Renewable fuels

Renewable fuels and their impact on mobility

We need to reduce CO₂emissions from transportation by making it easier for society to choose between different alternatives. But how exactly can we accomplish this? We are clear on one thing: that there is no single path. Reducing CO₂emissions from mobility efficiently and in an agile manner means using all the technologies that can help us meet this goal. That, of course, is where renewable fuels come in. But what are renewable fuels, exactly? How are they produced? And what impact do they actually have on reducing CO₂ emissions from transportation?

What are renewable fuels?

Renewable fuels are chemically similar to conventional fuels, but their production process is different. They are produced from non-fossil feedstocks and contribute to reducing net CO₂ emissions. These feedstocks can be of biological origin, coming from biomass and organic waste (vegetable or animal waste from the agri-food industry, agriculture, livestock, forest cleaning, municipal solid waste, etc.), or of non-biological origin, which are commonly called RFNBO (Renewable Fuels of Non-Biological Origin).

Compared to fossil fuels, the use of these renewable fuels entails a significant reduction in CO₂ emissions during their production and use. The CO₂ emitted during combustion comes from the CO₂ that was previously captured to produce that very same renewable fuel, whether by photosynthesis in the case of biomass or by direct capture of CO₂. So, if we analyze the process from feedstocks to end use, net CO₂ emissions can be reduced by up to 90% compared to the fuels of mineral origin they replace.

Renewable fuels can be classified into two types, depending on whether or not they are of biological origin:

Advanced biofuels are fuels made from non-food feedstocks, such as lignocellulosic biomass, which includes wood and forestry residues, agricultural residues (straw and stubble), and energy crops or residues (e.g., industrial waste, used oils and fats, or solid waste). There are multiple technological pathways depending on different magnitudes (raw material, volume, location, cost, etc.), such as fermentation (ethanol), hydrogenation (HVO), or transesterification of oils and fats (FAME); thermochemical conversion routes such as BtL (gasification and Fischer-Tropsh synthesis); or pyrolysis/hydrothermal liquefaction (HTL).
Synthetic fuels or e-fuels are obtained from hydrogen produced by water electrolysis, accomplished using renewable electricity and carbon dioxide (CO₂) captured either from a concentrated source (combustion gases from an industrial facility) or directly from the air.

Characteristics of renewable fuels

The characteristics of renewable fuels help us understand why they are an effective alternative for reducing CO₂ emissions that doesn't impact the competitiveness of transportation:

Renewable fuels meet the quality specifications required in Spain and internationally that ensure engine safety, compatibility, and performance.
They are analyzed at each stage of the process, from the origin of feedstock to end use, to calculate the actual reduction in CO₂ emissions. Why? Because it's important to evaluate the entire cycle, not just the combustion occurring at the end. This approach makes it possible to compare different fuels with homogeneous and transparent criteria.
They complement existing solutions (such as electrification or hydrogen) that make it possible to immediately and significantly reduce CO₂ emissions from transportation. This is true even where electrification is not yet viable, such as aviation or maritime transportation. Renewable fuels can be used in existing vehicle, ship, and airplane engines. This means we can leverage current infrastructures to facilitate the energy transition.
They come from raw materials that, when used for this purpose, reduce waste while promoting the circular economy. These materials include used cooking oils, forestry residue, advanced biomass, agricultural by-products, and animal fats.
They are an opportunity for rural areas affected by depopulation and unemployment, as their production generates economic activity and offers a way to maintain jobs at fuel production plants.
Renewable fuels help shore up Europe's industrial strength and leadership in internal combustion engines, hybrid EV engines, and the automobile value chain, thereby enabling the creation of new high-skilled jobs.

How renewable fuels are produced

At Repsol, we produce renewable fuels from waste products and feedstocks of biological origin using advanced industrial processes. The most representative example is hydrogenation, which takes place at our plant at the Cartagena Industrial Complex to manufacture 100% renewable-sourced Nexa Diesel and SAF (sustainable aviation fuel).

The renewable fuels produced in the plant at our Cartagena Industrial Complex plant successfully avoid up to 900,000 metric tons of CO₂ per year compared to the fuels they replace

Hydrogenation involves causing a reaction when used cooking oils and other organic fractions are brought into contact with hydrogen. This process removes impurities and oxygen from the waste product, transforming it into molecules very similar to those of conventional fuels. The result is our Nexa Diesel of 100% renewable origin, compatible with combustion engines without the need for adaptations and which can be distributed and marketed using existing infrastructures.

The Cartagena plant is the first on the Iberian Peninsula exclusively dedicated to the production of 100% renewable fuels. It has the capacity to produce 250,000 metric tons of 100% renewable Nexa Diesel and SAF per year, all from 300,000 metric tons of organic waste such as used cooking oil, and it can avoid up to 900,000 metric tons in CO₂ emissions per year compared to the fuels it replaces.

The sustainable aviation fuel (SAF) that we also produce at the Cartagena plant can be mixed with conventional aviation fuel and used in today's aircraft without modifications to engines or airport infrastructure, allowing flights with a lower carbon footprint and collaborating with airlines and manufacturers in accelerating the transition of the aviation sector.

