Prof. Shelie Miller’s Top 5 Recommendations on How Your Household Can Reduce Its Food Impacts:

1. Only buy what you will eat!Our lifecycle assessment research assumes that you only buy ingredients in the recipe and doesn’t even take into account any impulse purchases. So unless you really have a plan for that acorn squash, stick to your list and only buy what your household can realistically eat before it spoils.
2. Eat the leftovers.
3. Plan multiple meals that will use similar ingredients to reduce potential for leftover ingredients.
4. Reduce consumption of environmentally intensive foods, particularly red meat.
5. Use public transportation to the grocery store or bundle multiple trips together to avoid dedicated grocery store miles.

Undergrads Weigh In

The other authors of the published paper are U-M undergraduates Mayur Bandekar (Program in the Environment) and Benjamin Vassar (A. Alfred Taubman College of Architecture and Urban Planning).

“It was clear early on that this project would demand both thoroughly planned-out data collection methods and thoughtful writing on the project’s implications for American consumers. Managing several hundred cells of data across several excel spreadsheets—a harrowing task at times—will certainly help me manage any future project demanding information at such a scale.

“Although my career interests still lie in architecture and potentially journalism, doing this project undoubtedly gave me knowledge on global warming science that led me to join the Climate Action Movement this year. Although the university remains reticent on climate change action even after the Global Climate Strike on March 15th, we plan to continue our activities until the university commits to carbon neutrality by 2030.”–Ben Vassar

“When coming up with this idea for a potential sustainability-related topic for a research project, I originally thought that this project would last only one semester; now it has turned into a published research project with over a year of work put into it, which I cannot be more excited about! This project has helped me improve my data collection, research, and (hopefully) cooking skills, while providing me with a better understanding of companies’ supply chain models, the carbon emissions intertwined with them, and how the overall food industry functions.

“One major takeaway for me was that I never realized how much fun research can be, especially if you are studying a topic you truly care about. This experience helped me dip my toes into the holistic field of sustainability, and has led me to exploring even more topics that are encompassed in this field. Currently, I have a strong interest in tackling sustainability-related issues in the renewable energy field, which I believe is the next phase of my career.

“This summer, I will be working on an honors thesis through the Program in the Environment department which explores the complex social dynamics towards wind energy sites in Michigan. In Fall, I will be recruiting for a job/internship in the energy industry, aiming to obtain some work experience in this particular industry to be able to come back to the University of Michigan in the future to pursue the Erb Institute Business Sustainability Dual Degree (MBA/MS) Program full time.

“I cannot thank Dr. Miller, Brent, and Ben enough for the collaboration on this project—this is just one more step taken towards improving the overall future of humanity.”–Mayur Bandekar

Read the Michigan News Press Release at http://myumi.ch/JyyAN

Read the paper, "Comparison of Life Cycle Environmental Impacts from Meal Kits and Grocery Store Meals."

Brent Heard, a doctoral candidate in Resource Policy and Behavior at SEAS, is lead author of a new study on the overall carbon footprint of meal kits versus the same meals purchased at a grocery store. The study was published April 22 in the journal Resources, Conservation and Recycling. Shelie Miller, Jonathan W. Bulkley Collegiate Professor in Sustainable Systems and director of the undergraduate Program in the Environment, is one of the study’s coauthors. Here they share insights gleaned from this novel research.

What's the backstory on this study? How did you come up with the idea to do it?

MILLER: I have a number of friends who really like ordering meal kits but kept expressing guilt over all of the packaging. The more I heard people assume that meal kits had to be terrible for the environment, the more I felt compelled to do a study that analyzed the whole system. That’s the point of doing life cycle assessment work–to look beyond the directly obvious and visible environmental impacts and take a more systematic approach. 

I suspected that meal kits could actually be better for the environment. Due to the overall amount of food waste Americans generate at home, proportioned meal kits might actually combat food loss. Turned out my suspicion was right.

The study shows that the meal kit manufacturers are on the right track. If you were coaching them, how would you advise them to reduce their carbon footprint even more?

HEARD: Meal kit manufactures could reduce their environmental impacts further by doing all they can to minimize food loss in the pre-portioning process. They could also reduce packaging to the minimum necessary to protect and contain pre-portioned food. They could choose refrigerant packs that are as benign as possible (i.e. largely water-based), and they could consider limiting how many environmentally intense food products (such as red meat) are offered on their menus.

