Rome is trying to get people moving on recycling – by offering credit towards public transport tickets in exchange for waste plastic bottles.

The "+Ricicli +Viaggi" scheme (the more you recycle, the more you travel) allows passengers to return plastic bottles in exchange for a 5c credit, which can be used towards purchasing digital tickets.

Through the MyCicero app, users scan their personal barcode on a special recycling machine, insert empty plastic bottles inside a compactor, and digitally buy rides.

A standard ticket, valid for one metro ride or 100 minutes on all buses allowing transfers, costs €1.50 – or 30 plastic bottles.

The eco-friendly trash-for-tickets initiative was launched by Rome Mayor Virginia Raggi on behalf of Rome's transport network Atac.

The recycling machines will be in place in three metro stations for a 12-month testing phase.

Many Romans are enjoying this new way of saving cash.

"If you use money to involve people [in recycling], even those who have no civic sense will recycle," Rome resident Claudio Perelli told Reuters.

"Finally, plastic bottles are being recycled in Rome," Luca Alberto Di Lauro added.

But it isn't all good news.

Rome is spiralling into decline, with rubbish spewing out of bins and, after decades of neglect, tourists and residents can literally smell the problem affecting the city.

Rubbish litters the ancient streets of the Eternal City, with hundreds of tonnes of garbage lying uncollected, with flies dining on rotten food, often in front of ancient monuments.

"The situation is quite disastrous," President of environment group Legambiente, Stefano Ciafani, said.

"Rome has failed to create an efficient system for differentiated waste collection, as Milan has done, and it has not built the recycling plants that are fundamental for a city where three million people live.

"If the waste treatment plant is closed and no recycling plants are created on the territory, the waste will continue to be exported outside the region as it is today."