Andalusia has positioned itself on the European energy map by making a strong commitment to hydrogen as a clean fuelAnd it's doing so not only with large green hydrogen plants, but also with cutting-edge research seeking new ways to produce it. One of the most promising comes from the University of Cádiz, where a scientific team has managed to obtain this gas from biodiesel industry waste using bacteria.
In a context in which the region It consumes approximately 40% of the hydrogen used in Spain. And with the aim of establishing itself as a leading energy hub, this development fits perfectly within the logic of the circular economy: transforming an abundant and problematic waste product, glycerol, into an energy source with a low environmental footprint. The result is a laboratory-proven biotechnological system that adds value to waste and paves the way for its integration into existing biorefineries.
A biotechnological process that adds value to the glycerol in biodiesel
The work is signed by the group of Molecular Biotechnology in the area of ​​Biochemistry and Molecular Biology Researchers from the University of Cádiz (UCA) have designed a method to produce hydrogen using glycerol as a raw material. Glycerol is a byproduct generated in large quantities during biodiesel production. This compound, which comes from biorefineries, accumulates in such volumes that it has become one of the sector's main environmental challenges.
According to the researchers, more than 50 million tons of glycerol annually associated with the biodiesel industry. Although it has various industrial uses, its excess causes management and storage problems. The underlying idea of ​​this study is simple yet powerful: to take advantage of this residue as it comes out of the process, unrefined, to transform it into a high-value-added energy resource.
To achieve this, the UCA team has developed an integrated system involving two microorganisms in a chain reaction. In the first stage, one bacterium transforms glycerol into an intermediate organic compound; in the second, a different bacterium uses that compound to generate hydrogen in the form of biogasAll of this is done under controlled conditions in the laboratory using advanced biotechnology techniques.
The project is part of the transition towards more sustainable production models, where the circular economy It's not just a theoretical concept, but a concrete strategy: what was once waste becomes raw material for a new process. In this case, a fuel destined to play a central role in the decarbonization of the energy system.
The research has received support from Ministry of Universities, Research and Innovation of the Regional Government of Andalusia and the Cepsa Foundation Chair, which reinforces the involvement of the Andalusian knowledge system and the business fabric in this line of energy innovation.
How the chain of bacteria that produces hydrogen works
The system designed by the Cádiz team relies on two bacteria well known in the field of microbiology: Escherichia coli y Rhodobacter capsulatusBoth act sequentially, so that the product of the first becomes the food of the second.
In the first phase, a genetically modified strain of Escherichia coli is used to redirect its metabolism. This bacterium, which normally inhabits the human intestine harmlessly, has been "re-engineered" to efficiently transform residual glycerol into malic acid, an organic acid naturally present in many fruits.
The transformation is carried out through a process of dark fermentationIt is called "non-light" because it does not require light to be produced. Under these conditions, E. coli consumes the crude glycerol from biodiesel production and converts it into malic acid, something this bacterium does not normally do without metabolic engineering.
During laboratory tests, the team managed to achieve malic acid concentrations close to 11 grams per liter in about 24 hoursThis figure, which the authors themselves point out as one of the highest reported when using glycerol as a carbon source, was also found to be within 72 hours of operation. During this period, acid production doubled without any change to the initial concentration.
Once malic acid is generated, the second bacterium in the chain, Rhodobacter capsulatus, enters the scene. This microorganism has the ability to produce hydrogen through photofermentationThis is a process in which light energy drives a series of biochemical reactions that release biogas. In this stage, the malic acid obtained in the previous phase acts as the main substrate.
Metabolic engineering, systems biology and microreactors
The heart of the breakthrough lies in how the first bacterium has been modified and optimized. To design the Escherichia coli strain that efficiently converts glycerol into malic acid, the researchers used two key tools: metabolic engineering and systems biology.
Metabolic engineering allows for the reorganization and adjustment of a cell's internal biochemical pathways to direct resources toward the production of a specific compound, in this case, malic acid. It's essentially reprogramming the bacterium's "internal circuitry" to prioritize a particular output over other possibilities.
For its part, systems biology provides mathematical models and bioinformatics tools that help predict the behavior of the modified metabolism. refine genetic interventionsThanks to this combined approach, E. coli becomes a small biological reactor capable of processing abundant industrial waste and converting it into a useful raw material for the next stage of the process.
The experiments were carried out using advanced microreactors at the Institute of Biomolecular Research (INBIO) of the University of Cádiz (UCA). This equipment allows for real-time monitoring and simultaneous control of variables such as temperature, dissolved oxygen levels, and pH—parameters that are crucial for the yield and stability of both malic acid and hydrogen production.
