Coffee Grounds Save the Day

by Randy Lau


On busy mornings, people usually brew a fresh pot of coffee to stay awake. People are always downing cup after cup, but they never wonder about what is left behind. Coffee grounds. These leftovers always end up in the trash can or a compost bin to waste away. Many people think coffee grounds have no use in their daily lives. However, these recycled grounds have more benefits than meets the eye.

Coffee grounds have many functional uses in people’s lives as:  facial scrubs, meat marinades, natural deodorants, fertilizers, and much more. More importantly, it can be used to remove the heavy metals in our drinking water. This water purification process, however, is complicated. In a study issued in ACS Sustainable Chemistry and Engineering, Despina Fragouli and her colleagues, at the Italian Institute of Technology, described their simplified process for using the coffee powder for water purification. It involves infusing the coffee grounds into a porous-like foam that can help remove heavy metals from water.

Fragouli and her team, at the Italy Institute of Technology, develop new compounds from agricultural waste and use them - like turning something from non-preservable to material that can preserve objects. “We use a lot coffee here in Italy,” said Fragouli, the author of the study. With that in mind, they wondered, “What about coffee?” Surprisingly, coffee is made out of chemical compounds that work well with trapping dangerous metals such as: mercury and lead, which are common, poisonous metals in our water supply.

Researchers have tried to remove metals from water before, but they used coffee grounds as it was. However, Fragouli’s team plans on using the coffee grounds as a foam. In order to develop the coffee foam, Fragouli’s team dried coffee grounds (espresso) and mixed it with sugar and silicon. After the new mixture solidified, her team dipped the product into water in order to dissolve the sugar within. Once they dipped it in water, the sugar completely dissolved and left behind holes to create a sponge-like texture.  They then dropped their porous-like block into some water that contained mercury and lead and measured its water concentration for periods of time. This example, which has a metallic concentration of 16 parts per million (1,000 times greater than what the Environmental Protection Agency thinks is a possible threat), a foam block that is the size of a postage stamp removed 99% of the impurities from metals within 30 hours. The metals in the water need time to make contact with the foam, so it is not as effective in running water. It only removed 67% of the impurities from metals and soon the foam block reached its absorption limit. According to Fragouli, this is the same efficiency to remove heavy metals as store filters provide.  

Fragouli’s team is working hard to improve the integrity and silicon mix of the coffee foam so it is the only filter people need. Scientists are also testing with other waste products from foods and other food companies to seek out different chemical properties in materials and hope that it will extract a variety of other chemicals. In the near future, we might finally have an all-natural filter that can do its job to the fullest.