“Generally, the aviation industry means jet fuel derived from a source other than petroleum. Specifically, CAAFI and the Alternative Jet Fuel community means a fuel produced to the requirements of ASTM D7566. It can include drop-in jet fuels produced from a broad range of hydrocarbon sources (feedstocks) using a wide range of conversion processes. We sometimes refer to these fuels as synthetic fuels too—fuel produced from sources other than petroleum via biochemical or thermochemical processes.”

Commercial Aviation Alternative Fuels Initiative,
http://www.caafi.org/resources/faq.html

“An alternative fuel could be any generic fuel derived from a source other than petroleum. It could include compressed natural gas, liquefied natural gas, hydrogen, alcohols, biodiesel, etc. However, none of these fuels are suitable for jet powered aviation, either current models, or those in development. The aviation community needs jet fuel for safe and efficient operation, whether that is produced from petroleum, or sources other than petroleum.”

Commercial Aviation Alternative Fuels Initiative,
http://www.caafi.org/resources/faq.html

“Drop-in alternative jet fuels are completely compatible with a conventional (typically petroleum-derived) jet fuel in terms of materials, safety, and composition. A drop-in fuel does not require adaptation of the fuel distribution network or the engine fuel systems, it can be used “as is” in vehicles and engines that have historically operated with only conventional fuel. Some alternative jet fuel blending components may become “drop-in” only after being blended with a conventional fuel to a certain prescribed proportion. Currently, approved drop-in fuels only supplement petroleum-sourced jet fuels in blends. A list of approved fuels and blend levels is available on the Fuel Qualification page. Certain alternative jet fuel concepts do have the potential to be used without blending, but have yet to be approved. Drop-in fuels align with CAAFI’s goal of bringing Sustainable Aviation Fuels to market.”

Commercial Aviation Alternative Fuels Initiative,
http://www.caafi.org/resources/faq.html

Yes. SAF+ jet fuel is expected to be sold as a blend of up to 50% (m%) with conventional jet fuel and will be a drop-in alternative to JET A-1. SAF+ jet fuel will not need to be newly approved, nor will the jet fuel blends containing it, because it is part of the Fischer-Tropsch Hydroprocessed Synthesized Paraffinic Kerosene (FT-SPK) family, the first to have successfully met the ASTM 7566 standards and be approved for use of up to 50% with conventional jet fuel. 

“The two chief barriers to deployment (in many cases) include the availability of capital to construct the required initial infrastructure, as well as the availability of reasonably priced feedstocks and supply chains. CAAFI, through its members, partners, and work programs are attempting to drive down these barriers to implementation. In the long run, all of the parties involved in CAAFI understand that being the first transportation mode to move forward with drop-in, sustainable, alternative fuels will help ensure aviation’s economic viability and environmental acceptability.”

Commercial Aviation Alternative Fuels Initiative,
http://www.caafi.org/resources/faq.html

Aviation sector is facing a challenge of significantly reducing greenhouse gas intensity of aviation fuels in order to be compliant with stringent and increasingly demanding CORSIA requirements. By converting industrial emissions into clean drop-in jet fuel with 80% lower GHG footprint than conventional jet fuel by using renewable electricity, SAF+ is bringing a solution that tackles both CO2 emissions reduction and sustainable aviation fuel (SAF) availability. 

PtL is a process which consists in generating a synthetic liquid fuel by using carbon dioxide from the atmosphere or other sources, water and renewable electricity. In this process CO2 is mixed with hydrogen (obtained by electrolysis of water) to produce syngas, that is then introduced into a Fischer-Tropsch reactor, where liquid fuels are generated through a catalytic synthesis process.