This event was an very specific flight test required for certification done once for every new aircraft/engine combination to prove the ETOPS capability of the aircraft.
Between 3 and 5% of man made CO2 comes from aircraft. Of course this number is growing as aviation continues to grow and they’ll become a bigger proportion as other sectors reduce….but unlike cars jet engine are getting a hell of a lot more fuel efficient and in 10 years time they’ll be 15 – 20% more fuel efficient than today’s generation of engines, and most aircraft are flying on a biofuel/Kerosene blend.
You want to make flying more environmentally friendly? Then find a more environmentally friendly way to get to and from the airport, because the biggest polluters in the aviation industry are passengers getting to and from airports. Airports themselves are not particularly environmentally friendly too.