As coffee is one of the most widespread drinks in the U.S., a huge amount of used grounds is left over each year.
According to researcher Despina Fragouli, millions of tons of used coffee grounds is produced annually worldwide by people in their homes, restaurants and the beverage industry. Some of this is reused as a biodiesel source, mixed into animal feed, or applied as fertilizer, but the bulk lands up in landfills.
An article in the journal ACS Sustainable Chemistry & Engineering describes an inventive way to reduce this waste and address another environmental problem at the same time. Scientists integrated spent coffee grounds in a foam filter and used it to remove harmful mercury and lead from water.
Researchers are also studying it as a possible material for reversing or stopping environmental damage to water. Experimental results show that powder made from used coffee grounds can purge heavy metal ions that could cause health problems from water. An additional step is however required to separate the powder from the decontaminated water. Fragouli and his colleagues explored ways to simplify this process.
The team placed spent coffee powder in a bio elastomeric foam, which was used as a filter. Over a 30-hour period, the foam removed up to 99 percent of mercury and lead ions from still water. This experiment was followed up with a more practical test where lead contaminated water was allowed to flow through the foam. As a result, up to 67 percent of the lead ions were removed from the water.
Fragouli explains that as the coffee is restrained, it becomes easy to handle and no additional steps are required to discard it after use.