In May 2016, Oregon Department of Environmental Quality began field work on a year-long statewide waste composition study, with assistance from Metro, Marion County, Lane County, Washington County, and the cities of Portland and Beaverton. Field work for the study was conducted by Sky Valley Associates, and involved collecting and sorting 974 samples of solid waste weighing on average more than 200 pounds each, collected at 55 landfills, transfer stations, and mixed solid waste processing facilities throughout an entire calendar year. Samples were sorted into 138 material categories. All beverage containers in the samples were counted by beverage type and container material type. In all, 103.7 tons of solid waste were sorted, and 17,727 beverage containers were counted throughout Oregon.
DEQ is still completing analysis of the data and preparing a final report, which will be available here when complete. The Excel tables below give preliminary detailed information on the composition of wastes disposed in different parts of the state. These tables were updated in July 2018 to include disposal of single-material loads such as shredded tires that were not included in the waste composition sampling, and to deduct estimates of materials salvaged from burner ash and from three transfer stations post-disposal.
How to read the report
The first sheet of each Excel file provides an explanation of what is in the other sheets. The second sheet gives the composition of the jurisdiction as a whole, and subsequent sheets give the composition of specific waste sources in that jurisdiction, such as “residential route trucks,” “commercial route trucks,” and “loose drop boxes.”
The methodology used in the 2016/17 study is very close to the methodology described in the 2002 study. A description of each of the material categories is linked below:
This study, like previous DEQ waste composition studies, gives two values for the composition of each materials in the wastestream, “Field Results” (columns B and C of each sheet) and “Contamination Correction Results” (columns D and E of each sheet). “Field Results” are based on the weight of each material as sorted and weighed at the disposal site. However, many materials in the garbage are dirty and wet. For example, cardboard may have become wet from rain or from absorbing moisture from food in the garbage, and there may be materials inside of cardboard boxes or that adhere to the cardboard when sorted at the disposal site. This study cleaned and dried samples of the materials in the field to estimate “contamination correction factors” that can be used to estimate how much “clean, dry” material is present in the dirty, wet materials as sorted at the disposal site. Columns D and E show these “contamination-corrected” results. The methodology for this part of the study is explained in Appendix C of the 2002 study. For estimating the tons of each material disposed each year, it is best to use the contamination-corrected results. For comparing this study to studies in other jurisdictions though, it is best to use the field results as most waste composition studies do not attempt to estimate the cross-contamination of materials being sorted.
Each Excel file was updated in July 2018 to provide estimates and make adjustments to the overall waste composition for:
- Shredded tires, gypsum wallboard, and medical waste that was disposed as a single material or stream that was not sampled as part of the waste composition study
- Scrap metal recovered from ash from the Marion County Energy Recovery Facility in Brooks, Oregon, and
- Material recovered from mixed waste from drop boxes and self-haul vehicles at three Metro-area transfer stations at a point after we had collected and sorted the solid waste samples at those facilities.
These estimates and adjustments were made only for the waste disposed overall in the jurisdictions included in the Excel file, and not for any of the individual waste substreams, as explained in the first tab of each Excel file.