Bamboo has become very popular in recent years, taking on cotton as the fabric of choice for things we wear close to our skin, and for sheets and other bed linen.

It's marketed as a more eco-friendly fibre than cotton, with a smooth, silky feel and even anti-microbial qualities.

Are claims like this true? It's complicated.

Bamboo textiles are rarely natural bamboo. They're usually a semi-synthetic such as bamboo viscose, lyocell or rayon (depending on the production method used) – but may not be labelled as such. Although derived from bamboo fibres, the finished fabrics don't retain all the properties of natural bamboo fabric, which is similar to linen.

Bamboo textiles are rarely natural bamboo 

And when comparing fabrics, there are other variables that determine how they perform, apart from the properties of the original fibre.

So, to help us with the cotton versus bamboo comparison, we picked the brains of two textiles experts, Dr Rebecca Van Amber and Dr Saniyat Islam, who both lecture at RMIT's School of Fashion and Textiles.

First, let's look at where bamboo and cotton come from. Is one greener than the other?

Cotton vs bamboo: The basics

Cotton and bamboo are both plant-based fibres. Cotton plants produce flowers, then fruit, and as the fruits mature into seed pods, they produce a fluffy lint material.

The lint is collected by mechanical harvesters, and sent away for processing. This involves drying, cleaning, removing the seed from the lint, cleaning again and baling. It is then graded according to various characteristics, before being carded, combed and eventually spun into yarn.

Conventional cotton processing uses a variety of harmful chemicals including ammonia, azo, heavy metal-based dyes, flame retardants, formaldehyde, petroleum scours and softeners. However, if a cotton is certified as 'GOTS organic', harmful chemicals should not be used in its production. 

Some cotton is grown in Australia, but most of it comes from overseas.

Australia has a cotton-growing industry, but most of the processing is done overseas. The biggest growers of cotton are China, India, the US and Brazil.

Bamboo is grown mostly in South East Asia, particularly China. Some of it comes from managed plantations, and some from natural forests.

It's a fast-growing plant, and it regenerates quickly – as anyone who has bamboo in their garden knows only too well! And as a plant with a very tall, upright growth habit, it produces a high yield in a small space.

With little to no need for watering, fertilisers or insecticides, forest-grown bamboo compares very favourably with cotton, which is reliant on irrigation and sprays. However, plantation bamboo, according to Dr Islam, can have similar water, energy and chemical inputs as cotton.

It's difficult to say if bamboo from natural forest is a more sustainable option than plantation bamboo overall – there are many factors to consider, including farming practices. And this is just one reason why it is difficult for a consumer to know if the bamboo sheet set they're buying is a more sustainable choice than cotton sheets. But bamboo is a highly renewable resource.

Turning bamboo into viscose

Things become less 'green' when bamboo is processed. To create the soft, silky fabric we love in bamboo sheets, the raw bamboo fibre is put through chemical solutions to extract the cellulose, dissolve it, and regenerate it into a smooth, fine fibre.

When using chemical processing there are generally two main methods. 

The rayon process uses harsh chemicals to help break down the crushed fibre, after which it is extruded through spinnerets, reconverted into cellulose and then spun into yarns. 

The lyocell chemical method uses solvents to dissolve the bamboo, which is again forced through spinnerets, rehardened, reconverted into cellulose bamboo fibre, and spun into yarn.  

When sheets feel silky and have a high lustre, that's a giveaway that you're not handling natural bamboo

The chemicals used are varied but can include sodium hydroxide, carbon disulphide and sulphuric acid, which can be hazardous for those who handle them.

Dr Van Amber says that when sheets feel silky and have a high lustre, that's a giveaway that you're not handling natural bamboo, regardless of what the packaging says.

True bamboo has a coarser texture, and products made with it are rare. "I don't know that I've ever actually seen anything that was real bamboo fibres, but my understanding is it would be more like linen," she says.

Absorbency and comfort

There's no clear winner between bamboo and cotton when it comes to comfort.

So, how do cotton and bamboo viscose perform as bed sheets, blankets, doona covers and pyjamas? One much-discussed quality is absorbency, and whether they keep you cool or warm.

"For me, the main difference between cotton and bamboo viscose or rayon is that the cotton is going to be much more absorbent in terms of moisture," says Van Amber. "This is really advantageous in managing what we call a 'bedding microclimate'.

