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Any article about biodegradable plastics should start with advantages over cellophane/cellulose.

People have figured out how to make it a hundred years ago, it's already used for food packaging, known properties, abundant and cheap - made from trees / other plants.

The article starts as if it's some breakthrough miracle which is unheard of. I can literally just buy compostable bags for organic waste made of corn starch on Amazon. It's already a product.

Journalist demonstrate less awareness than 8B LLM. Scientist tells you about a new plastic? Ask them how it's better than what's already on the market.

> Story Source:

> Materials provided by Flinders University.

It's not that the "journalist" didn't think to ask, it's that this is a PR piece sent out to media outlets from the university that did the research. Nearly all universities have a PR team that sets fluff pieces out to the media to promote the work of the university.

The person who wrote this is being paid not to ask tough and important questions around this research.

> I can literally just buy compostable bags for organic waste made of corn starch on Amazon.

They compost, but they don't biodegrade. The difference is whether it breaks into microplastics or dissolves/is digested in the ocean.

My understanding is that cellophane generally does biodegrade in most settings. Polylactic acid (those cornstarch-derived bags) mostly biodegrades in hot enough compost or (after several years) in ambient-temperature soil, but not very well in cooler water (One study: "The half-life period of degradation [of polylactic acid in artificial seawater] is 12 [days at 90° C] or 468 days [at 60° C]").

That can't be right - even 60 C is 140 F. No normal water bodies are near that hot.

If it's actually 60/90 FAHRENHEIT, very few water bodies are (currently) 90 F. That's above even most equatorial temps.

>> 12 [days at 90° C] or 468 days [at 60° C]

Those temperatures are certainly hard to find in nature, outside of hot springs! Even if this is an error and we are talking about 90°F/60°F, the higher temperature is pretty much constrained to the tropics, so we're talking a year+ to degrade in real conditions. It is better than centuries, but not exactly rapid?

Yeah, I imagine it's considerably slower at ambient ocean temperature. Don't throw your PLA bags in the ocean or a river. Here's a different paper:

> For example, PLA is not biodegradable in freshwater and seawater at low temperatures [32,36–39]. There are two primary reasons for this: (i) The hydrophobic nature of PLA, which does not easily absorb water [40–42]. In aqueous environments, the lack of hydrophilicity diminishes the hydrolysis process, which is crucial for the initial breakdown of PLA into smaller, more degradable fragments. (ii) Resistance to enzymatic attack; the enzymes that degrade PLA are not prevalent or active under typical freshwater and seawater conditions [39,43,44]. The microbial communities in these environments may not produce the necessary enzymes in sufficient quantities or at the required activity levels to effectively breakdown PLA. Additionally, the relatively stable and crystalline domains of PLA can further resist enzymatic degradation.

Also:

> It should be emphasized that neat PLA cannot be classified as a completely biodegradable polymer, as it generates microplastics (MPs) during biodegradation.

> Any article about biodegradable plastics should start with advantages over cellophane/cellulose.

Well, I guess it starts with the plastic being thermoplastic.

Milk is surprisingly intensive in terms of greenhouse emissions. It is somewhere around 1 to 3 kg CO2-equivalent per kg of milk.

Milk protein costs around 95 kg of CO2-equivalent emissions per kg of protein, which is apparently what was used in the production of this plastic [1]

[0] https://www.sciencedirect.com/science/article/pii/S002203022...

[1] https://ourworldindata.org/grapher/ghg-per-protein-poore

It's possible to use manufacture whey protein without cows:

https://en.wikipedia.org/wiki/Whey_protein#Microbial_product...

It's not theoretical either. You can buy vegan dairy products made from this method today.

I'd be interested in knowing what the CO2 emissions were from these. You still need to feed the yeast, so you'll have the CO2 emissions involved in growing a crop associated with this. And if you look at the chart in the OP, you'll see that grain production is about half the CO2 emissions of milk. That's likely part of the milk CO2 production accounting.

In addition, you'll need more cleaning/sterilization/mixing. I'd guess that it's lower, but I wonder how much lower.

