Chemistry, Materials & Packaging
Additives to Biodegrade Plastics Offered False Hope, Says Latest Study

The world today has a plastic addiction, a vice that creates major environmental issues by entering waterways and clogging up our landfills and oceans. The problem is that conventional plastics have a half-life (the time it takes for half of the product to degrade) of hundreds of years — basically, once the plastic is discarded, it’s in the environment for the long haul.

Solutions including “bioplastic” and “biodegradable” plastics have been proposed and often marketed to consumers as such. One of the possible remedies is the use of additives in plastics, which help break them down in the environment. Could they be the answer?

A new study concluded by Michigan State University says no. The results show that several additives that claim to degrade polyethylene (the compound used for plastic bags) and polyethylene terephthalate (i.e. plastic drinks bottles) don’t work in conventional disposal environments such as landfills or composting.

“Making improper or unsubstantiated claims can produce consumer backlash, fill the environment with unwanted polymer debris and expose companies to legal penalties,” said Susan Selke, co-author of the study and packaging professor at Michigan State University.

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The results — published in the current issue of Environmental Science and Technology — are the outcome of a three-year study that focused on five different additives and three processes of biodegradation. These cover most of the methods available and used on the market today.

The three processes of natural breakdown covered were biodegradation with oxygen (as would occur in an aerobic environment such as composting); biodegradation without oxygen (in an anaerobic environment such as a digester or landfill site); and the alternative of simply burying plastics. The results seemed to show no notable difference between plastics with and without additives included.

“There was no difference between the plastics mixed with the additives we tested and the ones without,” commented Rafael Auras, co-author and Michigan State packaging professor. “The claim is that, with the additives, the plastics will break down to a level in which microorganisms can use the decomposed material as food. That simply did not happen.”

Even organic materials in anaerobic environments take a long time to decompose. William Rathje, the late Arizona paleontologist and founder of the Tucson Garbage Project, once revealed that even after years buried underground, chicken bones still had meat on them, grass was still green and carrots still retained their orange color. It’s therefore not surprising that plastics (with or without additives) would take decades or even centuries to break down. If additives are not the answer, what is?

“The solution is to not make claims that are untrue,” Selke said. “The proper management of waste plastics is the proper management of waste plastics.”

Selke suggests that none of the disposal methods or additives used in the study should be used as feasible waste management options. The key is really to address the plastic problem at source by making users more conscientious about their footprint. Several US states and some countries have attempted to do this by imposing a tax/regulation on the retail use of plastic bags (one of the largest polyethylene waste sources), for example.

Plastic manufacturers are also hunting for more viable solutions.

“Package-user companies funded this study because they wanted to know if the additives that are being marketed to them work,” she said. “They wanted scientific proof to evaluate the products and disposal approaches that are available to them to break down plastic.”

Research published late last year by the 5 Gyres Institute estimates that more than five trillion pieces of plastic (amounting to almost 269,000 tons) are floating in the world’s oceans today — but that doesn’t even touch the mass collected on the ocean floor.

There has been much debate as to the long-term viability of bioplastics vs. supposedly biodegradable plastics; and whether recycling is the best alternative?

It’s also been suggested that recycling durable plastics into new products may be the best solution, because it prevents all the embodied energy used in creating the product in the first place from going to waste. The ultimate solution however is widely agreed upon: reducing consumption of plastic at source so we have less to deal with in our waste piles.

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