What do you need to make a good espresso? Ground coffee, of course; a machine capable of generating pressure; and hot water, preferably heated to between 195 and 205 degrees Fahrenheit. And that’s it. But could one perhaps do without that last element? Not the water itself, but the need to heat it.

Francisco Trujillo from Colombia led a team at Australia's University of New South Wales which claims to have invented what they call “ultrasonic espresso.” It is described as a room-temperature brewing process that uses high-frequency sound waves to extract the flavor, oils, aroma and caffeine from ground coffee. Although this method takes longer than the conventional approach (three minutes compared to 30 seconds), it consumes 75 percent less energy—making it highly beneficial for commercial settings.

The experimental system directs ultrasonic waves directly into the filter containing the ground beans in water. The technology harnesses a phenomenon known as acoustic cavitation, which involves the formation and collapse of tiny bubbles that generate microcurrents to facilitate extraction from the coffee. A device has been designed to transmit these ultrasonic vibrations throughout the entire filter basket, transforming it into an acoustic reactor.

The researchers adjusted variables such as grind size, ultrasound power, and brewing time. Using a fine grind and 100 watts of power, they obtained beverages with levels of dissolved solids and extraction yields equivalent to those considered ideal by the Specialty Coffee Association. Sensory tests showed no notable preference between ultrasonic espresso and conventional espresso, but participants generally preferred the ultrasonically processed version for filtered coffee.

The new technique could offer significant environmental benefits as it uses just 24 percent of the energy consumed by a typical espresso machine to produce beverages of comparable intensity. This opens up possibilities for developing new coffee makers that can prepare everything from espresso to filtered coffee and cold brew using the same technology, potentially replacing the characteristic sound of an espresso machine with inaudible vibrations.