Measuring Your Recycling Rate: Understanding Metrics
No, I’m not talking about that awkward moment in grade school when someone first tries to explain that the rest of the world has 30 centimeters on a ruler instead of 12 inches. I’m talking about the different metrics that we use to measure and contextualize our recycling data.
% Discards Recycled: As I mentioned in my first blog on this subject, this is the recycling rate that most waste generators are talking about.
How it contextualizes recycling tonnage: shows recycling tons in relation to everything thrown away. Basically, of everything thrown away, what % was thrown into a recycling bin.
What the formula would look like: % = (tons recycled)/(sum of both trash and recycling)
Primary advantage: Is relatively economically neutral. Trash and recycling tonnages tend to go up or down as much because of the economy as because of any individual action. This metric tends to better track individual action. If recycling goes up because of the economy, typically trash goes up as well. As a result, changes in recycling % are more likely to be due to changes in individual behavior or programmatic action.
Disadvantage(s): The big problem that this metric has suffered from is how to define your total discards. When it was first used, it was pretty straight forward. Typically, you were talking about a residential community, or a college, or an office and a fairly well defined waste stream. Essentially we were talking about routine recyclables and routine “wastebasket” trash.
Where things really started to unravel in when we started using this metric as a goal and a compliance requirement. Unfortunately, as we started to apply this to more materials, the metric started to devolve. Do you include leaf and yard waste composting? If so, northern states with shorter growing seasons will likely never compare well with southern states that have a 12 month growing season. Arid states will never compete with more fertile regions that produce much more of this heavy dense material. And what about the people that leave their grass clippings to mulch on the lawn and compost their leaves in their own backyard garden? How do you compare that to someone who puts all their stuff at the curb to be picked up?
Do you include scrap metal, or concrete? If so, how do you account for disaster debris? I had a colleague out in California years ago that asked a simple question: could she include scrap metal and asphalt in her recycling rate. Here’s the thing, her region had just suffered through an earthquake, and if she could include those materials, she would have had a 99% recycling rate that year because of all the scrap metal and concrete recovered during the disaster cleanup.
Per-capita recycling or Per-capita trash (per-person recycling and trash measurement)
How it contextualizes recycling tonnage: shows recycling tons (or trash tons) in relation to a given population.
What the formula would look like: Per capita = (weight [typically in lbs])/(population)
Primary advantage: Works best to contextualize changes in recycling tonnage in a given place from year to year. When comparing the same area over two sets of time (e.g. last year vs. this year), per capita recycling helps you to figure out whether any increases or decreases in recycling are a result of behavior change or because of a change in population.
Disadvantage(s): Per-capita recycling is that it rewards affluence and consumption. Want to increase your per-capita recycling? Use more paper and drink more stuff in bottles & cans. As long as you put the results of your overconsumption into the recycling bins, you will look great. Conversely, if you have done a good job of waste reduction, and being efficient, and limiting your consumption, you will be penalized on your per-capita recycling numbers.
For per capita trash, the exact opposite is true. The goal is to have a lower number not a higher one. The metric penalizes affluence and rewards efficiency even if neither is tied to behavior. Categorically, small private colleges will have higher per-capita trash rates than large public universities. When you pay $35,000-$50,000 per student per year, you get more services and more stuff per student than when you pay $20,000 or less per student per year. All those extra services mean more consumption per capita and in most cases, more waste per capita. That is true even if the school is doing a good job of recycling or reducing waste compared to other like institutions.
If you use it to compare and contrast schools or businesses or municipalities, I urge you to only compare like communities.
So if both % discards recycled and per capita recycling and trash numbers have significant flaws, why keep them. The key is that when you look at them in combination, you start to see some very interesting and useful trends. In my next post, I’ll show some of the trends that you can see by looking at both metrics.