By Cynthia M. Mitchell and Charlie Pioli
As more attention has turned to waste minimization, waste diversion and reuse over the past few decades, it has become of greater interest to understand what materials are filling up landfills across the country that could be used beneficially elsewhere. While it is feasible to manually sort through MSW samples to get statistically valid data, various approaches have been taken over the years in attempt to realistically estimate the composition of bulkier industrial, construction and demolition (non-MSW) loads. During the 2016-2017 Missouri Waste Characterization Study (WCS), MSW Consultants deployed an electronic field form developed to provide real-time QA/QC on the visual volumetric estimates. With built-in material densities, it also allows comparison of estimated weights with each sample load’s scale ticket. The field surveyor navigates the program to accurately reflect the weight of the load, for instance adjusting average densities when material observations deem so for atypical circumstances, such as moisture, compacted materials, etc. Figure 1 shows the staff getting an initial look at a load of industrial waste.
Figure 1: That’s a lot of onions from an onion ring manufacturer.
The Visual Surveying phase of the 2016-2017 Missouri WCS involved detailed volumetric measurement of the truck and load dimensions, followed by the systematic observation of the major material components in the tipped load. Loads were first classified into ten major categories by percentage, then further subcategorized into forty-five materials as percentage of the major category. Figure 2 below displays a portion of the form used for in-field immediate characterization. By characterizing materials in major categories hauled by various vehicle types during field observation at facilities, overall material volumes can be extrapolated by applying the data to the breakdown of the overall waste stream as determined during gate surveying activities.
Figure 2: Excerpt from the visual waste characterization field form.
Organics collection and composting programs are becoming more prevalent, especially in urban areas. Figure 1 shows an industrial load, predominantly containing organic waste. Similar to traditional materials identified for recycling through large-scale Visual Waste Characterization, such as Old Corrugated Containers (OCC) and metals, compostable quantities identified through this methodology can also play a large role in shaping the future of sustainable material management. Accurate material composition data enables local, regional and state planners to closer identify contaminants in the waste stream, likely sources of materials that could be diverted, or to assess the BTU value in biogas recovery for anaerobic digestion systems. Educational efforts and any other available resources can be directed toward these targets. MSW characterization data is also useful and important along similar lines, but targeting the non-MSW load materials can ultimately be more impactful on a per generator basis due to large volumes and have not been acutely captured in past visual waste characterization studies.