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Are Compostable Plastics Really a Sustainable Solution?

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Despite claims made by some companies, very few composting facilities will accept so-called compostable plastics, and the small number that do require adherence to a strict set of guidelines.

For more than a decade now, compostability has been pursued as a way to make plastics in the environment magically disappear. I’ve sat through many a conference presentation on compostability and heard all the reasons why we need compostable plastics as a viable solution to waste in the environment. As good as that all sounds, there is still no way to make plastic simply vanish.

I’ve received press releases from companies that try to sell me on the idea that their material will break down into “soil.” Yes, really! I’ve asked for references of composting facilities that will take compostable plastics. Sometimes the company responds with a list of a few composting facilities that claim to take compostable plastics. When I check with them, however, they invariably tell me they don’t really take any type of plastic.

I often get pushback from readers of PlasticsToday when I write about compostable plastics and the lack of infrastructure that will accept these materials. Recently an anonymous reader contradicted me about my inability to find composting facilities that will accept compostable plastics. This reader included a link to a site showing a map of the United States with lots of red and green dots on it. The red dots indicated composting facilities that are traditional composting facilities, and the green dots indicated composting facilities that accept compostable plastics.

There were quite a few green dots in the east. Hovering my mouse over the green dots, I captured the names of the composting facilities that reportedly accept compostable plastics. I chose 12 companies and went to the website of each one to get further information. Ten of those companies take yard waste/organic matter/horse manure, food, and clean wood chips. Most of them specified “no plastic.”

Secondhand Soil in Forsyth, GA, will accept compostable plastics labeled “certified BPI (Biodegradable Products Institute) compostable” to ASTM 6400 D6868 standards. Green Mountain Compost in Williston, VT, accepts compostable materials that adhere to the specific guidelines on the company’s website, noting that it takes time and energy to use compostable items responsibly. No bioplastic and no oxo-degradable plastics — only compostable plastic with the BPI logo that meets ASTM standards is allowable.

I’m sure if I continued my research I would find similar results. Most would say “no plastic” or accept some types of compostable plastics within the framework of BPI guidelines.

Novomer Inc. recently announced a new compostable polymer. Novomer CEO Jeff Uhrig told PlasticsToday that Novomer is aligned with the use case hierarchy that has broad-based global support. When asked for some comments on compostable polymer’s role in sustainability, Uhrig responded, as follows.

“First, if there is alternative material that is economic, sustainable, and meets the requirements of the use case, then that alternative should be pursued.

“Second, all polymers including compostable polymers, should be reused to the extent possible. It is a common misconception that compostable polymers fulfill only single-use cases.

“Third, all polymers that can be recycled should be recycled. The Rinnovo polymer [just unveiled by Novomer and profiled here] is a unique compostable polymer in that it can be easily recycled and processed post use to make acrylic acid. We advise the primary post-consumer use of Rinnovo be in the production of acrylic acid. Acrylic acid from Rinnovo polymers dramatically reduces the [life cycle analysis] versus incumbent routes to compostable polymers.

“Fourth, Rinnovo polymers should be composted post use. As a compostable polymer primarily intended for film applications, the degradation rates will be fast and can be home or industrially composted. Alternatively, these materials can be anaerobically digested for biogas production,” he concluded.

Uhrig added that Novomer does not recommend any waste ever be sent to landfills and, of course, no waste should ever find its way into the environment. (If people would actually care enough about the environment, the waste would not “find” its way into the environment. People put waste in the environment — waste doesn’t just wander there by itself.)

Perhaps expectations continue to be too high for what can be possible with biopolymers that come with a promise to degrade in a short time frame or be suitable for composting. I remember a presentation that Professor Ramani Narayan of Michigan State University gave at an SPE Thermoforming conference, where he said that people want to believe we can make plastics simply disappear by using an additive or a process. Plastics were never made to disappear — they were designed to be durable and to replace other materials that are more expensive in terms of energy and resources.

People become disappointed when plastics do not magically become soil. But compostability hasn’t proven to be even a nominal solution. However, plastics can be turned into many other things via chemical recycling, such as Novomer’s acrylic acid and other products. I could support that effort. Compostability? Not so much.

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