The key to this partnership between Sacyr Agua and Dutch company RedStack lies in removing salt from brackish water while generating energy in the process. The two companies will collaborate on various electrodialysis solutions to make this possible.

Electrodialysis reversal (EDR) enables the desalination of brackish water from diverse sources. Its counterpart, reverse electrodialysis (RED), generates energy by exploiting the salinity gradient between brine and freshwater.

Sacyr brings significant experience with EDR technology, having built the world’s largest EDR facility: the Abrera plant in Barcelona, with a capacity of 200,000 m³/day. We also operate other plants, such as Valle Guerra (San Cristóbal de La Laguna, Tenerife), where we desalinate treated wastewater using a membrane bioreactor (MBR) to produce high-quality water for irrigation.

Reverse electrodialysis (RED) generates energy by utilizing the salinity difference between two water streams—typically brine and freshwater. We are especially interested in applying RED to recover energy from the combination of brine from desalination plants and effluent from municipal wastewater treatment facilities.

Sustainable use of brine

Sacyr and RedStack have successfully tested RED technology at a pilot project through the LIFE HyReward project, funded by the European Union. The project has achieved energy recovery rates of up to 0.3 kWh/m³.

In LIFE HyReward, we explored the potential of generating renewable electricity from the brine produced during desalination. The goal was to enhance the energy efficiency of the process by combining reverse osmosis with reverse electrodialysis. Integrating this approach with conventional technologies makes desalination more sustainable by recovering electrical energy from brine before it is discharged into the sea, thereby reducing CO₂ emissions.

As part of their long-term collaboration, Sacyr will deploy REDstack’s EDR and RED systems in projects focused on salt removal and energy generation from brine streams. Additionally, the two partners are currently evaluating the site for a pilot plant that will use RedStack’s next-generation EDR technology, which offers advantages such as greater productivity and lower energy consumption compared to other solutions on the market.
 

The terrain that characterizes the surroundings of the Sicilian city of Catania is unique due to the omnipresence of Mount Etna. The eruptions over time have shaped a capricious and highly variable subsoil. 

In this environment, we will develop a major railway project: the Metropolitana di Catania expansion, with a budget of nearly 800 million euros. The extension covers almost 14 km of line, of which eight and a half are underground sections of various kinds. This expansion will connect several towns in the metropolitan area.

Ferrovia Circumetnea (FCE), an agency under the Italian Ministry of Infrastructure and Transport, awarded SIS—a permanent consortium formed by Finninc (51%) and Sacyr (49%)—a section between the towns of Misterbianco and Paternò in September 2023, and in December 2024, a complementary section between Monte Po (Catania) and Misterbianco, connecting with the currently operational line.

This project will feature the use of a new and uncommon tunnel boring machine known as the Variable Density TBM (VD-TBM). Only about 20 machines of this type have been ever operated worldwide. 

The handover ceremony for the TBM took place on May 27, with representatives from Herrenknecht (the TBM manufacturer), SIS (Finninc and Sacyr), and FCE (Ferrovia Circumetnea) in attendance.
 

It stands out for its adaptability to the area’s changing geological conditions. Additionally, due to the frequent seismic activity generated by the volcano, it is necessary to comply with strict seismic standards for both permanent and temporary works.

“A few years ago, the city already undertook a metro project using a conventional TBM, and it ran into significant difficulties due to the unfavorable geological conditions”, explains Miguel Ángel Montón, tunnel manager for this project.

“The ground is extremely complex due to its heterogeneity; there are fissures, cavities, and frequent alternations between basaltic rock—lava—and softer soils. Our TBM is highly adaptable to current conditions; its operating mode can be changed on the fly using four different excavation modes, allowing us to respond in real time to the terrain. It is more complex to operate, but offers that flexibility”, Montón adds.

This isn’t the first time that Montón faces this kind of challenge, as he had a similar experience on Line 3 of the Guadalajara Metro (Mexico). “It was more complicated than usual, but not as challenging as this project,” he states.
 

The TBM began manufacturing in August 2024  and operational testing started in May this year.  Disassembly and transport to the construction site are scheduled to begin in June, with arrival expected in July.

The heaviest components will be transported across the Alps using special convoys to the port of Ravenna (Italy), from where they will be shipped to Catania. The smaller components will be transported by truck to across the Strait of Messina to reach Sicily. 

On-site assembly of the machine will take around three months, followed by approximately two weeks of commissioning and testing. Excavation is expected to begin by the end of December or early 2026.

“We will excavate around 5 km of tunnel with this TBM. The initial contract was for 3,200 meters, and with the most recent award, an additional 2 km were added,” Montón explains.

