Researchers produce urea in the field using system powered by biobatteries and solar energy

The CONFETI project, coordinated by the Universitat Autònoma de Barcelona (UAB), has concluded three years of research with the commissioning of a pilot system capable of producing urea, a nitrogen fertilizer widely used in agriculture, directly in the field using renewable energy. This fertilizer is produced from carbon dioxide (CO₂) and nitrates in an electrochemical reactor powered by energy from biobatteries and solar panels.

The experimental installation, located in an agricultural setting in Viladecans, also incorporates a photochemical reactor that produces ammonia, a key compound used in urea production, using sunlight.

Bringing this system into operation is one of the main milestones of the project, which has taken the technologies it developed into the field to explore alternatives to conventional nitrogen fertilizer production processes. The prototype has continued to operate throughout the summer and following recent periods of heavy rainfall, while the consortium continues to study its performance under real-world conditions.

"The main challenge has been moving the device from the laboratory to an agricultural setting. It has been one of the most difficult tasks," explains Gonzalo Guirado, a professor in the UAB's Department of Chemistry and project coordinator. "Thanks to the team's efforts, it has been possible to validate the devices and their components in the laboratory and bring them here for testing in a real-world setting," he adds.

Sustainable technologies

The CONFETI system combines three complementary technological developments. The first is an electrochemical reactor that produces urea from CO₂ and nitrates. The reaction produces this fertilizer through a process that offers an alternative to conventional industrial methods, which are energy-intensive and have a high environmental impact.

One of the system's distinctive features is that the reactor is powered by a combination of biobatteries and solar panels. The biobatteries use microbial activity and organic matter present in the soil to generate electricity. An electronic system manages this energy together with the energy from the solar panels to power the electrochemical reactor. Both energy generation systems are operating at the pilot installation and constitute the second development.

The third is a photochemical reactor that converts nitrates in water into ammonia, using sunlight and a photocatalyst. The process also allows this material to be separated and recovered for reuse. The technology is designed to make use of nitrates that crops do not absorb, with the aim of recovering them and reusing them as fertilizers.

The challenge of moving from the laboratory to the field

Integrating the different devices into an installation in an agricultural setting has been one of the project's main challenges. Unlike laboratory tests, the pilot system is exposed to weather conditions and the specific characteristics of its surroundings, allowing its operation to be studied under conditions closer to those of a future application.

The trials are helping to characterize the different components and the integrated system, and to identify the technical issues that will need to be addressed in subsequent stages of development.

"What we want to demonstrate with CONFETI is that there is another way to produce fertilizers, using pollutants such as CO₂ and nitrates and converting them into value-added products with green energy," says Guirado. "In addition, our technology allows fertilizers to be produced sustainably at the very place where they will be used, and supplied on demand, so that they do not need to be stored."

This vision raises the possibility of developing local fertilizer production systems in the future that make use of resources available in agricultural settings. Further research is now needed to assess the technical, environmental and economic viability of commercial application.