This article has been provided by
the non-profit organisation World Centric you can find them at www.worldcentric.org
Bioplastics
are a new generation of biodegradable
& 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 to carbon dioxide, water, biomass
etc. in the environment when discarded. Corn starch is currently the main raw
material being used in the manufacture of bioplastic resins. Mater-Bi (main
component corn-starch), and Polylactide (PLA) (made from corn-starch as well)
are currently the 2 main resins (raw materials), being used today in the
production of compostable & biodegradable plastics and are certified for
compostability under standards set by international organizations. However,
other resins are coming into the market made from potato starch, 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 with new materials and technologies being worked on and
being brought to market.
Heat
Resistance
Corn-starch based products (bags, corn
cutlery, cold cups, drinking straws) - 120 degrees F
Potato and tapioca starch based products
(potato cutlery) - 220 degrees F
Biodegradability &
Compostability
Bioplastics can take different length of
times to totally compost, based on the material and are meant to be composted in
a commercial composting facility, where higher composting temperatures can be
reached and is between 90-180 days. Most existing international
standards require 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 site 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." American Society for Testing &
Materials (ASTM). In order for a
plastic to be called compostable, three criteria need to be met:
- Biodegrade - break 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 microorganism, such as
bacteria, fungi etc. over a period of time. Note, that there is no requirement
for leaving "no toxic residue", and as well as no requirement for the
time it needs to take to biodegrade.
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 is no requirement that the plastic has to be
degrade from the action of "naturally occurring microorganism" or any of the
other criteria required for compostable plastics.
Standards
There are currently few international
organizations which have established standards and testing methods for
compostability, namely:
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 CO2 produced over a certain time period by the biodegrading
plastic. ASTM, ISO and DIN standards require 60% biodegradation within 180
days. The EN13432 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.
In the USA, the BPI ( Biodegradable Products Institute ) certifies bioplastics under the ASTM
ASTM-6400-99 , standard for "compostable plastics" and
awards their logo to products which pass this certification.
see also Bio Plate facts
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