Transcript Plastic and Recycling - NTU

Plastic Alternatives
The manufacture of plastics requires the use of nonrenewable materials such as petroleum and natural
gases. Many plastics are harmful to the environment as
they take years to biodegrade and can leach chemicals.
An alternative must be found.
Alternatives
Carrier Bags:• An alternative to using plastic bags would be to use reusable bags
such as cloth bags which are durable, reusable and washable so
they do not have to be thrown away and will not contribute to the
build up of waste in land fill sites.
Plastic Bottles:• An alternative to using plastic bottles would be to use glass bottles
as they do not contain BPA and are therefore better for us and
babies as glass does not leach such chemical when heated like
plastic does.
Biodegradable Plastics
•
These plastics break down when exposed to sunlight (UV), water, dampness,
bacteria, enzymes, wind abrasion and some instances rodent pest or insect
attack are also included as forms of biodegradation or environmental
degradation.
•
This degradation in some cases only works if the conditions are right for it,
i.e. at landfill and composting systems.
•
Starch powder has been used. It has mixed with a plastic as a filler to help
it degrade more easily but it does not completely breakdown the plastic so
is not all that good for the environment as it fragments the plastic.
•
Bacteria have been genetically engineered which synthesise a completely
biodegradable plastic but they are very expensive at present.
Bags are Used, Reused and Recyclable.
2. The degradation process is triggered
by heat, UV light and/or mechanical
stress.
3. In approximately 2 years bags are
fully degraded to carbon dioxide, water
and biomass - photosynthesis begins,
trees and green plants grow!
Biodegradable Plastics
Ecoflex:• A biodegradable polyester for food packaging has been
made by a German company who specialise in chemicals
called BASF.
Oxo-biodegradable:• It is a polyolefin plastic to has metal salts added to it that
act as a catalyst.
• As long as the plastic has access to oxygen (as in a littered
state), these salts speed up degradation.
• Once degraded to a small enough particle they can interact
with biological processes to produce to water, carbon
dioxide and biomass.
• The process is shortened from hundreds of years to
months for degradation and thereafter biodegradation
depends on the micro-organisms in the environment.
Compostable Plastics
 Compostable Plastics are a new generation of plastics which
are biodegradable and compostable.
 They are derived generally from renewable raw materials like
starch (e.g. corn, potato, tapioca etc), cellulose, soy protein,
lactic acid etc.
 They are not hazardous/toxic in production and decompose
back into carbon dioxide, water, biomass etc. when
composted.
 Some compostable plastics may not be derived from
renewable materials, but instead derived made from
petroleum or made by bacteria through a process of microbial
fermentation.
Degradation of
compostable
plastics…
Compostable Plastic Resins
 Currently, there are a number of different compostable plastics
resins available in the market and the number is growing
every day.
 The most commonly used raw material for making the
compostable plastics is corn starch, which is converted into a
polymer with similar properties as normal plastic products.
 Other compostable resins are available made from potato
starch, soybean protein, cellulose and as well from petroleum
and petroleum by products.
Corn Starch Polymer
Compostible Plastic Resins Continued…
 It is counter intuitive to think that compostable resins could be
derived from petroleum, when all normal plastic products are
derived from petroleum and are non compostable.
 However, there are certified compostable resins available in
the market, derived from petroleum and the field of
compostable plastics is constantly evolving with new materials
and technologies being worked on and being brought to
market.
 There is even research underway to make compostable
plastics from carbon dioxide which would utilise the gas
produced by burning fossil fuels.
However, we want to try and
reduce our use of fossil fuels
and move toward the use of
raw materials…
Biodegradability and 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 90180 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 important to make the distinction between
degradable, biodegradable and compostable. These
terms are often (incorrectly) used interchangeably.
Criteria for Compostible Plastics

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.
Biodegradeable Plastics:
 Biodegradable Plastic is plastic which will
degrade from the action of naturally occurring
microorganism, such as bacteria, fungi etc.
over a period of time.
 However, there is no requirement for leaving
"no toxic residue", and as well as no
requirement for the time it needs to take to
biodegrade.
Degradeable Plastics:
 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.
 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.
Estimated Composting Times
Home Composting
 Home composting rates are slower and can
vary, depending on how frequently the pile is
turned over, the moisture and material content
and the temperature.
Commercial Composting
 Commercial composting facilities grind the materials, turn
over the piles and reach high temperatures, thus reducing
the amount of time it takes to compost and, is thus, the
recommended method for composting these products.
 http://biobasics.gc.ca/english/View.asp?x=790