Anything that produces less emissions will be well regarded by all but the most hard line environmentalists. Heck, if it costs less to operate than today's commercial airliners, airlines will be lining up to buy them.
While I'm not convinced the bio fuel will be less polluting unless or will have a smaller impact than regular fuel since you still have grow the stuff the rocket engines certainly sound like a good advance.
Quote:
The rocket engines, powered by hydrogen and oxygen whose only exhaust is water vapor, propel the plane to a cruising altitude of 32 kilometres (20 miles), compared to today's passenger jets which fly at around 10,000 metres.
Water vapor seems more desirable than CO2.