Food waste is a major contributor to climate change. What are the solutions?

Emissions don’t just come from the burning of fossil fuels such as coal, oil, and gas. Food waste sent to landfills contributes up to 10% of all emissions, equivalent to more emissions than that of the entire aviation sector, and if considered a country, it would be the third-largest emitter. 

Food waste decomposes in landfills and produces methane, a greenhouse gas approximately 28 times more potent than carbon dioxide in its warming potential.

“It is nearly impossible for the globe to meet emissions targets set forth by the Paris Accords without reducing waste from the food system,” said Robert Sanders, an assistant professor of marketing and analytics at the Rady School of Management who is one of the world’s top experts on this issue.

Sanders sat down with university communications to discuss why he studies food waste, why it’s a major problem for the United States and what solutions work best to reduce emissions from food consumption.

What drew you to study food waste?

Reducing food waste is pretty much the most actionable measure humanity can take to mitigate greenhouse gas emissions in the short and medium term.  It’s easy to find policymakers, consumers, and business leaders with strong opinions on how to mitigate food-waste emissions, but when I started my career, there was amazingly little empirical, scientific research on the topic. 

For example, policymakers and scholars have a hypothesis that 7–10% of all food waste stems from confusion about the meaning of expiration-date-label formats (e.g., “best by” vs. “use by”). California even passed a law (AB 660) on the basis of these claims about these date labels, hoping to motivate people to not dispose of food that’s safe to eat, but there's still no scientific evidence of how these date-label formats actually affect purchases and waste in the field—that is, when real choices are made.

Broadly speaking, I am motivated to find out what policies actually work to reduce greenhouse gas emissions from food waste. That’s where I think the scientific approach is important, because, as a researcher, I don’t have any stake in my findings going one way or the other. If a policy doesn’t work, but society thinks it does, that’s just as important as confirming that the policy does indeed work. And as a scientist, it’s also my job to investigate why a policy is or is not working. I want to find the truth of how we can address this problem that is a major contributor to the climate crisis.

What are some of the most effective ways to reduce food waste?

In 2023, the total emissions from food waste was 5.4 billion metric tons, and food waste also costs the grocery retail industry about $47 billion every year. So what can we do about this problem? My research in this space focuses on two potential solutions: food-waste landfill bans and dynamic pricing. 

So let's take these solutions one at a time. First, food-waste landfill bans are a way for the government to directly regulate food waste by imposing a penalty on retailers who try to send their food waste to landfills. The problem is food waste bans don't work all that well for a couple of reasons. So first, these penalties aren't typically large enough to get retailers to really change their behavior. Also, it turns out governments aren't all that great at enforcing these bans. My coauthors and I investigated the efficacy of the first five food-waste bans in the United States, and we found that only one state, Massachusetts, has been successful at diverting food waste away from landfills. The data suggest that the success is likely because the state enforces its ban, the ban is the easiest to understand of the five, and the state has a superior composting network.

The other solution I investigate is dynamic pricing. More than 10% of food waste comes from grocery retailers that throw out surplus perishables past their expiration date. Dynamic pricing spurs retailers to throw out less food by applying an algorithm that determines when grocery stores should reduce the price of perishables depending on their inventory and expiration date. This way, vendors can change the price of food multiple times a day, compared to static pricing in which products have the same price all day. It also makes perishables, which are less processed and generally healthier, more affordable. In most cases, it saves grocers money, consumers money and creates less food waste.  To an economist, it’s actually really weird that grocery stores don’t dynamically price their perishables. Why should you, the consumer, be paying the same price for milk that will expire one week from now as you would for milk expiring three weeks from now?  Not only is it unfair, it’s inefficient.

What can people do to reduce their food waste?

Composting is better than sending food to landfills, but it’s best to not create food waste to begin with. This starts with meal prepping. Know what’s in your fridge before going shopping. Make a note to eat leftovers if you often forget (like I do) and plan your meals ahead of time based on the food you have. 

Another tip is, if you are planning meals for an event or party, try as accurately as possible to forecast what the demand for food will be at that event. This can be done, for example, by surveying attendees in advance. 

With that, everyone in California should have a green bin for food scraps. I strongly urge folks to use those. If you are going to throw out food, do your best to make sure it goes into a compost bin.

With so many cuts to federal research grants, have you been impacted?

My work on studying the impact of expiration dates on consumer choice has unfortunately been negatively impacted by the cuts to federal research grants.  

I have a recent stream of papers seeking to understand how consumers use expiration dates to make decisions, both in the stores and at home. In one paper, my coauthors and I conducted the first scientific field study of how consumers make choices across different expiration dates, particularly in the presence of discounts (e.g., milk expiring two days vs. one  week from now).

We found evidence for two types of consumers: The first type doesn't care about expiration dates at all and will switch to older products even for tiny discounts. The second type cares about expiration dates, but discounts can stop them from rummaging through the shelf looking for the freshest item, which helps reduce waste by moving the oldest units first.  

In the next paper, my coauthors and I want to investigate how expiration-date label formats (e.g., “best by” vs. “use by”) affect consumer purchases and waste. There has been a lot of debate and some new policies about the impact of expiration-date label formats on food waste, culminating in the California law AB 660 that I mentioned. We were in communication with the National Science Foundation about obtaining a grant that would help us collect data on expiration dates, in part addressing the USDA/FDAs request for more information. Given the pauses in funding, the reduction in grants, and the fact that our work related to climate change, we are seeking funding from alternative sources.