Geology for Global Development

#EGU2014: Cleaning with Coffee


Source: Martin Fisch, Flickr

We’re drinking an enormous amount of coffee in Vienna this week, but the residues at the bottom of the cafetière usually end up in the bin. Kalliopo Fotopoulou, from the University of Patras in Greece, has found a way to transform that residue into something far more useful.

Baking coffee residues in an oven changes them into a carbon rich “biochar”, which can be added to soils to soak up carbon, improve soil fertility and absorb unwanted chemicals from the environment.

The residue is easy to come by – the samples in Kalliopo’s study came straight from her university coffee shop. There is no competing use for the residue, it would otherwise have been thrown away, so blitzing the coffee residues in an oven isn’t denying resources to agriculture or other industries.

The biochar they produce is porous and has a high surface area, and it does a good job of purifying water. The filtered water could be recycled within coffee shops to produce a better tasting coffee. Coffee purists may notice the difference, as biochar removes odours in the water that interfere with the coffee’s aroma.

The team have demonstrated that coffee biochar cleans up mercury from its surroundings pretty effectively, but Hrissi Karapanagioti, a coauthor on the study, is optimistic that they can find a better application. “Our goal is to try out new metals, such as arsenic, and see if the coffee biochar could clean that up too”.

Arsenic contamination affects 137 million people worldwide, many of whom reside in developing countries. With a little more research, coffee biochar could deliver a low-cost method to clean up dirty water.


Read more about arsenic contamination in water supplies, and the associated health problems, in our previous post.

This work is being presented here at EGU in Vienna. You can catch the poster on Friday 2nd May in the blue poster area (B151).

Rosalie was the Himalayas Programme Officer for Geology for Global Development and writer for the GfGD blog. She is a geochemist and a postdoc at the University of Oxford.

1 Comment

  1. How does it work for removing dissolved contaminants?

    With regards to global application, how long do you need to cook the residue for and how much filtering can a given amount of biochar achieve?

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