The progressive accumulation of greenhouse gases (GHG) in the atmosphere leads to an increase of the earth’s average temperature with dramatic consequences on the climate. The main cause is CO2 whose emissions deriving from anthropogenic activities far exceed the absorption in the biosphere and oceans, with the result that, on average, its concentration in the atmosphere grows at an impressive rate of 2 - 3 ppm/year. The international scientific community agrees that, to contain climatic changes within acceptable limits, it is necessary that the increase in the earth\'s average temperature does not exceed 1.5°C compared to the pre-industrial era. This implies the achievement of the ambitious net-zero emission goal by 2050, through the adoption of different actions in the field of energy efficiency, development of renewable energy sources, progressive abandonment of the most polluting fossil sources (coal and oil), electrification of the energy system.
To this end, Carbon Capture & Utilization (CCU), despite not having the potential size of geological storage, has the advantage of using CO2 in alternative technological paths to the current ones in a circular economy perspective, thus reducing the use of fossil sources and, above all, generating value.
CO2 reduction with green H2 to e-fuels (the so-called Power-to-X, PtX, routes, where X can be Gas, methane, or Liquid, methanol, liquid hydrocarbons) represents an important alternative for the energy transition. It does not provide for a permanent sequestration of the CO2, which is re-emitted when the e-fuel itself is used; in spite of that, the PtX routes are the most suitable for O&G companies, that already possess the infrastructures for managing both the gas and liquid products.
Regardless of the technological path, the necessary condition is represented by the availability of green H2, i.e. produced by the electrolysis of water with renewable electricity. The products directly obtainable from CO2 reduction with green H2 are methane (SNG) and methanol, while liquid hydrocarbons require more complex chains that pass through the production of syngas (CO/H2 mixtures) to feed a Fischer-Tropsch process (e.g. e-jet fuel production) or via methanol then converted to gasoline (Methanol-to-Gasoline, MtG process) or to light olefins (Methanol-to-Olefins, MtO) from whose oligomerization fractions of liquid hydrocarbons for specific uses (e.g., e-jet fuel) can be obtained.
Remaining in the production of SNG and methanol, there are already several initiatives at the pilot-demonstration level. However, new approaches are needed to increase overall process efficiency by better managing the apparently simple reactions, whose high exothermicity makes their control complex. In this perspective, Eni is going to install a demo plant for SNG production at its Centro Olio Val d’Agri facility (Basilicata, Italy). The demo unit will produce 10 kg/h SNG by processing CO2 coming from reservoir and green H2 generated by high efficiency Solid Oxide electrolyzer (SOEC). CO2 and H2 will be converted into SNG through a modular innovative catalytic reactor thermally integrated with green H2 production unit. This integration will lead to the optimization of technology utilities and energy consumption, hence obtaining a significant decrease in SNG production cost and carbon footprint. Synthetic methane product will be sent to local gas grid, hence demonstrating the possibility to use green H2 and CO2 to produce an e-fuel perfectly equivalent to the fossil one. Moreover, the coupling of renewable energy with gas grid will help managing unbalances between renewable energy production and energy demand, hence allowing higher levels of renewables penetration.