According to the research team, the system becomes more efficient using crude glycerol than pure glycerolThis is a particularly relevant aspect from an industrial point of view. Working with the waste as it comes out of the biodiesel plant, without additional treatments, simplifies the operating scheme and significantly reduces the cost of the entire process.
From biorefinery to renewable hydrogen: circular economy in action
One of the most notable advantages of this approach is its fit within the model of integrated biorefineryThe scheme proposed by the researchers allows that, within the same facility, biodiesel can be produced from organic raw materials and, in parallel, the surplus glycerol can be used to generate hydrogen.
This means that a waste product that previously posed an environmental and economic problem becomes part of a process that generates a much-needed energy source. Integrating the system into existing plants could increase the overall efficiency of the industrial complex and reduce its environmental impact without requiring major structural changes.
Another relevant contribution is that the method dispenses with the purification of malic acid between the first and second phases. The photosynthetic bacterium Rhodobacter capsulatus is able to directly use the fermentation medium where the acid has been produced, taking advantage of the compounds present without intermediate cleaning or refining steps.
This feature reduces the complexity of the process, cuts costs, and brings it closer to industrial viability. Fewer operations mean less energy consumption, less investment in auxiliary equipment, and ultimately, a potentially more competitive system compared to other renewable hydrogen production methods.
The authors emphasize that the system flexibility It allows for adaptation to different conditions, and although it has only been tested at laboratory scale so far, the results lay a solid foundation for future scaling up. The possibility of adapting this technology to biodiesel biorefineries in Andalusia and other parts of Europe aligns with EU strategies to promote the circular economy and reduce dependence on fossil fuels.
Hydrogen and the energy transition: potential and pending challenges
Hydrogen has become one of the cornerstones of European roadmaps for the energy transition. Its great appeal lies in the fact that, when used as a fuel, It does not generate direct carbon dioxide emissionsHowever, the origin of that hydrogen is key to assessing its true environmental impact.
Currently, much of the hydrogen produced globally still comes from fossil fuels, through processes such as natural gas reforming. This production, commonly known as "gray" hydrogen, involves significant CO2 emissions, which limits its actual contribution to decarbonization.
Therefore, one of the biggest challenges is developing technologies capable of producing hydrogen from renewable sources, either from electricity from clean sources (green hydrogen) or through biotechnological processes and waste valorization, such as the one being explored at the University of Cadiz.
These types of initiatives not only provide new production methods but also help solve other environmental problems associated with the accumulation of industrial waste. In the case of glycerol, its valorization as a raw material for energy generation offers a double benefit: it reduces the waste burden and yields a product of high strategic interest.
The researchers are cautious and point out that further research is still needed. optimize system performance and analyze its large-scale viability before considering commercial applications. However, they emphasize that the results achieved position this approach as a realistic option within the range of solutions for the energy transition.
New lines of research and the role of Andalusia in hydrogen
The work carried out at the UCA is not limited to glycerol. In parallel, the team maintains another line of research, in collaboration with Professor [Name]. Gema Cabrera, from the Chemical Engineering areaThe research focuses on studying an equivalent system for the valorization of brewer's spent grain. This solid residue, from the brewing process, is also being evaluated as a raw material for producing hydrogen through similar processes.
This diversification of sources reinforces the idea that various organic wastes, from both the energy and agri-food industries, can play a significant role in the production of biogas and clean energy carriers. This, in turn, expands the possibilities for implementing these technologies in different productive sectors.
In the specific case of Andalusia, the development of these types of systems is in addition to the existence of eight green hydrogen production plants distributed throughout the region, according to data from the Andalusian Energy Agency. The combination of large industrial projects with basic research consolidates the region as one of the main energy hubs from southern Europe.
Institutional and business support, materialized in the funding from the Andalusian Regional Government and the Cepsa Foundation Chair, further strengthens the connection between the university and the productive sectorThis cooperation is essential so that the advances that are currently being validated in the laboratory can, in the future, make the leap to real industrial environments.
Everything suggests that, in the medium and long term, technologies like the one developed in Cádiz could coexist with other forms of renewable hydrogen production, creating a mosaic of complementary solutions. Whether hydrogen produced from bacteria and biodiesel waste becomes commonplace will depend on how costs, regulations, and the ability to integrate these processes into existing value chains evolve, but the first steps, at least, have already been taken firmly.
