Change the paper dispensers in the lavatories, often many tissues come at a time. Get single tissue dispensers. Save paper and avoid overfilled bins that looks untidy.

Use more big size bottles and not small cans/bottles

Automatic opening of trash-lid on planes with hand gesture above it. Saves excess use of papertowels and bonus: increases hygiene and bacteria spread

Create an ability to share a seat in your car with other passengers on the flight. It's better than everyone riding their car.

Digital, reusable RFID bagtag instead of paper stickers.

Bio fuel / green fuel as default, and having to pay more as a passenger if you want to fly on fossil based airplane fuel.