What should an outdoors traveler know about the biodegradability of plastic?

Question

I was wonder how long it takes plastic to biodegrade and if there is anything a person can or should do to facilitate the process for plastics in the outdoors.

I know that optimally "Carry in, Carry Out" and "Leave no trace" mean you should not see any plastic in the outdoors that gets left behind. Things don't always go perfectly and, so if there is a plastic item that is not going to be leaving the area with you what should you know and do?. Related What should I do about large trash left by others on USFS land?

I did a little research and found

• Plastic can be biodegradable and that is good. For more on this please read: Are Plastics Biodegradable?

• Plastics can take hundreds or 1,000+ years to biodegrade and that is bad. For more information read the following: How Long Does It Take a Plastic Bottle to Biodegrade?

• Plastics can biodegrade fast and that may be worse (Plastic Breaks Down in Ocean, After All -- And Fast).

So me and a piece of plastic are alone in the great outdoors, and we are not leaving together. There is no chance we will see each other again, and very little that a new human will bond with the plastic in next year or even for decades. What do I need to know to limit the environmental impact of plastic in the outdoors?

Answer 1

"Things don't always go perfectly" - what does that mean? There is no reason at all you should ever leave plastic behind.

1. Bring in as little plastic as you can. Pack your stuff in reusable containers.
2. If something is plastic-wrapped or in a plastic bag, be a person who cares and don't let that plastic blow away or drop from your hand. Stick it in a pocket right away, and have a place to keep it so you can take it back out with you
3. If you come across someone else's garbage, whether plastic, glass, tin or whatnot, take it out. Put it in the "place to keep it" - I use the garbage bag that backcountry parks issue you with your permit number written on it. (Usually I find nothing and I have no garbage of my own so the bag comes out empty. I keep it in my glove compartment and take it in on trips where one wasn't issued to me. It serves as a good visual reminder that it contains garbage, something that is highly unusual on my trips.)
4. If you spot someone else's plastic from a distance, and can't safely get to it to clean it up, you also don't know anything about its chemistry, so there's nothing you can do. Console yourself with the fact you did numbers 1-3.
5. If you come across a piece of plastic waste so large it's impossible for you to remove it, take a picture, ideally geotagged, and report it to the park people or landowner when you leave. If the land is entirely public, investigate to see if there's someone you can report to. For example a 1000L tank of dubious liquid is something you have to leave behind, but should still act on in some way.

If it matters to you that plastic isn't left behind, plastic won't be left behind. And that's the only reasonable approach, really.

Answer 2

Answering the title question - What should you know or what do you need to know - the answer is nearly nothing or nearly everything.

If you know nearly nothing, you should know at least know that a vast majority of plastics take a very long time to biodegrade and can be harmful to flora and fauna.

If you decide you want to know more, its presumably so you can make an informed decision if its OK to leave a piece of plastic behind. In that case, you will need to know everything about the plastic, how it breaks down under varying conditions (Exposed, buried etc), its chemical toxicity, its strength under various conditions (will break if wrapped around an animals leg), its digestibility in various local animal species, its attractiveness in new and aged forms to various animals.

Once you have spent a life time studying biology and material engineering, you would then know enough to make an informed decision what to do with that piece of plastic and would carry out with you.

Answer 3

First, avoid doing it! Carry other hiker's trash when possible to minimize the impact. As an owner of a plastic industry, I can affirm that the decomposition time depends of the type of plastic we are speaking of and many ambient conditions.

For plastics that are not naturally UV resistant, like Polystyrene and PETE (water bottles), they get brittle and will slowly become dust in a few years after heavy exposure to UVA and UVB sunlight. PS, PETE, PLA (biodegradable!)

For plastic bags, shampoo bottles, made of Polyethylene for example, they last awfully long, usually more than 50 years in direct sunlight, maybe even more. HDPE, LDPE, ABS and PC also falls into this category.

As rule-of-thumb, leaving most plastics under heavy sunlight will degraded them to a point where it can be further broken into smaller parts by environmental factors and bacterias, integrating back those broken monomers to the natural cycle. But if the environmental factors are not optimal (a PETE bottle in the woods) they will be there for hundreds of years, maybe more.

So, if you MUST leave plastic, do it where it will have strong-steady sunlight and far from rivers, streams and lakes. If that's not an option, I would bury it in a 50cm (1.5 feet) depth hole, so animals would not interact with it.

Hope it clarifies your doubt!