MILLER: And for those meals that do contain meat, they could keep the meat portions small and bulk up the meal with less environmentally intensive foods.

Same question for grocery stores. What can stores do to cut down their environmental impacts and make meals purchased at the store more environmentally competitive with meal kits delivered to your door?

HEARD: Grocery stores can improve their environmental performance by reducing overstock (which results in retail food loss) and by better predicting customer volume using analytics. Stores can also create partnerships with food banks to donate food that would otherwise be lost or wasted.

For some products, grocery stores can reduce their environmental impacts by stocking the products in smaller or variable portion sizes—for example, allowing customers to buy a single chicken breast rather than three packaged together, or allowing customers to select the number of mushrooms they want from a bin rather than packaging them in set volumes.

MILLER: And each store can look for its own creative ways to reduce its carbon footprint. The key is to reduce food waste and energy consumption.

Tell us about the relative impact of different variables in your study. Which variables are key and how do the variables scale? For example, if you are feeding a family of eight, does it make more sense environmentally to buy four meal kits or to make meals purchased at a grocery store? 

HEARD: The key variables creating a difference between meal kits and grocery meals are store retailing (including retail food loss); the final transportation of the meal to the household; and household food waste.

Meal kits allow consumers to circumvent the grocery store retailing process, which reduces retail food loss and emissions from store retailing. Meal kit delivery also optimizes the final (“last-mile”) transportation of meals to the customer. These changes can be expected to remain roughly equally advantageous (on a per-meal basis), whether two or eight meals are being considered.

The factors that generate household food waste are multi-faceted and complex, leaving the change for this variable ambiguous with respect to the number of meals considered. However, it is clear that pre-portioned ingredients (like those in meal kits) result in less food waste generated by a household. Assuming there is no reduction in food waste for a larger family, meal kits will still be the lower-impact way to supply meals, due to ingredient pre-portioning (which limits household food waste) and through circumventing the traditional retail and transportation process.

Tell us more about why the cheeseburger meal had fewer GHG emissions if purchased from the store. That finding is not intuitive!

HEARD: The cheeseburger meal had fewer GHG emissions because the meal kit cheeseburger had ingredients (hamburger buns and beets) that were over two-and-a-half times heavier than the ones we bought from the store. Heavier/larger ingredients carry greater environmental impacts than smaller ones, and not all foods are of the same size. When we standardize the mass in our analysis, however (e.g. assume all beets are the same mass), we find the meal kit cheeseburger’s GHG emission to be lower than the grocery meal’s, in line with the relationship seen for all other meals.

We already know from other CSS research that eating less meat is the best way to lower the carbon footprint of your diet. Besides meal kits (which can get expensive), tell us some other ways--especially budget-friendly ways--for consumers to lower the carbon footprint of their grocery shopping trips and the food they prepare and/or eat at home.

MILLER: One very budget-friendly way to reduce the carbon footprint from what you eat is to reduce your food waste! Meal planning (scheduling when you will use the ingredients you buy, when you will eat your leftovers, etc.) has been connected with lower household food waste and makes sure you use as much of the food you paid for as possible. This practice allows you to eat meals made from leftovers or extra ingredients you have instead of buying new food.

Another way for consumers to reduce their carbon footprint and to save money is to group as many grocery store trips into one vehicle trip as possible (as long as you are able to consume everything you buy). This will save gas money from driving multiple times to and from the store, and transports as much food as possible during a trip, reducing per-meal emissions.

Just for fun: Anybody want to recommend some must-try meal kits?

MILLER: I’m not sure any of us are avid purchasers of meal kits, but one fun fact to mention is that both of the undergrads on the project had to secure an appropriate “research lab” (ahem… kitchen), so had to bribe friends and relatives with the promise of dinner. Neither student is an accomplished cook, so some of their best learning experiences beyond data collection involved actually learning how to prep and cook meals. And making meals has an added challenge when your advisor tells you to weigh and categorize everything, from each plastic bag to the amount of faro you left uneaten.

Media mentions

• NPR
• GRIST
• Smithsonian
• Popular Science
• CBC News
• Forbes