Seville, with its intricate architecture, friendly locals, and tantalizing cuisine, is one of the jewels of southern Spain.

Its streets are lined with trees filled with bitter oranges and fragrant Azahar (orange blossoms), which are harvested to make jams, perfumes, essential oils and flavourings enjoyed throughout the world, as well as the Cointreau and Grand Marnier liqueurs.

However, the city’s 48,000 trees create 5.7 million tonnes of orange waste that falls onto the streets, according to The Guardian.

These oranges create a walking hazard for pedestrians and end up getting smushed under cars.

To put this waste to better use, Emasesa, the water treatment entity serving the Seville metropolitan area, has launched a pilot project to create biogas from the juice of leftover bitter oranges.

The programme will initially use 35 tonnes of oranges to generate clean energy to run a water treatment plant. The fruit will be sent to a facility that is currently being used to create energy using organic matter. As the oranges ferment, the emitted methane will be gathered and used to run the generator.

“The juice is fructose made up of very short carbon chains and the energetic performance of these carbon chains during the fermentation process is very high,” explained Benigno López, the head of the environmental department at Emasesa. “It’s not just about saving money. The oranges are a problem for the city and we’re producing added value from waste.”

5 Incredible Sustainable Uses for Citrus Waste

While the biogas will be used to run water purification plants, the eventual aim is to generate electricity for the city’s residents. According to a press release, 1,000 kilogrammes of wasted oranges could generate enough energy to power five homes for a day.

“We hope that soon we will be able to recycle all the city’s oranges,” said Benigno López, the head of the environmental department at Emasesa. He estimates that such a feat would require an investment of about €250,000.

If all the city’s discarded oranges could be converted into energy, Emasesa predicts that the resulting electricity could power 73,000 homes.

“Emasesa is now a role model in Spain for sustainability and the fight against climate change,” Seville mayor Juan Espadas Cejas told a press conference at the launch of the project.

“New investment is especially directed at the water purification plants that consume almost 40% of the energy needed to provide the city with drinking water and sanitation,” he said. “This project will help us to reach our targets for reducing emissions, energy self-sufficiency and the circular economy.”