Millions of people start their day with a cup of coffee, but few think about what happens to the used coffee grounds afterward.
Most of them end up in landfill.
Now, new research from Loughborough University shows that this everyday waste could be turned into a powerful, low-cost tool for cleaning contaminated water.
In two recent studies published in Biomass and Bioenergy and Clean Technologies, researchers demonstrated that spent coffee grounds can remove harmful heavy metals such as lead, copper, and zinc from water.
These metals are common pollutants from industrial activity and can pose serious risks to human health and the environment.
Coffee is one of the most widely consumed drinks in the world. Global consumption now exceeds 176 million large bags each year, and that number continues to grow.
With it comes an enormous amount of waste, especially spent coffee grounds. These leftovers are rich in organic material and naturally porous, which makes them well suited to absorbing pollutants from water.
The research team, working with collaborators from Banaras Hindu University in India, explored two main ways of using coffee waste.
In one study, they heated used coffee grounds collected from a university cafeteria to create biochar, a carbon-rich material often used in agriculture.
By carefully controlling the temperature and heating time, the researchers produced a highly porous material that was extremely effective at trapping heavy metals. The biochar was able to remove up to 98 percent of lead from contaminated water, holding nearly five milligrams of lead per gram of material.
In the second study, the team showed that coffee waste does not always need extra processing. Raw, untreated coffee grounds were able to remove copper and zinc from water, especially when metal concentrations were relatively low.
This makes the method even cheaper and simpler, as it avoids additional energy or chemical treatments.
The researchers also tested combinations of coffee waste with other natural materials, such as rice husks. They found that while raw coffee grounds worked best at low pollution levels, mixtures performed slightly better when metal concentrations were higher.
In many cases, more than 96 percent of the metals could be removed from the water.
Dr. Monika Mahajan, lead author of one of the studies, said the research shows how a common waste product can be transformed into something valuable. By keeping the process affordable and environmentally friendly, the team demonstrated a practical solution for real-world water treatment problems.
Dr. Basmah Bushra, who led the second study, emphasized the broader message. Materials we often throw away can play an important role in reducing pollution and easing pressure on landfills. Turning waste into useful resources is a clear example of circular-economy thinking.
According to Dr. Diganta B. Das, the findings prove that coffee waste is far from useless. With further development, this approach could be scaled up to help clean polluted water in many parts of the world, offering an eco-friendly solution using something people already consume every day.
