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Applications from coffee waste - the golden resource of the Central Highlands
Every day, millions of cups of coffee are brewed around the world, generating vast quantities of coffee grounds that are typically regarded as waste. The question that started my research was simple: could we turn an agricultural by-product that is normally thrown away into a high-value porous material that solves two problems at once, organic waste and greenhouse gases? After the coffee farm in Thái Nguyên, I could not stop asking it.
I took the question to the laboratory at Hanoi National University of Education, where I worked under the guidance of M.Sc. Tran Minh Duc. The hardest part of the experiments was controlling the temperature (between 400 and 700°C) and the ratio of KOH activation so that the surface of the carbon would become as porous as possible. I carefully prepared the spent coffee-ground samples, carbonized them, activated them with KOH, and followed each of them through a chain of careful analysis. My mentor helped me think more rigorously, to approach a problem from its root and to stay objective about every result, whether I liked it or not.
Using SEM, BET, FTIR, XRD and TGA, I could see what the eye cannot: the micro-structure of the material, its surface area and its chemical groups. Theory turned into pictures and data. In a way, it felt like holding the hat from Huế up to the sun.
The best material reached a surface area of 876 m²/g and adsorbed up to 4.8 mmol/g of CO₂, and it kept 91.7% of its capacity after six cycles of reuse. When those results came in, I felt proud and happy. Weeks of work in the lab had become clear evidence that coffee grounds could be used to protect the environment. My manuscript is now under review at the journal Environment Protection Engineering.
Not everything worked. When the humidity rose from 0% to 80%, the material’s adsorption capacity dropped from 3.0 to 1.8 mmol/g, a fall of 40%. That result showed me the gap between a controlled laboratory and the real world, where air is rarely dry. It also taught me to be more careful and disciplined when preparing samples, and to control every variable in an experiment. If I continue this research, my next step is to make the carbon resist moisture better and to refine the process so that it keeps its performance in natural conditions.