There is an emerging trend in the packaging industry today and its name is oxo-biodegradable plastic carry bag. By now most of the general public has either heard, experienced or read about this new type of packaging technology. But has it gained the popularity it deserves? Why is it not in large scale circulation? There are still a number of misconceptions about this kind of carry bag simply because it carries the tag line of ?plastic?.
Because polyolefins are not made by nature, many environmentalists assume that there are no biological mechanisms for their biodegradation. They ignore the fact that abiotic processes play a vital role in biodegradation.
What then is oxo-biodegradable plastic? Conventional plastic bags used weren’t biodegradable, but now can be made biodegradable by adding certain transition metal compounds. These bags are economical and better for the environment.
The commonly used transition metal ions in commercial oxo-biodegradable plastics are manganese, iron, cobalt and nickel. None of these are ?heavy metals? and none have been shown to be eco-toxic. 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 Plastic bags. At the end of its useful life the plastic bag falls apart and completely biodegrades leaving no harmful residue. And whats more interesting to note is that the plastic does not just fragment, but will be consumed by bacteria and fungi. When it has reached the stage of fragmentation it is no longer a plastic, its just like any other natures wastes, and , is biodegradable in the same way as that of nature’s waste , such as straw and twigs. This process will continue till the entire material has biodegraded to nothing more than carbon dioxide , water and humus . It does not leave any fragments of plastic in the soil (ASTM 6954-04). Therefore biodegradation is the process of breaking down of organic substances with the help of other living substances like bacteria and microbes.
Ours is a tropical climate. Biodegradation is favored by a tropical climate which in turn favours the growth and proliferation of temperature loving bacteria known as thermophiles. They aid in the rapid oxo biodegradtion of oxo biodegradable bags also know as Life Controlled Plastics.
Although oxo-biodegradable plastics were invented for use in packaging and in agriculture over 30 years ago, they had not until recently gained the popularity.
One misconception is that oxo-biodegradable plastic causes pollution of oceans and seas due to plastic wastes floating in the ocean currents and consequent damage to sea mammals that ingest them by mistake as food. In other reports, mammals have become entangled in some forms of packaging and in particular by netting from fishing vessels. They are unlikely to be oxo-biodegradable polyolefins since most of these materials float on the surface where they are rapidly oxidised under the influence of UV light and oxygen.
Another common misconception is that transition metal ions that are present in oxo-biodegradable plastic is harmful to soil and has adverse effects on humans through the food chain but on reality a risk analysis carried out by the UK Food Standards Agency has shown that all the important transition metal ions used as catalysts of oxo-biodegradation are widely distributed in agricultural soils and taken up by the foods that humans eat, and in drinking water. Some of them, typically iron, cobalt and manganese are essential trace elements, all obtained from foodstuffs and drinking water. For example, high concentrations of cobalt are found in fish (0.01 mg/kg), nuts(0.09 mg/kg), green leafy vegetables (0.009 mg/kg) and fresh cereals (0.01 mg/kg).Cobalt is also included in some multi constituent licensed medicines, at a maximum daily dose of 0.25 mg. Cobalt is an essential trace element and Co deficiency has not been reported in humans presumably because of its widespread availability from food and water. Similarly, nickel is present in a number of enzymes in plants and microorganisms, and in humans it influences iron absorption and metabolism. It is found in a variety of foods as ionic Ni, particularly in pulses, Oates and Nuts.
Oxo ? biodegradable plastic is believed to leave residual plastic particles in the soil after its biodegradation, but this is not true either. Oxo-biodegradable plastics, after modification by environmental oxidation, are no longer plastics. Before oxidation, they are hydrophobic and cannot support the growth of micro-organisms, After exposure to environmental influences (oxygen, light and/or heat) they act as nutrients for bacteria and fungi, which colonise the surface of the oxidised plastic. And whats more interesting to note is that the plastic does not just fragment, but will be consumed by bacteria and fungi. When it has reached the stage of fragmentation it is no longer a plastic, and , is biodegradable in the same way as that of nature’s waste , such as straw and twigs. This process will continue till the entire plastic has biodegraded to nothing more than carbon dioxide , water and humus . It does not leave any fragments of plastic in the soil (ASTM 6954-04).
Oxo-biodegradable plastics can be recycled with conventional plastics. They can also be incinerated for complete energy recovery.
Any bag cannot be called a biodegradable bag unless tested under a standard specification.Tests performed according to ASTM D6954-04 tell the industry and consumers what they need to know about the bag ; degradable, biodegradable and non phyto-toxic.
Many plastic bags end up in landfills due to the collection of municipal solid waste. It is a fact that the temperatures in landfill is much higher than the ambient temperatures and has a lot of microbial activity and moisture. At the surface and several meters below there is enough oxygen and water for aerobic biodegradation of organic matter to take place. When oxo biodegradable plastic is used these factors speed up the process of degradation. This will allow free flow of air and water through the upper layers of the land fill which will in turn biodegrade organic materials rapidly in the MSW aerobically and thus eliminate the production of deadly methane. This again reduces the volume of waste in the landfill and increase the life of the land fill.
Having sorted out these common misunderstandings it is clear that oxo-biodegradable plastic is not an evil, but instead the need of the hour for a safe and environment friendly form of packaging. We need biodegradable plastics today. Oxo- Biodegradable plastics pass all the usual and compulsory eco-toxicity tests carried out in accordance with the international standards laid down by American Standards for Testing and Materials (ASTM D6954-04). Action needs to be taken today to switch to biodegradable plastic before millions of tonnes of synthetic waste is accumulated in the environment . Oxo-Biodegradable bag is the new technology bag that uses low resources compared to other types of materials, it is recyclable, incinerate-able, safe for environment, food grade, FDA approved and also biodegradable.. The new age mantra!!!! .
Ref: Oxo biodegradable plastics ? Prof. Dr. Gerald Scott 18th July 2008
Oxo Biodegradable plastic – Dr G Scott
Oxo biodegradable plastics in landfill – EPI
Author: Goldwin Fernandes