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Biodegradable plastics are plastics that will decompose in the natural environment. Biodegradation of plastics can be achieved by enabling microorganisms in the environment to metabolise the molecular structure of plastic films to produce an inert humus-like material that is less harmful to the environment. Bioplastics are biodegradable plastics whose components are derived from renewable raw materials. The use of bio-active compounds compounded with swelling agents ensures that, when combined with heat and moisture, they expand the plastic's molecular structure and allow the bio-active compounds to metabolise and neutralize the plastic.

Contents 1 Advantages and disadvantages 2 Mechanisms 3 Environmental concerns 4 Cost of production 5 References 6 See also 7 External links

The advantage of biodegradable plastics is that, in the proper conditions (sun, moisture, oxygen, etc), the plastics degrade to the point where organisms can digest them. This reduces problems with litter and reduces harmful effects on wildlife. Composting is a good methodology.

The main disadvantage with oil-based biodegradable plastics is that their degradation contributes to global warming through the release of carbon dioxide as a main end product. This does not apply to starch based plastics as they are formed from carbon which is already in the ecosystem (via photosynthesis). Another disadvantage with biodegradable plastic is that degradation occurs very slowly, if at all, in a sealed landfill. Also, biodegradable plastics cannot be mixed with other plastic sent for recycling: This damages the recycled plastic and reduces its value.

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Materials such as polyhydroxyalkanoate (PHA) biopolymer are completely biodegradable. Fully biodegradable plastics are more expensive, partly because they are not widely enough produced to achieve large economies of scale.

Other types are semi-biodegradable, but avoid increased costs by using existing manufacturing processes and are based mainly on conventional non-biodegradable resins. These plastics can be manufactured to be clear or opaque, and in any color. A disadvantage of this approach is that the products of degradation of the conventional material will remain in the environment for years.

Over 200 million tonnes of plastic are manufactured annually around the world, according to the SPE^{[citation needed]}. Of those 200 million tons, 26 million are manufactured in the United States. The EPA reported in 2003 that only 5.8% of those 26 million tons of plastic waste are recycled, although this is increasing rapidly.

Two widely cited articles by T.Gerngross et al. in 1999^[1] and in 2000^[2] indicate that the energy required to produce one kilo of polyhydroxyalkanoate (PHA) biopolymer (by fermentation) from plants was equivalent to the consumption of 2.65 kg of fossil fuel while the production of one kilo of polypropylene required only 1.54 kg of fossil fuel.^[3] These balances include the energy required to produce the feedstock as well as the polymer.

Life cycle assessment data for the production of polyhydroxyalkanoates from sugar cane (Brazil) was not mentioned in these studies. Manufacturing of PHAs by fermentation in Brazil enjoys a favorable energy consumption scheme where bagasse is used as source of renewable energy.^[4]

Technology to produce PHA is still in development, and energy consumption can be further reduced by eliminating the fermentation step,^[5] or by utilizing food waste as feedstock.^[6]

Starch-based biopolymers (produced by various manufacturers) and polylactide (produced by NatureWorks in the US) require less fossil fuel than polymers from non-renewable sources, but have the disadvantage of competing against food production.^{[citation needed]}

1. ^ T.Gerngross et al (1999) Nature Biotechnology,17, 541-544
2. ^ [1]
3. ^ Association of European Plastic Manufacturers
4. ^ PHB Industrial, Brazil
5. ^ Metabolix
6. ^ Microbes manufacture plastic from food waste Technology News, April 10, 2003. Last retrieved June 13, 2007.

• Biodegradable waste
• Plastic bag
• Photodegradation
• Bioplastic

• The European Bioplastics Association Information on Bioplastics and Biodegradable Polymers, Market Information
• bioplastics24.com News and market directory for the bioplastics industry
• Biopolymer.net : Links to organisations, companies and everything related to biopolymers/bioplastics.