Compostable coffee cups: Understanding the relationship with moisture

Holly Szakal
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December 8, 2023
compostable coffee cups, Kaffeine, takeaway coffee cups, sustainable coffee cups, eco-friendly coffee cups,

Prioritising sustainability in the specialty coffee sector has developed past being ‘the norm’. It has become an expectation. More consumers are demanding that brands use eco-friendly alternatives to plastic, such as recyclable coffee bags and compostable coffee cups.

Notably, a recent survey found over 50% of consumers want to support brands that advocate sustainability. As this global self-awareness continues to gain traction, compostable coffee cups are emerging as a promising solution.

Compostable coffee cups have become one of the most popular options within the specialty coffee industry. This is because of their ability to break down naturally without leaching toxic residues into the environment. These eco-friendly alternatives are often made of plant-based materials and aim to address the environmental concerns associated with traditional single-use cups. 

However, as compostable cups are designed to break down easily, how can coffee roasters ensure their beverages will not compromise the material’s integrity? Understanding the relationship between compostable coffee cups and moisture can ensure brands store these items properly. 

To learn more, I spoke with Sam McCallum, a specialty coffee barista working at Kaffeine in London.  

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Understanding the lifecycle of compostable coffee cups

Compostable takeaway cups are made using plant-based materials. Typically, these comprise paper, cardboard, or specialist plant-based plastics, with polylactic acid (PLA) being one of the most common.

Another widely used solution is a cup made from kraft paper with an environmentally friendly PLA coating. This inner coating helps provide the cup with more durability and helps it better retain its structural stability in moist environments, or when filled with coffee.

Either way, the materials are designed to break down entirely and leave behind only organic matter. Compostable cups biodegrade into a combination of unreactive natural matter, such as carbon dioxide, water, and substances that help to enrich the soil.

However, it is important to note compostable cups are specifically designed to biodegrade in a composting environment. If buried in a landfill, compostable coffee cups can take up to 100 years to break down. This increases the risk of them emitting methane: a powerful greenhouse gas that contributes to the effects of global warming.

Beyond this, compostable cups left in landfills have the potential to generate over 52,000 metric tonnes of carbon dioxide. This amount is equivalent to the annual operating cost of 33,300 cars. However, when placed in a commercial setting with the correct environmental factors, compostable coffee cups break down in around 90 days.

These cups require a carefully controlled environment to break down properly. One where they are exposed to the right levels of heat, moisture and microorganisms. Therefore, they will need to be directed to a commercial composting facility that accepts PLA. Usually, the internal temperatures in these environments are high and are set between 55°C (131°F) and 60°C (140°F), as this increases the number of microorganisms.

Elemental factors such as moisture content, aeration, pH levels, and the carbon-to-nitrogen ratio are meticulously regulated by the facility. The resulting compost also undergoes quality control analysis to ensure compliance with compost specifications.

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How does moisture affect compostable coffee cups?

Moisture plays a pivotal role in the decomposition journey of compostable coffee cups. Humidity significantly influences their decomposition process and overall impact on the environment.

However, excessive moisture can expedite the degradation process. This may cause the cups to break down prematurely, potentially before reaching the composting facility and affecting their natural process. Conversely, insufficient moisture may impede decomposition, thus prolonging the cup’s presence in the environment and delaying its total breakdown.

Additionally, if compostable cups are exposed to moisture during storage, it can affect their structural integrity. More importantly, it can impact their ability to be effectively processed in composting systems. 

If compostable coffee cups are exposed to water for any reason, businesses are encouraged not to dry them for use. Instead, the cups should be disposed of. In excessively wet conditions, water occupies the pore spaces essential for air circulation, leading to the potential development of anaerobic conditions.

Overall, it is recommended that compostable coffee cups be stored in a cool, dry place away from areas prone to moisture or humidity. 

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Ensuring compostable cups are disposed of correctly

To ensure compostable coffee cups are discarded properly, coffee roasters and cafes must consider three factors: education, clear labelling, and correct in-store disposal systems. It is also vital to ensure that any extra elements used, such as lids, are also compostable.

Sam explains the in-store processes Kaffeine has implemented to ensure correct decomposition processes. “The biggest problem with compostable cups is usually the lid,” he says. “I’d recommend serving without the lid; then the customer can decide if they want to use one. Additionally, it will also give it the least contact time with the coffee to help preserve its integrity.”

Sam also shares the issues he’s faced with non-compostable elements added to compostable packaging. “Many compostable cups are difficult to compost, depending on your local garbage management. Or, some may have stickers or ink added to them that aren’t compostable, making the environmental benefits null and void.” 

Specialty coffee roasters and cafes are encouraged to contact their local compostable and recycling facilities to determine if they accept certain materials. Furthermore, brands should be able to guide consumers on how to dispose of compostable cups correctly. 

For example, local facilities may request that compostable coffee cups be kept in designated bins. Therefore, businesses should gather as much information as possible, to ensure they are following the correct procedures. 

By switching to compostable takeaway cups, coffee shops can continue serving coffee to-go while limiting their impact on the environment. Not only will this put them ahead of competitors, it will also improve the sustainability of the coffee supply chain.

This is why at MTPak Coffee, our compostable coffee cups are in full compliance with the European certification standard (EN 13432), which means they degrade harmlessly into the soil over time. Additionally, the paper used to create our compostable cups is certified by the Forest Stewardship Council, ensuring your customers receive a fully sustainable product.

Our compostable coffee cups are available in sizes from 4 oz to 24 oz and can be designed with a PLA or aqueous coating to prevent leaks. 

Images courtesy of Kaffeine.

For more information on compostable coffee cups, contact our team.

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