Tuesday, October 02, 2012

How to conduct a garbage audit for plastic bags

From time to time, news coverage of discussions of plastic bags contains the results of various garbage audits, where they look at a sample of garbage and see how many plastic bags are in it.   These numbers are often used to support the author's thesis about which measures do and don't help, but I find that the garbage audits I see cited tend to be less thorough - and therefore less useful - than they  need to be.

Here are the questions a plastic bag garbage audit needs to answer in order to be truly informative:

- How many shopping bags are being used as garbage bags?  These would likely be replaced with garbage bags if shopping bags were banned, and therefore would not be eliminated from the total landfill plastic.

- How many garbage bags are there in total (including shopping bags being used as garbage bags)?  If the audit counts shopping bags being used as garbage bags, it also needs to count garbage bags being used as garbage bags.  If there's a reduction in the number of shopping bags but a corresponding increase in the number of garbage bags, banning shopping bags didn't change anything.

- How full are the garbage bags?  I empty my kitchen garbage every day, for a minimum of 365 garbage bags a year.  They aren't always full, I just don't leave food waste overnight for sanitary reasons.  If a significant percentage of garbage bags aren't full, the smaller shopping bags would actually be a better choice because there would be less plastic.

- What is the total quantity of plastic?  Remember how plastic grocery bags got bigger when they introduced the five cent fee?  Suppose I was using 400 bags a year for my garbage before they got bigger (because I occasionally have more than one bag of garbage).  Then suppose the new, bigger bags are always big enough for my garbage needs, so I'm using 365 a year.  If the new ones are 20% bigger, that's actually the equivalent of 438 of the old bags, so I'm throwing out more plastic.  If, in the future, I'm forced to use the even-larger kitchen catchers, that's even more plastic being thrown out.

- How many plastic bags are in the recycling stream? Sometime after we started talking about plastic bags, I became aware that plastic bags are recyclable.  I don't know offhand if they first became recyclable then or if they were already recyclable and I just found out then, but the fact of the matter is that awareness of their recyclability has increased in recent years. If there are, say, 100 fewer bags in the landfill but 100 more bags in recycling, nothing has changed in terms of what we throw out.  Obviously it's better for things to be recycled than to go in the landfill, but you can't claim a reduction in usage if the same things are just being recycled now.

- What is the condition of plastic bags that are in the landfill or recycling but not being used as garbage bags?  I have heard some people complain that they hate plastic bags because they rip.  This is not my experience.  However, regardless, it would be informative to see how many of the plastic bags not being used as garbage bags have ripped. If, for example, 87% of the thrown-out bags have ripped, that suggests we have a high reuse rate and people aren't throwing them out as trash unless they can't be reused normally.  It might be worth investigating whether it would be more efficient to manufacture higher-quality bags.  (Obviously they take up  more resources to manufacture and have more plastic in them so there's a tipping point in here somewhere, but it should be looked into if it turns out to be applicable.)

No comments: