I might be very ignorant here, but I would think that anything that goes down the drain is very biodegradable (it's food). Sure, it's better for the environment if we didn't contaminate the water with food, but I don't think it can compare to the time it takes for plastic or paper to break down.

And the soap/detergent and food remnants being processed at the sewage plant, or the septic pumping truck that cleans out your tank and transports the waste.

Certainly more environmentally friendly, although transitioning to those for public settings requires more maintenance and procedure than simply having a waste basket in the bathroom.

My girlfriend did exchange in Brazil and fell in love with bidets there.