Where the roads are paved with coffee

Melbourne is a city well known for its obsession with coffee, but while there is a café on every street corner, in the future those streets could literally be paved with the stuff. At least that’s what will happen if Professor Arul Arulrajah, leader  of the geotechnical group in the Centre for Sustainable Infrastructure at Swinburne University of Technology in Melbourne, has his way. Arulrajah has made a career out of exploring novel uses for by-products and waste material in civil construction, but few have been as close to his heart as this. “It’s essentially just an idea that I had because I’m an avid coffee drinker – I drink four to five cups of coffee per day – and I just noticed that the baristas throw it away and I’m aware that it then goes to landfill, so I thought why not have a look at this as an  engineering material and examine what I need to stabilise it and make it work for road fill applications,” he tells Global Coffee Report. “I started off looking at it as a non-structural fill material, which was without any additives mixed with it, but now I am looking with my PhD student [Teck-Ang Kua] at how to stabilise it to make it work as a structural material, which is a higher grade of fill material.” Arulrajah and his student put the coffee through a process whereby it was dried at 50 degrees Celsius, then mixed with slag that is commonly used in steel manufacturing and an alkaline solution to bind it all together. The result, they found, was a material strong enough to be used as the layer of road that sits under the surface and provides foundations. “If it’s treated adequately and stabilised adequately, then it can be used as a valuable resource as a building material, but it has to go through the right treatment process to make it work.” Arulrajah says that this new use for coffee grinds could come in handy as we move towards becoming a society that is more conscious about the waste we generate. “There is a significant amount of this material going into landfill and sooner or later I think that it will have to be addressed,” he says. “I am just trying to open up some doors so that some other industries or road constructors or even local councils will look at it as a viable material – for example if a local council can look at it and then look at the number of cafés they have in their local area.” Arulrajah points to the fact that this concern with excessive waste production is also gaining traction in the halls of government in his home state of Victoria, Australia. “Our state government is looking at zero-waste policies and I think these sorts of ideas will start to help to create avenues for everyone from the small business owners who are running the cafés right up to the local councils who are making the roads to address that,” he says. While Arulrajah has spent many years investigating the viability of different materials for use in these ways, he says that none have ever caused a splash quite like this one. “I was joking with my colleagues that while some of my other research has been funded and on a large scale, this seems to have generated the most amount of interest and I think that is because of our strong coffee culture in Melbourne,” he says. GCR