“Biodegradable” cup claims don't wash

“Biodegradability” claims binned after our investigation.

Reusable coffee cups on green background

Coffee lovers wanting to swap single-use takeaway cups for a “greener” option may be tempted by claims reusable “bamboo” mugs are better for the planet.

The Manna Hydration Bamboo Fibre Mug, which we bought at Mitre 10, was tagged as “biodegradable & renewable” and made from “natural bamboo material”.

However, bamboo wasn’t the only substance used to make these cups – they also contained plastic. Bragging the cups are “biodegradable” also risks misleading consumers about what they’re buying.

What they're made from

The plant matter used in the cups is powdered bamboo or bamboo fibre. It’s held together with a binding agent such as melamine-formaldehyde resin (MFR) – a thermoplastic (see “Is melanine safe?”).

But from the labels on most cups, you wouldn’t know MFR was in them. We found cups at Farmers, Mitre 10, Stevens, T2 and The Warehouse advertised as either “bamboo” or “made from bamboo fibre”. Briscoes’ website stated its Prestige cup was made from “mainly bamboo powder”. However, neither melamine nor any other binding agent was mentioned.

Biodegradable coffee cup
The Manna Hydration Bamboo Fibre Mug, bought at Mitre 10, was tagged as “biodegradable & renewable” and made from “natural bamboo material”.

Several stores – Briscoes, Farmers, Mitre 10 and The Warehouse – also claimed their bamboo cups were “biodegradable”. But melamine isn’t going to decompose anytime soon – and none of the companies could provide us with evidence to back their claims.

After we questioned the stores, Mitre 10 removed its bamboo cups from sale. It said it had asked its supplier for evidence to substantiate the cup claims: “At this stage, we are not satisfied with the documentation we have on hand.”

The Warehouse said it didn’t have “appropriate verification” from its supplier to back up its biodegradability claim, so it would drop the statement.

Briscoes and Farmers have also dropped their claims.

Is melamine safe?

Provided they've been manufactured correctly and aren’t used at high temperatures, melamine products are considered safe to use – but poorly made items can contaminate food and drink with melamine and formaldehyde.

Melamine is suspected of causing bladder and kidney diseases, while formaldehyde can irritate the skin, respiratory system and eyes, as well as cause cancer in the nose and throat area when inhaled.

In July, German consumer watchdog Stiftung Warentest tested 12 bamboo cups. Seven cups leached higher-than-acceptable levels of melamine and formaldehyde, with “cheaper” products proving especially porous. Chemical migration increased when the items were subjected to high temperatures (70ºC) for extended periods, reiterating why melamine products should not be used to microwave food or drink.

Of the retailers we contacted, Stevens and Briscoes were the only stores to provide us with laboratory reports to show their bamboo-based products had been tested and complied with the European Union’s acceptable migration levels for melamine and formaldehyde. Stevens said it intended to relabel its cups to list melamine as an ingredient. Briscoes' website stated its 300ml bamboo travel mug was "microwave safe" but it's now removed the claim.

Member comments

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Patricia L.
21 Dec 2019
What about plastic electric jugs?

I'm interested in your remarks about melamine leaching from reusable coffee cups. have you done tests on electric jugs, and are older jugs more likely to leach undesirable chemicals than new ones?

Consumer staff
23 Dec 2019
Re: What about plastic electric jugs?

Hi Patricia,

We haven’t tested kettles for leaching so we don’t have a definitive answer to your question regarding older jugs. Although the plastic used in kettles is supposed to withstand the stress of repeated and prolonged exposure to high temperatures, it’s conceivable that leaching may occur, especially as the kettle ages. We’d advise discarding an electric jug where the plastic is discoloured, scratched or otherwise showing signs of wear and tear (including giving off a “plastic” smell). If you’re in the market for a new kettle, there are plenty of stainless steel and glass models to choose from.

Kind regards,

Julia - Consumer NZ writer