And then there's the other products that generally get thrown into the mix to make up for things like missing fats. For example, a vegan cheese based on bacteria will often include coconut oil, probably to get the same fat profile.

Whey is an interesting product in general because it's a waste product of cheese making.

It’s likely to be vastly better.

Feed efficiency is critical when doing these calculations as cows inherently need energy to survive not just produce milk. As such even if you use the same crop two different sources of protein can have wildly different levels of CO2 emissions embedded in their creation. https://en.wikipedia.org/wiki/Feed_conversion_ratio

I think it is likely more efficient. That said, cows do have the advantage that the food they consume needs little to no processing in order to produce milk. The yeast needs pretty precise processing of the incoming mash both to make sure a wild yeast strain doesn't make it's way in, and to make sure the yeast ultimately produces the right proteins.

You can't just throw in grass clippings into a vat and get whey. You can throw grass clippings into a cow to get milk (though, TBF, I dislike grassy milk).

I am very much sympathetic to nature conservation, decarbonization, degrowth etc. but really, there are more important considerations at this very moment than shaving few kgs of CO2 by ditching milk.

And, as much as some powers try to convince us, not everything can be reduced to carbon footprint.

But we can also produce milk from yeast now. Perfect Day, for example, produces milk without cows.

So it's not out of the question we could scale that up to meet plastics demand.

I remember when people still knew what milk was ... and what was not milk.

That was before multi-billion-dollar companies came up with marketing strategies that manipulated people into not understanding what milk was, instead making them believe that milk is whatever they tell people.

Usually, the reaction to this is "Well, language and the meaning of words change." ... Sure, but that argument comes in complete ignorance of the fact that it only happened, because people with too much money and power can manipulate millions into believing whatever these millions of people are supposed to believe.

Thus now anything can be milk, as long as some profit-oriented company decides that people shall call it milk.

This practise has become the norm to a degree that people will not only generally accept it, but also generally defend it. Pure madness.

Language changes. In this case just the spelling though.

"Almaund mylke" is all over medieval cookery manuscripts, among other options.

We’ve been using milk for non-animal products for longer than we’ve spelt milk with an i, and for longer than we’ve had companies, let alone multi-billion-dollar ones.

To be clear, Perfect Day doesn't make "milk" like plant-based milks (think almond "milk", oat "milk", etc). They bioengineered some yeast to grow whey protein directly. The milk they make (made?) probably wouldn't be considered "milk" in the strict sense (they had to get the fat and sugars from plants), but there's really not a good reason to distinguish between "whey protein from cows" and "whey protein from yeast" when it's the same stuff.

You understand that the product I'm talking about is the same proteins as milk, and is essentially whey, right?

I'm not talking about grinding up nuts or grains and calling it milk, I'm talking about engineering yeasts to literally produce the proteins that milk has to create a product that isn't just milk-like, but is literally identical proteins.

Whey is just a small part of milk, though. You can't isolate one aspect and pretend it's fair to call it (cow) milk.

You wouldn't call whey protein powder mixed in water milk.

You wouldn't call butter mixed with water milk.

You wouldn't call casein powder mixed with water milk.

The large diary producers are forcing things that everyone understand what is — “Oat milk” and “Almond milk” — to be called “Oat drink” and “Almond drink”. New terms for things that have existed for decades.

Really, we should be calling the OG milk “cow milk” and let the good times roll.

Big milk have been pushing questionable health research and narratives for cow milk for quite some time.

All this coming from someone (me) who drinks 0,5L of cow milk every day.

Yes, yeast milk is milk too. Just like coconut milk.

I thought the reason things are called "Oat Drink" versus "Oat Milk" is because non-dairy "milks" have to be fortified with vitamin D and calcium and the stuff that's labeled a "drink" is not fortified.

The first documented use of the word coconut milk in English dates from 1698 ( Philosophical Transactions of the Royal Society, volume 20, page 333) and the use of almond milk goes quite a bit further back, to at least 1390 (The Forme of Cury).

Is this going to result in net less greenhouse gas emissions?

