Based on what I’ve been able to find this design is using propulsion technologies developed in the earlier “Great Horned Owl” program, where an internal turbine is powered by conventional fuels and generates electricity to power electric ducted fans for the propulsion. It’s a bit more fuel efficient than traditional designs but it appears that the military’s main interest is that it can operate much more quietly, and can switch off the turbine to run on stored battery power for short durations. Basically it’s like a flying Prius, which is a step in the right direction at least.
For really clean-running longer-range designs batteries aren’t quite there yet, but there are other options like hydrogen fuel cells or sustainably-created aviation fuels.
