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Degradable, biodegradable or compostable

So most plastics are made from oil and most plastics do not biodegrade. See how and why here…

And yet you will find plastics described as

  • degradable
  • biodegradable
  • compostable

What do these terms actually mean when applied to plastic?

Remember that

  • Most traditional, oil-based plastics do not biodegrade.
  • Biodegradable products break down as the result of the actions of naturally occurring microorganisms, such as fungi or bacteria, over a time.
  • Plastic breaks, tears and cracks. It weathers and sunlight makes it brittle, It falls apart – it degrades – but only into smaller pieces of plastic.
  • Find out more about the lifecycle of plastic here.

Degradable Plastic

All plastic degrade – i.e. they fall apart into smaller pieces of plastic. BUT when a plastic is described as degradable it could just describe the falling part process  OR it could mean t a degradation initiator has been added to make it fall apart faster.

Degradation Initiators and Bio-Degradable Plastics

But suppose there was a way of making plastic biodegradable? The industry argue that they can do just that by means of chemical additives known as degradation initiators. Very basically, these additives break the long unnatural plastic polymers into shorter recognisable polymers that microbes can attack and digest – or biodegrade (N.B. lots more research need to be done on this. It is by no means proven).

Because the degradation initiators are biologically  based they are sometimes described as biodegradable. So some traditional plastic bags have been labelled biodegradable.

This is  at best confusing if not deliberately misleading. This  is not the same process as natural biodegrading. Unlike truly biodegradable products they don’t always break down into harmless substances and may leave behind a toxic residue.

More so as  there are some compostable plastics which are also described (correctly) as  biodegradable which do actually compost down into biomass.

Read more about degradation initiators here.

Compostable Biodegradable Plastics

Truly biodegradable plastics are compostable.

Biodegradable products break down through a naturally occurring microorganism into simple, stable compounds which can be absorbed into the ecosystem. To be classed compostable, items must biodegrade within a certain time (around the rate at which paper biodegrades) For a man-made product to be sold as compostable, it has to meet certain standards. One such is the European Norm EN13432.

Compostable Plastics  meet all of these criteria. You can find out more here.

Infographic

Yes they have a vested interest making as they do compostable plastic goods but the info still stands.

Vegware factsheet

 

 

 

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Compostable Plastics

Plastic was the name given to early synthetic products such as cellophane,  that were derived from cellulose. These plastics  were biodegradable. Then they learnt how to make similar products from oil. Or rather from the bits of crude left over after they had finished making petrol. The same name was then given the oil derived product. But there were crucial differences. This new product was  made in a very different way and did NOT biodegrade.Since then yet more “plastics” have hit the market. Made from all kinds of things. Some from plant starch and some are certified compostable.

To conclude;
Currently, non- biodegradable, oil derived plastics are the most commonly used and so we tend to ascribe their qualities to all types of plastic.
In fact plastics can be made in a variety of ways from a variety of materials; shale gas, oil, plants even chicken feathers;
And different plastics have very different qualities. Some plastics do biodegrade and are certified compostable
Want to know more about plastic? Read up here

Biodegradable, Compostable Plastics

Just to remind you:
What is biodegradable? Biodegradable products break down through a naturally occurring microorganism into simple, stable compounds which can be absorbed into the ecosystem. More about biodegrading here
What is compostable? To be classed compostable, items must biodegrade within a certain time (around the rate at which paper biodegrades), and the resulting biomass must be free of toxins, able to sustain plant life and be used as an organic fertilizer or soil additive.
For a man-made product to be sold as compostable, it has to meet certain standards. One such is the European Norm EN13432.
You can find out more here.

Home Or Industrial Compostable?

Home Composting
Composting is usually done on a small scale and most people will be familiar with the concept of a backyard heap or garden compost where household waste is rotted down into garden mulch.
Industrial composting
However large-scale schemes are becoming increasingly popular. In the UK communities band together to compost a whole street is worth of waste. Even city councils are getting in on the act.
These larger projects are sometimes called industrial composting

The difference is is that industrial composting is a lot hotter and can work more quickly.

Home Compostable?
Many products ( especially compostable plastics), have been tested under industrial composting conditions. Therefore, while a product might be classed as both biodegradable and compostable, it might not break down in a backyard compost bin.
That said I have composted many such products in my own bin.

Compostable Plastic Products

These compostable plastics, like oil derived, are extremely versatile.
They can be thin and flimsy which means they can be used to make

PLA Compostable Plastic Bags
And liners to for paper cups to make them waterproof.

They can be harder and more rigid making them ideal for making

Disposable Cutlery 
Straws

Deli pots
Rigid packaging for food
Bottles

And longer lasting products like
Phone cases
Or sponges

See a wide range of compostable products HERE

Compostable Plastics Types
Cellulose derived plastics such as Cellophane.
Starch based PLA plastics. They are certified compostable.
Polyhydroxyalkanoates or PHAs  are linear polyesters produced in nature by bacterial fermentation of ­sugar or lipids.
chicken feathers bioplastic.

