Supermarkets earn $71m bag windfall

Supermarket giants Coles and Woolworths appear set to rake in around $71 million in gross profit from the sale of their 15c heavy duty plastic carriers following the ban on single-use plastic bags.

Queensland University of Technology's Professor Gary Mortimer has calculated the big retailers are also saving $170 million a year by not providing shoppers with free plastic bags.

Prof Mortimer says he has sourced an online provider of heavier bags at 9c, rather than 15c, "But if you are buying in bulk, you would get a cheaper price," he told News Corp Australia on Wednesday.