Biodegradable plastics – the truth

The truth about biodegradable plastics is that most of them are not

by Michael Smith (Veshengro)

Most of us are aware of how long-lived petroleum-based plastic bags and packaging are, I am sure. we have seen the trash along roadsides and in our lakes and oceans and festooning our trees.

Some new so-called “bioplastics” claim to be “100 percent compostable,” but tests have revealed that most of these claims are misleading at best and at worst they are blatant lies.

Basically, there are two kinds of “composting.” Composting at home usually involves small-scale piles with low temperatures and less-than-optimum humidity. Then there’s large-scale commercial composting, in which materials are shredded, mixed and maintained at 140 degrees Fahrenheit – a much higher temperature than that of any typical home compost pile and even a backyard composting bin cannot reach such temperatures. Many cities compost yard waste, but only a few sites – about 100 in the entire USA – will also accept these “degradable” plastics and, as far as can be ascertained there are basically none that do in the entire UK.

You will also have seen those bags for kitchen waste, liners for those peely bins, that are supposed to compostable in the home composting environment. Well, they are not, at least not in the claimed three months; more like three years.

In a test conducted in the USA five types of bioplastic bags were tested to see how well they would compost. None of them broke down completely after 25 weeks in home compost conditions (77 degrees).

A product from Italian bioplastic manufacturer Novamont came closest to what we would call truly compostable with a product called Mater-bi. Mater-bi is “made of corn starch, vegetable oil derivatives and biodegradable synthetic polyesters” and in those tests that product was the only one that was compostable at typical home compost pile conditions.

Three other brands did fairly well in commercial composting conditions, but they showed little or no degradation in home compost conditions. One type, Oxo-Biodegradable, did not begin to break down even after 25 weeks at 140 degrees.

Most bioplastic products currently being marketed carry incomplete and/or misleading labeling and the bottom line is that most plastic packaging that claims to be “biodegradable” or “compostable” will only partially, if at all, break down under the conditions typical of most residential compost piles and some even have problems in commercial hot composting environment.

It boils down, once again, to total greenwash and misleading the consumer and everyone else. In the same way that Coca Cola claims to have a 100% plant-based PET bottle which has 30% plant material. In addition to that the material is PET which does not compost and, according to sources in waste management, also cannot be recycled in the same way as ordinary PET.

Other misleading claims are when it says on plastic grocery bags “Made with 100% recycled plastic” as that simply does not compute. The absolute maximum recycled content for any plastic grocery bag – the absolute maximum – is 50% and most are way less than that in recycled content.

Greenwash all the way and the consumer, that's you and I, pay for this.

© 2013