Amounts Collected and Destinations and Applications of Materials
More that 2,700 curbside collection programs may be operating in the United States(Glenn and Riggle, 1991). Operating or planned MRFs exceed 100 in 1991, and the number of such facilities is increasing rapidly (ICF Inc., 1991). The destination of the material collected by programs that are not operated in association with an MRF is unclear. Inadequate data are available on the amounts of materials actually collected, recovered, and sold or beneficially used; most sources report on the design capacity of MRFs.
The field of materials recovery is still relatively new, and systems for encouraging participation, collection, and processing continue to evolve. Better estimates of the amounts of material collected by curbside programs are needed. The validity of the frequent assertion that additional education can motivate greater participation has apparently not been tested, and no study has established the maximum sustainable levels of participation. Some sources have reported nationwide data on the effectiveness of dropoff programs, especially by comparison with curbside collection programs. Limited data are reported in Appendix E (see page E-20).
The effects of "bottle bill" legislation on amounts of materials set out in curbside programs remain unclear. One study has covered that issue, but confirmation of the results would be useful (White et al., 1990). In particular, no data are available on the effect of bottle bills on the total diversion of containers from MSW disposal (that is, the total number of containers set out at curbside or returned for payment at redemption centers). One study included a model to estimate potential effects; however, the results give no clear indication whether bottle bills have a consistently positive or negative effect (Ackerman and Schatiki, 1991).
The yield of reusable glass, metals, and paper that is picked up for separation is not well documented. For example, the breakage of glass during collection is substantial in some communities as a consequence of the trucks that are used. The broken, mixed color glass cannot be sold, and becomes process loss. One community reports that the reason for wetting all the paper it receives is "to prevent blowing." The extra water distorts the accounting of actual yields.
Little information is available on the effectiveness of mixed waste MRF programs. The few reported data suggest that such programs divert twice as much recyclable waste as curbside collection of separated materials. If so, research to encourage the mixed waste approach is needed.
If additional studies make it clear that certain materials are unlikely to find a market in certain regions, then alternative uses need to be found for those materials in those regions. For example, new economic uses for mixed paper and glass are clearly needed in some areas.
Energy
Transport/Collection
Reliable data on actual fuel use in collection and processing for materials recovery are not available for comparison with fuel use for standard MSW collection and disposal. Most MRF studies assume that the trucks used for transporting reusable materials have the same energy consumption as a packer truck, but differences between the two may be significant.
Processing
The estimates of energy used for processing are based on design documents. Estimates for operating MRFs of actual power use per ton processed would be more reliable.
Recycling/Reuse
All the detailed comparisons of energy use for recycling with energy use for production of virgin metals and glass are now 14-17 years old, and process improvements may have strongly affected the conclusions (Battelle, 1975; Kusik and Kenahan, 1978). In addition, no energy balances were found for reuse of collected materials in applications other than remanufacture of the original product (e.g., glass used as a substitute for sand in glasphalt, or mixed plastic used as a substitute for wood composites to produce "plastic lumber").
Environmental Releases
Transportation
Like data on energy use, emissions data for operating collection programs are sparse. Specific needs include:
Only anecdotal accounts of environmental releases from actual MRF operations have been reported. Good data are not yet available.
Recycling/Reuse
Studies of the environmental advantages of recycling individual materials (e.g., paper, metals, and glass) seem to be based on limited data and analysis, and they need to be updated. Many of the advantages claimed for recycling assumed high effluent levels for virgin manufacture that no longer reflect actual current practice.
Costs
Cost data available in the literature are limited, the range of capital and operating cost estimates is extremely broad, and most sources of cost data fail to clarify the basis for the estimates. As a result, published cost estimates are inadequate for comparing the costs of materials collection, separation, and recycling with those of other MSW options.
The capital cost variations reflect inconsistencies in the sources of the estimates rather than predictable variations based on the type of technology or the size of the facility. Similarly, the O&M costs are affected by site-specific conditions such as labor rates, labor contracts, safety rules, the size of the crew, and so on. Information on these factors is rarely provided in the literature.
The unavailability of information of this type makes it impossible to determine the reasons for the broad variations in the cost estimates published by various organizations. Comparisons of actual costs of various technologies should be based on site-specific quotations from individual vendors of the systems under consideration. To facilitate comparisons of the various strategies for managing MSW, costs for all the systems should be built up using a consistent set of assumptions and factors.
System Evaluations
Most recycling of waste and of materials that would otherwise become waste occurs outside the traditional MSW management system. Waste paper, postindustrial plastic, and scrap steel are widely collected and recycled in the secondary materials business. A systems study on secondary materials reclamation could show the effectiveness of various industry-commercial community initiatives and their interactions with recycling efforts.
The present inability of the market to absorb all locally generated recovered materials shows that parts of the system are unable to keep up with supplies available. The supply of separated material is under the control of a waste management authority. Demand for the separated material is under the control of a large number of consumers. Obvious imbalances between supply and demand are reflected in the current prices for some separated materials. Research is needed to determine the effects of such imbalances on the ultimate benefits of curbside collection programs.
Reliable system studies will depend on the availability of cost data generated on a consistent basis, as outlined above.
NOTES:
(1) It is inappropriate to include compost that is used in a landfill in estimates of quantities recycled because the "recycled" material is not diverted from the landfill. California legislators showed awareness of that distinction in choosing incentives to encourage development of new commercial uses for the glass recovered in California's redemption program. The state pays a fee to organizations for each ton of glass that is used in ways that are likely to keep it out of a landfill. Using the glass as daily cover or as part of the compost for the final cover would not be considered to divert it from landfill, and therefore would be ineligible for payment (California Beverage Container Act 14581.5).
(2) Those assumptions can be changed in the data base.
(3) Energy for transporting finished products to market is not relevant because products based on virgin raw materials would require the same amount.
(4) The assumptions for these calculations are built into the data base and can be varied by users to fit a local community's conditions.
(5) To standardize the presentation of costs, all published estimates have been updated to a mid-l991 time frame by using SRI International's PEP Cost Index. Unit capital costs and operations and maintenance (O&M costs) are presented in dollars per ton of MSW as collected. If information on individual cost items was unavailable in the literature, estimates based on reasonable assumptions were used. The bases for the data are described in detail in Exhibit I.
(6) Estimates of revenues in 1989 from two planned mixed waste MRFs and one MRF that handles curbside-collected separated waste showed a range of $25 to $70 per ton. The facility with the lowest revenues is in the Northeast; the one with the highest is in the South (wTe, 1992).
(7) San Jose, California, has paid $160 per ton for recycling services, compared to $93 per ton to landfill the MSW (Forbes, 1991).
(8) All integrated strategy examples compare other technologies with a strategy of landfilling alone because none can eliminate the need for landfill; thus, all integrated strategies involve adding other technologies to landfilling.
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