Composting food scraps can prompt people to make other earth-friendly choices, new research has found.
When one California city started a composting program to keep food waste out of its landfill, residents began to pay more attention to other environmentally sound practices, such as taking shorter showers, according to a study led by Nicole Sintov, an assistant professor of behavior, decision making and sustainability at The Ohio State University.
"In our study, one pro-environment change appeared to lead to other benefits and that could be important to know as city leaders and others consider conservation projects," said Sintov, formerly of the University of Southern California.
The study was part of a larger effort to look at the success of the composting program. Sintov's study included 284 residents of Costa Mesa, a Southern California city that in 2015 began offering curbside recycling and compost pickup for its residents. Prior to the program, no curbside recycling was offered, Sintov said. The research appears in the journal Environment and Behavior.
Sintov and her colleagues were interested in a scientific concept called "spillover," in which one behavior prompts another. This can work in good ways - such as a person going to bed earlier because she has started an exercise program. But it can also work in bad ways - say someone thinks it's now OK to eat more doughnuts because he's eating salad a few times a week.
"The idea is if you're investing all these resources - composting bins and trucks and new facilities - is it possible that this could lead to any other pro-environment behavior, or do people start to slack off in other areas, which we don't want," Sintov said.
She expected that the program might be a good way to test spillover when it comes to conservation - largely because composting is such a hands-on and arguably unappealing endeavor.
The researchers asked participants about three food-waste prevention behaviors, including planning meals before shopping. And they asked about seven energy and water-waste prevention behaviors, including taking shorter showers and unplugging electronics when they're not in use.
When they examined survey results and compared them with the onset of composting, they found that those who began composting food waste also engaged in more efforts to conserve water and energy compared to those who did not compost.
What surprised Sintov was that none of the three food-conservation behaviors appeared to differ much between Costa Mesa residents who started composting relative to those who did not.
"This may have been because so many people in the community were already doing a good job planning meals and paying attention to how much food they bought and used. There wasn't a lot of room for improvement to begin with," Sintov said.
The researchers did not see any of the concerning "negative spillover," which would have been identified if residents began to be less careful with food and natural resources after the curbside composting program kicked off.
The study took place in a relatively affluent, well-educated community and further research will be necessary to determine if its findings extend to other populations, Sintov said. But it begins to bolster the argument that these types of civic conservation projects may have multiple benefits - including those that might not be as obvious, she said.
Beyond demonstrating that composting was tied to greater conservation efforts, Sintov and her collaborators also found a possible psychological explanation for why that happens.
"We know that humans desire consistency in our thoughts, feelings and actions. That's well-established, and that's tied to our self-perception," Sintov said.
She and her colleagues dug a little deeper in this area, looking for possible scientific links - or "mediators" - between composting and the spillover behaviors.
"Our study found that this happened because waste was on their minds, or 'cognitively accessible,' and this thinking about waste seems to lead you to manage waste in other ways."
The study is relevant to policymakers because it highlights the importance of acknowledging the potential that government programs and other changes could trigger unexpected behavior, Sintov said. It's also one of the first to examine environmental spillover in a community setting outside of a college campus.
"If we can figure out how to institute changes that would encourage people along the path of positive spillover, that would be really cool," Sintov said.
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