The Gardens New World has, for the past 15 years, allowed students to take their fully laden shopping trolleys home.
They are collected later by a company van.
Since the introduction of charges on plastic bags at the supermarket last month, more customers were opting to forgo using the bags, store manager Bianca Parry said.
Instead, their goods were being loaded directly into trolleys, helping reduce the environmental footprint of their purchases.
New Zealand International Science Festival director Sue Clarke wanted to see more of that type of community initiative.
Ms Clarke is the organiser of The Next Step - Waste as a Resource workshop on sustainability initiatives, to be held in Dunedin on September 19.
The event was expected to attract more than 100 people, including policy-makers, academics, business people and members of the community, from Dunedin and around New Zealand, for a mix of presentations, discussions and a site visit to the Green Island landfill.
Ms Clarke said the event aimed to encourage new ideas and initiatives, and the green use of trolleys was an example of a business and community initiative that could help by reducing the use of plastic bags.
"It's giving an easy option for people to make that change. It's a good initiative," she said.
