Energy conversion and renewables: The potential and limits of CO2 large scale capture and recycling
Carbon dioxide is turning image and there are increasing attempts to consider it a resource and a business opportunity rather than a waste with a cost of disposal. This closing lecture of the CO2 Forum will attempt from one side to discuss the general energy scenario for introducing renewable energy and the constrains and opportunities for solar fuels, and from the other side will analyse the possibilities and opportunities in recycling carbon dioxide to fuels, as a complementary technology to carbon sequestration and storage. The potential and limits of CO2 large-scale capture and recycling are discussed.
It is remarked that the requisites for this objective are (i) minimize as much as possible the consumption of hydrogen (or hydrogen sources), (ii) produce fuels that can be easily stored and transported, and (iii) use renewable energy sources. From this perspective, the preferable option is to produce liquid fuels (alcohols and/or hydrocarbons) from CO2 and water using directly solar energy. The different possibilities to realize this challenge objective are discussed and compared.
In contrast to this longer term vision, on a shorter term the more feasibly approach is the catalytic conversion of CO2 to methanol/DME and their eventual conversion to ethanol, using ex-situ produced hydrogen. A critical aspect to solve is water formation during the reaction (particularly, during the reverse water gas shift) which inhibits the reaction rates of the consecutive reactions. A possible way to overcome the problem is by coupling the catalyst with water permeoselective membranes.
The lecture will provide useful outlooks and scenario to the community of scientists and entrepreneurs dedicated to CO2 revalorization. The final part will be thus dedicated to put CO2 in the general context of the energy conversion and renewables, to identify the R&D roadmap in this area, based on the indications emerged during the conference, to replay to the question of the potential and limits of CO2 large-scale capture and recycling. It will thus provide indications and recommendations that could improve policy decisions in favour of the revalorization solutions.