Scientists and government officials increasingly recognize food waste as a major contributor to climate change. Across the globe, producing and disposing of uneaten food accounts for about half of the greenhouse gas emissions from the entire food system.

Massachusetts was among the first states to pass regulations curbing food waste, and according to new research published in the journal Science, it’s the only state where the rules are working.

Massachusetts Department of Environmental Protection (MassDEP) Commissioner Bonnie Heiple said the state is proud to be recognized as a national leader.

“This has been a long time coming,” she said.

In the United States, About 35% of food produced is never eaten. Much of it winds up in landfills where it gives off methane, a greenhouse gas that contributes to climate change, as it decomposes. Methane emissions from Massachusetts landfills have the same climate impacts as about 116,000 cars on the road for a year.

To stem the flow of lettuce (and other food) to landfills, nine states and a handful of cities and towns have enacted food waste bans — laws and regulations that prohibit sending organic waste to landfills or incinerators.

Massachusetts was among the first five states to enact a food waste ban — the others were California, Connecticut, Rhode Island and Vermont. Massachusetts’ first food waste ban, enacted a decade ago, required any business producing more than a ton of food waste per week to keep it out of landfills or incinerators. Instead, businesses were told to divert edible surplus food to charities or food recovery services, and send food waste to compost facilities or anaerobic digesters that turn it into energy. Massachusetts enacted a stricter ban in 2022, lowering the threshold to a half-ton of food waste per week.

In the new study, researchers looked at data from five states from 2006-2018, the years with the best data available. They found that food waste bans had no effect in California, Connecticut, Vermont and Rhode Island during that time; only Massachusetts saw a significant decline — about 7% — in food waste sent to landfills and incinerators.

Massachusetts has continued to increase food waste diversion since then. Before the first ban took effect in 2014, the state was diverting about 100,000 tons of food waste from landfills and incinerators, according to state data. That number now stands at about 380,000 tons per year, a nearly fourfold increase.

“That downward decline in food waste has caused us to reduce our emissions — really slash our methane emissions from food waste — by more than 25%,” said Heiple.

By 2030, the state’s goal is to divert 780,000 tons of food waste per year.

The study’s authors suggested three possible reasons for Massachusetts’ success: simple regulations, affordable options for managing food waste, and stronger enforcement and monitoring than other states.

“These bans can work, and when they are successful, they can substantially reduce landfill waste,” said Fiorentina Zoi Anglou, a PhD candidate at the University of Texas, Austin and the lead author on the study. “These laws are important, and they hold a lot of potential. But in order for them to be truly effective, they need more than just good intentions, they need careful implementation.”

Despite the high marks from researchers, environmental groups are pushing Massachusetts officials to do more.

A 2024 report from MASSPIRG and other environmental advocacy groups found the state fell 20% short of its food waste diversion goal in 2020. The authors noted the state will need to double its rate of organic waste diversion to meet its ambitious 2030 goal. The report suggested better public education, tax incentives for food donation and renewed investments in composting.

“We appreciate the efforts of the DEP,” said MASSPIRG Executive Director Janet Domenitz, but she added, it’s not enough. “We’re still burying and burning over a million tons of food waste a year here, and that makes methane — the worst kind of contributor to climate change.”

John Fischer, deputy division director for solid waste at MassDEP, said the state’s 2030 goal is “aggressive.” To reach it, he said, regulators will need to start focusing on food waste from homes.

“We’re at a pivot point,” he said. While continuing to divert commercial food waste, his department is beginning to shift attention to residents. “That will be proportionally more of our focus going forward.”