In general, published data on composting of MSW and yard waste are quite limited. Important gaps are summarized in the following subsections.


Municipal Solid Waste

To date, success in composting MSW to produce a marketable product is quite rare. Facilities for large-scale composting of MSW are encountering engineering and process control problems (Allen, 1992). Increased application of the technology may depend on research to identify the causes of those problems and engineering development work to find better solutions to operational problems.

Mechanical processing, either before or after composting, has been a major technical barrier to successful MSW operations because some systems are inappropriately designed (CRSI, 1989). Many appear to be designed to minimize initial capital cost or to minimize O&M costs. Initial operations often indicate the need for significant modifications of such plants (CRSI, 1989).

Troublesome problems with odor have been reported at some plants. Biofiltration is used for odor control at some composting facilities, but it requires relatively large areas and sophisticated operational control, and performance is frequently poor. The fate of odoriferous compounds absorbed in the biofilter is not well known.

Yard Waste

Some communities are quite restrictive about the types of yard waste they will accept for composting. Such restrictions are apparently required because of the equipment that the communities have chosen. The influence of such barriers to public participation has not been well characterized.


Municipal Solid Waste

MSW-derived compost fares worse than composts derived from sewage sludge, manure, and yard waste in the competition for available markets (Hammer, 1992). Acceptance of MSW derived compost will require a clearer understanding of appropriate uses for it. Solutions to that problem might include:

Yard Waste Data on the following important topics were limited, unreliable, or unavailable:

Environmental Releases

No data on emissions from collection for composting were found. Once compost is made and applied to land, it may undergo only aerobic decomposition; if so, it would release little methane. No studies of any emissions from compost in use were found.

Municipal Solid Waste

No quantitative information was found for the following subjects:

Yard Waste Little information is available about the nature and effectiveness of programs for curbside collection and composting of yard waste. Missing data include:


Few comparisons of the costs of composting with those of other MSW management options have been published. Cost data on a consistent basis are needed to provide the foundation for such comparisons. (Exhibit I describes the difficulties in developing cost comparisons in greater detail.) Cost estimates for many installations have been notoriously inaccurate (CRSI, 1989).

System Evaluations

The benefits and costs of composting programs have been examined less carefully than those of other components of MSW management strategies because composting has been a small-scale contributor to the field. Given the increasing popularity of composting, a thorough evaluation seems overdue.

The value of composting of either yard waste or MSW to an overall management strategy is difficult to evaluate because limited data are available on:

A system study could help to fill these data gaps.

(1) To standardize the presentation of costs, all published estimates have been updated to a mid-1991 time frame by using SRI Internationals PEP Cost Index. Unit capital costs and operations and maintenance (O&M costs) are presented in dollars per ton of MSW as collected. If data on individual cost items were unavailable, estimates based on reasonable assumptions were used. The bases for the data are described in detail in Exhibit I.
(2) All the integrated strategy examples in this report compare other technologies with a strategy of landfilling alone because no strategy can eliminate the need for a landfill; thus, all integrated strategies will involve adding other technologies to land filling.



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