plastic bag

July 17, 2015

Subjects: Post landfill use/ life expectancy/plastic grocery bags

Hello, I am just looking for a little information about landfills and am hoping that someone in your organization can help me out. This is what’s going on here in my region. Some local citizens along with the Sierra Club are pushing for a ban on the plastic grocery bags used by most grocery stores. A local survey found 80% against such a ban and 20% in favor.

Anyway, one of the supposed reasons for such a ban is that the plastic bags do not decompose in a landfill and essentially last forever. My response is–so what? As long as it is in a landfill there are lots of other things that will be there forever also. Isn’t that what a landfill is for?

I am a little familiar with the construction of a modern landfill, a good thick bottom liner, drains for liquids accumulation, gas vents, a good capping method, etc. All the modern stuff I am sure you guys are good at; when I was young, it was just dirt on the bottom and the top.

I am just not sure what is supposed to happen to the contents of the landfill over a period of time after it is closed, 50, 100, 500 years. Maybe you could give me some input. Also, what does society do with a completed landfill to put the area back to use after it is full, covered up and growing grass? Is it ever expected to be drilled or dug into for construction purposes?

I would really appreciate a response from you guys, even though you probably have lots bigger fish to fry.

Thanks for your note, and for your interest in SCS Engineers. Bans on plastic bags and similar strategies such as taxing their use have been adopted by several communities, and the subject is controversial.

Personally, the best argument we’ve heard in support of trying to restrict the use of plastic bags is that the bags too often turn up along highways and waterways in the form of litter. Birds and other wildlife can become ensnared in the bags, and they can remain unsightly for a long time (unlike paper bags).

Now to your questions; our general opinion is that our goals for solid waste management are first and foremost to protect human health and the environment. If we can avoid throwing something like a plastic bag away, or if we can reuse the plastic bag for some other purpose, or if we can recycle the plastic bag, those are preferred to disposal.

If the plastic bags need to be disposed of, a modern landfill or solid waste-to-energy facility are safe and environmentally responsible means of disposal. As you say, a plastic bag might linger in a landfill for centuries, but the bags make up a small percentage of the volume of the solid waste disposed of in modern landfills.

Eventually, landfills can be redeveloped for other purposes, and many older landfills have been redeveloped. Organic materials in the landfill will decompose over time, but a substantial portion of the disposed waste material will remain, perhaps including small volumes of plastic bags. In my opinion, plastic bags in a landfill do not present a threat to human health or the environment.

Thanks again for contacting SCS Engineers.


Additional Information and Resources:

The Washington Post has had several articles and blog postings on the subject over the last few years:

Bag Fees — Declining Use of Bags

Plastic Bag Lobby — San Francisco Ban

Posted by Diane Samuels at 10:15 am