Hemp fabric vs cotton and bamboo: how sustainable is it?

Not many people are yet familiar with hemp fabric. Hemp fabric and marijuana both come from Cannabis sativa. Over thousands of years, growers have developed two different strains of it. Marijuana comes from the one high in psychoactive compounds. What’s now known as industrial hemp comes from the one bred for stronger fibers.

Cultivation of hemp started at least 10,000 years ago, mostly for medicinal purposes. Development of hemp fabric began at the start of the Iron Age. In the US, George Washington, Thomas Jefferson, and Andrew Jackson all cultivated industrial hemp. 

Since both uses come from different strains of the same plant, most people haven’t known or cared about the difference. 

Beginning in the middle of the nineteenth century, much of the world outlawed marijuana. In the US, the Marihuana Tax Act of 1937 essentially destroyed production of industrial hemp as well as marijuana, although the tax was not collected during the Second World War. 

Not until the 2018 Farm Bill did the federal government again encourage industrial hemp. The rest of the world has likewise started to cultivate industrial hemp on a larger scale. 

Industrial hemp uses the stalk of the hemp plant, which has two layers. The outer layer has the bast fibers used to make cloth. (Bast fiber simply means that it comes from the stem of a plant as opposed to somewhere else. Other bast fibers include flax, jute, and stinging nettle.) The woody inner layer makes building materials, fuel, and animal bedding.

Growing industrial hemp and making sustainable fabric from it

Hemp grows in mild to tropical climates with high humidity. It grows in all kinds of soil, including poor soil and contaminated soil. In fact, it actually removes the contaminants. Growing hemp was part of the effort to decontaminate the soil after the Chernobyl meltdown. Like all plants, hemp takes nutrients from the soil, but unlike many plants, it returns about 60-70% back to the soil. 

What’s more, hemp grows very rapidly. It’s possible to harvest hemp up to three times a year. It is naturally resistant to insects and so doesn’t require pesticides to thrive. Because it grows so densely, it crowds out other plants. Therefore, it doesn’t need herbicides, either.

For that matter, needs little water once it gets established, so irrigation is also not necessary.

Small hemp operations can handle all the work by hand. Large-scale production requires some machinery, although certainly not as much as crops that require considerable irrigation and chemicals. 

After harvest, the hemp stalks ret in the field for 4-6 weeks. That is, it soaks in water to facilitate the next step.

Then a hammermill separates the outer stalk from the inner stalk. Once the bast fibers are carded into strands and cleaned, they are ready for processing. For making fabric, a process called steam explosion turns it into a weavable fiber, which is then spun into yarn and woven into a linen fabric. 

Some manufacturers market “hemp viscose,” rayon in other words, which uses the same chemical processes as any other viscose. It’s softer than hemp linen and faster and cheaper to make. Some people may consider it a less sustainable fabric.

While 100% hemp fabric has its fans, manufacturers often blend it with cotton or silk to make it softer.

Uses of hemp fabric

Hemp can make such products as paper or rope and serve as a building material. As far as hemp fabric is concerned, it can make very absorbent towels. Except as viscose or a blend, it isn’t soft enough for sheets, but it is very useful for blankets and duvets. It makes a very durable upholstery fabric. Hemp also makes very good canvas for such items as tents, sails, shopping bags, or backpacks. 

I have also seen reference to hemp coffee filters and milk bag strainers.

More and more people are wearing hemp clothing. This category includes uppers for shoes, as well as the more expected shirts, trousers, dresses, tops, and exercise apparel. 

Hemp linen has a texture comparable to cotton—not so much really soft cotton but canvas. It’s sturdier and more durable. It doesn’t shrink. It resists pilling. A typical cotton tee shirt wears out in 10 years or sooner. A hemp tee shirt can last more than 20 years. Its long fibers soften with every washing and do not degrade even after being laundered dozens of times. 

Also, hemp clothing is lightweight and breathable. Because it wicks moisture from the skin to the atmosphere so easily, it is ideally suited to hot climates. It takes dye easily. Not only that, but it resists mold, mildew, and pathogenic microbes.

Hemp vs cotton

Growing cotton requires a lot of water, fertilizer, herbicides, and pesticides. Hemp grows so large that it crowds out any weeds that try to get established. It is also ready for harvest more quickly than cotton. 

What’s more, an acre of hemp produces 1,500 pounds of fiber. An acre of cotton produces only 500 pounds. Organic cotton produces even less, although it used more nearly natural chemicals. 

For these reasons, cotton—even organic cotton—has a much higher environmental cost than hemp. 

Although producing hemp fibers is more efficient and simpler than cotton, hemp fabric is now considerably more expensive. In part, that’s because of hemp’s relative novelty and the much larger-scale production of cotton. It stands to reason that if hemp becomes as popular as cotton, it will also become less expensive. 

Hemp vs bamboo

In comparing hemp fabric to bamboo fabric, both are more sustainable than cotton. In some ways they’re equally sustainable. In others, one or the other has the edge. 

• Both have little environmental impact when it comes to growing them. They need little or no fertilizers, pesticides, or irrigation. 
• They grow quickly. Hemp is ready to harvest three or four months after planting. Bamboo is ready in three to five years, but harvesting doesn’t kill the plant. So while the harvested culm regrows, others are coming ready for harvest. Therefore, both hemp and bamboo can provide new raw materials every few months. 
• Right now, China is the world’s leading producer of both bamboo and hemp. Transportation from there to manufacturing facilities probably has a similar carbon footprint for both materials. Hemp will grow in cooler climates than bamboo, however. Cultivation of either plant anywhere else is probably closer to production facilities and therefore still equivalent.  
• Both hemp and bamboo are easy to launder and care for. You can wash them in all water temperatures. You won’t need bleach or other harsh, toxic chemicals, 

Here’s where bamboo has the edge:

• Bamboo is mainly harvested with hand tools and not machinery. Manual labor doesn’t burn fossil fuels and therefore contribute to greenhouse gas emissions.
• As I said, harvesting bamboo doesn’t kill the plant. A new culm will grow in the same place. Hemp, on the other hand, must be replanted, which means the field must be plowed and tilled again. Again, that process emits greenhouse gases.
• Most bamboo fabric is softer than hemp fabric.

Here’s where hemp has the edge:

• Hemp can grow in contaminated soil and even restore it.
• So far, at least, nearly all commercial hemp fabric is a kind of linen. Most bamboo fabric is a kind of rayon, which requires harsh and toxic chemicals. Hemp has the edge comparing hemp linen to bamboo rayon. Consider it a tie in comparing one linen or one rayon to another.
• Hemp fabric is more durable than bamboo fabric. 

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Sources:

Hemp vs cotton / How Stuff Compares. 2013

Is hemp or bamboo clothing more sustainable? – 10 deciding factors / Ecotero. January 27, 2021

What is hemp fabric: properties, how it’s made and where / Boris Hodakel, Sewport. April 28, 2021