Green coffee: Italian engineers roast coffee beans with sun power
Antonio Durbe monitors the functioning of the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
by Associated Press
Nov 07, 2021 4:32 pm


Coffee and sunshine... What could be more Italian? Okay, maybe add pizza to the mix. But, pizza aside, the former duo of Italian delights has been the subject of two engineers' special project in Rome as they created an environmentally friendly way to roast coffee beans without electricity or gas.

Antonio Durbe and Daniele Tummei have spent almost six years building and perfecting their sunlight coffee roaster.

The result is a system that needs a piece of land about the size of half a tennis court and sunny weather to roast up to 50 kilograms (110 pounds) of coffee an hour.

A steel basket containing fresh coffee grains rotates while toasting them in "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
Antonio Durbe collects freshly toasted coffee grains from the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
Antonio Durbe collects freshly toasted coffee grains from the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
Daniele Tummei monitors the functioning of the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)

The plant is run entirely by energy from the sun. Rays of sunlight are concentrated by a set of mirrors on a coffee roaster and even the few electrical parts are powered by a small solar panel. Sensors controlled by a computer allow the mirrors to follow the sun throughout the day and focus its light on a rotating steel basket that contains the fresh coffee beans.

The basket reaches peak temperatures of about 240 to 250 degrees Celcius (450 to 480 degrees Fahrenheit), depending on the sun's brightness, and can roast the beans in 20 minutes.

The process isn't only environmentally friendly and economically convenient. According to Durbe and Tummei, it also better preserves the coffee’s aroma, giving it a richer flavor.

Antonio Durbe (L) and Daniele Tummei monitor the functioning of the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
Antonio Durbe (L) and Daniele Tummei collect freshly toasted coffee grains from the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)

Unlike conventional hot air ovens, which are typically gas-powered, the concentrated sunlight roasts the coffee without heating the air around it – penetrating the grains in a more uniform way and without burning the exterior.

Naturally, the system does depend on good weather. On cloudy days or after sunset, coffee lovers need to turn elsewhere.

However, in sunny southern Italy, a plant with 40 mirrors is capable of roasting up to 30,000 kilograms (66,000 pounds) of coffee a year, saving about 60,000 kilowatt-hours of electricity, according to the inventors.

Sun is reflected in the mirrors of the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
Daniele Tummei measures the temperature as he grills meat with a barbecue in their "Purosole," Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
Antonio Durbe monitors the functioning of the "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)
Antonio Durbe (L) and Daniele Tummei grill meat with a barbecue in their "Purosole," or Pure Sun, solar light coffee roaster, in Rome, Italy, Oct. 13, 2021. (AP Photo)

Their Purosole, or pure sun, coffee can be bought online, but the main goal of the inventors is selling their solar coffee roasting plants to small businesses who are sensitive to the environment. Right now, they are operating their plant in the garden of a friend.

The system can be put to other uses as well. At the end of a long work day, Durbe and Tummei place a grill in in front of the mirrors to prepare some delicious sunlight barbecue.

Last Update: November 07, 2021 17:49