Some companies have been claiming that they have created an additive that can be added to traditional plastics to make them biodegradable. These products become what is called OXO-Degradable, and sometimes is incorrectly identified as OXO-biodegradable.
Photo: boranmopack.com
Although this allows the plastic to return to the environment, these products are not biodegradable. Instead, the additive allows the plastic material to break down physically when exposed to water, into pieces small enough to be accidentally ingested by microbes. However, the microbes are not able to actually break this material down further. The end result is therefore a material that combines biomass with polymer residue. The plastic never decomposes as a result of interaction with the organisms. This process is therefore more accurately called “disintergration” rather than “biodegradation”.
Products made with this very common chemical formulation with millions of people producing OXO-Degradable additives are in actuality taking the chemical formulation of plastic adding a chain that is broken when placed around humidity or water which turns the bag or product into smaller films which then can be digested by microbes unknowingly. After the microbes have then digested the film the biomass that is created is a polymer residue and biomass combined. This is not biodegradation, because you are not allowing the microbes to digest the molecular structure of the plastic. Therefore this is disintegration.
OXO-Degradable plastics are one solution to this problem. There are others. Plastics of biological origin which are produced from sustainable sources such as starch are also beginning to be used. However, the energy cost of producing these is high and hydrocarbon use in their production can be greater than that used for the production of polyolefins.They are not a carbon neutral product. Thus, if OXO-Degradable plastics are allowed to decompose totally, their life cycle carbon dioxide production is still no greater and mayindeed be less than that from bioplastics. OXO-Degradable plastics therefore provide environmental benefits in comparison with untreated plastics even assuming that all of the carbon is released as carbon dioxide on breakdown.
A proportion of the carbon from the degradable polyolefins is converted into biomass when they degrade in biological systems. The proportion of carbon incorporated into biomass will vary with differing conditions. The electron micrograph below shows OXO-Degradable polyethylene after incorporation into compost. A dense population of cocci growing on polyethylene film containing OXO-Degradable catalyst. The film had been incorporated into compost.
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