Published 2 years ago.
About a 4 minute read.
Image: Oranges littering the streets of Seville | Richard Obeirne/Flickr
Emasesa saw an opportunity to treat the 5.7M kilos of oranges littering the streets of Seville each year not as food waste, but as a powerful circular solution.
In the Andalusian city of Seville, the spring air is sweet with the
scents of orange blossom and limonene. But come winter, it’s not so sweet —
there is no escaping the 5.7 million
of fruit littering the streets. Deposited from 48,000 orange trees, the oranges
— too bitter to eat — cause huge disruption and inconvenience to the people of
Seville. Some oranges are shipped to England to be made into Grand
Marnier, Cointreau and marmalade — and the peels used in bitters; however,
with such vast quantities, the city has struggled to find a solution of how to
deal with the millions of kilos left over.
“When fruit falls, it should not be ‘waste’; with the right planning and
subsequent management, the oranges should be used for good with minimal
environmental impact, adding value to the city of Seville,” Benigno López,
Head of the City’s Environment Division, told Sustainable Brands™.
And that is exactly what Emasesa, a municipal water
company based in Seville, has done. Through the technology available at its
wastewater treatment plant (WWTP), the company has launched a pilot scheme
collecting this unwanted fruit and transforming it into energy through a process
known as co-digestion or joint-anaerobic.
“The juice extracted from pressing the oranges is introduced into the digester
at the wastewater treatment plant,” López explained. “It then undergoes a
biological process in which organic matter is broken down due to the existing
bacteria in the environment. The process is essentially carried out due to the
absence of oxygen.”
Limonene, a component of orange peel, is an antimicrobial
that impedes biogas production when digesting peels. However, if the oranges are
pretreated and the limonene removed before the digestion process, then the
methane yield emitted from
the oranges increases through the process known as anaerobic
This methane generated through the gaseous fuel from the
can then be used as fuel for electricity.
Emasesa harvests the oranges manually with the help of around 200 workers. “This
is the most economical way to do it, as the distribution of orange trees
throughout the city is uneven. They are scattered through avenues, squares and
streets for example, with an unequal production per unit ranging from 45 and 130
kilos per tree,” López said. “The oranges collected are then converted into
energy — every 1,000 kilos of oranges generates 50kW of energy, which is about
the consumption of 5 homes a day.”
Image credit: Booking.com
Emasesa boasts that the WWTP is a benchmark for a circular economy, and the
company anticipates that the Copero WWTP will eventually become an environmental
innovation centre in itself.
“We are hoping that this site will allow for innovative solutions surrounding
water and waste treatment, as well as generating a self-sufficient energy
supply,” says Alberto Ortiz, Head of the Department of Environmental
Management and Climate Change at Emasesa.
Furthermore, Emasesa is also planning on creating quality compost by recovering
the WWTP sludge
(semi-solid material that is produced as a by-product during sewage treatment of
industrial or municipal wastewater) and biomass (pruning remains) from the parks
and gardens of Seville.
“We are hoping to promote the co-digestion of waste with a high organic load.
Then, in order to produce more biogas, we are planning to investigate whether
the waste from the pre-water treatment (sand and floating) could be used to
digest urban solid waste generated in the city,” López explained.
When asking Emasesa about the environmental implications of using biofuels, they
say that the majority of aspects are positive. However, Ortiz acknowledged that
“energy performance can be quite low. And waste can be accumulated — for
example, we have to utilize 45-50 percent of the resulting weight after pressing
the pulp; in our case, by compositing.”
He further went on to explain the complications of biofuel: “The biggest problem
is actually getting to it — the biogas generated must be purified and
transformed before it can be used as biofuel. This process requires investments
in equipment and technology, and so therefore can be very expensive.”
Despite this, and with the advantages outweighing the disadvantages, Emasesa
continues forward on its quest for sustainability. Spain is heavily invested in
environmentalism and renewable energies; and in 2018, the government launched an
ambitious scheme to have 100 percent renewable energy by
— initiatives such as Emasesa’s will only help fuel the scheme's success.
Published Aug 23, 2021 8am EDT / 5am PDT / 1pm BST / 2pm CEST
Scarlett Buckley is a London-based freelance sustainability writer with an MSc in Creative Arts & Mental Health.