Scientists have developed a sustainable and efficient filter for water from something most houses have in excess: coffee grounds.

The coffee filter and a chart showing the filtration of lead ions. Credits: Chavan et al, 2016.

Restaurants, coffee shops and many houses produce millions of tons of used coffee grounds every year. Some of it is used as a fertilizer, some of it is mixed into animal feed and some is used in biodiesels, but much of it still ends up in landfills. Scientists have looked at several options to make something useful and sustainable from it and now, they might finally have a solution for it.

Creating water filters for lead is not unprecedented. In fact, it’s something that’s been done quite a lot – but creating cheap and eco-friendly filters is still a challenge. Scientists now report in the journal ACS Sustainable Chemistry & Engineering an innovative way to create such filters while also addressing another environmental issue: organic waste. The study writes:

“The fabricated foams can be used for the continuous filtration and removal of metal ions from water, demonstrating their versatility, in contrast to the sole coffee powder utilized so far, opening the way for the reutilization and valorization of this particular waste.”

“The incorporation of the spent coffee powder in a solid porous support, without compromising its functionality, facilitates the handling and allows the accumulation of the pollutants into the foams enabling their safe disposal.”

The filters they designed incorporate spent coffee grounds in a foam filter. The grounds are fixed in a bioelastomeric foam and the device reported an excellent efficiency in still water, removing 99 percent of lead and mercury ions from water.

But there are still some issues with the technology. In a more practical test with flowing water, the filter only removed 67 percent of the lead ions – which is still a decent result, but not truly satisfactory. Furthermore, while the filter also showed some potential for water remediation, some of the (harmless) organic matter still passed through. In other words, the water would taste a bit like coffee. Arguably, that’s not really a problem when your water is contaminated with lead, but it’s still something you’d want to fix before releasing a commercial product. While this shows a lot of promise and might make a big difference someday, we’re still a while away from these filters reaching commercial status, though.