Portland has announced a major change to their community compost system – as of March 1, 2015 they will no longer be accepting compostable plastics such as forks, spoons and cups. In fact, any food scrap loads with more than trivial amounts of compostable plastics will be diverted to the landfill. This also means that compostable plastics should not be marketed as compostable in Portland because they are not allowed in the system.
This decision comes as a surprise to many restaurants who have diligently converted to compostable plastics trying to “go green”. Unfortunately, what they were not told when they were sold on the “compostable plastic” was there is many different plastics that will compost, some provide value while others do not. There are natural plastics such as starch and ENSO RENEW that are virtually identical to food waste. There are other synthetic plastics that will compost, such as PLA, that are not similar to food waste (and will not biodegrade in your back yard either). These second types of compostable plastics add absolutely no value to the compost system. Current ASTM D6400 requirements for compostable plastics require that the plastic convert 90% to CO2 within 120 days. These requirements are also built for commercial compost systems that operate at extremely high temperatures – much higher than most compost piles ever reach (why? because PLA requires the high heat to break down). The result? You end up with plastics that turn into greenhouse gas or don’t break down at all in the compost system. Either way, there is no value or benefit left in the soil.
Contrary to popular belief, these synthetic compostable plastics are not the same as plant matter in the compost. Plant matter degrades slowly over time and results in carbon retention in the soil as well as minerals and nutrients (together all of this known as humus). The value of composting is to create nutrient rich top soil – not to convert everything into air or to leave plastic fragments in our soil.
As we move toward more natural compostable materials such as ENSO RENEW, perhaps it will help Portland to reconsider accepting plastics in the compost system.