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Could Coffee Grounds be a Sustainable Alternative to Synthetic Dyes?

Your daily cuppa may be good for more than just a morning pick-me-up. Researchers from Iowa State University (ISU) have discovered a way to use leftover coffee grounds to add color to clothing.

Sustainable alternatives to synthetic dyes are always a good thing. The textile industry uses millions of tons of chemicals every year and contributes to 20 percent of the world’s water pollution, according to the World Bank.

Changhyun “Lyon” Nam, an ISU graduate student in apparel, events and hospitality management, wondered if he could translate his coffee addiction into something tangible. He began by brewing a pot at home, then adding the grounds to fabric. The stain stuck. “Once I realized it worked, I went to local coffee shops and asked for their leftover grounds,” Nam said in a statement.

With the help of assistant professor Chunhui Xiang, Nam decided to experiment further, first by drying the coffee grounds for three days, then by boiling them with purified water to extract the dye, which he applied to cotton, linen, rayon, silk and polyester using different mordants to help bind the dye to the fibers. This resulted in a variety of shades of brown, said Nam, who recently published his research in the International Journal of Fashion Design, Technology and Education.

Scaling up the process shouldn’t be a problem, said Xiang. The Statistic Brain Research Institute estimates that 100 million Americans drink a cup of coffee every day. Not only would there be an adequate supply but repurposing used grounds would also divert additional waste from the landfill, he noted.

Neither is colorfastness an issue because the mordants help reduce fading. As with other natural dyes, however, a coffee-based colorant has at least one downside: consistency.

“One disadvantage of natural dyeing is that it’s hard to measure the quantity needed to get the exact same color,” Xiang said. “For each batch of dye, there may be a difference in the type of beans or maybe the coffee was brewed twice. Creating an exact match is a challenge, especially for manufacturers.”

More work is therefore needed, the researchers said, before coffee dyes become a reliable option for mass production, though Xiang says that concerns over color consistency may become moot as consumers become more amenable to the quirky and unique value proposition natural dyes offer.

For his part, Nam is experimenting with the coffee dye and a cellulosic fiber derived from kombucha tea to make shoes.