"Carbon dioxide offsetting is not a perfect solution to address all the carbon emitted into the atmosphere, it is just one part. For years Flight Design has considered the importance to reduce the C02 emissions on our airplanes. Flight Design began by improving the aerodynamic, which then led us to the F2 & F4 programs. Then the company implemented the Rotax 912 iS Sport engine with less fuel consumption and emissions. In the next step, they changed the C4 with a traditional aviation engine to the F4 with the modern small and more efficient turbocharged Rotax 915 iS engine and finally, the electric F2e being released by the end of 2021 and more projects being developed."
Source: A portion of the documentation associated with a program