Maybe but probably not zero, from parents article: "The use of such treated fertilizers will be most relevant for reducing the carbon footprint of milk in countries such as the United Kingdom, Ireland, and the Netherlands, where N fertilizer is a major contributor to the footprint."

In case you are unaware much of the nitrogen in plant matter (food for yeast or cows) comes from fertilizer. And that is extracted using the Haber process (see: https://en.wikipedia.org/wiki/Haber_process ). This runs on natural gas, because it's effectively a waste product of other hydrocarbons being extracted.

But to put this in context, the average American family’s carbon footprint per year is roughly 50,000 kg, and one flight is usually on the order of >1,000 kg, or ~300kg/700 pounds of milk, assuming that 3kg CO2 per kg milk high end figure. So if you like milk, there are probably other places you can cut first.

Does seem like a lot of carbon for a kg of plastic, though, how does that compare to normal plastic’s carbon footprint?

>... >1,000 kg, or 700 pounds of milk

Why do you mix your units like that.

Because I'm American, so I use metric in scientific contexts, and weird medieval units in everyday ones :-)

I'll edit a bit for clarity for you all who live in more consistent places.

Where are these emissions coming from? For instance, if this is counting the emissions involved in logistics, none of that inherently or necessarily requires greenhouse emissions—you can electrify trains, tanker trucks, and refrigerators.

If this is counting the methane emissions of the cow itself, that’s not a fair or complete accounting. The cow produces methane in her digestive system after eating grass, and the grass grows by, among other things, extracting CO2 from the air. Then the cow burps methane, the methane combines with atmospheric oxygen and breaks down to CO2 and water, and you have a closed loop; the cow cannot belch more carbon than she eats, and that carbon came from the air in the first place.

> vanishes in soil in just 13 weeks.

Part of the problem with waste management is that we don't really put it in the soil. Your household garbage is mostly biodegradable, but if it ends up buried in a lined pit under tons of other garbage, even paper and orange peels will probably sit there for centuries. I'm not sure it makes much of a difference what kinds or quantities of plastic end up buried in the landfill.

I think the solutions here are more on the supply side than the landfill side. The question there is what are we trying to solve.

Energy use? Most alternative packaging materials are energy-intensive too, so it's less about plastic and more about retail and consumer preferences to have everything individually wrapped and packaged in bags or boxes with colorful graphics, nutrition information, and so on.

Environmental pollution? There, the problem is the plastic that doesn't end up in a landfill. Including our "recycling" shipped overseas.

> I think the solutions here are more on the supply side

This is why nothing happens there, yet common folks receive higher and higher burden.

It still biodegrades within the pit. In fact, that's actually a problem because it can generate fire starting temperatures! (Crazy I know) It's also a problem because a part of biodegrading is producing CO2 and CH4.

But I generally agree. The big issue here is we as a society have moved away from biodegradable packing and distribution. I get it, plastic prevents waste and mold. That's why we use it. It's also dirt cheap. It's a byproduct of oil refining (literally cheaper than water).

The ultimate solution to the plastic problem is making plastic more expensive, and the way to tackle that is by reducing oil consumption. Fortunately, that's sort of just naturally happening.

I’m hoping this is a first step toward using some other protein(s). There are some fairly high protein plants like chickpeas and soy that are less intensive to produce than milk.

Are proteins fungible? I thought different protein sources provided different amino acids.

In case of plasticizing it, it should be fungible in terms of use the cheapest and/or least healthy to make plastic-like single use goods.

That said, the question I have is given the nature of calcium (and its relation to limestone), I'm wondering if the milk protein here is especially useful to plasticizing because of its calcium content? A quick search does classify calcium caseinate as both a protein and technically a calcium salt.

No they are not but they can be combined to produce a "complete" amino acid profile.

> Plastic production has climbed from 2 million tonnes in 1950 to 475 million tonnes by 2022, roughly equivalent to the weight of 250 million cars.

That's 60 kg/person/year of plastic, which is a lot. Or about 4800 kg for a person living 70 years. Obviously, there is wide variation in this number across the human population.

Worth noting that casein is a very very old technology - people have known how to use it (well, milk) to make a type of glue for thousands of years.

