The results of a typical waste characterization studyis shown in Table 1 [1]. This study was performed onMSW in the metropolitan area of Portland, Oregon,from August 1986 to July 1987. The study involved32four seasonal waste stream sampling periods at threeseparate waste disposal sites. During the course of thestudy, a total of nearly 200,000 kg (440,000 lb) ofrefuse was sampled. This study and its results providedthe basic data used to design the facility. This studyis probably more detailed and complete than manystudies of this type. Many communities do not havestudies of such detail and, therefore, any design forwaste processing must accommodate significant variationsin its character.FlexibilityAny facility processing MSW must be as flexible aspossible. At this time, waste disposal is a very dynamicindustry. As sanitary landfills are filled up, and newsites develop, the cost of waste disposal is increasingdramatically. This change not only makes alternativesto landfilling, such as composting, economically viable,but it also provides incentives for recycling efforts.These efforts can and do change the character of theMSW stream, and can have significant impact on themass flow through the plant. For example, an increasein the amount of plastics or metal recycled prior toarrival at the plant will increase the percentage ofcompostable material in the MSW stream. In a plantdesigned to process a given number of tons of MSWper year, a higher tonnage of compost could be expectedto be produced. Conversely, if recycling effortsof paper products reduce the amount of paper in theMSW arriving at the plant, the amount of compostproduced would be smaller. Reasonably large variationsin the make-up of the waste stream must beconsidered when sizing major components of the compostingprocess.In addition to variations of the characteristic of thewaste stream, seasonal effects can have significant impacton the design as well. For example, in Portland,yard debris varies from about 10.5% to 14.5% of thewaste stream in the fall, spring and summer months.During the winter, this percentage drops to less than3% of the total waste stream.Finally, the flow rate of material into the plant canvary greatly during the day. Early morning and lateafternoon hours are periods of peak activity when themajority of the day's' delivery can be expected. Receivingareas and handling equipment must have adequatesurge capacity.
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