From disposable headphones and plastic cutlery to food scraps and toilet waste, the average airline passenger leaves behind over three pounds of garbage, according to one estimate. To get travelers and airlines thinking — and talking — about that rather large pile of trash , a British design firm has refashioned the economy meal tray, replacing plastic with renewable materials such as coffee grounds, banana leaves and coconut wood .

Jo Rowan is the associate strategy director of the firm, PriestmanGoode, which has spent more than two decades applying design thinking to the air travel experience, including airport lounges and cabin seating.

Now, she said, the firm is turning its attention to the less “glamorous” side of things.

“Onboard waste is a big issue,” she said. “Knowing that you have four billion passengers per year, it all adds up very quickly.”

The redesigned items are featured in an exhibit, “Get Onboard: Reduce.Reuse.Rethink,” that opened last month at the Design Museum in London.