Compostable packaging: putting our coffee cups to the test

Following my theme of Plastic Free July, this week we will talk about compostable coffee cups, lids and PLA.

Are they really compostable in your normal compost, worm farm or Bokashi?

Can I process compostable coffee cups at home?

Some compostable coffee cups will break down in the compost and Bokashi, but by far the best method for these is to rip them up and put them in your worm farm, if they are indeed compostable. After a few months, they will have all but disappeared – or so we are told. The ones I tested in my very active worm farm took between 7 and 9 weeks for the paper component to break down, and in the traditional compost there were still traces after 3 months.

To my horror, what I was left with was a plastic film. So they are not home compostable at all! After doing some research over the past few days and quizzing cafes, they tell me that they pay a higher premium for these products, so that they are seen to be doing the right thing. Yet in fact most of these compostables are not home compostable at all.  Also most countries do not have facilities to process these so, yet again, they end up going to landfill!!

Compostable coffee cups, lids and PLA really need to have the words ‘Hot Compostable’, which is where you have a compost heap that is consistently over 60 degrees. Here on Waiheke, we have a commercial hot compost trial going that has been successfully run over the past 18 months processing the PLA and compostable cups and lids. For this to work successfully, we have found that the hot compost needs to be sitting consistently at around 70 degrees and all products need to go through a shredder first.

What is PLA and can I compost it?

PLA is polylactic acid, which is derived from fermented plant starch such as corn, sugarcane and beet pulp.


These cups are only hot compostable after shredding. I have read reports from companies claiming that you can just throw them in a normal compost, but my trials have shown that after 3 months in a normal compost, it still resembles a cup. Really we need to be labelling these cups as ‘biodegradable’.

The definition of biodegradable means an item that can break down into natural materials in the environment without causing harm, but it doesn’t specify how long this will take. Some products break down easily, like various paper items, but some products will take years to eventually biodegrade.

Can I process compostable coffee cup lids at home?

Most of these lids are made from PLA and are charged at a premium price to cafes looking to offer their customers environmentally-friendly alternatives. However, most of these still end up in landfill because, across the country, there are not enough facilities of commercial HOT composting that makes this a viable option.

In my opinion, the answer comes back to us as the consumer and that is to get a ‘Keep Cup’ for our coffees and take these with us to events to drink our beverages from.

Sadly, it is a very confusing world out there with ambiguous wording – perpetuated by the industry – so that, as a consumer, you don’t know if you’re buying a product that helps or hinders the environment! When you have been composting in various forms like me over the past 30 years, you can guarantee I will put them to the test.

Next time you go out, read the wording on the product and see what it says. If it’s compostable, put it to the test in your home compost and share the results with us here at Grow Inspired.

Over the next few days on my Facebook page, I will be sharing some more interesting links on these products.

Next week, we will be back in the garden and talking about growing juicy peas and broad beans.

Happy gardening!

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