Seville's leftover oranges turned into electricity

(21 Mar 2021) LEAD IN:
The Spanish city of Seville is turning its leftover oranges into electricity.
The city's water company is extracting methane from the fruit's juice to power a purification plant. The clean energy could be used to charge city transportation too.

STORY-LINE:
Seville's green revolution is orange-coloured.
This time of year, the Spanish city turns orange. The capital of southern Spain's Andalusia region transforms into one of Europe's largest orange groves, with Seville oranges - as they're known - hanging from its trees.
But these bitter oranges - native to Southeast Asia and spread by humans across the globe - are rarely consumed here.
Some of the bitter fruits from the city's almost 50,000 orange trees are exported to Britain, where they're made into marmalade.
But the rest is often left to fall on city streets, where they rot, get squashed by car wheels, or potentially cause city residents to slip up.
"It is one of the trees that most represents the image of the city, and one of its tourist attractions," says David Guevara from Seville city council.
"Above all, because of the smell of orange blossom in spring that makes many people come to the city (of Seville). But also, when the fruit falls to the ground, it generates difficulties and many problems for citizens."
But now, the city is turning this potential nuisance into clean energy.
Seville's water utility company Emasesa started a pilot scheme that uses citrus from the city's streets to generate clean energy that runs one of its purification plants.
"We realised that the orange that (nowadays) is only used in a residual way for the production of marmalade - this bitter orange is historically very appreciated in the United Kingdom - had - both the juice and the peel - the possibility of combining them with sewage sludge to generate energy," says city mayor Juan Espadas.
First, the oranges are collected, then transported to a facility that generates electricity from organic matter.  As the oranges ferment, the methane captured is used to drive a generator.
Benigno Lopez, head of Emasesa's environmental department, says they have also trialled olives and sewage water as part of the project.
"Oranges are the last of the (organic) residues we are testing. We have been testing oranges for (the last) two years," he says.
"This year, we have valued 60,000 kg (60 tons) with which we are going to produce the energy equivalent to (the energy consumed by) three hundred homes in one single day."
Results of the pilot suggest one ton of oranges can produce up to 50 kilowatt-hours (kWh) of electricity, enough to power five homes for one day.
Emasesa says if all Seville's oranges were harvested, they could create enough electricity to power 73,000 homes.
Lopez says the key is methane, obtained from the fruit's juice. The skin and pips aren't useful for the process, but are used to make organic fertiliser for farmland and gardens.
"50 percent of that orange is juice. Through this juice we generate a gas that is rich in methane that we use to produce energy through a cogeneration engine. It is a very simple process," says Lopez.
"It is a process that does not require any type of additives and it is an environmentally controlled process and it closes the circular economy of urban waste, which also means that this facility contributes to the mitigation of climate change by self-sufficient energy."
The energy generated is currently being used to power a city water purification plant, providing Seville with clean drinking water.

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