TORONTO -- The best way to efficiently brew espresso with the least amount of wasted coffee is to use coarser grinds that do not clog the filter, according to a new study led by researchers at the University of Portsmouth in the U.K.

Using mathematical modelling, researchers calculated how water flowed through the espresso machine and how different variables such as grind setting, tamp force and water flow rate can affect how much waste is generated per espresso shot.

The findings were published in the science journal Matter. The paper titled “Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment” found a “critical minimum grind size” that allowed for homogenous extraction of espresso shots that minimized drink variation and dry coffee waste.

The researchers implemented their new critical minimum grind size and waste reduction protocol at a café in Eugene, Oregon in 2017 and then monitored its sales from September 2018 to September 2019. The data revealed that the café saved US$0.13 per drink which amounted to a revenue increase of US$3,620 per year.