Composting Plastic At Home
While most agree that PLA plastic is indeed compostable, many say that it can only composted in large scale municipal schemes.
They are wrong. I have been composting plastics for years.
Read more HERE

To be sure you are using a compostable plastic get one that has been certified compostable. Check out the logo.

Compostable Plastic Products

See a wide range HERE

A Note On Bioplastics
Most compostable plastics are also bioplastics. Bioplastics are made from natural materials such as corn starch.
However not all are compostable. For example ethane based plastics as used Coca-Cola’s PlantBottle which replaces 30 percent of the ethanol in their normal polyethylene terephthalate (PET) plastic bottle with 30 percent plant-derived ethanol. This means the bottle is still considered PET and can be recycled but is NOT biodegradable. Find out more here.

Other Plastics
There is research being done into developing a compostable, oil-derived plastic. Watch this space BUT don’t fall for the old *biodegradable plastic bag trick see below.

*Compostable versus biodegradable plastics
You might see some plastics labelled described as biodegradable. You could be forgiven for thinking that this is the same as compostable plastic. It is not. Some “biodegradable plastics” are oil derived plastics with a degrading initiator added to make them fall apart (degrade) more  quickly. Unlike compostable plastics they don’t always break down into harmless substances and may leave behind a toxic residue. Read more here

More

Check out all our composting posts HERE
Want to know more about plastic? Read up here
See our big list of plastic types here

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Biodegrading and degradation – Plastic Lifespan,

So most plastics are made from oil and most plastics do not biodegrade. See how and why here…

But what does that actually mean?

Biodegrading

Biodegradation refers to the breaking down of organic substances by natural means. Natural means, means the breaking down is done by naturally occurring entities – things that are made in the body such as enzymes ( clever things that enable chemical break downs) or micro organisms that inhabit the teeny tiny world ( bacteria, fungi and exceptionally small plants and animals ). Any plant-based, animal-based, or natural mineral-based product has the capability to biodegrade

The key point is, is that the process of biodegradation is an integral part of the natural cycle. This process could be called rotting or decomposing or other nasty sounding things and yes it can be smelly but it is the very basis of life. Because as natural materials break down they release all kinds of nutrients that are used to feed other living organisms. Orange rind becomes compost which releases nutrients the orange tree can utilize. The tree feeds and so has the energy to make fruit which we eat discarding the peel which then biodegrades into compost – feeding many other creatures along the way including worms. It’s a kind of magic

In short…..

Biodegrading is the breaking down of organic substances,  (plants, dead animals, rocks, minerals etc.), by natural means. It  happens all the time in nature. We live, we die, we rot and so we feed the next generation. Even if you are a rock. All plant-based, animal-based, or natural mineral-based substances will over time biodegrade.

Here’s how long it takes for some commonly used products to biodegrade, when they are scattered about as litter:

Paper ~ 2-5 months 
Cotton rags ~ 1-5 month
Natural fiber rope ~ 3-14 months
Orange peel ~6 months
Wool socks ~1 to 5 years
Leather shoes ~25 to 40 years
Tin cans ~ 50 to 100 years

Plastic – years? centuries? maybe never!

Why Plastic Doesn’t Biodegrade

Because they are man made, the majority of plastics do not biodegrade. “Nature doesn’t make things like that, so organisms have never seen that before ” says Kenneth Peters, an organic geochemist at Stanford University, quoted in this fantastic article I recommend you read

Which means the enzymes and the micro organisms responsible for breaking down organic substances  do not recognize plastic. Therefore plastic products are pretty much indestructible – they do not rot or biodegrade.

Except…

Plastic Eating Microbes

Of course it is not quite as simple as that. Some bacteria it seems can digest plastic. Don’t get too excited. They are rare and don’t eat a great deal but you can read the latest reports here

Biodegradable Musings

That said the term biodegradable can be difficult to define. It is often about the time something takes to biodegrade – the rate at which something breaks down. Arguably  everything, even man-made products, will eventually biodegrade. However if it takes centuries to do so, it is generally considered to be non-biodegradable.

It also depends where a product is dumped.

Why Landfill Doesn’t Work

“Many products that are inherently biodegradable in soil, such as tree trimmings, food wastes, and paper, will not biodegrade when we place them in landfills because the artificial landfill environment lacks the light, water and bacterial activity required for the decay process to begin.”

This is why newspapers landfilled back in 1952 can still be easily read!  The Garbage Project is an anthropological study ofwaste conducted by a group at the University of Arizona. From Greengood

Too Much Trash

The sustainable rate of biodegradation is only what an ecosystem can deal with. Too much and the microorganisms get overwhelmed and collapse sobbing, unable to cope.

