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19 Biodegradable Facts

So before we get into the terminology and definitions, we wanted to address some questions on the site regarding Biodegradable Facts.

Biodegradable Facts

What does “biodegradable” mean?

‘Biodegradable’ means that living organisms, usually bacteria, can completely break down a substance. This can happen in different ways:

– photo biodegradation – the material is broken down by UV radiation from the sun;

– biological degradation – the material is broken down by biological agents such as bacteria, algae, or fungi. These agents can be found everywhere in nature.

What does compostable mean?

Compostable means that a substance or product has been designed to biodegrade under industrial composting conditions. This means that the material must undergo specific treatment steps under controlled environmental conditions (with a specific temperature and oxygen supply). Industrial composting is used to speed up the process of biodegradation. The resulting material, known as ‘compost’ can be used for different purposes;

What does ‘oxo-degradable’ mean?

The term “oxo-biodegradable” or “Oxo-Degradable” refers specifically to plastic materials that have been manufactured with additives that cause the material to degrade in a two-stage process involving photolysis and subsequent oxo-biodegradation. In the first stage, exposure to light causes the plastic’s polymers chains to become weakened by scission so that they readily break into shorter segments. In the second stage, these shorter segments are degraded by microbes into carbon dioxide, water, and essential organic nutrients. In the final stage of oxo-degradable plastic’s biodegradation process is the same as those from traditional photo-biodegradable plastics without additives.

What does ‘photo-biodegradable‘ mean?

Photo-biodegradable means that a material or product has been designed to biodegrade under light exposure. This means that the material must undergo specific treatment steps under controlled environmental conditions (with required temperature and humidity) before being exposed to UV radiation from the sun. When exposed to sunlight, either in open air or through glass, photo-degradation occurs much more rapidly than when no light is available.

Photo-biodegradable plastics are often wrongly named as “oxo-biodegradable.” The two processes are different and incompatible because oxo-degradation requires the addition of metal catalysts to speed up the process. These metals can not be used in photodegradation.

What does ‘compostable packaging’ mean?

Suppose a plastic film or bag is labeled with “compostable” or “100% compostable”. In that case, it means that the entire product will break down into the water, carbon dioxide, and biomass at the same rate as plant materials during industrial composting conditions (see What does ‘compostable’ mean?). If there is no indication on how to dispose of this packaging, it should go to the regular waste.

What does ‘consumer’ packaging mean?

Packaging marked with “consumer” or “domestic” indicates that the package is made out of conventional plastics; it is not designed for composting. These products can be recycled at appropriate recycling facilities (see What facilities are there?).

Where can biodegradable materials be recycled?

Like conventional plastic items, Biodegradable plastics may be recycled where they are collected for recycling. This list evolves depending on new technologies and business initiatives; ask your city or county about facilities near you. However, only products carrying the OK Compost logo will break down within a composting system. Products without this logo can be recycled in a landfill or incinerated.

What is the OK Compost Label, and why should I only choose products carrying this logo?

The US-based organization, OK Compost, certifies compostable plastics and other packaging materials that biodegrade under industrial composting conditions (see What does ‘compostable’ mean?). Only compostable plastics bearing the OK Compost label are designed to work within a composting system; these can not be recycled in landfills or incinerated.

The compostable film may break down, but it will leave behind particles of plastic that will contaminate the Compost and thus will cause problems for users and producers.

What is Compostable Packaging?

Compostable packaging is plastic that breaks down in commercial or industrial composting facilities. It differs from biodegradable plastics as it does not break down at home or in backyard composts, which are less than 40 degrees Celsius (see What happens to plastic under heat?). ACCORDING TO ASTM INTERNATIONAL STANDARDS, the OK Compost label tells you that the product has been certified by an independent authority.


Is PLA, a bio-plastic from corn, compostable?

No. It biodegrades at home and in backyard composts because the heat generated by active bacteria in these systems exceeds 120 degrees Fahrenheit/50 degrees Celsius. In industrial composting (see What happens to plastic under heat?), temperatures are regularly between 110-130 degrees F/45-55 degrees C; this is not hot enough for PLA to break down into carbon dioxide, water, and biomass. For this reason, only products carrying the OK Compost label should be placed in commercial or industrial composting (see What does ‘compostable’ mean?).

What about Bioplastics made with non-food crops like switchgrass?

