15 votes

The little-known unintended consequence of recycling plastics

Posted by skybrian
Tags: recycling, plastics, author.allyson chiu, source.the washington post, paywall
https://www.washingtonpost.com/climate-solutions/2023/05/22/plastic-recycling-microplastic-pollution/

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Title
How recycling centers could be making our plastics problem worse
Published
May 22 2023
Word count
955 words

8 comments

  1. [2]
    skybrian
    Link
    From the article: [...] [...] The study is here.

    From the article:

    A recent peer-reviewed study that focused on a recycling facility in the United Kingdom suggests that anywhere between 6 to 13 percent of the plastic processed could end up being released into water or the air as microplastics — ubiquitous tiny particles smaller than five millimeters that have been found everywhere from Antarctic snow to inside human bodies.

    [...]

    The study was conducted at a single plastic recycling facility, but experts say its findings shouldn’t be taken lightly.

    “It’s a very credible study,” said Judith Enck, a former senior Environmental Protection Agency official under President Barack Obama who now heads the Beyond Plastics advocacy organization. She was not involved in the research. “It’s only one facility, but it raises troubling issues, and it should inspire environmental regulatory agencies to replicate the study at other plastic recycling facilities.”

    [...]

    While there are many different types of plastic, many experts say only things made out of No. 1 and 2 are really recycled effectively in the United States. At recycling facilities, plastic waste is generally sorted, cleaned, chopped up or shredded into bits, melted down and remolded.

    It’s unsurprising that this process could produce microplastics, Enck said. “The way plastic recycling facilities operate, there’s a lot of mechanical friction and abrasion,” she said.

    Brown and other researchers analyzed the bits of plastic found in the wastewater generated by the unnamed facility. They estimated it could produce up to 6.5 million pounds of microplastic per year, or about 13 percent of the mass of the total amount of plastic the facility receives annually.

    The researchers also found high amounts of microplastic when they tested the air at the facility, Brown said.

    The study also looked at the facility’s wastewater after filters were installed. With filtration, the estimate of microplastics produced dropped to about 3 million pounds a year.

    Even with the use of filters at the plant, the researchers estimated that there were up to 75 billion plastic particles per meter cubed in the facility’s wastewater. A majority of the microscopic pieces were smaller than 10 micrometers, about the diameter of a human red blood cell, with more than 80 percent below five micrometers, Brown said.

    The study is here.

    5 votes
    1. vektor
      (edited )
      Link Parent
      It should be noted, that if I'm reading the article right, this is a misinterpretation. So in the facility, they have some filtration in place. That's the two different ranges we see (96 – 2933...

      A recent peer-reviewed study that focused on a recycling facility in the United Kingdom suggests that anywhere between 6 to 13 percent of the plastic processed could end up being released into water or the air as microplastics — ubiquitous tiny particles smaller than five millimeters that have been found everywhere from Antarctic snow to inside human bodies.

      It should be noted, that if I'm reading the article right, this is a misinterpretation.

      This equates to 96 – 2933 tonnes per annum of MP discharged in pre-filtration water and 4 – 1366 tonnes per annum of MP in post-filtration water. Given 22680 tonnes of plastic waste are brought the PRF for processing per year, the MP released relative to the tonnage imported to the plant is up to 0.06 tonne/tonne for post-filtration discharge. This equates to approximately 6% of the mass of plastic waste brought to the PRF for recycling (0.004-0.13 tonne/tonne), but rises to up to 13% if no filtration is provided to the wash water.

      So in the facility, they have some filtration in place. That's the two different ranges we see (96 – 2933 tonnes unfiltered and 4 – 1366 filtered) in Section 3.3. I haven't found yet where those ranges come from, but given what I've read about the methodology, it's probably to account for the fact that their sampling procedure has quite large margins of error, considering they sample from the top layer of a tank of stagnant waste water, making assumptions about the distribution of MP particles (Second paragraph of section 3.1). The 6% and 13% figures are the upper end of the estimates for filtered and unfiltered discharge (i.e. 1366 and 2933 tonnes). The more proper way to compute the potential range as reported by the article ("anywhere between 6 to 13 percent of the plastic processed could end up being released into water or the air as microplastics") is to take the lower end of the filtered figure. Which would give you 0.017%. In short, WP reports the worst estimate of the filtered waste water and the worst estimate of the unfiltered waste water as the total range. They completely ignore that the best cases are several orders of magnitude better.

