Home Composting Trial Confirms Breakdown of Biodegradable Films

An informal trial conducted by Convex Plastics has confirmed the home compostability of three biodegradable packaging films, and clearly shown NatureFlex cellophane as the one that breaks down the quickest.

In March this year Convex Managing Director Owen Embling carried out a home composting trial to compare the breakdown rate of bags made from three different biodegradable packaging films: Greensack (made from cornstarch), NatureWorks Poly Lactic Acid (PLA) and NatureFlex cellophane.

Owen filled one bag of each type of film with approximately one kilogram of compostable kitchen waste, including potato peelings and grape stalks. He then buried the bags amongst lawn clippings in three adjacent compost heaps at the back of his property.

Owen conducted his first breakdown test five weeks later by uncovering the bags to see how much they had degraded. At that point, on the 10th of April, the NatureFlex cellophane film was almost completely gone (between 90% and 100% degraded), and the Greensack film was about 80% gone. By comparison, the PLA film was still only in the early stages of degradation, but there was evidence that the breakdown process had started.

Owen says, “At the five week point the PLA bag was very brittle, which indicated that some breakdown had occurred, but it was still basically a plastic bag that held together. This was most likely because the compost piles were located behind a south facing wall, with plenty of moisture but not much heat or sun, and PLA break downs down better in high heat. For that reason we recommend that PLA is commercially composted rather then home composted, although the trial did show that the material would still break down in a home composting situation, albeit at a much slower rate.”

All three bags were checked again in late June, 12 weeks after they had been composted. By this stage the NatureFlex cellophane film was completely gone, the Greensack film was about 95% gone, and the PLA bag was about 50% gone.

“Even though this trial was both informal and unscientific, I was very happy with the results,” says Owen. “The trial clearly showed that these films do breakdown in a fairly typical home composting situation.”

The three films tested all feature on Convex Plastics Environmentally Friendly Packaging Options Chart that was developed last year to compare the best uses, environmental impact and source of the key currently available biodegradable and recycled films. You can view the chart here:

 Environmental_Packaging_Options_Chart.pdf (1,874 KB)

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