Shoot trash into a black hole in space, or create one to put it in. It would compress and eat up the garbage via a laser that shoots into the hole.
Creating the ability for humans to breath in CO2/greenhousee gases and release oxygen with help of a special mask. Make this mask trendy and give tax cuts to fashion houses who promote it.
Have a type of tree that absorbs gases and filters them out into a material like yarn or a textile through its roots or branches. The material would be able to be peeled off like onion skin and regrow.
A serum that you drop into the water to turn micro bits of plastic into safe food for fish, and, later, humans.
Ban all products manufactured in sweatshops in an effort to promote universal free trade, not just US free trade.
Have there be a globally enforced minimum wage by something like the UN.