Are paper cups biodegradable?  Can they be composted?

  • Date: May 13, 2022

Paper cups are often a great option for a party host – no washing up required and easy to throw in the trash. What’s not to like?  Although not the only concern, a product’s ability to biodegrade is an important factor in whether it is regarded as eco-friendly or not. Many people assume that paper cups are all biodegradable. And you can see why – paper cups are made from paper, and paper is biodegradable. But is this the case? Are paper cups biodegradable and can they be composted?

Firstly, what are paper cups made from?

If we know what a product is made from it gives us a good idea as to whether it is biodegradable or not. Paper cups are just made from paper, right? Not quite. Unfortunately, all paper cups are not made equal.

In order to serve their purpose safely without hot liquids seeping through, paper cups are often coated. As with paper plates, this coating is usually plastic-based. However, a bio-plastic coating (derived from sources such as cornstarch) is increasingly being used by environmentally conscious manufacturers. This coating serves the same purpose as the plastic.

So, are paper cups biodegradable?

For a paper cup to be deemed ‘biodegradable’ it must have the ability to break down naturally into its component parts with the help of micro-organisms such as bacteria. For an item to be biodegradable, and return to nature, it must have come from nature initially. The paper part did, so that will biodegrade if the bacteria can find its way to it. However, the plastic that coats a lot of paper cups did not come from nature – plastic is very much a human creation. The plastic part will break up into smaller and smaller pieces, but it will not biodegrade. There is, however, some good news. The bio-plastic alternative will biodegrade – it came from natural sources such as cornstarch.

However, it is important to be aware that even the most biodegradable of paper cups will not biodegrade in their optimal timescales if they are not in suitable conditions. For example, in landfill, they may not biodegrade for a long time. Landfill sites are jam-packed which makes air flow and moisture levels poor.

Are paper cups compostable?

Composting can be a great way to reduce the amount of waste you send to the trash – or recycling plant – and produce some nutrient-rich fertilizer for your garden too. Everybody wins!

Many people think that the terms ‘biodegradable’ and ‘compostable’ mean the same thing. This is not the case – if an item is biodegradable it does not necessarily mean it is fit for composting. For example, a biodegradable item that contains nasty chemicals may contaminate your compost pile. To be compostable, however, an item must be biodegradable – all compostable items are biodegradable but not all biodegradable items are compostable! Since plastic is not biodegradable we can rule out the plastic-coated cups straight away. They can’t be added.

Those coated with the bio-plastic alternative, however, make a great addition. There are two main types of compost ingredient – nitrogen-rich ‘greens’ and carbon-rich ‘browns’.  As with other paper and cardboard items, paper cups contribute to the carbon-rich ‘browns’. It is important to ensure you have a suitable mixture of ‘browns’ and ‘greens’, such as food scraps, in your compost pile. You might need to adjust as you go, but we find a simple 1:1 ratio works well. Just make sure you monitor it – a shift away from a suitable ratio will show fairly obvious signs such as dryness or bad odor.

Some considerations when composting paper cups…

Although not strictly essential, you can make the process quicker by ripping or cutting the paper cup into smaller pieces. As well as giving the bacteria more surface area to work on, it also means that you can spread the pieces throughout the pile. Spreading out different composting ingredients will mean that the ‘browns’ and ‘greens’ are mixed up, but also a sudden gust of wind won’t blow your paper cup into the neighbors garden…

Paper cups (without the plastic coating, of course) are probably one of the easier items to compost – it should only take a matter of months to see results.  If you are new to the composting arena, check out the answers to some beginners FAQs here. Good luck!  

The bottom line

People often assume that paper items are just that – paper. Unfortunately, this is not the case. Plastic coatings are especially prevalent in hospitality-related paper items. Although it serves a purpose, the plastic coating causes havoc in terms of disposal. Composting is not an option for these types of cups. Thankfully, biodegradable alternatives are available – these make a useful carbon-rich ingredient for the compost pile. In terms of single-use cups, the bio-plastic coated options are the way to go!