Seville's municipal water company is piloting a scheme to produce electricity using leftovers from the city's famous oranges. The project showcases the Spanish city's commitment to the circular economy.
In the southern Spanish city of Seville, the municipal water company has introduced a pilot scheme to produce electricity using methane from fermented oranges.
EMASESA, a member of Aqua Publica Europea (European Association of Public Water Operators), aims to achieve energy self-sufficiency for its EDAR Copero Wastewater Treatment Plant (WWTP) in the city, an existing facility that already generates electricity from organic matter. The plan is to put surplus electricity into the grid by 2023.
"The project started as a result of EMASESA's interest in achieving energy self-sufficiency in the urban wastewater treatment process," the company's CEO, Jaime Palop, told DW.
In this way, facilities such as the Copero WWTP, which consumed around 13 GWh/year in 2020, achieved levels of self-sufficiency close to 95%, the CEO said. "The Copero WWTP, due to its treatment capacity, location and level of technology, can be a benchmark environmental center," he added.
"EMASESA's current challenge is to ensure that the success of the Copero WWTP is achieved in the other WWTPs," he says, adding that the average self-sufficiency of the four large plants operated by EMASESA is around 70%.
The city collects 5.7 million kilos (126 million pounds) of the fruit deposited on the streets by the city's 48,000 trees in winter and uses 35 tons (39 US tons) of it to generate clean energy to run EDAR Copero. The city council employs about 200 people to collect the fruit.
The 35 tons then go through a process of juice extraction for the generation of electric energy through biogas, while the peel is composted to become fertilizer used in farming. In the purification process, the organic matter in the wastewater is stabilized through anaerobic digestion that generates a methane-rich biogas (65%), which is used as fuel in cogeneration engines for the production of electricity, Palop explained.
The plant is expected to generate about 1,500 kWh, equivalent to the consumption of 150 homes. To achieve this, the city needs to invest €250,000 ($310,000).
Trials have shown that 1,000 kg will produce 50 kWh, enough to provide electricity to five homes for one day. If all the city's oranges were recycled and the energy put back into the grid, 73,000 homes could be powered.
The region produces about 15,000 tons of the oranges, but much of the fruit from the region is exported to the UK, where it is made into marmalade.
Seville has also implemented the organic waste collection system put in place by the urban waste management company Contenur, with 340 containers installed in the city and 340,000 electronic cards provided to the public.
A representative of the mayor told DW that the city aimed to encourage the selective collection of biowaste, increase the rate of recycling, raise public awareness of waste management and send less waste to landfill.
"This process consumes approximately 65% of the energy of the urban water cycle. Achieving self-sufficiency of WWTPs is a clear climate change mitigation action," said Palop.
Spain has launched a plan to switch its electricity system entirely to renewable sources by 2050 and fully decarbonize its economy soon after that.
Greenhouse gas emissions would be slashed by 90% from 1990 levels under the country's draft climate change and energy transition law.
"EMASESA is in the process of drawing up a manual to encourage other companies 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," Palop said.