Production, use, and fate of all plastics ever made
advances.sciencemag.org
advances.sciencemag.org
Plastics are not readily biodegradable. Plastics buried in landfills hardly biodegrade. Plastics that are buried under soil or that sink to the bottom of bodies of water hardly biodegrade. There are a variety of biological processes that degrade plastics that remain exposed to atmosphere or in upper layers of bodies of water, particularly when enhanced by ultraviolet fragmentation of high-molecular-weight polymer chains. I'd say more like "the commonly used plastics exhibit variable and typically low degradation rates in the natural environment, making it difficult to quantify natural breakdown of plastics not recycled or incinerated."
Here's one of the most fascinating papers I've ever read, about biological colonization and breakdown of floating plastic trash in the oceans:
"Life in the “Plastisphere”: Microbial Communities on Plastic Marine Debris"
https://macaulay.cuny.edu/eportfolios/branco2014/files/2014/...
And an article about polyethylene biodegradation by thermophilic bacteria:
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2005....
And an article that you may have seen before, about polyethylene degradation by waxworm gut bacteria:
http://pubs.acs.org/doi/abs/10.1021/es504038a?journalCode=es...
If you search Google Scholar for polyethylene biodegradation rates you'll find many articles. Some thermoset plastics and halogenated polymers are effectively immune to UV, biological, and combined-effects breakdown. They'll endure into deep time like ceramics. But the most common plastics do degrade, albeit slowly.
"There are essentially three different fates for plastic waste. First, it can be recycled or reprocessed into a secondary material (22, 26). Recycling delays, rather than avoids, final disposal. It reduces future plastic waste generation only if it displaces primary plastic production (30); however, because of its counterfactual nature, this displacement is extremely difficult to establish (31). Furthermore, contamination and the mixing of polymer types generate secondary plastics of limited or low technical and economic value."
Interesting point about how hard it is to determine how much recycled plastic displaces production of new plastic.
More statistics:
"Before 1980, plastic recycling and incineration were negligible. Since then, only nonfiber plastics have been subject to significant recycling efforts. The following results apply to nonfiber plastic only: Global recycling and incineration rates have slowly increased to account for 18 and 24%, respectively, of nonfiber plastic waste generated in 2014 (figs. S5 and S6). On the basis of limited available data, the highest recycling rates in 2014 were in Europe (30%) and China (25%), whereas in the United States, plastic recycling has remained steady at 9% since 2012 (12, 13, 34–36). In Europe and China, incineration rates have increased over time to reach 40 and 30%, respectively, in 2014 (13, 35). However, in the United States, nonfiber plastics incineration peaked at 21% in 1995 before decreasing to 16% in 2014 as recycling rates increased, with discard rates remaining constant at 75% during that time period (34). Waste management information for 52 other countries suggests that in 2014, the rest of the world had recycling and incineration rates similar to those of the United States (37). To date, end-of-life textiles (fiber products) do not experience significant recycling rates and are thus incinerated or discarded together with other solid waste."
Sad to think how little is accomplished by recycling a plastic bottle. Although that won't stop me from doing it.
High quality plastics are designed to be recycled almost infinitely: we should consider them technical nutrients to manufacturing systems. They should never become waste hence never be downcycled.
"TOWARD ESTIMATING DISPLACED PRIMARY PRODUCTION FROM RECYCLING: A CASE STUDY OF U.S. ALUMINUM"
http://econ.ucsb.edu/~startz/Aluminum.pdf
Absolutely fascinating, and not surprisingly leads down the path to the law of unintended consequences:
"At this point, it would be natural to wonder, “If secondary production doesn’t fully displace primary production, where does the ‘extra’ material go?” ... The common assumption that recycled material displaces primary material of the same type is depicted in the left-most circles in Figure 4. However, two other outcomes are possible that result in partial displacement. ... First, as discussed in the introduction, secondary aluminum may displace production of materials other than primary aluminum. Recycled aluminum may, for instance, displace primary or secondary steel, copper, magnesium, or plastic."
"Second, increased aluminum recycling can also affect overall aluminum demand. For instance, it is possible that increased recycling can lower prices of both primary and secondary material, and thus increase demand for aluminum (similar to the energy efficiency ‘rebound effect’). Note that this market increase is independent of any exogenous growth that may occur simply as a result of global economic forces. Production and consumption data show that both aluminum recycling rates and the size of the aluminum market have been growing rapidly for the last 100 years; it is possible that some of this increase is a result of decreased material prices from increased recycling."