The Cartagena plant will be joined by a second plant dedicated exclusively to the production of fuels of 100% renewable origin in Puertollano, which will be operational in the coming months. Our 100% renewable Nexa Diesel is now available at over 1,500 service stations in Spain and Portugal. Our 100% renewable Nexa Diesel, produced from organic waste, reduces CO₂ emissions by up to 90% and is compatible with current engines and existing infrastructures. This means that anyone can contribute to reducing CO₂ emissions without changing vehicles or their routine. More than 150 transportation companies already rely on this solution.

And over at our Tarragona Industrial Complex, we've successfully produced 100% renewable-sourced gasoline on an industrial scale for the first time ever.

The production of renewable fuels already has an impact on the main forms of mobility: heavy road transport, passenger vehicles, aviation, and the maritime sector

Nexa 95 Gasoline of 100% renewable origin is obtained from renewable feedstocks and is compatible with any gasoline or hybrid vehicle without the need for engine modifications or alterations to the existing distribution and refueling network, reducing net CO₂ emissions by more than 70% compared to conventional gasoline.

We're also present in maritime transport through the manufacture and planned future supply of renewable marine fuels to international cruise lines such as Royal Caribbean Cruises and Norwegian Cruise Line in the Port of Barcelona. We've also partnered with companies such as Navantia to develop renewable solutions that reduce CO₂ emissions on ships and ferries, a key sector for the competitiveness and sustainability of our economy.

As a result, the production of 100% renewable fuels already has an impact on the main forms of mobility: heavy road transportation, passenger vehicles, aviation, and the maritime sector. In each of these cases, the goal is the same: to use waste and renewable feedstocks to offer an alternative that reduces CO₂ emissions and can be integrated into existing transport systems. But we're not stopping there.

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Innovation and research in renewable fuels

Research is key in the development of renewable fuels. At Repsol Technology Lab, we develop formulas, analyze new renewable feedstocks, and study their behavior in engines and propulsion systems.

In addition, alongside research institutes and government agencies, we promote projects that allow us to explore new raw feedstocks, technologies, and solutions to reduce CO₂ emissions in sectors where electrification is not viable in the short term.

This is where we participate in Círculo SAF, an initiative by the airline company Iberia that brings together leading companies to promote the use of this type of fuel. Repsol, Amadeus, BBVA, and Telefónica are part of the founding group that is already contributing to reducing CO₂ emissions from corporate and cargo flights by encouraging the use of SAF.

We are also part of Madrid Vuela Sostenible, with support from the Madrid regional government and the European Union. Alongside IMDEA Energía, ARIEMA, and EvoEnzyme, we help spread the knowledge of CO₂ reduction technologies and the circular economy, thus promoting the transformation of waste products into renewable fuels for aviation.

We are researching solutions that will take center stage in the future, such as synthetic fuels produced from renewable hydrogen and captured CO₂. In Bilbao, we have begun construction on a demo plant for synthetic fuels, equipped with a 10-MW electrolyzer which will produce liquid synthetic fuels made from captured CO₂ and renewable hydrogen while furthering carbon-negative technologies overall.

Al in all, we understand innovation in renewable fuels as an ongoing process. Through the combination of participating industrial plants, agreements with transport companies, the development of fuels for different types of vehicles, and e-fuel pilot projects, we are better able to explore the potential of renewable fuels to the fullest while reinforcing the role of Spanish industry in the transition towards mobility with lower CO₂ emissions.

Impact on mobility, industry, and the Spanish economy

The industrial development of these products in Spain boosts economic activity, generates quality employment, and adds to the strength of Spanish industry. It also contributes to greater energy autonomy by diversifying sources of supply and reducing external dependence.

However, there is still much to be done, especially from a regulatory point of view, as advocated by Repsol alongside industrial, energy, and automotive companies such as Bosch, Air Liquide, Enerkem, Raízen, BMW Group, Navantia, and Técnicas Reunidas.

In a joint manifesto, these companies have called for stable and predictable regulatory frameworks, as they are essential for planning industrial investments that require years of development. Without this certainty, especially in technology-intensive sectors, it is difficult to accelerate the construction of new plants, expand capacities, or promote innovation projects.

In addition, these companies have underscored the importance of tax policies aligned with actual CO₂ emission reductions, based on life cycle carbon intensity measurements. This approach makes it possible to compare technologies on equal terms and reward whomever reduces emissions the most, regardless of the technological path taken.

Overall, this manifesto states that only with a clear, stable, and fair framework will it be possible to attract the necessary investment, accelerate production, and ensure that renewable fuels contribute effectively to climate goals.

This international effort is complemented, among others, by the work of Plataforma para los Combustibles Renovables and the association CRECEMOS, which work in Spain and Europe to spotlight the role played by these fuels and promote the creation of regulatory instruments that allow for their swift and competitive deployment.

In short, we are advancing an alternative that requires no modifications to vehicles or infrastructures. The development of these technologies, their integration into different forms of mobility, and their ability to foment industry and job growth make them a key piece in the menagerie of solutions needed to move towards more competitive transportation.