  1) Heat 1 cup milk, not to boiling.
  2) Add 4 tablespoons vinegar.  Stir for a few minutes.
  3) Strain out curds.  Squeeze to remove as much liquid as possible.
  4) Form into a shape or press into a mold, let dry.

That's literally a recipe for paneer cheese. Tastes awesome fried and mixed into many Indian dishes.

There was a variation of this in a midcentury science book for a children that I'd check out from the library as a kid. It was used to demonstrate how to make your own 'plastic' action figures.

Products that involve clay as an ingredient tend to have issues with lead contamination (along with other heavy metals) as it likes to absorb them, and the sources are highly variable.

Luckily, producing milk is completely environmentally friendly!

/scnr

The paper doesn't talk about thermal properties, which is a shame. Would be good to know if this is a thermoplastic.

sounds like bakelite to me. you can get a disposable polymer from polylactide as well, and it can be obtained from silage (so-called green refinery, although the term seems to have been broadened in the last decade)

PLA is also biodegradable and cheap but it does not biodegrade that fast, certainly does not vanish in 13 weeks. Im not sure what the usecase is here but I'm sure it could have some uses.

PLA does not break down naturally. It will last centuries in the environment.

PLA does break down naturally, it is a good source of carbon for many types of bacteria. It takes a long time, and happens more quickly in industrial composters where it's shredded to microplastics first but it does happen.

Take a look at something people have been using for eons with saltwater aquariums: bio-pellets. These are tiny beads of PLA that are fluidized to allow high turnover of water through the PLA, this encourages bacteria to colonize and digest the PLA, then break off and move into the water column (the bacteria) and be removed by the protein skimmer. Because of the red field ratio, each 106 mols of carbon from PLA removed this way also removes 16 mols of nitrate, which is a major pollutant in aquariums. It also removes 1 mol of phosphate, a major pollutant as well, but that's not significant. Phosphate is best done by fluidized reactors with ferric oxide

CNC Kitchen put 3D printed PLA into their composted for over three months. I don't remember the specifics, but results were underwhelming.

As someone who constantly prints temporary jigs and spacers, I'm interested in compostable filament. Bonus points if it is comparable to PLA in price.

There are a decent amount of plant parts that don't break down much at all in 3 months - doesn't mean they aren't biodegradable ultimately, although hoping for biodegradation as a way to eliminate litter is a nonstarter with this approach.

3 months? Most organics will not break down in that time. 6-12 months is recommended, and even then, not everything is broken down. I've had egg shells last 2 years or more in my compost bin.

I made no claims about the speed at which PLA breaks down, only that it does. Biopellets in reactors tend to last years.

New subscription model coming to plastics! Products last only 13 weeks.

I know - long lived plastics are bad. We need some kind of middle ground thats as cheap as the current plastics and doesn't last as long.

Its called paper, wood, glass, ceramics or metal depending how long you want it to be around for and what you are putting in it.

Only lasts 13 weeks in soil. It presumably lasts a whole lot longer when you don't bury it in the ground.

I agree. https://en.wikipedia.org/wiki/Galalith is made of casein and formaldehyde. It was popular 100 years ago and there are plenty of pieces still around. I searched formaldehyde in the article but I din't find it, I'm not sure if they hide it or they are using a very different method.

We go through a lot of single-use plastics.

Is this going to drive up the price of milk? Corn went up when we started making ethanol from it for gasoline.

Do you have any evidence for that? From what I understand, the corn to ethanol pipeline was created to keep corn prices from dropping below what the farm bill would pay for.

How long before a bacteria learns it can eat this and starts breaking it down much more quickly?

I've said before that we need a short term plastic that completely dissolves into harmless organic compounds that can then be forgotten in nature with no ill effect. 13 weeks is just about right!

Yup. We certainly don't want "Plastic is made from milk and vanishes in 13 days" but I'd rather not have a linkbait "This" so took a non-this route.

Or remove "is"

>vanishes in 13 weeks

Well then it's not plastic is it? Plastic's defining characteristic is that it is not decomposable

The defining characteristic of plastic would seem to be the definition of the word from which they are named. That is, that plastics are plastic. It means they are easily shaped, molded, formed, or extruded.

