Are compostable bio-plastic cups any better for the environment than regular plastic cups?
Not really. When bio-plastic - plastic made from plants not petroleum - first came out, many thought this was the solution to the single use oil-based plastic problem; however, it just creates another set of problems.
There are many terms to untangle so I organized this post using headers and questions to break it down - no pun intended!
What is plastic?
Here is a nice summary of the history of plastic. And a brief definition of plastic is moldable materials that are typically made from long chains of smaller molecules joined together, which is why their names often start with the prefix "poly" — for example polystyrene or polyethylene.
Almost all plastics are oil-based, and non biodegradable and non compostable. So our landfills are filling up with plastic refuse, taking hundreds of years to 'break down,' leaving toxic microplastics behind, and using up our limited sources of petroleum. Broadly speaking, bio-plastics could solve the oil problem.
What is bio-plastic?
Some definitions of types of plastic according to Ecocycle.org:
Bio-based Plastic (bio-plastics) is made from a bio-based origin, such as corn, sugar, or starch as opposed to a fossil- based carbon source; not necessarily compostable.
Thermoplastic (complex starch/composite plastic) is derived from blending starch from plant-based products with other plastics (bio-based and/or oil-based)3 ; some are compostable, some are not.
Compostable Plastic undergoes degradation by biological processes during composting to yield carbon dioxide, water, inorganic compounds and biomass at a rate consistent with other known compostable materials; leaves no visible, distinguishable or toxic residue.
What are the differences among biodegradable, degradable and compostable?
Many companies are using the terms ‘biodegradable' and ‘compostable' interchangeably. Here are some definitions according to the site Green Matters :
Biodegradable: An item can be disintegrated into its base elements by bacteria, fungi, or some other biological process. Biodegradation is just the process of nature breaking down materials into their component parts. Most fruits, vegetables, and other plant-based foods are biodegradable, in that if you buried them in your backyard without a proper composting setup, they would eventually biodegrade.
Compostable: Organic material that can, through the process of decomposition, be turned into nutrient-rich soil or fertilizer. So a compostable product “can” be turned into compost as long as it's under the correct conditions.
Technically, everything will 'break down' or 'fragment' or 'degrade' over decades or hundreds of decades. If something is biodegradable, it does not mean it's necessarily compostable; though if something is compostable, it is necessarily biodegradable!
“You can have oil-based plastics that are compostable and plant-based plastics that are not compostable,” says Michele Young, organics manager for the city of San Jose. You also can have bio-plastics that are not biodegradable, and oil-based plastics that are. Gah! It's all about the chemicals used to create the plastic.
For example, non-compostable plastic (could be bio-plastic or oil-based plastic) will never fully degrade but never fully biodegrade as it leaves toxic microplastics behind.
There is also something called with oxo-degradable plasticwhich is made from fossil fuel derived polymers such as PE (polyethylene), PP (polypropylene), and PS (polystyrene) with ingredients added to ...speed it up so [it] will degrade at the end of its useful life in the presence of oxygen, much faster than ordinary plastic. But remember, that does not mean it biodegrades.
Compostableplastic (bio-based or oil-based though it's more common to be bio-based) biodegrades and in doing so, also add nutrients to the earth. As quoted from Sustainable America: "If [compostable plastics] are sent to an industrial-scale composting facility with actively managed piles of compost under controlled conditions, and fed a diet of digestive microbes, PLA cups will break down in less than two months. In someone’s backyard compost heap, it could easily take more than a year." Compostable products should not leave behind any toxins though some compost facilities accept compostable containers that are lined with plastic.
Common compostable bio-plastics:
PLA – Polylactic Acid (corn-based)
PHA – Poloyhydroxy Fatty Acids (corn-based)
Bagasse – by-product of sugar cane/sorghum juice extraction
Paper
Wheat straw
Bamboo
Palm fiber
Corn starch
You can read more about the different types of compostable plastics here.
Are compostable bio-plastics less harmful to the environment than oil-based plastics?
Not really. Producing single use plastic items still is using a lot of energy and ultimately, creates waste.
While plant-based sounds better than oil-based, many find issue with growing plants for plastic as it means diverting land from food production, creating pollution from the fertilizers used, and producing a lot of emissions through transportation, manufacturing, processing and distribution.
The actual carbon footprint to produce these compostable plastics isn't entirely clear. An article on Eater.com, sites that the "environmental impacts of producing compostable products can be 10, 50, or 100 times higher, depending on the source materials, packaging, and production process."
So what’s the main problem with using compostable bio-plastics?
Compostable bio-plastics often aren't composted because most people do not have access to industrial compost facilities. Instead they end up in the trash bin, or very often, the recycling bin.
Compostable plastic cups look like normal plastic so people might think they can go in the recycling bin. However, according to an article on Grist.org, "When clear compostable cups end up in the recycling bin, they can actually contaminate the plastic recycling process." And if the recycling facility "is able to identify the compostable items, they can screen them out, but that means extra steps (and, probably, extra labor costs)."
If compostable plastics end up in a landfill, they will take much longer to break down and will contribute to the problems that composting is meant to avoid: adding to the already full landfills, producing methane gas, and leaving microplastics behind (just like oil-based plastics do). If they end up as trash in marine environments, they'll break down into microplastics, last for decades, and endanger marine life.
In conclusion: what should you use?
Companies are greenwashing these bio-plastics as better for the environment than oil-based plastic, when in reality, they can create the same negative environmental impact. People are confused as how to depose of them after use. Ultimately, it's best to refuse single-use plastics - bio-plastic and oil-based plastic - all together. Encourage your friends, family and local businesses to do the same!
GREEN: A compostable bio-plastic cup, reused as much as possible and then taken to an industrial compost facility post use (or if you can find a compostable cup that can turn into compost in a home compost, even better!). Click here to search for composters.
GREENER: Paper cups (bamboo, paper) not lined with plastic that you recycle or compost (though some compost accepts plastic lined products...more on that in a later post).
GREENEST: A reusable to go mug, or tumbler that you wash and reuse many times over.
xx
Hannah