Degrading

Of course plastic breaks, tears  and degrades – but only into smaller pieces of plastic. Read more about that here

 

Useful stuff to know

Degradable, biodegradable or compostable

So most plastics are made from oil and most plastics do not biodegrade. See how and why here… And yet you will find plastics described as degradable ...
Read More

Compostable Plastics

Plastic was the name given to early synthetic products such as cellophane,  that were derived from cellulose. These plastics  were biodegradable. Then they learnt how to make ...
Read More

Biodegrading and degradation – Plastic Lifespan,

So most plastics are made from oil and most plastics do not biodegrade. See how and why here... But what does that actually mean? Biodegrading Biodegradation ...
Read More

Plastic eating microbes

Is this a good idea?- much as I hate bad plastic I am rather attached to the computer and Dyson. Will they disappear before my very eyes ...
Read More

Degradation Initiators & Degradable Plastic

Traditional plastics do not biodegrade. Of course plastic breaks, tears and cracks. It weathers and sunlight makes it brittle, It falls apart – it degrades – but ...
Read More

 

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Plastic eating microbes

Is this a good idea?- much as I hate bad plastic I am rather attached to the computer and Dyson. Will they disappear before my very eyes. Here are some reports on plastic degrading microbes

Daniel Burd, a student at Waterloo Collegiate Institute, recently demonstrated that certain types of bacteria can break down plastic. During his scientific research, Daniel discovered that some types of bacteria in the soil can effectively degrade polyethylene plastic. He eventually isolated two microbial strains belonging to the genus Sphingomonas and Pseudomonas . Here’s a link to his research paper.

You can isolate your own plastic degrading microbes here http://www.instructables.com/id/How-to-isolate-plastic-degrading-bacteria-from-soi/?ALLSTEPS

According to Wikkipedia Nylon 4 or polybutyrolactam can be degraded by the (ND-10 and ND-11) strands of Pseudomonas sp. found in sludge. This produces γ-aminobutyric acid (GABA) as a byproduct.[1]Nylon 4 is thermally unstable.[2]

Studies

The nylon4 portion in the blend films composed of nylon4 and nylon6 was degraded and completely disappeared within 4 months in two kinds of composted soils gathered from different university farms as well as pure nylon4 film reported previously, while the nylon6 portion remained even after the burial test for 15 months. Nylon4 powder was also degraded to carbon dioxide in the degradation test in an activated sludge obtained from a sewage disposal institution in Kogakuin University. Three species of microoganisms (i.e., ascomytous fungi) were isolated through the inoculation from the nylon4 film partially degraded in the soil on a medium containing nylon4 powder as a carbon source. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2307–2311, 2002

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Degradation Initiators & Degradable Plastic

Traditional plastics do not biodegrade. Of course plastic breaks, tears and cracks. It weathers and sunlight makes it brittle, It falls apart – it degrades – but only into smaller pieces of plastic. And that can take hundreds of years. See Why Plastic Doesn’t Rot.

Plastic litter is not surprisingly increasing exponentially with disastrous environmental consequences.

But suppose there was a way of making non-biodegradable plastic, biodegradable? The plastic industry argue that they can do just that by means of chemical adatives known as degradation initiators.

Types Of Degradable Plastics

The ISO (International Organization for Standardization) has defined six types of degradable plastics.

  • Degradable – breaks down in some way.
  • Photodegradable, broken down by light
  • Oxidatively degradable broken down by oxygen.
  • Hydrolytically degradable. Broken down by water
  • *Biodegradable – can be broken down by microbes to mass, water and co2 but with no indication of how long that might take. May also need chemical addatives to make this process possible.
  • *Compostable – degrade at a rate that’s similar to other types of compostable materials, and they result, again, in water, carbon dioxide, humus, and inorganic compounds. Compostable plastics biodegrade naturally.They do not need additonal addatives to break down the polymers as they made from natural materials that microorganisms recognise.

This is a confusing list because the last two (*) seem to refer to the natural process of biodegrading while the others refer to  plastic with added degradation initiators. It is important to note that there is a huge difference. Degradable does not mean biodegradable despite what the plastics industry tries to imply.

What Are Degradation Initiators

Degradation initiators are added to the plastic mix in amounts of up to 2% of the total composition. Very basically, these addatives break the long unnatural plastic polymers into shorter recognisable polymers that microbes can attack and digest – or biodegrade.

English: illustration of the Oxo-Bio-Degradati...

English: illustration of the Oxo-Bio-Degradation is, as the name describes, a two-step process whereby the conventional polyolefin plastic is first oxo-degraded to short-chain oxygenated molecules (typically 2-4 months exposed) and then biodegraded by the micro-organisms (Bacteria, Fungi, etc.). (Photo credit: Wikipedia)

The process happens as follows.

