Bus passengers in Indonesia’s second-largest city of Surabaya can now “pay” for rides on red city buses using plastic bottles, Reuters reported.

Ticket prices depend on the amount of plastic goods deposited. For instance, a two-hour bus ride could cost around 10 plastic cups or five plastic bottles.

Local resident Linda Rahmawati said the scheme helps clean up the environment and also reduces the workload of garbage collectors. Statistics indicate 15% of Surabaya’s daily waste production, or about 400 tonnes, is plastic waste.

A singe bus can take up to 550 lbs of plastic bottles a day.

The plastic objects taken in by the bus company are auctioned off to recycling companies, whose payments fund green spaces and bus operations in the city.

Indonesia is statistically the second-worst culprit when it comes to dumping plastic waste in the oceans, behind only China. The head of Surabaya’s transportation department Irvan Wahyu Drajad said the department hopes to use the scheme to raise awareness on environmental issues.