PLA is often made with corn, but increasingly producers are turning to switchgrass or other non-food crops. These are also not compostable because they need the same temperature and humidity conditions as PLA. When in doubt about a bioplastic product, check its package label for information on what it takes to dispose of it safely (see What happens to plastic under heat?). If there is no indication of how to dispose of these products, they should go to the regular waste.

Are there any advantages to using compostable packaging over conventional plastic?

Compostable plastics are not designed to replace conventional plastics, which remain necessary in many cases. Films marked with “consumer” or “domestic” are made of conventional plastic, not PLA material. However, the advantage of PLA is that it does break down within a time frame where it doesn’t pose problems for landfills and incinerators (see How long do biodegradables last?). Therefore, if the product’s primary use is only temporary, then PLA has benefits because it can be recycled or biodegraded more easily than alternatives like paper or cotton.

What is compostable plastic made out of?

PLA (Polylactide), a type of PLA called PHA (polyhydroxyalkanoate) or Mater-Bi, are the most common materials used in compostable plastics. These plastics are derived from cornstarch, tapioca roots, sugar cane, and other forms of biomass. However, increasing quantities are being generated from switchgrass and other non-food sources. Like their conventional counterparts, these products use fossil fuel resources to make them; however, they biodegrade more quickly than alternatives like paper or cotton.

Does compostable packaging make a difference?

Yes! The shelf life for PLA films is approximately one year or less before decomposing. In contrast, conventional plastics can take up to 1000 years to biodegrade under certain conditions (see How long biodegradables last?). If you buy compostable cups or other disposable PLA products, you will not have to sort through your trash digging for the plastic cup in a year. The cup will biodegrade much more quickly and become part of the soil for new crops.

What happens to plastic under heat? For compostable plastics or other materials to be truly compostable, two conditions must be met: [1] high temperatures (110-130 degrees F/45-55 degrees C) AND [2] a certain level of moisture or humidity. When these proposed standards are met, microorganisms, such as bacteria and fungi, break down the material to return to natural elements. Many cities have facilities designed to treat organic waste this way; however, most backyard composters cannot generate this heat.

Can products made out of compostable material really break down within one year?

If conditions are right, PLA has been known to biodegrade in as little as ten weeks (see How long biodegradables last?) However, time will vary depending on what type of composter is used. An industrial composter designed to reach the ideal temperature and humidity level for optimal breakdown can process it in a matter of days or even hours.

If you are using a backyard compost pile, however, PLA may only break down over the course of months or even years. Without exception, your municipal composting facility must meet certain requirements before they are allowed to accept organic waste with compostable packaging (see What the compostable packaging standards are?).

What are the compostable packaging standards?

As of June 2010, no state or federal laws have been passed regarding compostability. However, all products containing organic material must meet certain breakdown criteria before they are allowed to be sent to a commercial composter. This is enforced by each municipality that sends its waste to one of these facilities. Some areas require that items biodegrade under anaerobic conditions (without oxygen), at 130 degrees F for over five days, while others may only require three months under ambient aerobic conditions (with air) at 70 degrees F. Furthermore, only clean, uncontaminated material will be accepted by most commercial operations; meaning items cannot contain any non-compostable materials, such as paper or plastic.

What is the difference between biodegradable and compostable?

Generally speaking, anything that will break down into natural elements can be considered “biodegradable.” This does not mean that it will necessarily break down in a certain amount of time or under specific conditions. A product could take months to break down, even years, but so long as the material is eventually converted back to the soil, it is considered biodegradable. Many manufacturers commonly confuse the terms because they are popular buzzwords used to describe their products’ environmental benefits. Because there are no standards for what qualifies something to be called “compostable,” one must look at other factors, including how quickly it breaks down, how easy or difficult it is to break down, and what conditions are required for it the process of breakdown. For more information on compostable plastics, see Compostable Plastics.

What does PLA stand for?

Polylactic acid (PLA) is an organic compound made from lactic acid derived from plants such as corn or sugar beets. It has a plastic appearance; however, it will biodegrade when placed in ideal composting conditions. PLA is commonly used in disposable items meant to be composted after use, including food containers, cups, cutlery, and packaging materials.

How long do biodegradables last?

     Sometimes manufacturers will not label their products as biodegradable unless they can compost within ten weeks. If the label states that it meets ASTM standards, this means that the product has been tested and verified on a scientific level so you can be sure that your waste is being handled properly. However, some manufacturers may misinterpret these guidelines by grossly overstating how quickly their items will break down, so always check with your municipality first before composing any of these materials.

Edgar Mclaughlin
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