What solutions can we take to eliminate money and go back to bartering or freeganism?

Look at the venus project and mister Fresco's theories.

We have to make the cities a clean selfsupporting ecosystem and grow everything within the city. Use the newest technology to make all needfull things plentifull. That way, we can trade and barter within the city borders and only need money or some kind of objective value system to trade with other cities that have other products and riches in other climates or situations.

It's a free country. Many communities do a lot of bartering. If that is what you want, nothing is stopping you.

There are none.

You would need something like a huge natural disaster or nuclear war in order to set us back that far.

nothing is stopping you from bargining right now