Stay away from bamboo coffee cups, German consumer group warns

Stay away from bamboo coffee cups, German consumer group warns

You might think you’re doing your bit for the environment by using a bamboo cup - but new research by German consumer group Stiftung Warentest has shown that you might be risking your health in the process. 

Stiftung Warentest: “Keep your hands off bamboo cups”

Bamboo cups are officially in vogue: a much-lauded alternative to disposable coffee cups, which are responsible for 36.000 tonnes of waste per year, these “natural” cups are marketed as being environmentally-friendly, ecological and biodegradable.

Therefore, it may come as a surprise that the Stiftung Warentest, a reputable consumer organisation that investigates and compares goods on the German market, has warned people to “keep [their] hands off bamboo cups” and opt for other reusable drinks containers instead.

All bamboo cups contain melamine resin

Testing 12 different bamboo cup brands, Stiftung Warentest found that buyers are generally given the impression that they are buying natural products. With descriptions such as “bamboo mug” or “made from bamboo fibres”, producers gloss over the fact that the cups are made from a powder of finely-ground bamboo fibres that are then glued together. 

All of the cups tested contained melamine resin, a kind of plasticky glue made from formaldehyde and melamine. Melamine is suspected of causing damage to the bladder and kidneys, while formaldehyde is a known irritant and can even cause cancer if inhaled. Still, as long as certain conditions are met, melamine resin is not considered a dangerous substance. 

Cups unsuitable for hot drinks

One of these conditions, however, is that it is kept under 70 degrees celsius. And these cups are being specifically marketed for hot drinks. So, when the Stiftung Warentest testers simulated the process of adding coffee to the cups, they made a concerning discovery. 

The cups were filled with a hot, slightly acidic liquid (akin to coffee) and left for two hours. This process was repeated seven times per cup. After the third and seventh fillings, the liquid in each cup was tested for chemicals. 

The results showed that four of the twelve beakers contained “high” levels of melamine after the third filling, and three more after the seventh filling. Many of them were also releasing high amounts of formaldehyde. Even more concerning, the results were sometimes higher after the seventh test, suggesting that the harmful chemicals don’t evaporate but continue to seep into drinks with prolonged use. 

Misleading packaging

Stiftung Warentest also slammed the manufacturers for not properly warning about the dangers of placing the bamboo cups in the microwave. When heated to high temperatures, the cup’s material will begin to decompose: as the cup’s surface is destroyed, it will release even more melamine and formaldehyde. One cup’s packaging simply stated that it should be kept out of the microwave to prolong its life. 

Many of the cups also suggested that they were “biodegradable” or “recyclable”. Stiftung Warentest maintains that this is a barefaced lie. Of course, natural bamboo fibres will biodegrade over time, but the cups will not rot, even if you give them years. Neither can they be recycled via standard methods - the only option is to burn them. 

Their overall advice? Pick a different kind of reusable cup. 



Abi Carter

Managing Editor at IamExpat Media. Abi studied German and History at the University of Manchester and has since lived in Berlin, Hamburg and Utrecht, working since 2017 as a writer,...

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Leave a comment

natm 14:58 | 29 July 2019

Hey! Wow, what about bamboo cutting boards? I got one from Ikea half a year ago

Miri 20:37 | 29 July 2019

The problem is not the bamboo itself, but the glue that is holding the fibres together to make a cup. If your cutting board is only made from bamboo, there's no problem

Marilyn Stanley 19:53 | 31 July 2019

What about bamboo toothbrushes ???

ecomondo 13:17 | 10 October 2019

Bamboo Toothbruses are other 100% solid bamboo without additives.

Catherine O'Connor 00:59 | 2 August 2019

How is it acceptable to injecte formaldehyde into small babies to create an immune response, yet drinking your coffee from a cup containing it is not?

ShoutingInTheWind 11:41 | 3 August 2019

Because in both cases, bamboo cups and vaccines, the formaldehyde is one ingredient in a chemical compound which is safe. The problem with the cups is that when you heat them to 70C or above, that chemical compound breaks down, releasing actual formaldehyde. Make sure that after you get your children vaccinated that you don't heat them to 70C or above, and you won't have any problems.

Jandee 10:32 | 6 August 2019

Can you provide links to peer reviewed journals to confirm this information please? I am not doubting but it is always a good idea to cite an article so that readers can research further. Thank you.

Vivian.Hendriksz 14:03 | 7 August 2019

ecomondo 13:30 | 10 October 2019

Safe according to official test from Tüv Rheinland:

Travis Britton 13:44 | 28 August 2019

Sounds like KeepCup commissioned this report? Can you ask do tests on the plastic keep cups to see how much of that leaks into your drink please.

brjgray1969 22:07 | 8 September 2019

Have they done any similar tests on the plastic version of reusable cups? Plastics are known to leach also. It would be useful to get a view across all options, with a recommendation for ceramic or stainless steel if that is what’s ‘safest’.

Clare Albert 12:50 | 1 October 2019

These test were for coffee mugs but there is a whole market out there for toddlers and children's feeding sets, my grandson uses a bamboo plate and bowl for most of his dinners, is this safe because often the food is put in hot and allowed to cool?

Roger Bishop 09:14 | 8 October 2019

The problem is..........why do you need to take the coffee away..........try being old fashioned and maybe sit down and drink out of a real cup and take some time to enjoy your surroundings and fellow human beings!!!!!!!!

ecomondo 13:27 | 10 October 2019

This test is highly controversial. It's a Worst Case Scenario test. Just like a crash test for cars, so of course things will break, but it has nothing to do with daily normal use. Ecoffee Cups are safe to use and the official test reports from both TüV Rheinland & Intertek prove this. It would be fair to research also the billions of disposable paper cups (which ALL contain plastic) and plastic cups (because less than 1% of these are recycled).

Valerah 10:21 | 16 October 2019

Why would anyone leave coffee in a cup for two hours? However the test results are concerning, and the warning about microwaving, and end-of-life disposal valid. As others have said, ALL 'disposables' need comparative testing. Silicon is the new plastic - how does that fare on use, leakage of materials, and end-of-life recycling etc

David Bauman 23:45 | 14 November 2019

Interesting. Was this published in a peer-reviewed scientific journal? Have other independent studies found similar results? Thank you for the article.

Teodoro Lupo 11:10 | 15 November 2019

Sorry, but it's not really correct: there is 5 grade of melamine food safety. If you buy cheap bamboo dishes it will probably be a non A5 grade of food safety (A5 heat 120 degrees, A1 / A3 heat 80 degrees). So, my suggestion is to buy better: for example EKOBO is totally safe.

Paul Fickinger 16:22 | 13 February 2020

what about the new cups from Blue Bottle?

Paul Fickinger 16:22 | 13 February 2020

what about the new cups from Blue Bottle?

TanveerMunir2 14:05 | 5 October 2020

So this story is describing the effect of glues and surfactants used to make bamboo cups. Sure there are bad effects of those chemicals, that's why there are only a few types of glue recommended for food contact surfaces. Bamboo degradation would take about 13 years of time depending upon the environmental conditions. Here are some studies about use of untreated wood.