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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

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16 thoughts on “Degradation Initiators & Degradable Plastic

  1. I hope this one works – for some reason I cannot reply to you. Yes, I totally agree with you – that is where we, the consumer, have to educate ourselves, change our habits and so change the world. Hmmmmm…….thoughtful pause….. Thanks for dropping by -nice to see you over here.

  2. Hola, si la degradación de los pláticos no es una buena opción, que pasa con los plásticos que van completos al ambiente?, entiendo que la manera más viable es desarrollar pláticos unicamente biodegradables, pero no todo producto proveniente de los polímeros podría ser sostenible a nivel económico, por lo tanto la mayor parte de la población mundial, que se encuentra en un nivel socioeconómico medio-bajo, los podría consumir por su alto costo. Me parece que su posición acerca del efecto que este proceso causa en los seres humanos y animales es un poco radical.
    Yo soy de Costa Rica y en nuestro país tenemos un sistema de procesamiento de la basura que se denomina relleno sanitario, el cuál, no deja salir de su perímetro ningún tipo de material de desecho al ambiente.

  3. They should go out of business. Their products are crap, they break within three months of minimal/normal use and the staff will not answer any questions. So unless you know of a person who can fix these crappy machines don’t waste your time. There are better water filters out there. And seriously if you have no electricity what good will this product do for you…. That is of course if it is still working. Go with another more well trusted brand.

  4. Biodegradable plastic and packaging is a modern necessity for our ever-endangered environment.
    Now PLA has been used to line the indoors of Paper Cups in place of the oil based lining additional usually used, create Plastic Cups, Plates, Carrier Bags, Food Packaging and even Nappies.
    Eco Pure is our proprietary blend of organic materials that does not modify the base resin to which it is added.

    Thanks a lot for your information

  5. Great info, thanks. I live in Egypt and we are ‘TRYING’ against all odds. I was checking the internet for a magazine article and all I needed was explained above.

  6. I’ve been screaming about disposable plastics for years. When I blogged about the Great Pacific Garbage Patch, I included the same findings about plastic disintegration as Biodegradeable Girl. Plastic fragments leach the same toxic chemicals as we’ve been warned about when microwaving food in plastic containers, and heating plastic baby bottles that leach bisphenols. Yet we environmental bloggers still argue with people that we are indeed impacting everything on earth with our trash. The disbelievers just don’t get that earth and it’s atmosphere is a CLOSED SYSTEM. Everything ends up somewhere else.

  7. This is excellent information. Please check out the website for Ecoloblue.com
    and link to their Ecolo-Life link. I would greatly value your feedback on
    where you believe this product falls.

    Thank you

  8. Compostable Plastics versus Degradable Plastics

    Worldwide, both industry and consumers have experienced a significant push to purchase environmentally-responsible products. Unfortunately, some companies have responded to the green movement by developing less than responsible products and falsely marketing them as environmentally-friendly. Degradable or oxo-degradable plastics are a prime example of these misleading products. This paper is meant to fully explain the severe problems associated with degradable plastics and the vast differences between degradable plastic and truly compostable plastic materials.

    For several years degradable or oxo-degradable plastic products have appeared on the market claiming to be biodegradable and compostable. Degradable plastic is manufactured by combining polyolefines with metal-containing additives which, when exposed to sunlight, allow the plastic material to break down into small fragments over a relatively short period of time. These types of plastics pose large health and environmental concerns. The additives used to trigger the fragmentation process contain heavy metals which have been proven to cause adverse effects on humans and the environment. Because conventional plastic is not biodegradable, the tiny fragments left behind from degradable plastics work to transport these heavy metals and carry an extremely high potential of persistency in the environment and bioaccumulation of heavy metals and plastic fragments in organisms.

    The plastic fragments attract and house hydrophobic elements such as Polychlorinated biophenyls (PCBs) and Dichloro-Diphenyl-Trichloroethane (DDT) up to one million times normal background levels. As a result, floating plastic fragments act as a poison pill and cause endocrine disruption in the food chain. Endocrine disruption is caused by the absorption of synthetic chemicals into the body. The chemicals can either mimic or block hormones and disrupt normal body function. Both animals and humans can experience significant health problems due to endocrine disruption, such as reduced embryonic development, increased miscarriages, severe birth defects and cancers. In addition to their potential for endocrine discruption, the fragments from degradable plastics pose a large threat to marine life, birds and small mammals. Due to their small size, the plastics fragments are easily transported by waterways and ocean currents. They are often mistaken by animals, especially marine life and birds, as food. Because plastic has a high molecular weight and the nature of its chemical bonds – plastics cannot be digested and do not provide any nutrients. Once ingested, animals experience a false feeling of hunger satisfaction, which will eventually lead to problems such as, reduced migration, reduced reproduction, starvation and death.

    Industry and consumers looking for a true sustainable substitute to conventional plastic materials should instead choose a certified 100% compostable plastic. Biodegradable material will, under ambient conditions, be broken down by microbes in the environment and be consumed as a food source. This is the process that converts carbon into energy and maintains life.

    In order for plastics to fully biodegrade they must go through a two-step process. First, the long polymer chains are shortened at the carbon-carbon bonds. This process is initiated by heat, moisture, microbial enzymes or other environmental conditions, depending on the polymer. This is referred to as degradation, because the plastic becomes weak and will easily fragment. The second step occurs when the shorter carbon chains pass through the cell walls of the microbes and are used as an energy source. The carbon chains are consumed as a food source and are converted into water, biomass, carbon dioxide or methane. A true biodegradable material must go through both steps of the process, unlike degradable plastics which only complete the first step. (See Figure Below)

    When products are designed to be fully compostable, they should meet ASTM Standard D6400 (for Compostable Plastics). Products which meet the ASTM requirements will:

    1.Be converted to carbon dioxide, water and biomass at the same rate as kraft paper and other organic materials.

    2.Completely disintegrate and not be visible or need to be screened out after composting.

    3.Be completely safe for the environment. Degradation must not cause any harmful by-products and the compost must be able to support plant growth.

    True compostable plastic products have been tested in an approved third-party laboratory for conformance to the ASTM Standards and the results have been confirmed in an independent scientific analysis. Compostable products which meet all requirements per the ASTM Standard carry the Compostable Logo. Usage of the Compostable Logo is regulated by the Biodegradable Products Institute (BPI) and the US Composting Council (USCC).

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