Next time you’re sipping on your skinny, frothy mochachocafrappalatteccino with maple syrup and cinnamon at the local Costabucksorthree coffee shop and surfing on their EasyHack(TM) wireless internet spare a thought for the grounds. The burnt out and scalded fragments of beans gone by that in this household are recycled via the compost bins but on the industrial scale represent an international commodity waste product you might not at first appreciate but represents a truly pressing issue.
Big coffee drink image c/o Shutterstock
Thankfully, there are researchers who are working on potential alternative uses for this organic waste material. Indeed, I vaguely recall writing for New Scientist back in the early 1990s about an alternative outlet for waste coffee grounds…but it may well have been Brazil nut shells, or both. Anyway, a team based at Boumerdes University and the National Polytechnic School in Algeria know all about the problem of coffee grounds. There are an estimated two and a half billion cups of coffee consumed each day (I know at least one classic radio presenter who imbibes a goodly proportion of that number) with Algerians using about 3.5 kilograms of coffee per head annually. That’s slightly behind the US at 4.2 kg, but way behind Finland at 12 kg. UK is 2.8 kg, global average is 1.3 kg.
However you look at it, it’s a lot of grounds to cover.
The Algerian team, writing in the journal IJEWM (reference below) explain how they can use zinc chloride and phosphoric acid to convert coffee grounds into “activated carbon” at 500-700 Celsius in just quarter of an hour. The final product, they also show, can be used as a potentially sustainable filtration materials for waste water treatment to remove organic pollutants and dyes. Coffee grounds as a source of activated carbon might preclude the need for using coal, wood or peat, and co-exist with coconut shells as a source. Given that in Algeria alone there are about 300 tonnes of coffee grounds generated daily, that could be a useful feedstock for the activated carbon industry provided sustainable collection and processing infrastructure can be put in place.