They conclude:
"While the environmental benefits of reuse and recycling come entirely from their potential to displace more impactful primary production processes, alarmingly little is known about actual rates of displacement. ... While this case study is just a first step towards a better understanding of displacement, it does suggest that we are currently systematically overestimating the environmental benefits of reuse and recycling. ... That the current environmental benefits are lower than we think they are does not mean we should stop recycling. Instead, it tells us that recycling currently does not fulfil its environmental potential, and recycling efforts should therefore focus on maximizing displacement rather than simply maximizing collection, reprocessing, and market development for secondary resources."
As a suggestion to all the robotics / computer vision / AI geeks out there: Build an automated trash sorter with a very high degree of accuracy.
If you want the incentive, here it is. Everybody has 3 separate bins. By having 3 separate bins, not only do we force lazy people to think about how they classify their waste into those 3 separate bins, but we also end up with 3 different waste trucks driven by 3 different drivers back and forth between 3 different waste depots. And we still get it wrong, misclassifying compostable things as recyclable, recyclable as trash, etc., forcing us to pay for processing costs to sort out the 40+% of stuff that gets misclassified.
This adds up. Waste management is a $75B industry [0]. Let's break down how money is spent, and how your system will help:
1) 55% is spent on collection. Your sorter can eliminate up to 2/3 of that, but due to variant efficiency factors maybe it is only 1/2. This is about $21B in potential savings.
2) Treatment and disposal account for 20%. This includes remedial sortation (fixing the problems created by people who misclassified their waste), type-based sortation (things like separating glass from plastic, as well as separating the different types of plastic). A good automated sortation system will save at least 20% of these costs, resulting in another $3B in potential savings.
3) There are unaccounted for missed opportunities. Sortation costs force us to make compromises; instead of the more expensive sorting of thermoplastics from thermosets, which would result in higher resale value, we sometimes chop them all up and sell them as a lower valued aggregate for things like road asphalt. I have no idea how much is missed, but I do know that recycled thermoplastics have a resale value that is a good 10x higher than what they get out of that chopped aggregate.
4) Additionally, we have massive landfills that have accumulated billions of tons of trash that, due to oxygen starvation in landfills, isn't biodegrading any time soon. If your system can extract valuable recyclable materials from trash and resell them, you could meaningfully create a second-hand mining industry with basically free land rights. I have trouble seeing anywhere less than 10s of billions of dollars in annual market from this alone.
So there you have it. You can make everyone's lives easier, save us time, save us money, save the environment, and you'll have the waste management industry groveling at your feet at the chance to save them $24B a year, possibly much much more. Do it already.
[0] https://www.gridwaste.com/news/2014/8/20/10l92d52vzaw1zdsf0z...
Because from what I understand, the whole idea of having individuals sort their trash is stupid, and done either beacuse of cargo-culting environmentalism, or just to make people feel like they're making some difference.
Centralized trash sorting seems like a much more efficient solution (due to the usual reasons centralized solutions are much more efficient than distributed ones). In fact, many times I've seen the segragated bins on streets being dumped into one pile on a single trash truck. Besides it being more efficient this way, it's also safer - you generally can't trust regular people not to screw up such a task, so some centralized sorting before processing is required anyway.
If segregated bins are ultimately dumped into one big mixed waste stream, it's stupid cargo culting to have people separate things. But that's not how I have seen it work in the cities I have lived in. Some centralized checking/sorting before processing is still required even if people are supposed to separate their own, but much less than if you just give people one giant bin to hold everything they want to get rid of.
If you had a centralized waste sorting machine that could separate as well as human labor, but was much cheaper, that would be even better. (Though it wouldn't completely remove the need for household level separation: some perfectly recyclable clean paper becomes un-recyclable if people indiscriminately mingle it with food scraps or other dirty things before collection.)
How is this supposed to work? Sorting trash into many containers takes me a little more time and effort and pretty much exactly as much energy as putting it all in one place. It also keeps the materials from mixing (that is, becoming dirty). How would it help to first mix it all, compress it together (which is pretty much required to keep transport efficient) and then sort it again?
Even if you want to use a sorting machine, would it not be better to have presorted ("richer", in mining lingo) input material streams?
a) can't trust that you'll do your sorting perfectly, and won't occasionally throw e.g. glass into metals bin out of hurry, carelessness, spite, or while drunk. And even if you are perfect, your neighbour isn't.
b) might want to change the segregation rules to better optimize recycling process; you don't want to force an entire city to update their bins and/or habits in lockstep with whatever the waste processor does.
Point a) means they have to sort themselves anyway, at which point individuals doing the sorting is just wasted effort.
Sure, the processor will want to seperate, say, aluminum from iron, and remove any glass from either stream, but I am fairly sure that these tasks become significantly easier if the stream does not also include diapers, orange peels and wet cardboard
My point is, they can't even trust the stream won't include those. General population can't be trusted like that.
He's a story about a New York facility that does a lot of what you ask, note that they import the machinery from Europe:
https://arstechnica.com/science/2015/01/inside-new-york-city...