|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 7times 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
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.
Oxo Biodegradable plastics - Prof Gerald Scott.
Oxo biodegradable plastics- Michael Stephans.
Biodegradability of Plastics- Processes & Standards-Prof Gerald Scott.