EST – Eni Slurry Technology: reduced emissions and consumption

The proprietary technology we use to convert refinery residues, heavy oils and bitumen into high-quality fuels and light products.


Developed in our own laboratories and research centres, the Eni Slurry Technology process is able to obtain high-quality fuels from oil residues, heavy crude oils and bitumen that would otherwise not be processed and would be treated as waste or fuels with a high environmental footprint. The first EST plant in the world has been in operation since 2013 at our production site in Sannazzaro de' Burgondi (PV). It also refines the “bottom of the barrel”, that is the densest and most viscous hydrocarbon components remaining following standard processing procedures or those that are extracted directly from the oilfields. Thanks to a special catalyst patented by our researchers, these low-quality products are now becoming a new raw material for obtaining naphtha and diesel containing low levels of sulphur, nitrogen, metals and other pollutants. In the downstream sector, meanwhile, it is the first major Italian innovation in 40 years and we have already exported it to France, China and a number of other countries through dialogue with major international players.


Our refineries currently work at a conversion rate that does not generally exceed 70%. The EST means that we can achieve a conversion rate of 92%, reducing the corresponding by-products almost four-fold. The technology is flexible enough to be able to handle very heavy feedstocks containing high levels of asphaltenes, metals, sulphur, nitrogen and other contaminants. Applying it to the refining plants already in operation in Italy and around the world will allow us to exploit unconventional resources without generating carbon coke or fuel oil, which generate high levels of CO2 emissions and environmental contaminants when burned in industrial plants or large marine engines. Staying with the maritime sector, the Eni Slurry Technology also enables us to produce marine fuels with a low sulphur content, in keeping with IMO (International Maritime Organization) regulations. The EST and its various applications therefore present the dual advantage ofcreating business opportunities by reducing emissions and energy consumption.    

Technological challenge

We started working on the Eni Slurry Technology in the 1990s, with the aim of improving refinery performance. Our scientists at the San Donato Research Centre’s initial insights led to an intense study initiative that saw us verify and validate the process on an ever-increasing scale, up to and including the actual industrialisation stage, which led to the creation of the EST unit at the Sannazzaro de' Burgondi refinery (PV). The core of the technology lies in the process of feedstock hydroconversion, combining a special nanodispersed molybdenum-based catalyst in the slurry phase (hence the name Eni Slurry Technology) with a current of pure hydrogen, derived from methane. This is where the long hydrocarbon chains are cracked into shorter molecules to make lighter products. Once the insight had been gathered we conducted a series of careful experiments and process simulations, optimised the method and choice of materials and assessed the environmental compatibility with local institutions and communities. This lengthy task resulted in the first application of an industrial plant based on the process of catalytic hydroconversion in the slurry phase on a global scale.

Industrial integration

The fact that we have developed EST in-house gives us a major competitive advantage in the form of the opportunity to integrate the technology within our downstream plants and bring it to market. We launched the first unit at our Sannazzaro de' Burgondi refinery, which has been in operation since 1963, in 2013. The plant now runs at a conversion rate of around 92-95% and we plan to further increase this percentage to 96-98% by reinvesting the expertise we have gained in introducing upgrades - promoting process “purging” through a procedure known as controlled sorting. The two fractions obtained in this way - a clarified liquid and a solid - can be enhanced in different ways, with the option of further processing the former in the refinery and using the latter in steelworking to replace anthracite. One of the great benefits of the EST is the possibility of incorporating it into existing refineries in synergy with other process units, thus minimising the levels of new investment required. Large international refining groups are very much aware of its great industrial and environmental value and have come to us to have it installed at their plants. In 2015 it was bought by French firm Total, followed by Chinese firms Zhejiang Petrochemicals and Sinopec, which are now building large EST units in China.

Environmental impact

In allowing us to obtain fuels even from low-quality crude oils and waste, the Eni Slurry Technology helps to reduce the overall emissions of the downstream sector in line with our decarbonization policy. Further benefits include the possibility of recycling the molybdenum catalyst, thus optimising resources, and reducing the sulphur content of the corresponding fuels, thus decreasing the environmental impact. In more general terms, the possibilities of exploiting unconventional feedstocks and incorporating it directly into existing refineries mean that this technology has great potential for international distribution, representing a significant industrial asset for optimising processes and reducing emissions in the downstream sector.