There are a number of ways to look at data from a waste sort depending on the goal you are looking to achieve. Here are some of the common, useful metrics that can be analyzed from waste sort data:
Diversion and Potential Diversion Rates
The most common metric for measuring a waste management program is diversion rate. A diversion rate is simply the amount of waste from your waste stream (usually in weight) that is not being sent to the landfill.
The diversion rate formula is:
(Weight of Diverted Waste / Weight of All Waste) x 100 = Diversion Rate
Even if your organization has not yet started an organics or recycling program, you can still use this formula to learn the potential diversion rate for your organization. Simply substitute “weight of all potentially divertable waste” for “weight of diverted waste.” This is a great way to inform a realistic waste diversion goal for your organization!
Composition Percentages and Reduction Prioritization
A composition percentage allows you to see what percentage each material category you included in the sort contributes to your overall waste stream. Here is the formula to find the composition percentage of the overall waste stream:
(Stream Weight/Weight of all Waste) X 100 = Composition Percentage
Another way to use the data from a physical waste sort is to identify high impact areas for further diversion including:
The areas of your facility that offer the greatest diversion opportunities
The specific materials or items that offer the greatest reduction and potentially cost saving opportunities
Contamination Rates and Composition
While identifying waste reduction and recycling opportunities are important, making sure your streams are clean is equally important. Contamination refers to material found in a stream that doesn’t belong (e.g. trash in the recycling stream or recyclables in the trash stream). Here are the formulas for finding the overall contamination rate and the overall contamination rate for each major stream:
(Overall Contamination Weight / Weight of All Waste) X 100 = Contamination Weight
(Weight of Contaminants in Recycling Stream/Weight of all Materials in the Recycling Stream) X 100 = Recycling Contamination Rate
(Weight of Contaminants in Landfill Stream / Weight of all Waste) X 100 = Landfill Contamination Rate
(Weight of Contaminants in Organics Stream / Weight of all Waste) X 100 = Organics Contamination Rate
If you found a significant amount of contamination in a stream, you might be interested to learn more about what area(s) the contamination stems from or what material types are the largest sources of contamination. Depending on if you tagged bags by area and/or how many categories you included in your audit, you should be able to drill down further into the sources of contamination!
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