The streets of Seville, Spain are rife with unwanted oranges: The city is home to 50,000 orange trees—more than any other European metropolis—but the fruit is too bitter to be eaten by itself. And as the oranges fall from the trees, they end up on the streets, posing a hazard to pedestrians and motorists. The glut prompted local municipal water company Emasesa to launch a pilot that would recast some oranges bound for the landfill or fertilizer as the power ingredient for clean energy at one of its wastewater treatment plants.
The project involves the fermentation of 35 metric tons of oranges for biogas. The methane released by the oranges as they ferment is converted to power—allowing the plant to become energy self-sufficient. The remaining peels will be composted, transformed into fertilizer and reused in the fields.
It’s the kind of bold thinking required as Spain attempts to transition to renewable electricity by 2050.
“New investment is especially directed at the water purification plants that consume almost 40 percent of the energy needed to provide the city with drinking water and sanitation,” Seville Mayor Juan Espadas Cejas said at a press conference. “This project will help us to reach our targets for reducing emissions, energy self-sufficiency and the circular economy.”
The company’s primary goal is to use the clean energy extracted from oranges to run water purification plants, but it eventually aims to put surplus electricity back onto the grid. Given the amount of fruit at the company’s disposal, there’s big potential: The team has calculated that if all the city’s oranges were recycled and converted to energy for the grid, 73,000 homes could be powered.
“Emasesa is now a role model in Spain for sustainability and the fight against climate change,” Cejas said.
To power up interest, the company is creating a manual to encourage other firms in the water sector “to increase gas production through codigestion of organic waste and to enable this action to be replicated in other companies and cities,” Emasesa CEO Jaime Palop told Deutsche Welle.