  • Microbes are attracted to the additive;
  • They “crack” the long polymer allowing acces to other microbes and water.
  • Eventually these will break down huge polymers into smaller and smaller bits.
  • These smaller bits are then vulnerableto other microbes.

More Research

That’s the theory and it sounds good BUT as Green Plastics point out

“you can add an additive to normal, petroleum-based plastic that will make it become brittle and crumble in sunlight: this is referred to as making “photodegradable” plastic. Other additives can be put into plastic that will make plastic break down by oxidation: this is referred to as making “oxo-degradable plastic.”

These methods will make the bulk of the plastic appear to disappear; however, the small pieces (or even find “sand”) that is produced by this effect is still small pieces of plastic.  Nothing has changed. Over a matter of years, it is possible for the pieces to become small enough to be assimilated by microorganisms, but there is still a lot of research that needs to be done to verify how long this might take.  In the mean time, they are just very small pieces of plastic.”

Or this by Eco Savvy

“The only difference between “oxo-biodegradable” plastic and petroleum based plastic is the presence of an oxo-formulated additive in concentrations of 1-3% (metal salts) within the petroleum based plastic.  This additive allows the petroleum based plastics to degrade in the presence of oxygen, light, heat and moisture.

Oxo-biodegradable plastic is designed to degrade in the open environment and this short timeframe of biodegradation is not necessary. Furthermore, a high rate of conversion is not desirable because the conversion to greenhouse gases such as carbon dioxide contribute to the warming of the atmosphere, hole in the ozone layer and depletion of carbon available for the soil.”

The Right Place At The Right Time

The difficulty is of course ensuring that the plastic doesn’t start biodegrading in normal conditions so that the strength of the plastic product is not jeopodised. Biodegradation is designed to start in certain extreme conditions.

As 75% ofplastic ends up in landfill, most addatives are designed to work in landfill conditions.

While products may start to degrade outside of  the specified conditions but the process will take much longer.

The obvious flaw in this solution is the wrong product in the wrong place. For example plastic that has been manipulated to degrade quickly in a landfill conditions ending up as litter on the roadside where it will not degrade quickly.

Other Considerations

So, to become degradable, plastic has to be further chemically engineered. Obviously, this is by no means a natural process (as biodegrading is normally understood to be), rather it requires complex chemical eginerring.

The composition of these chemical addatives is secret and known only to the companies who produce them.

Biodegradable plastics are made using traditional (usually petrochemical based) plastics. They don’t always break down into harmless substances.

Confusing & Misleading Marketing

Because the initiators are bio-based this has led to the process being described as bio degradable. .

Which has led to confusion because now bio -degradable plastic could be a compostable plastic that biodegrades naturally OR plastic that has had a degradation initiator added to make it bio-degrade.

Compostable plastic is a plastic that can biodegrade with out chemical addatives within a certain amount of time.

The Guardian reported in October 2014 that

Last month, the FTC sent warning letters to 15 additional marketers, informing them that their claims “may be deceptive”. The FTC also requested “competent and reliable scientific evidence proving that their bags will biodegrade as advertised”. This time, the term of offense is “oxodegradable”, implying the bag will break down in time when exposed to oxygen.

And

“The plastic is not degrading, it’s fragmenting,” Greene said. Over time, as opposed to breaking down into less hazardous organic components, these plastic products break down into lots of small, equally toxic bits.

Why make plastics degradable?

Why go to the effort of making degradable plastic bags when we already have naturally compostable products such as paper bags and cornstarch bags. Why not use plastic for things we don’t want to rot away like drainpipes and use naturally biodegrading materials for disposable packaging?

Useful stuff to know

Degradable, biodegradable or compostable plastics – whats in a name
Why leaves rot and why most plastics don’t at Why Plastic Doesnt Rot

Degradable, biodegradable or compostable

So most plastics are made from oil and most plastics do not biodegrade. See how and why here… And yet you will find plastics described as degradable ...
Read More

Compostable Plastics

Plastic was the name given to early synthetic products such as cellophane,  that were derived from cellulose. These plastics  were biodegradable. Then they learnt how to make ...
Read More

Biodegrading and degradation – Plastic Lifespan,

So most plastics are made from oil and most plastics do not biodegrade. See how and why here... But what does that actually mean? Biodegrading Biodegradation ...
Read More

Plastic eating microbes

Is this a good idea?- much as I hate bad plastic I am rather attached to the computer and Dyson. Will they disappear before my very eyes ...
Read More

Degradation Initiators & Degradable Plastic

Traditional plastics do not biodegrade. Of course plastic breaks, tears and cracks. It weathers and sunlight makes it brittle, It falls apart – it degrades – but ...
Read More