That's what they told me in school, too.

But then I got out in the real world, and noticed plastics just falling apart all around -- including stuff that is not intended to fail and which is otherwise still within its useful life.

Like: One year, I bought some used pickle buckets from a local burger joint to use as planters. Within 6 months, they were falling apart: It was easy to break them apart in chunks with my bare hands.

Or the plastics used for cars: They often eventually turn brittle and fall apart, whether interior or exterior. Plastic lenses on USDM cars turn foggy and useless; some types of wire insulation disintegrate. (If we want to talk about environmental cost, can we also talk about the impact of building a new car?)

In some areas, we once used polybutylene water pipes. These tended to fail and damage homes. There was even a billion-dollar lawsuit about it in the 1990s. It was not good.

Meanwhile, a red Solo cup or a plastic drinking straw, once landfilled, will be there a very long time -- but eventually, they will also decompose.

And the UHMW cutting boards I use in my kitchen will probably outlive my grandchildren's grandchildren before they start falling apart on their own accord.

Plastic isn't always forever, even though some people seem fond of saying that it is. Plastic isn't necessarily cheap, either, even though "cheap plastic" is a common expression -- some plastics are very expensive and resoundingly durable (and there's only partial overlap of these two qualities on a Venn diagram).

The truth is somewhere in the middle, but is rather nuanced and variable and difficult to pin down in absolutes.

But plastic (as a noun) does, broadly speaking, have the material property of being plastic (as an adjective).

You have to put UV and temperature stabilizers in plastics to prevent them from breaking down outside. The sun is merciless and destroys everything in time.

Your buckets would have lasted longer if you had painted them with outdoor housepaint or outdoor water- or oil-based urethane, because those coatings contain uv stabilizers.

>Plastic isn't always forever

But molecularly, plastic is around forever. A wooden bucket will eventually breakdown to not be wood at all anymore. Products made from plastic is not what lasts forever, the plastic itself is.

That doesn't sound right to me, either. Let's use PLA as an example of a thing that is definitely plastic.

In the right conditions (hot aerobic compost, which is admittedly difficult to achieve), PLA rather quickly decomposes all the way back down to lactic acid.

Lactic acid is definitely not plastic. It's liquid, and is one of the primary products of the happy little microbes that I nurture in my pepper ferments at home.

Again, it's hard to pin the long-term properties of plastic (noun) down in absolutes.

Do you need to grind the plastic into dust for that to happen?

No, AFAICT.

Everything goes faster in hot compost with additional preprocessing, but it's not strictly necessary to reduce things to dust.

Hydrolysis of the PLA still happens whether it is dust or something larger. After that, the chains are small enough to be available for microbes to eat fairly quickly.

They're just eating one bite at a time; they don't know that they have an entire elephant to eat.

More surface area improves immediate availability and speed, but less surface area doesn't cause the process to cease.

I meant decomposable by bacteria.

It's trivial to make plastics that break, but then you have many microplastics which again don't decompose.

The breakage isn't even infinite, as the particles grow smaller, the shear resistance grows and it stops splitting, and again nothing decomposes it further

So decompose =/= break.

There are a lot of plastics that are disposable. The first plastics over 100 years ago were made from milk (I suspect the Romans knew the process - it wasn't industrially useful though). Many decomposable plastics have been made over the year. The PLA commonly used in 3d printers is decomposable (in the right environment).

Oil based plastics are generally a lot cheaper than the above though, and they are typically not decomposable. Depending on your use this can be good or bad (I don't want my plastic plumbing pipes to decompose, but other plastics are used up and I want them to decompose)

> Plastic's defining characteristic is that it is not decomposable

Behold, a plastic! holds up a rock

What? Plastic's defining characteristic is plasticity -- how moldable, shapeable, extrudeable, pressable, etc it is.

Also, one of the most widely used plastics is PLA, polylactic acid. Which is made from lactic acid from sugarcane, beets, or cassava, and is biodegradable.

Wow! Temporary boob implants!