Biodegradable polymers composts

Many types of biodegradable polymers are available to biodegrade in a variety of environments, including soil, air, or compost. Biodegradable polymers are primarily made from com in the United States, but can be made from sugarcane, wheat, cellulose, collagen, casein, soy, or triglycerides. 

To prove the ultimate biodegradability of a biodegradable polymer and that there is no adverse effect on the user or the environment, as well as to successfully market a plastic material as biodegradable, there are international standards in place according to which these materials can be certified. Both Ecoflex and Ecovio are certified worldwide as compostable and are approved for contact with food. 

For biodegradable polymers to achieve their full market potential, they should add greater functionality and productivity for the end user, if the relatively high prices are to be justified. So far there has been very limited development of an infrastructure for composting and thus the true benefits from using biodegradable polymers are not being realised. 

Biodegradability - Metabolix PHA offer hydrolytic stability under normal service conditions but when exposed to microbial organisms naturally present they break down enzymatically in soil, composting, waste treatment processes, river water and marine environments. They also rapidly decompose to carbon dioxide and water and will degrade in anaerobic environments, unlike some other biodegradable polymers. 

The solution is a combination of aliphatic polyesters and aromatic polyesters. This involves modifying the crystalline structure of PBT by incorporating aliphatic monomer (adipic acid) in the polymer chain in such a way that the material properties of the polymer would remain acceptable (e.g., melting point of the crystalline range still around 100 °C), but the polymer would also be readily compostable/biodegradable. In this way it was possible to combine the degradability of aliphatic polyesters with the outstanding properties of aromatic polyesters. 

DuPont offers a family of biodegradable polymers based on polyethylene terephthalate (PET) technology known commercially as Biomax. Proprietary monomers are incorporated into the polymer, creating sites that are susceptible to hydrolysis. At elevated temperatures, the large polymer molecules are cleaved by moisture into smaller molecules, which are then consumed by naturally occurring microbes and converted to carbon dioxide, water and biomass. Biomax can be recycled, incinerated or landfilled, but is designed specifically for disposal by composting. 

Degradation of Biodegradable Polymers in Real and Simulated Composting Conditions... 

At present these materials are too expensive to be considered as viable alternatives to the commodity plastics in packaging but they do have potential applications in biomedical products such as orthopaedic implants and even as temporary replacements for parts of the pericardium during open-heart surgery. In this kind of application, performance is much more important than cost. However, Biopol may be able to replace non-biodegradable polymers in paper coating which would then allow paper composite materials to biodegrade much more rapidly in compost and similar environments. 

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