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Every here and there I hear sayings like "plastic is bad, because it only degrades in hundreds/thousands/gazillion years, while paper is much better because it degrades fast" which are followed by implications that producing tons of disposable paper cups is okay. I saw quite a lot of trash in forests nearby (left by tourists or illegal waste companies) and I have to say that even old paper cups and other paper package looks quite good and not that degraded.

I'd like to setup an experiment - take a piece of paper something and put it somewhere and see how fast it degrades. I have access to a piece of land where this can be done without much harm and without disturbing anyone.

So I have a paper cup (like one used for coffee in McDonald's/KFC/Burger King). What next?

Where do I put it? Do I drop it onto ground and let if cover is leaves in autumn? Do I put it into a compost pile? Do I dig it into the ground (how deep should it be)? How often do I inspect the cup? What do I wait for - paper turning into what exactly?

So basically what would be an experiment that would validate a claim that "whatever, paper package degrades quickly"?

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    I'm not sure you're asking the right question (ie "How fast does it degrade?"). If we're going to use bulk quantities of paper cups and try to compost them or hope that they'll break down in the environment harmlessly, then we need to understand what can be defined as a "paper cup" and what counts as "harmless". If a paper cup has a wax or thin plastic coating, does that still count as paper? (I'd say no, or it should at least be tested separately) If there is a toxin or pollutant in the paper, then it may become concentrated as it breaks down. The result might look like soil, but be poisoned. – Highly Irregular Jun 30 '18 at 3:03
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    @HighlyIrregular Yeap, you listed the right concerns but let's ignore all that for a while. Let's just focus on paper breaking down to some reasonably broken state. – sharptooth Jul 2 '18 at 6:44
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While reading your question I get the feeling there are some misconceptions here, so let me start by clarifying a few things:

  1. Paper cups are not solely made of paper but have a plastic or wax lining. It's to prevent the cup from failing apart when it gets wet, but it also prevents or slows down (bio)degradation.

  2. Plastic degrades into increasingly smaller pieces of plastic, primarily under the influence of sunlight and heat. Paper on the other hand biodegrades when micro-organisms, fungi and worms turn the paper into CO2, water and compost. Although scientists recently found bacteria that can 'eat' a specific type of plastic like PET very slowly (see this question), it's still uncommon to refer to degradation of traditional plastics like PP, LDPE, PET as biodegradation. The exception is if you are referring to plastics that were specifically designed to be biodegradable.

  3. Not all paper biodegrades quickly. Laminated paper, waxed paper, large quantities of paper, or paper put in dry or cold conditions will biodegrade much slower. I'll explain more below.

Circumstances

How fast something biodegrades depends on many variables, but an important aspect is the availability of micro-organisms. This in turn is influenced greatly by the amount of oxygen and water that is present, and the ambient temperature (among others). Paper, or any other compostable material for that matter, will degrade more quickly if you do one of the following:

  1. Make sure the materials stay moist (not dry or soaked)!
  2. Keep temperatures around 40-60 degrees C
  3. Bury it under other degrading or already-degraded materials, so more surface of the material is exposed to micro-organisms (and cut thick material into pieces)
  4. Aerate regularly by turning the materials
  5. Keep a carbon-nitrogen balance of materials of around 25:1

Most plastics on the other hand will degrade most quickly if you expose it to sunlight (UV radiation and heat).

For your experiment the choice of environment will affect the outcome. Any situation you choose will most likely be more favorable for either plastic or paper. I think the fairest comparison is when you try to mimic what generally happens with litter; just leave it exposed somewhere between or on top of organic materials like grass or dirt. You could place it on some stones similar to litter in a gutter or on the pavement, but then you'd probably have to wait much longer for anything to happen.

Setup

I would suggest creating some sort of small enclosing on your land with chicken wire or perhaps something with a finer mesh. Basically anything to keep the materials you put into it from being blown away, but still leave them exposed to the elements. Then just leave the materials alone. For pure paper without any finish or lining you want to check weekly what's happening. For plastics or paper cups it will most likely take quite some time before anything happens, so at first I'd check that monthly.

Even though it would be most interesting to compare degradation of a plastic cup with a paper cup, I do not recommend using any traditional plastic or a plastic-lined paper cup. When the plastic degrades it will contaminate the soil with the toxic additives that are present in the plastic. Also the tiny pieces of (micro)plastics are very hard or impossible to remove.

My own experiences

For what it's worth, I regularly add paper napkins or cardboard to my worm bin to keep a proper carbon-nitrogen balance in the bin. I've had very mixed results depending on the type and thickness of the paper or cardboard and on the time of year. In summertime a small piece of paper napkin buried in the bin will be gone in 2-3 weeks. Multiple pieces of thick cardboard placed along the inside edges of the bin in late autumn (as extra insulation) remained fairly intact for up to a year. Also a small piece of compostable plastic (most likely PLA) remained fully intact after being in the bin for more than a year. I recently bought something that came in a certified 'home-compostable' plastic wrapper so I started a new experiment and added a few pieces to my worm bin, but I have yet to check how that is going.

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