An Evaluation of Municipal Solid Waste Composition Bias Sources

Abstract

The University of Central Florida (UCF) was contracted by the Florida Center for Solid and Hazardous Waste Management (FCSHWM) to develop a well-defined methodology for conducting municipal solid waste composition studies. This methodology must account for the statistical variations in waste composition, be economical and practical in implementation, and build on a consensus of waste management professionals. This paper identifies possible sources of bias in waste composition study results and provides guidance for future planning of local waste stream composition analysis. To accomplish this objective, a composition study was designed and implemented for Marion County, FL, in fall 1996. The potential sources of concern investigated in detail were sample weight and contamination.The methodology developed by UCF is statistically valid and if widely implemented would provide a better representation of the waste stream. Lack of contamination adjustment is a major contributor to error in the waste stream analysis and should be accounted for in the methodology. For sample sorts using a large number of categories, sample size may be a contributor to bias. This likelihood for bias can be reduced by increasing the sample weight to at least IMPLICATIONS Because of the highly variable nature of municipal solid waste, characterization studies are essential to proper waste management. Waste composition studies are frequently performed without adequate study preparation and planning. The research presented in this paper clearly demonstrates the need to consider many factors in planning a study to ensure high-quality results.

Methods for household waste composition studies

“…Household waste is generally collected mixed with waste from, for example, day care centers, schools, shops, food markets, restaurants, hairdressers, and other small enterprises in and around residential areas. When commercial waste is included, the variation in the waste content will increase (European Commission, 2004;Sfeir et al, 1999). With careful stratification and detailed sampling plans, all waste generators except households can be avoided, but since some small scale business are performed in people's homes, all measurements of household waste will include commercial waste to some unknown extent (RVF, 2005b).…”

“…The objective was to develop a method that was economical and practical in implementation, based on a consensus of waste management professionals, able to account for statistical accuracy and adapted to conditions in the State of Florida. Reinhart and McCauley-Bell (1996) recommend using the loads of ordinary waste transport vehicles for sampling and sorting into a minimum of 33 categories; they emphasize the risk of skewed results because of moisture, food and dirt contamination in lightweight materials (Sfeir et al, 1999).…”

Developing a monitoring method facilitating continual improvements in the sorting of waste at recycling centres

“…When evaluating the precision of the method emphasis was therefore primarily on determining the number of measurements at which no additional information about the incorrect sorting in the waste was obtained. Such knowledge is essential for the usability of all waste monitoring methods since it indicates how many samples, or in this case measurements, are needed in order to obtain saturation in the provided information (Sfeir et al, 1999; The Swedish Association of Waste Management, 2005b;Sharma and McBean, 2007).…”

Municipal solid waste as a resource: part 1 – specifying composition

“…This is supported by Coggins (2009) who suggests that 'if you do not, or cannot measure it, you cannot manage it'. Additionally, comprehensive specification data can help estimate material recovery, identify waste sources and allow for improved compliance with legal requirements (Fehr et al, 2006;Gidarakos et al, 2005;Joos et al, 1999;Lisa and Anders, 2008;Sfeir et al, 1999). Indeed, according to Lebersorger and Schneider (2011), current waste specifications are 'insufficiently described and not reproducible by a third party'.…”