Biodegradable Facts

Plastics belong to a chemical family of polymers they are made up of a long chain of molecules containing repeated units of carbon atoms. Because of this inherent molecular stability (high molecular weight), plastics do not easily breakdown into simpler components. However plastics do decompose though not fully and that too over a long period of time (100 to 500 years). Commercially available plastics (polyethylene, polypropylene, etc) have been further made resistant to decomposition by means of additional stabilizers like anti oxidants.

By suitably reengineering the polymer or deriving the polymer from a natural source. Such a kind of polymer will decompose in municipal land fills. The decomposition or degradation of such reengineered plastics which are constructed of carbon and hydrogen atoms, results from the breakdown of these bonds in each molecule, leading to a lowering of the molecular weight and a resultant loss of strength and durability. Hence the carbon nutrients which they contain can be made available to the environment.

Biodegradable Plastics need to meet the specified norms established to claim biodegradability, termed as EN 13432(European) norms and ASTM D 6400 (United States). The biodegradable products are tested in a specified laboratory and various tests under norms are carried on the plastics. The product has to be biodegradable within 90 days leaving no heavy metals or carcinogenic residue or heavy metals in the degraded environment.

Biodegradable Plastics are such that the biodegradation results from the action of naturally occurring micro-organisms such as bacteria, fungi, algae etc. This mechanism of degradation is referred to as Biodegradation. Biodegradable plastics are those which in a suitable environment completely disintegrate into carbon-dioxide, water and biomass.

Compostable Plastics where biodegradation results by a biological processes during composting to yield CO2, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and leave no visible, distinguishable or toxic residue.

Degradation is a process whereby very large molecules are broken into smaller molecules or fragments. Normally, oxygen is incorporated into these molecular fragments. Typically, strong, tough plastic films become weak and brittle as a result of oxidative degradation. This outcome is because the molecules of which the films consist become much smaller. Degradation can be caused by heat, or exposure to UV light and is enhanced by mechanical stress.

Biodegradation is the process by which microorganisms (microbes such as bacteria, fungi or algae) convert materials into biomass, carbon dioxide and water. Biomass is a general term used to refer to the cells of the microorganisms that are using the material as a carbon source to grow on.

“Degradable Plastic: a plastic designed to undergo a significant change in its chemical structure under specific environmental conditions resulting in a loss of some properties that may vary as measured by standard test methods appropriate to the plastic and the application in a period of time that determines its classification.” [ASTM D883-99] – American Society for Testing and Materials.

When degradable plastics break down into smaller molecules, eventually they will be small enough to be consumed by microorganisms and so biodegradation occurs. In essence then, all degradable polymers need to eventually biodegrade and so should be tested for 'biodegradability' than just 'degradability'.

The polymer system of biodegradation essentially requires modification of the polymer matrix to make the polyolefin biodegradable which leads to chain scissions and hence a lowering of molecular weight besides creating a hydrophilic surface which can be bio-assimilated by microorganisms in the soil. Hence the unique feature would be the controlled modification of the polymer matrix.

The biodegradable plastic product can only be used once. Once the polymer is rendered into a bag and its utility is complete. The bag can be disposed. The polymer cannot be retrieved from the bag by recycling. The life span for a converted product is 8 months to a year. The biodegradation time span is within 90 days in a compost facility.

Chemically the biodegradable film is different from a conventional virgin plastic film the chemical constituent is engineered such that biodegradation  can be initiated as the polymer reaches a temperature of 60°C in a compost facility. Physically the properties of the biodegradable film are only slightly modified but at the same time they do not in any way compromise on the integrity and utility of the film for the respective intended application.  

The degradation process starts by reaching temperatures of 60°C in a compost facility. Once this temperature is reached bacteria can feed on the polymer and biodegrade the product to biomass, water and CO2.

Colouring and Printing do not change the mechanisms of degradation. The quality and consistency of colouring and printing on degradable films is comparable to that of conventional virgin plastic films.

The degradable films are safe for use as they pass the toxicity tests as per EN 13432 and ASTM D 6400 norms. Hence their use in these kind of applications is not much different from that of virgin conventional plastic films.

Biodegradable films are non toxic and conform to toxicity tests as per accepted protocols. They are food grade and can be used for storing food items in similar applications as for virgin conventional plastic films.

• Responsible plastic that is environmentally accountable.  
• Saves tons of valuable landfill space. 
• Indirectly renders savings of space and disposing issues.
• Lower toxicity levels.
• Lower metal residue – no lead poisoning, etc
• No carcinogenic elements.
• The degraded polymer does not affect green plantations or farming.

The so-called ‘oxo-degradable plastics’ are not suitable for organic recovery. So called ‘oxo-degradable plastics’ (i.e.: polyolefins with metal-containing additives) are sometimes advertised as being ‘biodegradable’ or even ‘compostable’. Such claims are misleading if they are not substantiated by showing compliance with the relevant European standards EN 14995 or EN 13432. These, define the requirements for materials which can be called ‘compostable’. In the case of packaging, such claims are bound by legal definition under EN 13432. There are no known ‘oxo-degradable’ materials in the marketplace which fulfill either of these standards. Claims of compostability for such products are therefore wrong and untrustworthy.

In Italy and Australia lawsuits resulted in fines for using misleading claims in the marketing of such products. Industry companies providing truly compostable plastic products will make use of the established, producer independent certification schemes proving compostablity on the basis of tests according to EN 13432 or EN 14995.

ref: http://www.european-bioplastics.org/index.php?id=191 Document: European Bioplastics FAQ paper on bio-plastics