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Understanding Degradable / |
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Overview
Degradable
Materials that lose their chemical and mechanical properties within a period of time by any means. This can be caused by sunlight, heat, pressure or a combination of both.
Biodegradable
Material that decomposes into the basic elements of nature, such as carbon, hydrogen, oxygen and nitrogen, by the action of microorganisms.
The process
An organic decomposition process is called biodegradable, while a chemical process is called degradable. Once the chemical process has started, the resulting pieces change their molecular structure, resulting in smaller molecular weights that become bioactive, allowing them to biodegrade. These pieces are then thoroughly reincorporated to nature, through the action of microorganisms.
The Good News
Degradable products are not compostable. Most of the products using the label ‘Degradable’ (plastics) will degrade as a result of physical and chemical impact (fracture into smaller pieces of plastic). They are oil based products with special additives that assist their 'fragmentation'. Biological activity is not a significant part of the degradation of these products, or the process is too slow to earn the classification Biodegradable or Compostable (the Biological degradation will typically take many years).
‘Bioplastics’ are a new generation of biodegradable and compostable plastics, derived from renewable raw materials such as starch (e.g. corn, potato, tapioca etc), cellulose, soy protein, lactic acid, etc, not hazardous in production and decompose back into carbon dioxide, water, biomass, etc., in the environment where discarded. Corn starch is currently the main raw material being used in the manufacture of ‘bioplastic’ resins. Mater-Bi (main component corn-starch), and PolyActide (PLA) (made from corn-starch as well) are currently the 2 main resins (raw materials), being used today in the production of compostable and biodegradable plastics and are certified for compostability under standards for soybean protein, cellulose etc. Most of these are currently not certified for compostability, though some are for biodegradability. The field of ‘bioplastics’ is constantly evolving. New materials and technologies are continuously being developed brought to market.
Heat Resistance
Corn-starch based products (bags, corn cutlery, cold cups, drinking straws): 120° F
Potato and tapioca starch based products (potato cutlery): 220° F.
Biodegradability & Compostability
‘Bioplastics’ can take different length of times to totally compost, based on the material. These products are meant to be composted in a commercial composting facility, where higher composting temperatures can be reached, and the process can take between 90-180 days. Most existing international standards require a biodegradation of 60% within 180 days along with certain other criteria for the resin or product to be called compostable. It is also important to make the distinction between degradable vs. biodegradable vs. compostable as often these terms are used interchangeably.
Compostable Plastic is plastic which is "capable of undergoing biological decomposition in a compost as part of an available program, such that the plastic is not visually distinguishable and breaks down to carbon dioxide, water, inorganic compounds, and biomass, at a rate consistent with known compostable materials (e.g. cellulose), and leaves no toxic residue." as defined by the American Society for Testing & Materials (ASTM).
In order for a plastic to be called compostable, three criteria need to be met:
- Biodegrade - breaks down into carbon dioxide, water, biomass at the same rate as cellulose (paper).
- Disintegrate - the material is indistinguishable in the compost, that it is not visible and needs to be screened out.
- Eco-toxicity - the biodegradation does not produce any toxic material, and the compost can support plant growth.
Biodegradable Plastic is plastic which will degrade from the action of naturally occurring micro-organisms, such as bacteria or fungi, over a period of time. Note that there are no requirements for leaving "no toxic residue", as well as no requirements for the time needed for biodegradation.
Degradable Plastic is plastic which will undergo a significant change in its chemical structure under specific environmental conditions resulting in a loss of some properties. Please note that there are no requirements stating the plastic must degrade from the action of "naturally occurring microorganism" or any other criteria required for compostable plastics.
A plastic, therefore, may be degradable but not biodegradable - or it may be biodegradable but not compostable (that is, it breaks down too slowly to be called compostable or leaves toxic residue).
Recognized Standards
The following are current international organizations that Gordon Food Service® recognizes as having established standards and testing methods for compostability:
American Society for Testing and Materials ASTM-6400-99
European Standardization Committee (CEN) EN 1 3432
International Standards Organization (150) I S 0 14855 (only for biodegradation)
The ASTM, CEN and DIN standards specify the criteria for biodegradation, disintegration and eco-toxicity for a plastic to be called compostable.
Biodegradability is determined by measuring the amount of C02 produced over a certain time period by the biodegrading plastic. ASTM, IS0 and DIN standards require 60% biodegradation within 180 days. The EN 13432 standard requires 90% biodegradation within 90 days.
Disintegration is measured by sieving the material to determine the biodegraded size and less than 10% should remain on a 2mm screen for most standards.
Eco-toxicity is measured by having concentrations of heavy metals below the limits set by the standards, and by testing plant growth by mixing the compost with soil in different concentrations and comparing it with controlled compost.