Hemp Fabric vs Cotton: Is It Really More Sustainable?

Hemp was federally illegal to farm in the United States until 2018.

That’s the first thing to know, because it explains why a fiber humans have used for thousands of years is currently 0.05 percent of world textile production. It isn’t that hemp lost on merit. It spent 80 years banned by association.

Short answer: hemp really does beat cotton on the field metrics. It grows on rainfall in most climates where cotton needs irrigation, and it produces around three times the fiber from the same land. The complication is what has to happen after harvest to turn a stalk into something soft, and that step is usually chemical.

The 2018 Farm Bill

The Agriculture Improvement Act of 2018 removed hemp from the Controlled Substances Act definition of marijuana, defining it as Cannabis sativa L. at or under 0.3 percent THC by dry weight, and directed the USDA to build a domestic production program.

Growers now need a license under a state, tribal or federal plan. A real crop with real paperwork. The American supply chain for textile hemp is still being built from close to nothing.

Where hemp actually wins

The cleanest comparison comes from a 2005 Stockholm Environment Institute study prepared for WWF and BioRegional, and the strongest finding in it isn’t a number about litres.

It’s this: hemp in the UK needs 500 to 700 millimeters of water per season, which rainfall supplies entirely. No irrigation. Meanwhile 53 percent of the world’s cotton area is irrigated, and irrigated cotton yields more than twice what rainfed cotton does, which is exactly why growers irrigate.

Land is the other win. Comfortably. The same report found it’s possible to produce three times the amount of hemp fiber as cotton from the same area, and put organically grown UK hemp at the best ecological footprint of everything tested, against Punjab cotton at the worst.

There are litre-per-kilo figures in that report too, and we’d rather flag them than quote them cleanly. It’s a 2005 study, UK-scoped, its own tables disagree with its discussion section, and the authors later described the hemp processing route they measured as possibly unrepresentative. The rainfed-versus-irrigated point stands on its own without any of that.

Pesticides, and a quirk of the ban

Hemp needs very little in the way of pest control, partly because it grows fast and dense enough to shade out competition.

There’s a stranger reason too. Because hemp was federally illegal, there were no pesticides registered for use on it at all until December 2019, when the EPA approved its first ten hemp uses, nine of them biopesticides. The count has since grown past 90.

So the crop’s low-input reputation was partly agronomy and partly the fact that spraying it was illegal.

Now the part nobody markets

Here’s where it gets interesting. It’s also where most hemp articles quietly stop.

A hemp stalk is fiber glued together with pectin and lignin. Separating them is called retting, and the choice of method is the whole sustainability question.

A 2022 review in Materials lays out the trap. Water retting produces the best textile fiber, the cleanest and most thoroughly separated. It was also banned by most countries between the 1960s and 1990s for its wastewater, freshwater use, soil and air pollution and, in the paper’s own word, stench. It’s still done in parts of Asia and Egypt.

Dew retting replaced it. Far gentler on the environment. Also a less consistent fiber.

Mechanical decortication skips the biology entirely and, per the same review, delivers low quality, poorly separated bundles with high impurity content, unsuitable for textile purposes. To spin that into a soft shirt you have to degum it, typically with sodium hydroxide, potassium hydroxide or sodium carbonate plus chelating agents.

So the softest hemp is either water-retted, which is the dirty method, or caustic-degummed, which is chemistry the marketing never mentions. The cleanest method makes the roughest cloth. That tension is the honest center of this topic.

We’d also flag a claim you’ll see repeated everywhere, that most commercial hemp fabric is really processed as viscose in China. We went looking and couldn’t source it, so we’re not going to pass it on.

The certification that checks

GOTS is the one that verifies hemp claims, and it covers textiles made from at least 70 percent certified organic natural fibers, hemp included.

More interestingly, the current version contains a clause written for exactly the problem above: wastewater from industrial water retting of bast fibers must be treated to cut chemical oxygen demand by at least 95 percent for hemp. Somebody knew where the bodies were buried. Good.

What we’d actually tell you

Buy hemp when you find it, and buy it for durability rather than for a water statistic. It gets softer with washing instead of thinner, and a hemp shirt that lasts eight years beats a cotton one that lasts two by a margin no farming metric will ever match.

Look for GOTS if the label offers it, and for blends with organic cotton if pure hemp feels too rough, which is how most of it is sold anyway.

Keep the scale in perspective. Hemp is roughly 0.05 percent of world textile fiber production. It’s a better material and it is nowhere near being an answer at volume, which is a version of the point our sustainable fashion guide keeps arriving at: the fiber matters less than how long you keep the garment.

Frequently asked questions

Is hemp fabric actually more sustainable than cotton?

On the farm, clearly. It grows on rainfall where over half the world’s cotton area needs irrigation, produces roughly three times the fiber per acre, and needs little pest control. The processing stage is where the advantage narrows, because turning hemp stalk into soft fabric usually involves either polluting water retting or caustic degumming.

Why is hemp clothing so expensive?

Scale. Hemp is around 0.05 percent of global textile fiber, so there’s almost no processing infrastructure, and US cultivation only became legal again in 2018. The price reflects a tiny supply chain rather than an expensive crop.

Does hemp fabric get softer?

Yes, and unusually so. Hemp softens with wear and washing while staying strong, which is the opposite of cotton, where softness comes with thinning. It’s the main practical reason to buy it.

Is hemp clothing chemically treated?

Often, yes, and this is the part brands rarely discuss. Mechanically separated hemp fiber is too coarse and impure to spin for apparel without degumming, which usually means sodium hydroxide or a similar alkali. GOTS certification is the practical way to know something about how it was processed.