In a joint initiative between our Innovation team and Sacyr Water and Energy, we’ve launched a renewable energy project at the Pamasa P3 project in Palma de Mallorca. This initiative will support the asset’s decarbonization and help avoid 20 tonnes of CO₂ emissions annually.

Pamasa operates the 45.2 km highway connecting Palma de Mallorca and Manacor (Balearic Islands), a key transport corridor that plays a vital role in regional connectivity.

The new 32 kWp solar installation at Pamasa includes a 41 kWh battery storage system and two EV charging points. A total of 55 photovoltaic modules will generate approximately 47,021 kWh of renewable electricity each year.

Miguel Bauzá, Operations Director at Sacyr Concesiones, said:"This project reinforces our commitment to renewable energy and sustainable mobility".

Once operational, 42% of Pamasa’s electricity needs will be covered by solar panels, rising to nearly 70% with the addition of battery storage.

Of the total energy generated:

• 42% (19,749 kWh) will be used for direct self-consumption
• 27% (12,696 kWh) will be stored for use at night
• The remaining 31% will be fed into the grid

The project will also save an estimated 2,000 liters of fuel each year thanks to the new EV charging stations.
 

Driving decarbonization 

This is one of nearly 100 initiatives in our Decarbonization Plan, which spans Sacyr’s various business units.

These efforts are coordinated through specialized working groups that promote our climate strategy by tracking both emissions reductions and economic savings across each project.
 

Other solar installations

At the Turia Highway Control Center in Valencia, we’ve built a 120 kWp solar array using 570 Wp modules and a 100 kW inverter. This setup produces around 170,000 kWh annually — enough to meet 34% of the center’s energy needs.

In Cádiz, at the Aguas del Valle del Guadiaro facility, we installed a 250 kWp solar system with four 50 kW inverters, producing around 390,000 kWh per year and supplying 20% of the site’s energy consumption.
 

In Santa Cruz de Tenerife, at the Emmasa desalination plant and various water tanks, we’ve deployed multiple solar installations for both individual and shared self-consumption. Combined, they total 900 kWp using 585 Wp modules and a range of inverter sizes.

On Brazil’s RSC-287 highway, we’ve installed five solar power stations that collectively generate nearly 396,000 kWh annually.
 

Progress from 2020 to 2024

Since our baseline year of 2020, we have:

• Reduced Scope 2 emissions by 28,621 tonnes of CO₂ equivalent
• Generated 4,299 MWh of renewable energy
   

Tenemos nuevo capítulo de Sacyr iPodcast en el que hablamos de innovación con expertos que nos inspiran y nos ayudan a ampliar nuestra visión.

En este nuevo episodio, Marta Gil continúa la conversación sobre industrialización en los procesos constructivos con Ramón Sanchez y Antonio Jiménez-Peña.

Si te perdiste el anterior, puedes verlo aquí

En el capítulo nuevo, analizamos las ventajas de esta técnica constructiva, a través de ejemplos concretos de proyectos industrializados de Sacyr.

Aquí puedes verlo completo:

Today, June 23, we celebrate International Women in Engineering Day. To commemorate this date, we’ve brought together female engineers from Sacyr working on four projects in Chile, Colombia, and Spain, showcasing the faces of the professionals who represent our company globally.

At Sacyr, we are firmly committed to gender balance within our teams. Approximately 26% of the engineers at Sacyr are women. We want to continue encouraging girls’ interest and pursuit of careers in the STEM fields (Science, Technology, Engineering, and Mathematics).

To that end, we continue to collaborate with the ASTI Foundation Alliance through the STEM Talent Girl program, with the goal of increasing the future presence of women in our business activities.

We congratulate all our engineers for their talent and dedication.

Many thanks to the professionals who participated in this video, representing all our engineers:

Úzquiza Dam in Burgos, Spain

• Nuria Roldán Casado, Chemical Engineer

• María Dolores Izquierdo Guillén, Civil Engineer

• María Pilar Yun Moreno, Civil Engineer

A-32 Highway in Albacete, Spain

• Alba Hidalgo, Civil Engineer

• Cecilia Reinoso, Civil Engineer

• Alicia Velasco, Materials Engineer

Bridge over the Biobío River, Chile

• Camila Ruiz Aquevedo, Construction Engineer

• Valentina Fernanda Saavedra Salinas, Construction Engineer

• Francisca Catalina Koch Espinoza, Environmental Civil Engineer

• Yoselin Leticia Cárdenas Ojeda, Risk Prevention Engineer

• Paulina Padilla Pacheco, Risk Prevention Engineer

• Jessica Jeannete Sepúlveda Monsalves, Environmental Engineer

• Ingrid Viviana Figueroa Jofre, Industrial Engineer

Canal del Dique, Colombia

• Yurani García Quintero, Civil Engineer

• Olga Álvarez Medrano, Industrial Engineer