As a measure of conserving natural resources, we all have heard of recycling paper and wood to save trees and forests; recycling plastic to producing less new plastic; recycling metals to reduce mining; recycling glass to reduce the need to use new raw materials; but recycling, of all things, fruit to produce electricity was unheard of that is until recently, when the municipal authorities of an European town gave green signal for the purpose.
In spring, the air in Seville is sweet with the scent of azahar, orange blossom, but the 5.7m kilos of bitter fruit the city’s 48,000 trees deposit on the streets in winter are a hazard for pedestrians and a headache for the city’s cleaning department. The oranges look pretty while on the tree but once they fall and are squashed under the wheels of cars the streets become sticky with juice and black with flies.
Located in Southern Spain, Seville is the European city with the largest number of orange trees - more than 48000 – having a huge bumper crop year after year. Though oranges originated in Asia and were introduced to Spain about 1,000 years ago, Seville alone produces about 15000 tons of oranges per year. Until 1970, there were only 5000 orange trees in this town but ever since it has seen an orange boom. The tree is linked to the concept of happiness, which led people to start planting it in the streets. Even the Azahar flower that blossoms from the tree, has been associated with health benefits leading to its use in essential oils and perfumes. The oranges are also used as an ingredient of Cointreau and Grand Marnier.
Even after satiating the healthy appetite of its citizenry, it is left with a huge surplus of orange stock, which Seville didn't know what to do with, apart from exporting mainly to UK, where these are turned into marmalade. A solution was, however, fund rather recently that is only some months back. With trees scattered across the city, the excess of the fruit has become a sort of problem for the City Hall. Once they fall, the oranges are squashed under the wheels of the cars and the streets become sticky with juice and filled with flies. About 200 people are employed to collect the fruit from the streets.
There was understandably a need of a better solution, which now is being tried in a pilot rogram. The city has launched a pilot program with Emasesa, the municipal water company, through which 35 tons of fruit will be used to power a water purification plant. It is a simple mechanism. The oranges are placed in a facility that already generates electricity from organic matter. Once they ferment, the produce methane gas, which is used to drive the generator and produce electricity. The process involves transporting the fruits to a biogas-producing facility at the company’s sewage treatment plant. “The juice contains fructose which consists of very short carbon chains. The energy output of these chains during the fermentation process is very high,” explained Benigno Lopez, head of Emasesa’s Environmental Department. “It’s not just about saving money. Rotting oranges are a problem for the city and we generate added value from the waste,” he said, adding that “the remains of the oranges will be processed to produce fertilizer for the local agricultural fields.
“It’s an innovative experience of the circular economy through which we are taking advantage of organic matter. We want to recycle all the city’s discarded oranges,” Enrique Vaquerizo, head of residual waters at Emasesa, said in a statement. “Through the pilot, we are transforming a plant that used to consume a lot of energy to now starting to produce it.”
The electricity produced on-site will initially be used to supply power to Emasesa’s sewage treatment plant. In the future, it will also be fed into the city’s electricity grid. Tests have revealed that 1,000 kg of rotten oranges can produce up to 50 kWh of electricity – enough to cover the daily electricity need of five households. Experts at Emasesa hope that in the future they will be able to process all organic waste produced in the city to supply the local households with clean power. To fulfill these plans, local authorities will need to invest about EUR 250,000 in the project. For each ton of orange approximately 500 liters of juice and 500 kilos of peel are obtained. With the amount of fruit to be used in the water plant, the government expects to generate 1,500 KWh– enough electricity for 150 households. If the pilot works, the plant is expected to process about 1.700 tons of oranges, which would power 73,000 households. Seville’s Mayor Juan Espadas said the pilot will help to reduce the city’s greenhouse emissions too, push for a circular economy and allow the water plant to become an energy producer, using the surplus for the city’s needs.
“Emasesa is now a role model in Spain for sustainability and the fight against climate change,” Juan Espadas Cejas, the mayor of Seville, 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.”
Bhushan Lal Razdan, formerly of the Indian Revenue Service, retired as Director General of Income Tax (Investigation), Chandigarh.
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