August 30, 2021

Mission not impossible: High-grade denim made without chemicals



In 1966 Sakamoto Denim developed the first “automatic continuous dyeing machine” in Japan. Creating a wide variety of colors, the company has long been at the forefront of Japan’s indigo dyeing industry.

It is a little-known fact that the clothes we wear come at a significant cost to the environment. According to the 2019 United Nations Conference on Trade and Development, making a single pair of jeans requires 7,500 liters of water.

That is as much water as the average person drinks in seven years. Might that knowledge give you pause before you splurge on your next pair of jeans?

The fashion industry uses 93 billion cubic meters of water each year, an amount that would meet the needs of 5 million people. A vast amount of water is needed to wash fibers such as cotton before they can be dyed. Then, in the process of cleaning those fibers, 500,000 tons of microfiber (the weight of 3 million barrels of oil) is flushed into the sea each year. These two problems — the use and the contamination of large amounts of water — are key environmental issues facing the fashion industry.

Japan’s unique process of hand-dyeing has existed since the Edo Period. Craftspeople take several days to carefully dye the fabric by placing it in indigo, which has been fermented in a vat.

But one company is confronting both problems head-on: Sakamoto Denim, in the Hiroshima Prefecture city of Fukuyama, the second-most-populous city in the prefecture. It lies on the border with Okayama Prefecture, far east of the city of Hiroshima. The region around Fukuyama and extending into Okayama is known as Bingo, and it boasts a thriving textile industry. The area is particularly known for the production of thick fabrics such as denim and cloth for work clothes, and the quality of its goods is so high that even well-known overseas luxury brands outsource their denim production to factories there. Denim lovers from around the world know the area as a denim mecca that makes many highly sought-after products. Sakamoto Denim, founded in 1892, is a successful dyeing factory. But in recent years, its use of large amounts of warm water and detergent during the dyeing process began to weigh on the minds of its owners.

From around 2000, the use of environmentally friendly organic cotton became common in the denim industry. However, Sakamoto Denim President Ryoichi Sakamoto, a fourth-generation company leader, had reservations because even if the yarn itself was organic, it was inevitably drenched in chemicals during the production process. He also knew that Sakamoto Denim was using extremely large amounts of water — and warm water at that. This was because in order to dye denim well, it was necessary to first thoroughly wash away the cotton strands remaining from the process of making thread. And in order to dye the yarn evenly, it was necessary to wash the yarn with a large amount of detergent in warm water.

Inside the factory. Work is carried out efficiently using machines.

In response, Sakamoto set his sights on a new technology involving electrolysis. Electrolyzed water, produced by adding salt and running an electric current through it, can act as a detergent but contains no chemicals. Moreover, it produces satisfactory results even at normal temperatures, so there is no need to heat it. By adopting electrolyzed water in the cleaning process, Sakamoto Denim managed to decrease the amount of heavy oil it used by as much as 40 percent.

The company is also working on the development of new environmentally friendly dyeing technologies. Denim fabric is generally dyed with synthetic indigo. But Sakamoto Denim produces natural indigo dyes extracted from plants. However, unlike artificial dyes, natural dyes contain impurities such as bits of soil and roots, so it is often difficult to get the dye to bond to the fabric well enough to produce dark colors. To overcome this, the company developed a dyeing machine that achieves rich indigo colors that competitors cannot equal. It is also working on the development of new colors by experimenting with combining natural indigo and other natural dyes.

Sakamoto Denim handles the dyeing for the region’s Japan Denim project.

Gentaro Matsumoto, who is in charge of the Environmental Department at Sakamoto Denim, said: “Since the time of its founding, 130 years ago, our company has been here dyeing on this same land and using the same water. In recent years, we’ve been treating our wastewater ourselves, and every morning our employees bring in the sludge from the treatment process and mix it in with kitchen waste, composting it in a bio-processing machine and eventually using it in the company’s flower beds and on nearby farms. We will continue to aim to be the world’s most environmentally friendly dyeing and processing plant.”





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