Five meals a week: Scientists audit garbage to assess household food waste

Scientists spent weeks up to their elbows in coffee grounds and banana peels to come up with what they say is the most accurate measure yet of how much food is wasted in Canadian kitchens.

“To be honest, it’s not something you’d want to do forever,” said Michael von Massow, a food economist at the University of Guelph.

Food waste has become an increasingly hot research topic in recent years.

Previous efforts have relied on industry data or household self-reporting to assess how much uneaten food goes in the garbage. But people underestimate how much they chuck and industry figures provide little detail on individual homes.

The only way, von Massow thought, was to get down and dirty.

He and his research colleagues worked with 94 households in Guelph, Ont.. The scientists took out the trash, went through recycling, organic waste and composting, separated mushy asparagus from dubious rice and weighed it all out over the course of several weeks.

“Rubber gloves,” von Massow laughs. “It’s not as bad as you might think.”

Items commonly dumped down the sink, such as expired milk or mouldy yogurt, weren’t measured.

The detailed, teabag-by-applecore approach allowed von Massow to precisely measure just how much was thrown out and whether it was once edible. That was crucial for determining the value of what got tossed.

“If you have a T-bone steak and you throw that bone out, putting a value on that bone of whatever you paid for the steak seems inaccurate,” von Massow said.

Waste from the families, all of whom had young children, varied widely. Some threw out up to eight kilograms of once-edible food a week, some barely one-sixteenth of that. The median figure was 2 1/2 kilograms.

That represents enough calories to have an adult over for dinner five nights a week without adding a dime to the grocery bill.

The value of that food was about $18. Producing and disposing of it generated about 23 kilograms of greenhouse gases.

Bread, tomatoes and apples were the top three items. Chicken was the most frequent meat.

Von Massow’s figures are lower than those arrived at in some previous research. A 2017 study estimated the amount of avoidable food waste in Canada at 2.7 kilograms per household.

Von Massow attributes that to his exclusion of non-edible waste.

Going through the garbage was revealing, he said. People know the plastic wrap around that yucky cucumber should go in the recycling, but they toss it in the trash anyway.

“People hide things that they feel guilty about. I saw people hide batteries in a Pringles tube. They know they’re doing something they shouldn’t and I think the same thing happens with avoidable food waste.”

Von Massow acknowledges that his sample size is small and, to some extent, self-selecting. But he maintains his results are, if not statistically bulletproof, at least representative.

The point of the research, he said, is to eventually understand what works best to persuade people to cut down on food waste. For some, it’s an ethical issue. For others, it’s economic and for still others it’s an environmental problem.

For von Massow, spending weeks picking through garbage has already had one effect.

“We have not audited my house yet, but it sure makes me more cognizant of when I’m putting something into the garbage.”

Bob Weber, The Canadian Press