"Think of the blankets and duvet and everything going over the body. The microclimate includes the temperature of the air around the body, which the bedding is trapping, and also the level of moisture in that environment. And we know that the quality of sleep is often related to your body temperature and regulation."

Islam, however, believes it's hard to say whether cotton or bamboo viscose is more absorbent, and the difference in comfort might come down to how the fabric is made. "We need to look at the way it's woven or knitted, and how much moisture it can absorb."

It seems, then, on the matter of which fabric will keep your temperature more even through the night, it's either a point to cotton, or it's a matter of personal preference.

Cotton vs bamboo sheets: Pros & cons at a glance

Laundering and longevity

Van Amber and Islam agree that both cotton and bamboo viscose sheets can be machine washed and tumble dried. But they recommend you choose the gentler cycles and lower temperatures when laundering bamboo.

"You can wash cotton on very high temperatures," says Van Amber. "But bamboo viscose or rayon has a lower heat tolerance than cotton."

And will one wear out more quickly through repeated washing? Possibly. 

"Cotton becomes stronger when wet," says Islam. "Bamboo viscose gets mushy and loses its tensile strength. So, in terms of the longevity of the material, cotton products may be better. But then again, you can make viscose fabrics that have high tensile strength. And they can be washed the same as cotton."

Both cotton and bamboo viscose sheets can be machine washed and tumble dried

Van Amber says the main issue with bamboo viscose is the pilling.

"I find that especially if [bamboo viscose products are] very inexpensive, they often develop pills, which are the unsightly little fibres on the surface. That, to me, is an indication of poor quality.

"The reason you buy bamboo sheets is they feel really silky, really smooth… so if you wash them a few times and they get pills on them, well, that defeats the purpose of buying those sheets in the first place."

Bend and stretch: The shrinkage score

Last but not least, is the matter of shrinkage. It doesn't matter how nice your sheets are if you can't fit them over the mattress after a few washes!

Our sister organisation in the US, Consumer Reports, tested fitted sheets for shrinkage after 25 washes. Bear in mind that fabrics are pre-shrunk at the point of manufacture to ensure they don't shrink too much when the consumer gets them home. Islam says the industry standard of acceptable shrinkage during manufacture is three percent.

The test by Consumer Reports found that well before the end of the 25 washes, several of the sheets in their test couldn't fit even the thinnest mattress (a 20cm thick foam model).

They made a few key observations:

• Cotton sheets shrank by up to 6%
• Bamboo viscose sheets shrank by up to 15%
• Thread count and price were no indicator of performance
• The cotton sheets felt the same after 25 washes (the feel of bamboo viscose wasn't reported).

Based on the US test, it appears cotton is less likely to shrink than bamboo viscose. But again, other factors are likely to influence shrinkage, such as the type of weave.

Labels and false claims

A 2021 PWC Global Consumer Insights Survey into buying habits found that 49% of Australian shoppers are buying more biodegradable or eco-friendly products. More recently, a 2022 report by the Consumer Policy Research Centre found that 45% of consumers are always or often considering sustainability as part of their purchase decision-making. So, claims about responsible growing and manufacturing methods carry weight. 

What would you make of this label on a set of sheets: "100% organic bamboo. Standard 100 by OEKO-TEX"?

Sounds like pure, chemical-free bamboo? We showed it to Van Amber, who said, "This is quite misleading! The input was possibly 100% organic bamboo, but when I see that they're describing 'soft, silky sheets' – this is likely rayon."

As for the certification, Van Amber says the list of chemical substances it tests for does not include sulfuric acid or carbon disulphide, even though they have known health impacts.

The natural anti-bacterial properties and UV protection of bamboo fibre are often destroyed by the chemicals used in the processing

"Also, the OEKO-TEX certification is about detecting these substances on the finished product. It doesn't mean that the products have been manufactured without the use of any chemicals," she says. "So in that sense, it is very difficult for the consumer to understand what these types of certifications mean."

These same sheets are also listed as having anti-bacterial properties. The truth is, the natural anti-bacterial properties and UV protection of bamboo fibre are often destroyed by the chemicals used in the processing.

Although Van Amber says this labelling could be an example of greenwashing, she believes the only legal issue the company could potentially face is substantiating the anti-bacterial claims. But, as she says, who is checking? And it's possible such features can be added to a textile at the 'finishing' stage.

There's a senate inquiry into greenwashing under way in federal parliament, with a report due by 5 December. We'll keep you posted.

Stock images: Getty, unless otherwise stated.

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