Educating diners on the environmental harm caused by their leftover food leads to less waste, but this is reversed if they know scraps will be composted instead of dumped in a landfill, according to a new study. 

When composting enters the picture, educated diners waste just as much as those who havent learned about shrinking landfill space, dangerous greenhouse gas emissions and water and soil pollution.

This leads to a tricky situation for policymakers figuring out how to manage food waste, because the top tactics are prevention (through education) and diversion (through composting), said lead researcher Danyi Qi, a graduate student in agricultural economics at The Ohio State University.

“When you do both, they cancel each other out - they work at cross purposes,” said Qi, who is presenting the findings this week at the annual meeting of the Allied Social Science Associations in Chicago.

The discovery could help shape decisions by government, businesses and others looking to chip away at the vast amount of food that gets dumped.

Qi worked with co-author Brian Roe, a professor of agricultural, environmental and developmental economics and a member of Ohio States Food Waste Collaborative, which is exploring ways to reduce waste and create a more sustainable food system.

They recruited 266 students, staff, faculty and Columbus residents to participate in the study last summer who were all monitored during a meal provided by the researchers. The diners didnt know what the study was about, specifically, just that the research team was examining eating behavior. 

They were given information cards about food waste harms and about financial literacy. Around half of both of the groups were told their leftovers would be composted, reducing methane emissions and providing nourishment for plants, while the other half were told that their leftovers were destined for landfill. 

The participants could help themselves to food, choosing sandwiches, chips and apple slices. Neither sharing nor take away bags were allowed and the researchers weighed the diners trays after the meal to determine how much food they had left behind.

The results showed those who had read about the harm related to waste left behind almost 77 percent less as a group than those who received the financial literacy material, which means the educated diners were 39 percent more likely to clean their plates.

However, when the diners knew their leftovers were going to a “good” place the benefits of food-waste awareness seem to disappear. 

“We were very curious if these common policies work in harmony or in conflict,” Qi says. “It seems that if they feel that the social and environmental cost is lower, they may feel less guilty and that may cause them to waste more.”

Composting can be expensive and policymakers are looking for ways to limit waste regardless of wher it will end up, Qi adds.

“There are many new and innovative approaches being proposed to reduce food waste and to minimize its environmental impact. 

However, there exists little thought about whether various approaches are complementary or competitive,” says Roe. “This study is one of the few to consider how various approaches might interact.”

The study highlights the importance of first attempting to limit waste and how composting or donating unused food is great, but buying and preparing only what youll eat is better, Roe concludes.

“And if someone else says they will do something positive with food scraps, it shouldnt diminish your own good intentions and efforts to reduce food waste.”