      Now I'm not saying recycling is as good as we like to tell ourselves. But to have an error margin of three orders of magnitude just screams "we need to study this a hell of a lot more". And to be quite frank, I'm not buying the upper end of the range here at all. Losing 13% of the processed plastics to waste water seems a bit extreme.

      There's about 22680 tonnes worth of further experiments that could be done here. Sample MP pollution upstream and downstream of the discharge point. Sample the discharge water itself, not this weird tank nonsense. Try to figure out how much tonnes of plastics leave the facility as solid waste and as recycled pellets to work out how much is lost. Sample different facilities. Some of which I'm sure is infeasible, but there's got to be a way to get that error margin down.

      My main take-away from this is about how poorly the problem is understood, not about how bad the problem is.

      Edit: On second thought, the higher end of the range doesn't pass the sniff test. They report number of particles, but once you convert that into an actual concentration, as they do in the graphical abstract... well, let's just say I don't find "1% of the discharge water is plastic" (10^4mg/l) to be particularly convincing. Maybe my intuition is off here, but that seems like a comically large amount.

      8 votes
  2. [6]
    skybrian
    Link
    It would be interesting to know how this compares with plastic sent to a landfill. Seems like if were properly bagged, it would be pretty low, in the short term? Though it probably depends on the...

    It would be interesting to know how this compares with plastic sent to a landfill. Seems like if were properly bagged, it would be pretty low, in the short term? Though it probably depends on the landfill and the waste disposal process.

    2 votes
    1. [5]
      vord
      Link Parent
      Though a landfill is less obvious, the breakdown over time (courtest of worms and such) will also leech microplastics out into the environment over time. The best answer is to minimize our use of...

      Though a landfill is less obvious, the breakdown over time (courtest of worms and such) will also leech microplastics out into the environment over time.

      The best answer is to minimize our use of plastics. Especially thin films. We need to stop shrinkwrapping consumer goods in the stuff.

      4 votes
      1. [4]
        skybrian
        Link Parent
        Yeah, we know about leaching, everyone mentions it, but that's a very high-level, conceptual fact. It's probably going to vary based on landfill design and what you really want to know is how well...

        Yeah, we know about leaching, everyone mentions it, but that's a very high-level, conceptual fact. It's probably going to vary based on landfill design and what you really want to know is how well your local landfill is doing at containing plastics.

        On the other side, I thought the article I shared was about a pretty solid study (though of only one facility), but they didn't notice some pretty big problems with it that vektor pointed out.

        So in the end I just shrug. It's hard to find solid info about any of this stuff.

        3 votes
        1. [2]
          vektor
          Link Parent
          AFAICT, the authors of the study are well aware of the limitations. Their main conclusion is similar to mine, "we don't nearly know enough about this". The WaPo though... well, let's just say...

          but they didn't notice some pretty big problems with it that vektor pointed out.

          AFAICT, the authors of the study are well aware of the limitations. Their main conclusion is similar to mine, "we don't nearly know enough about this".

          The WaPo though... well, let's just say their business model is to optimize for readership, not truth.

          4 votes
          1. skybrian
            Link Parent
            Well, I doubt that's the motivation. The reporter interviewed some researchers and wrote about the study's limitations quite a bit. And the headline (though probably not chosen by the reporter) is...

            Well, I doubt that's the motivation. The reporter interviewed some researchers and wrote about the study's limitations quite a bit. And the headline (though probably not chosen by the reporter) is far from alarmist.

            1 vote
        2. vord
          Link Parent
          It is a great article, don't get me wrong. How much of a farce plastic recycling is, is fairly well known. Not to say that its neccessarily worse than not recycling any, but that the marketing of...

          It is a great article, don't get me wrong.

          How much of a farce plastic recycling is, is fairly well known. Not to say that its neccessarily worse than not recycling any, but that the marketing of recyclability exceeds ability.

          We'd be a lot better off if we returned to glass and metal in many ways. I like the idea of forcing bottling companies to collect every bottle they ship out, and pay a $1 tax for every bottle short they are. That should create a proper incentive structure to create durable containers, have customers return them, and reuse them.

          3 votes