Research & Reports

Study shows biodegradable bags are still intact after three years

A new study has found that bags that claim to deteriorate faster than traditional single-use plastic bags, are taking longer than three years to break down.

While some, such as compostable bags, did disappear within three months, others were still able to carry items after three years.

The study, published in Environmental Science and Technology, examined biodegradable, oxo-biodegradable, compostable, and high-density polyethylene (conventional plastic bags) for a three-year period.

These materials were exposed to three natural environments – open-air, buried in soil, and submersed in seawater, as well as in controlled laboratory conditions.

In the marine environment, the compostable bag completely disappeared within three months.

However, the same compostable bag type was still present in the soil environment after 27 months, but could no longer hold weight without tearing.

After 9 months’ exposure in the open-air, all bag materials had disintegrated into fragments.

The results of the study show that none of the bags could be relied upon to show any substantial deterioration over a three-year period in all of the environments.

The research concludes that it is therefore not clear that the oxo-biodegradable or biodegradable formulations provide sufficiently advanced rates of deterioration to be advantageous in the context of reducing marine litter, compared to conventional bags.

Bags that did disintegrate include compostable bags, which are readily available to the Australian market from companies such as Detpak and Biopak.

According to Detpak, its products, made from biodegradable and compostable materials, will break down within 90 days when treated in a commercial facility.

The company explained that treatment at a commercial composting facility means the products will be subjected to optimum amounts of sunlight, temperature and moisture to break down.

Compostable products can be placed in home compost bins, but the time it takes to break down will depend on how well the compost heap is tended to, according to Detpak.