In 2023, Europeans used about 53 billion coffee capsules. That mound of coffee-ground-filled capsules is proving a serious challenge for waste processing companies. Only a small amount of the materials are currently recycled, so the environmental impact remains significant. Which coffee capsules are currently the most sustainable? And what is the best way to process them?
A more sustainable economy does not just require sustainable production. It also takes a new perspective on waste. In other words: we need to aim for less waste and maximum reuse. A circular economy, with a minimum of fossil fuels and as little waste in landfills as possible. Where possible, materials should be reused for new applications. There is a specific group of products that don’t quite fit the waste processing system. As a result, raw materials are lost or processed in a less sustainable manner. Examples include small packaging (like medicine strips), products made of composite materials (like plastic/paper combinations) and packaging with food residue (like yogurt cartons). Coffee capsules, small cups still containing coffee grounds, are a key example of that latter group. This is why researchers of Wageningen Food & Biobased Research (WFBR) investigated this specific product. Which of the researched coffee capsules are currently the most sustainable? And what is the best way to process them?
Circularity indicators
While Europe is currently struggling, it uses about two billion coffee capsules per year, which shows the need for a local solution. About three-quarters of these are made of aluminium, while the rest generally consist of conventional plastic or compostable bio-based plastic. The European Union is currently working on new legislation regarding sustainable packaging, with special attention for coffee capsules. Which coffee capsules can be considered the most sustainable compared to others? The WFBR researchers helped answer that question through the development of a method that allows us to measure the sustainability of these kinds of problematic products.
'Coffee capsules illustrate how certain products poorly integrate into our current waste processing systems'
Roughly three-quarters of the capsules are made of aluminum, the rest from conventional plastic or compostable bio-based plastic. Photo: WUR
Karin Molenveld, programme manager Renewable Plastics, was involved in the research from the very start. ‘We gathered as much information as possible about a representative selection of the products currently on the market,’ she says, ‘divided into three categories: aluminium coffee capsules, conventional plastic ones and those made of biodegradable bio-based plastic.’ What exactly are they made of? How big are they? How much coffee do they contain? This information was gleaned from research literature or by investigating the capsules themselves, or supplied by the producers of the capsules. ‘We gather those data in a massive spreadsheet, which we use for our calculations.’ Molenveld and her colleagues judged the capsules based on various indicators, their CO₂ footprint and the so-called Material Circularity Indicator (MCI) key among them. The MCI indicator, developed by the Ellen McArthur Foundation, offers the most complete perspective on circularity. The indicator includes, among others, the reusability of the material, the way it can be recycled, as well as its average lifespan. ‘These factors offer a proper, widely-supported indication of which products are actually circular and have a low environmental impact.’
Compostable coffee capsules
Based on all these data, the researchers calculated various scenarios. ‘We considered a variety of processing options. What if all the capsules end up in the plastic, metal and drink cartons bin? What if we try to collect them? Or what if the capsules could be disposed of as organic waste? Based on those calculations, we eventually arrived at more sustainable options.’
Capsules are an easy, popular way to brew coffee at home, but they also cause a lot of waste. While ground coffee can be composted along with the filter, capsules aren’t always easy to reuse. This is due to the materials they’re made of. Researcher Karin Molenveld wanted to know which capsule would best suit a sustainable, circular world. To find out, she investigated the three most popular types of capsules, made of aluminium, fossil plastics and biobased materials.
The conclusion: disposing of compostable bio-based coffee capsules as organic waste is the best option. These capsules are circular and have a relatively low CO₂ impact. ‘The compostable bio-based materials these capsules are made of fully stay within the cycle if they are processed as organic waste and turned into a new product: compost. Bio-based capsules have a low climate impact thanks to the application of renewable sources and a relatively low power requirement. The coffee that remains in the capsules can also be processed completely in this manner. If the capsules are disposed of as general waste or LWP (Lightweight Packaging) , this coffee is incinerated. That’s a shame, as coffee grounds contain many useful nutrients. ‘Composting is often considered a inferior method of recycling, since you don’t get the same material back. But in this situation, it does allow us to recycle the entire product.’
Collecting aluminium capsules
Aluminium capsules took second place in this study, but only if they were collected separately. This results in the highest yield and quality of recycled aluminium. ‘And collection offers the added benefit that the coffee grounds in the capsules can also be recycled.’ However, it has proven difficult to encourage consumers to take their products to a collection point. ‘Collection points for aluminium capsules are already available at the producers’ stores, but only a quarter of consumers actually hand in their used capsules, the coffee sector estimates.’ Similar experiences with bottles and cans have shown that it is difficult to increase this number. Moisture leaking out of the punctured capsules can cause quite a mess. Consumers don’t like that.’
Low MCI scores
On top of that, aluminium extraction is a polluting process that takes a lot of energy. ‘Moreover, aluminium capsules only have an MCI score of 60%, because materials are lost in the recycling chain. Eventually, aluminium also suffers from pollution, which makes it too rigid for reuse in thin-walled products like coffee capsules.’
Sustainability, based on a combination of CO₂ emissions and circularity (MCI), compared across different types of coffee capsules. Image: WUR
Conventional/fossil plastics scored lowest in the study. ‘It is made of fossil resources and recycling plastic capsules is a difficult process. Unless they are collected separately, most of the coffee grounds are incinerated. As such, they have an MCI score under 50%.’ Molenveld can see various advantages if plastic capsules were to disappear. ‘It would make a serious difference from a sustainability point of view. This would also make the decision to allow compostable capsules to be disposed of as organic waste easier, as there would be no more plastic capsules to confuse the consumer. In this situation, aluminium and biobased capsules could potentially coexist.’
Switching to compostable materials
It is not yet possible to capitalise upon the results of the study. Right now, compostable, bio-based capsules cannot yet be disposed of as organic waste. Waste processing companies are afraid the consumer won’t be able to distinguish between compostable and plastic capsules, Molenveld says. ‘The quality of compost is carefully monitored, and for good reason: nobody wants to cover farm fields in microplastics. Aluminium capsules can be separated from the organic waste using magnets, but plastic causes serious issues.’ However, a switch like this is not completely unprecedented. Producers have made the switch to fully compostable packaging before, Molenveld says. ‘That was for tea bags. They used to present the same issue: packaging containing organic materials that could be reused.’ Back in the day, the bags still contained plastic fibres; nowadays, each bag can be disposed of as organic waste and turned into compost. ‘That switch was easier, however, since the products were very similar. Coffee capsules are made of many different materials. As soon as coffee producers become willing to seriously adjust their production process, we will be able to make the switch to bio-based, compostable coffee capsules.’
'In a good waste system, the coffee grounds are also recycled'
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