Nearly Two-Thirds Of Compostable Plastics Fail To Deliver As Promised, UK Study Finds

At this point, the shortcomings and failures of recycling are evident. Consumers are often unsure about what is actually recyclable and aren’t the most diligent in collecting and sorting trash accepted by curbside services.

To be more sustainable, or at least sound like it, manufacturers are introducing supposedly compostable packaging, including materials labeled as “home compostable.” It turns out consumers are just as confounded by compostable labeling. What’s worse, many compostable products don’t live up to the promises of home compostability.

Researchers from University College London conducted a two-year study published in the journal Frontiers, which included a 5-minute online survey, along with reporting on their experiments with home composting. In total, 9,701 citizens participated, with 1,648 folks taking part in the home composting investigation. The study found that even with guidance from scientists, participants included items marked as industrially compostable only, biodegradable, or with no apparent labeling, leading researchers to conclude that consumer confusion over labeling exists.

Alarmingly, the study also found that most "home compostable" packaging did not completely break down in home composters, including indoor wormers and outdoor and closed compost heaps. 

"Of the biodegradable and compostable plastics tested under different home composting conditions," wrote the researchers in the study, "the majority did not fully disintegrate, including 60% of those that were certified 'home compostable.' We conclude that for both of these reasons, home composting is not an effective or environmentally beneficial waste processing method for biodegradable or compostable packaging in the UK."

The citizen scientists were distributed throughout the country, and researchers found that while the length of time spent in the composter did help further break down materials, other factors, such as temperature, microbial communities, and nutritional pathways, were significant contributors to substance degradation.

The researchers concluded that the varying conditions of home compost environments make compostable labeling, which relies on testing done under lab conditions, an unreliable indicator of a material's true compostability. Furthermore, the scientists concluded that unregulated and uncontrolled home composting is mostly ineffective. The study’s authors called the sustainable materials a “widespread misconception” and that only a system of production, collection, and reprocessing of a substance can be considered sustainable or biodegradable, depending on the environmental impact of the entire lifecycle of a material.

As with recycling, consumers purchase products in compostable and biodegradable packaging and diligently compost at home with the best intentions. Sadly, they are having little impact on the plastic pollution crisis, and brands should be cautious of how certain their compostability claims really are.