Merging the Green-H2 production with Carbon Recycling for stepping towards the Carbon Cyclic Economy.

Hydrogen Economy and Cyclic Economy are advocated, together with the use of perennial (solar, wind, hydro, geo-power, SWHG) and renewable (biomass) energy sources, for defossilizing anthropic activities and mitigating climate change. Each option has intrinsic limits that prevent a stand-alone success in reaching the target. Humans have recycled goods (metals, water, paper, and now plastics) to a different extent since very long time. Recycling carbon (which is already performed at the industrial level in the form of CO 2 utilization and with recycling paper and plastics) is a key point for the future. The conversion of CO 2 into chemicals and materials is carried out since the late 1800s (Solvay process) and is today performed at scale of 230 Mt/y. It is time to implement on a scale of several Gt/y the conversion of CO 2 into energy products, possibly mimicking Nature which does not use hydrogen. In the short term, a few conditions must be met to make operative on a large scale the production of fuels from recycled-C, namely the availability of low-cost: i. abundant, pure concentrated streams of CO 2 , ii. non-fossil primary energy sources, and iii. non-fossil-hydrogen. The large-scale production of hydrogen by Methane Steam Reforming with CO 2 capture (Blue-H 2) seems to be a realistic and sustainable solution. Green-H 2 could in principle be produced on a large scale through the electrolysis of water powered by perennial primary sources, but hurdles such as the availability of materials for the construction of long-living, robust electrochemical cells (membranes, electrodes) must be abated for a substantial scale-up with respect to existing capacity. The actual political situation makes difficult to rely on external supplies. Supposed that cheap hydrogen will be available, its direct use in energy production can be confronted with the indirect use that implies the hydrogenation of CO 2 into fuels (E-fuels), an almost ready technology. The two strategies have both pros and cons and can be integrated. E-Fuels can also represent an option for storing the energy of intermittent sources. In the medium-long term, the direct co-processing of CO 2 and water via co-electrolysis may avoid the production/transport/ use of hydrogen. In the long term, coprocessing of CO 2 and H 2 O to fuels via photochemical or photoelectrochemical processes can become a strategic technology. • Hydrogen Economy and Cyclic Economy are discussed as an option for defossilizing anthropic activities and mitigating climate change. • In the short term, a few conditions must be met to make operative on a large scale the production of fuels from recycled-C. • In the medium-long term, the direct co-processing of CO 2 and water via co-electrolysis may avoid the production/transport/ use of hydrogen. • In the long term, coprocessing of CO 2 and H 2 O to fuels via photochemical or photoelectrochemical processes can become a strategic technology. [ABSTRACT FROM AUTHOR]