By Goldwin Fernandes [ Published Date: September 7, 2012 ]
In the wake of environment concern today, with
all the hype that the media has given to the so called ill effects the use of
plastic bags have on the environment, the consumers are led to believe that
plastic is an evil to be extinguished. They find themselves in a position of
whether or not to accept or refuse a plastic carry bag offered in a grocery
store, mall, shopping centre etc.
The solution to this is the use of
Oxo-Biodegradable bags. Plastic made from oil , i.e.,conventional plastic
bags used weren't biodegradable,but now can be made biodegradable by adding
certain salts of transition metals. These bags are economical and better for
the environment . They contain salts of cobalt , iron or manganese which are
trace elements required in the human diet and are hence not harmful. These
should not be confused with toxic heavy metals like lead , mercury, cadmium
and chromium which are not used in the manufacture of Oxo-Biodegradable bags.
At the end of its useful life the bag falls apart and completely biodegrades
leaving no harmful residue. And whats more interesting to note is that the
bag does not just fragments, but will be consumed by bacteria and fungi. When
it has reached the stage of fragmentation it is biodegradable in the same way
as that of nature's waste , such as straw and twigs. This process will
continue till the entire bag has biodegraded to nothing more than carbon
dioxide , water and humus . It does not leave any fragments of the bag in the
soil (ASTM 6954-04).
We need biodegradable carry bags today because
tonnes of synthetic plastic waste is entering the world's environment
everyday and will remain there for an extended period of time . Oxo-
Biodegradable bags pass all the usual and compulsory test such as
Degradability, Biodegradability and Toxicity tests carried out in accordance
with the international standards laid down by American Standards for Testing
and Materials (ASTM D6954-04).
One of the benefits of Oxo-Biodegradable bags
is that it can be recycled as part of the normal plastic waste stream. Apart
from that it can be composted (not as per ASTM D6400), left in a landfill to
naturally biodegrade or can be incinerated with energy recovery and be used
as fuel. This goes to show that there is always development in the field of
polymers.
Environmentalists who lack technical expertise
in this field suggest the use of paper bags , cloth bags or jute bags as an
alternative. They are unaware of the negative effect these alternatives have
on the environment. The process of making paper causes 70% more atmospheric
pollution than manufacture of plastic bags . Paper bags use 300% more energy
to produce and the process of making paper uses huge amount of water and
creates a very unpleasant waste . It would take around 7 times the number of
trucks to transport the same number of paper bags creating 7 times more cost
and transport pollution . Besides cotton and paper contributes to greenhouse
gases which are a main factor of the much dreaded global warming. Paper will
disintegrate when wet which is not the same as bio-degradation . Paper bags
are 5 times more expensive .
Oxo-Biodegradable bags are certified as safe
for the environment and for any food contact application . Another important
feature of the Oxo-Biodegradable bag is that it can be programmed to degrade
in whatever timescale required . The average life of the Oxo-Biodegradable
bag is 12months , but shorter periods such as 4 months and longer time
periods can be programmed during the manufacture. During this period the bags
are re-used for shopping , or for use as bin liners etc. This is a popular
choice of material for use in agriculture and widely used around the world.
Long term re-usable shopping bags, be it cloth
or jute or paper is not the answer to our problems. They are much thicker and
more expensive , and a large number of them would be required for the weekly
shopping of the average family. They are not hygienic unless constantly
cleaned after each use . They have the highest GWP (Global Warming Potential)
as per the latest report (Feb 2011) of UK Government Environment Agency -Life
Cycle Assessment of Plastic , Paper and Reusable bags. The GWP of cotton
carrier bag is 10 times more than that of any other carrier bag. Whilst
sometimes called “Bags for Life“ they have a limited life , depending on the
treatment they receive ,and become a very durable problem when discarded .
Shoppers do not always go to the shop from home , where the re-usable bags
would normally be kept , and consumers are unlikely to have a re-usable bag
with them when buying on impulse items like clothing , groceries , CD's ,
magazines ,stationery etc .
If people want to incinerate oxo-biodegradable
products with heat recovery , or recycle them , or re-use them , then that
can be done . The key point is what happens to the bags which is not
collected , and gets into the environment as litter. Conventional plastic
will subsist in the environment for many decades , but oxo-biodegradable bags
will degrade in a short time leaving no harmful residue . It would be
interesting to note that the total plastic consumption is only 6% to 8%of
litter , in which plastic carry bags represent a very small fraction.
The second main type of biodegradable bags is
hydrobiodegradable or compostable bag . The first stage of degradation is
hydrolysis. These materials biodegrade as per the specification 6400.(ASTM
D6400). The life of these bags is about 1 year. The compostable technology is
equally good; but a bit more costlier. The film can be composted in
industrial composting (ASTM D6400) in two months to become manure and in home
composting in 3-4months to form manure along with other organic matter.
When the film is dropped as a litter, the film
starts bio-degradation and the rate of bio-degradation depends upon the
environment it attains. If the film is exposed to water and organic matter
constantly it would biodegrade and become manure. If it is exposed to soil or
water or sewage conditions also it can biodegrade.
For a bag to be tagged as biodegradable they
need to be tested and certified under certain specifications. The
specifications of various countries for Oxo- Biodegradable are U.K. British
Standard 8472, U.S. ASTM. D6954-04, UAE 5009:2009, France French Accord T51-808.
The specifications for compostable bags are EN13432, ASTM D6400, IS/ISO
17088.
There is a lot of litter today, and there will
always be some litter. Hopefully education will reduce the litter problem
over several generations . Action needs to be taken today to switch to
biodegradable bags before millions of tonnes of synthetic waste is
accumulated in the environment . Oxo-Biodegradable and compostable materials
are the new materials. The new age mantra !! . Litter is the careless
behavior of human beings in relation to waste disposal . In the end all that
can be left to say is , nothing is as harmful as our attitude.
About the Author
Goldwin
Fernandes
B.E., M.Tech, M.I.E.,M.I.S.T.E., F.I.V
Completed Engineering in 1992, then worked as
an R&D Engineer for a brief peroid. He has also 7 years of experience in
the middle East before he returned to India . Since then he has been actively
involved in conducting seminars at all levels and sharing information about
the advantages of using various kinds of Biodegradable Bags and its effect on
the environment.
Material Reference
Oxo Biodegradable
plastics - Prof Gerald Scott.
Oxo biodegradable plastics- Michael Stephans.
Biodegradability of Plastics- Processes & Standards-Prof Gerald Scott.
Bioplastics -naturtec
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