Researchers at Loughborough University have shown that everyday coffee waste can play a powerful role in cleaning contaminated water.
Two new studies reveal how spent coffee grounds can remove toxic heavy metals such as lead, copper, and zinc. The research highlights a low-cost, sustainable approach that turns a common waste product into a valuable environmental tool.
The findings appear at a time when global coffee consumption continues to rise. In 2021–22, the world consumed more than 176 million 60-kg (132 lbs) bags of coffee. That demand generates massive volumes of spent coffee grounds, most of which end up in landfills.
Instead of discarding this waste, researchers explored how it could help address water pollution.
Turning waste into filters
Spent coffee grounds contain porous, plant-based structures that readily trap metal ions. This property makes them strong candidates for water filtration.
In one study, researchers heated used coffee grounds collected from Loughborough University’s Edward Herbert Building cafeteria. They worked with collaborators at Banaras Hindu University in India.
Heating the grounds produced biochar, a carbon-rich material known for its adsorption abilities.
After optimising heating temperature and duration, the team achieved striking results. The coffee-based biochar removed up to 98 percent of lead from contaminated water. Each gram of biochar held up to 4.9 milligrams of lead.
Dr Monika Mahajan, lead author on the first study, said: “This work demonstrates how an everyday waste such as spent coffee grounds can be transformed into a high-value, sustainable adsorbent for removing toxic metals from water.”
She added: “By optimising the decomposition conditions, we were able to significantly enhance the material’s performance while keeping the process low-cost and environmentally friendly.”
Raw grounds work too
The second study focused on simplicity. Researchers tested whether untreated coffee waste could clean water without extra processing.
They found that raw coffee grounds removed copper and zinc effectively at low metal concentrations.
This approach reduces energy use and processing costs, making it attractive for large-scale applications.
The team also tested blended materials. They combined coffee waste with rice husk to improve performance at higher contamination levels.
The experiments examined contact time, adsorbent type, and metal concentration.
Results showed that more than 96% of the metals could be removed.
Raw coffee waste performed best at lower concentrations. The coffee and rice husk mix worked better at higher copper and zinc levels.
Dr Basmah Bushra, lead author on the second study, said, “Our studies show that what we often dismiss as waste, like spent coffee grounds, can actually become powerful materials in tackling environmental pollution.”
She added, “By turning waste into adsorption material, we can not only reduce landfill burdens but also create affordable materials for cleaning up contaminants.”
The research highlights how coffee waste can support circular-economy practices. The material is cheap, abundant, and widely available worldwide.
Dr Diganta B. Das, Reader in Porous Media at Loughborough University, emphasised the broader impact. He said: “They have worked incredibly hard to deliver these results and show that coffee waste is not a waste at all — it can be transformed into high-value materials, enhance material circularity in our day-to-day activities and clean the environment.”
The studies suggest that coffee-based filters could scale up for real-world water treatment.
The approach offers an eco-friendly option for tackling heavy metal pollution while reducing waste.
The study is published in Biomass and Bioenergy and Clean Technologies.