a number of advantages and disadvantages, as listed below:

The first four advantages occur because MWP does not require public participation. However, this lack of public involvement in separating recyclables from waste can also translate into a disadvantage: participation in source-separation recycling programs acts as an educational tool that can, in turn, benefit waste reduction efforts. The other disadvantages result from general technical limitations inherent in MWP. When garbage is mixed, the value and recyclability of some materials may be reduced by contamination (such as newspaper) or breakage (such as glass). Also, only a fraction of potentially recyclable materials are recovered by hand-pickers with a conveyor system unless worker-to-conveyor-speed ratios are high. However, another benefit of MWP is that after processing but before disposal, the waste can be baled to conserve landfill space or shredded for incineration.

Recycling Rates and Costs

In addition to these advantages and disadvantages, costs and recycling rates are critical factors in the selection of a waste management option.

• Costs for sending material to MWP facilities tend to be higher than for landfilling but will vary with the region. Although five MWP facilities operated in North Carolina since 1991, two have closed because of low recycling rates and financial instability. According to data from the three remaining operations, local governments in North Carolina should expect to pay at least $36 per ton to cover the full cost of mixed waste processing.
• MWP recycling rates tend to be much lower than those for successful curbside or drop-off recycling programs. As shown in Table 1, North Carolina MWP facilities achieve recycling rates of only 1 to 11 percent. Much of the recycling occurs at the front-end of the facility before material enters manual or automated sorting lines.

In assessing its solid waste management options, a local government should determine the recycling rates it can achieve under various options and cost scenarios. These factors should be considered along with the advantages and disadvantages of MWP noted above.

Blue Bag Recycling

"Blue bags" can be used to increase recycling rates of a MWP system. In a blue bag program, participants put recyclable materials in a special blue plastic bag. This bag is then collected along with the regular garbage. A MWP facility can then segregate all blue bags from other waste and better manage this pre-sorted, cleaner material. Also, blue bags can offer straightforward recycling options for certain materials in office and industrial areas.

A blue bag program requires a mechanism for distributing or selling bags to residential, office, and industrial users. If the bags are sold, the price should be comparable to that for regular plastic garbage bags, if possible. Blue bag programs require close coordination with the MWP facility operators and comprehensive educational efforts. If the public is not properly educated about the importance of segregating recyclable materials into the blue bags, a MWP facility faces the danger of undermining such a program as people may believe that recyclables will be adequately sorted whether or not they participate. Also, blue bag programs in North Carolina have not achieved high participation rates.

Local governments that establish blue bag programs are in the unusual position of paying high tipping fees, perhaps $38/ton, to recycle segregated materials that otherwise could be more economically managed. A final concern about blue bag programs was raised by one North Carolina local government official who remarked that many blue bags burst while in compacting trucks.

Waste Reduction Before the MWP Facility

Local governments and other waste generators incur significant costs for every ton of material sent to a MWP facility; however, substantial cost savings (as well as increased recycling rates) can be realized if waste is minimized through source reduction and pre-facility recycling. For example, Pitt County, N.C., has an excellent recycling program centered around staffed collection centers; the county is planning to send only its garbage to a MWP facility while its source-separated recyclables are sold to regional recycling markets. In the absence of a comprehensive recycling program, pre-facility recycling could involve special recycling programs for materials not recycled by the MWP facility or for valuable items in the waste stream. Source reduction can be an even more cost-effective option than recycling and should be part of any solid waste management program.

Contract Concerns

Although a MWP facility may be a beneficial part of an integrated solid waste management program, local governments should carefully consider clauses in contractual agreements that could inhibit future waste reduction efforts. Note that the following recommendations may also apply to other solid waste contractual agreements that address options such as landfilling and incineration.

• Minimum Threshold ("Put or Pay") Obligations. Often capital-intensive waste processing enterprises such as MWP facilities need to guarantee that they process certain quantities of refuse to ensure their debt service can be paid. Such facilities frequently wish to include "put-or-pay" clauses into a contract. Such clauses obligate the generator of waste to bring at least a minimum threshold of material to the MWP facility. If that minimum threshold is not delivered, the generator is obliged to pay for the shortfall. Minimum threshold obligations could undermine waste reduction efforts and may punish the generator or community if changing demographics or technologies reduce the flow of waste. If a MWP facility insists on a "put or pay" clause, a local government should consider obligating only 50 percent of its waste stream, at the most.
• Long-Term Contracts: MWP facilities would like to guarantee waste flow to their facility over a long period of time. Hence, MWP companies often prefer 20- or 25-year contracts. Such long-term contracts may be inadvisable for communities and waste generators as they may stifle better options that may become available in the shorter term. The solid waste management field is changing rapidly; it is impossible to predict the types of superior technologies that may emerge in the next five to ten years. A good option may be to sign a 5-year contract with optional 5-year extensions.
• Waste Flow Obligations: In order to ensure a high flow of refuse, MWP contracts sometimes stipulate that all waste of an entity must come to the MWP facility. Such a clause may be detrimental to the community or waste generator as it could preclude future waste reduction or cost saving options. For example, a waste flow clause may undermine the community's or waste generator's right to recycle and sell aluminum cans or collect materials that are not recycled at the MWP facilities such as newspaper, yard waste, or office paper.

Conclusions

Despite some attractive features, the recycling efforts of a MWP facility alone will not enable a local government to reach a significant waste reduction rate or North Carolina's 40-percent waste reduction goal by the year 2001. Although it may be a beneficial component of an integrated waste management strategy, MWP does not end a local government's responsibility to develop complementary waste reduction and recycling programs.

The NC Division of Pollution Prevention and Environmental Assistance (DPPEA) at (919) 715-6500 can provide information on waste reduction activities that local governments can implement or more information on MWP. The table below lists contacts and telephone numbers of North Carolina MWP facilities. Also, in its continuing effort to help local governments evaluate options, DPPEA will conduct further research into MWP as well as other solid waste management options.

The North Carolina Division of Pollution Prevention and Environmental Assistance provides free, non-regulatory technical assistance and training on methods to eliminate, reduce, or recycle wastes before they become pollutants or require disposal. Contact DPPEA at (919) 715-6500 or 800-763-0136, FAX (919) 715-6794, or E-Mail nowaste@p2pays.org for information about our services and/or assistance with your waste reduction program.

Disclaimer This document is intended to offer information and guidance for waste reduction and management. Compliance with environmental and occupational safety and health laws is the sole responsibility of each business. All legal and regulatory references within this document are intended for informational purposes only. Businesses should contact the appropriate legal and regulatory authorities for current interpretation and implementation of regulatory requirements. Mention of a vendor or manufacturer does not represent an endorsement by the State of North Carolina. Neither the State of North Carolina nor the authors are responsible for practices or procedures implemented by individual firms.

DPPEA-97-04. January 1997.