How long do compostable coffee cups take to decompose?

Aidan Gant
-
July 15, 2022
How long does it take for a compostable coffee cup to decompose?

In Britain alone, around 2.5 billion single-use coffee cups find their way into the waste stream every year.

Of these, only one in every 400 is likely to be recycled. The rest are destined for landfill, where they could take up to 30 years to break down and may produce over 52,000 tonnes of carbon dioxide – the equivalent annual running cost of 33,300 cars. 

As the specialty coffee industry continues to prioritise eco-friendly packaging, it is clear more sustainable options are needed. While reusable options such as “keep cups” are available, data shows just 1.8% of drinks sold by coffee giant Starbucks are served in reusable cups. 

As a result, compostable coffee cups have become a popular choice for many coffee businesses. That said, when people hear the word “compostable”, they often think of home composting, and may be confused about how compostable coffee cups decompose. 

Read on to find out how long compostable coffee cups take to decompose, and what conditions are required. 

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A close up image of a compostable coffee cup with a black lid, in an article explaining the time it takes for compostable coffee cups to decompose.

How are compostable coffee cups made?

Many believe paper takeaway cups are easy to recycle, but the nature of hot beverages poses difficulties to a standard paper cup. 

Traditionally, the majority of single-use paper cups required a polyethylene (PE) film liner to prevent the liquid from seeping out. However, this lining can be difficult and expensive to separate from the paper, which means it often ends up in landfills or an incinerator. 

In recent years, sustainable alternatives to PE liners have been developed and the front-runner is one made from bioplastics, such as polylactic acid (PLA).

PLA is a thermoplastic polymer usually made entirely from plant-based materials. These bioplastics are commonly made from starches derived from corn, sugarbeet, and cassava.

The sugars in these plant fibres are fermented into a lactic acid, which then undergoes a process of polymerisation to achieve a workable material. 

The production of PLA compared to traditional polymers is a significantly more eco-friendly process. Notably, to create an equal weight of usable material, it takes 65% less energy to produce PLA than PE. Furthermore, the process creates 68% fewer carbon emissions. 

Right from the beginning of its lifecycle, PLA is a more sustainable alternative for lining single-use cups.

That said, there is more to a material’s eco-friendly credentials than its embedded energy. Roasters and coffee shops must look at the entire lifecycle of a material to get an accurate assessment of its environmental impact. 

An image of two white takeaway cups in an article explaining the time it takes for compostable coffee cups to decompose.

How does a compostable coffee cup decompose?

Compostable coffee cups require a specific set of circumstances to break down.

Care must be taken to ensure they are kept out of the general waste stream and disposed of separately so they can decompose properly.

It is important to note that unless explicitly stated on the material specification, most compostable coffee cups are not suitable for home composting. Therefore, the majority of used compostable coffee cups must be sent to a commercial composting facility that accepts PLA. 

In an industrial composting facility, the conditions are specifically designed to maximise the process of decomposition. Temperatures are high, between 55°C (131°F) and 60°C (140°F), as this increases the number of microorganisms.

Elements such as moisture content, aeration, pH levels, and the carbon to nitrogen ratio are carefully controlled. The final compost is then subject to quality control analysis to verify it meets compost specifications.

Around 170 such industrial composting facilities exist in the UK, but most governments do not redirect food waste to them. The majority of food waste is processed by anaerobic digestion, rather than being allowed to compost properly in the presence of oxygen.

Allowing compostable materials such as PLA to decompose in an anaerobic environment, such as a landfill, increases the risk of them releasing methane – a powerful greenhouse gas

PLA can be broken down in three primary ways. One is through photodegradation, where UV rays help to break it down. 

The second is by thermal degradation, which occurs when the polymer changes its properties under increased temperatures. 

The third is through hydrolysis, where it is broken down in water. Commercial facilities typically utilise a process of chemical hydrolysis followed by microbial action to disintegrate the polymer within the correct time frame.

That said, until more local governments review how compostable waste is processed, it is up to coffee shop owners and roasters to organise suitable waste collection for their used cups. 

An image of a white male holding a white takeaway coffee cup in an article explaining the time it takes for compostable coffee cups to decompose.

How long does it take for a compostable coffee cup to decompose?

In order to be classified as compostable, the European Union standard EN134321 states materials must break down to their non-toxic constituent parts within 12 weeks.

To break down fully, PLA requires oxygen, heat, and the right microbial environment. If compostable coffee cups were to be left in a home compost heap, it would take longer to disintegrate entirely. 

Nevertheless, it is likely to lose its structural integrity and break up after six months to a year. 

In a commercial facility, compostable coffee cups decompose in as little as a few days, but typically within a month. This also happens at temperatures exceeding 60ºC (140ºF), within an aerobic environment with the presence of the right microbial organisms.

Coffee shops and roasters who provide compostable coffee cups must advise customers on their proper disposal. This can be done on a face-to-face basis, through effective signage, as well as labels on bins. 

Additionally, disposal and recycling instructions can be printed directly onto the coffee cups using sustainable water-based inks or through green digital printing technology

Alternatively, customers can be encouraged to return empty compostable coffee cups to ensure they reach a proper commercial composting facility. This could be incentivised with discounts for used cup returns and other rewards systems.

An image of two kraft paper takeaway cups in an article explaining the time it takes for compostable coffee cups to decompose.

Roasters and coffee shops can benefit immensely by taking time to implement these policies. For instance, customers will recognise the brand as a sustainable one, which may encourage them to continue to support it. 

Furthermore, coffee professionals will know their business practices align with their personal ethics, while helping to secure the future of the specialty coffee sector. 

At MTPak Coffee, we offer 100% compostable coffee cups in three different sizes: 4oz, 8oz, 16oz, and 12oz. Made from PLA and kraft paper, they can be customised to ensure customers know how to dispose of them correctly. 

Furthermore, we can use digital printing to customise your cups or coffee sleeves, with a 40-hour turnaround and 24-hour shipping time. This allows us to offer low minimum order quantities (MOQs) of packaging and takeaway cups, no matter what size or material.

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

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How long do compostable coffee cups take to decompose?

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