BY MARIA BURKE
Researchers from the United Arab Emirates have recently patented a technology which uses coffee and plastic waste materials to capture carbon dioxide (CO₂) with potential for use in a wide range of industrial processes.
Activated carbon materials are widely studied as a possible way to absorb CO₂ because they can selectively bind gas molecules onto their surface. However, the conventional methods of producing activated carbon often require high temperatures, long reaction times and expensive raw materials, which make them expensive and environmentally unfriendly. Additionally, the adsorption rate is often not high enough to be economically feasible.
This new method involves the co-pyrolysis of specific ratios of spent coffee grounds and polyethylene terephthalate (PET) plastic waste at a temperature less than 500°C and mixed with potassium hydroxide as the activating agent (Google Patents, 2025, US12391556B1). The resulting ‘biochar’ is then heated to temperatures less than 700°C to become activated carbon.
The researchers say the process makes activated carbon with a significantly higher specific surface area and increased porosity than comparative techniques. It also introduces oxygen functional groups, which enhance the material’s capacity to adsorb. The rate of CO₂ adsorbed onto a surface of the synthesised activated carbon is greater than 8mmol/g at 0°C and ambient temperature.
For comparison, one study compared organic biomass precursors activated through physical or chemical processes for CO₂ capture and found coffee grounds had an adsorption rate of 4.9mmol/g while peanut shells came out top at 7.45mmol/g (M Karimi et al, Environ. Chem. Lett., 2023, DOI: 10.1007/s10311-023-01589).
‘What begins with a Starbucks coffee cup and a discarded plastic water bottle can become a powerful tool in the fight against climate change through the production of activated carbon,’ says lead inventor Haif Aljomard of the University of Sharjah. ‘This invention repurposes two abundant waste streams – coffee and plastic – into a high-performance adsorbent. The resulting activated carbon shows strong potential for capturing CO₂ from fossil fuel-based energy systems, contributing to the reduction of air pollution.’
The team cites a variety of industrial operations that could use the technology, such as gas purification, drinking water filtration and groundwater remediation as well as wastewater and sewage treatment systems. They also suggest applications in the energy sector, including solvent recovery, natural gas purification, flue gas cleaning at waste incineration plants, exhaust air treatment, process gas purification and emission control.
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