Cheese, butter, yogurt — all wonderful things to find when you’re looking for a snack, all not-so-great things to find once they’re past their expiration date. Dairy, as delicious as it is, can turn on you pretty quickly once it starts to go bad. Dairy’s past-its-prime odor, coupled with the fact that its high fat and moisture content make it decompose slower than fruits and vegetables, is exactly why you should be wary of adding it to your at-home compost pile or bin. 

While dairy can technically be composted at home, it’s one of those things that should be left to more experienced home composters. And although dairy can be composted in many city-run composting programs, some cities discourage residents from leaving these materials at compost drop-off sites. (In New York City, for example, dairy can be composted in collection bins but not at drop-off locations.) 

So, can you compost dairy at home? With the right information and some experience, you can — and here’s how.

Can you compost dairy at home? 

Dairy has a high fat content that creates water-resistant barriers around the waste particles, slowing decomposition by displacing water and slowing airflow. So, in comparison to the fruits and vegetables you may add to your compost piles, dairy will decompose much slower. It can take roughly six months for dairy to decompose, and while six months isn’t forever, it isn’t overnight, either. 

According to Andrew Carpenter, soil scientist at Northern Tilth, dairy’s unpleasant odor makes it likely to attract pests, rodents, and other unwelcome neighborhood wildlife when added to backyard compost operations. 

So, while the short answer is, yes, you can compost dairy at home, the more nuanced answer is that if you plan to compost dairy at home, you should be well-versed in the associated risks. You’ll also want to get familiar with a handful of tips and tricks that can smooth over the process when composting dairy in your backyard.

Tips for composting dairy at home

Composting dairy at home can be done, but how it’s done is what matters. Follow these tips for smooth sailing. 

Balance greens and browns

Good compost piles, ones that are microbially active and decompose efficiently, are created by establishing and maintaining an appropriate balance of nitrogen-rich green materials and carbon-rich brown materials. Generally, it’s best to keep a ratio of 3 to 1 browns to greens — this is especially true and necessary if you plan on composing dairy. 

Because of dairy’s high moisture content — particularly dairy like yogurt — it’s even more necessary to keep that ratio of greens to browns. Browns are materials like cardboard, dry leaves and yard waste, which will help balance out the extra moisture that comes from including dairy in your pile. Carpenter also recommends adding an additional 12-18 inch layer of browns without any greens to the top of the pile as a physical and odor barrier to prevent attracting any nearby wildlife. That could mean adding a solid layer of leaves, twigs, brown paper bags, and the like to the top. 

Opt for hot composting

Heat is an essential part of all composting, and especially when it comes to composting dairy. Hot compost is a composting method where the pile or bin maintains high temperatures — at least 135^oF. This high heat will help the dairy decomposition process, kill pathogens, and speed the process along, meaning less smells and less time. Regular pile maintenance, turning, and monitoring moisture levels and temperature are all necessary components of keeping a pile hot. If you aren’t able to maintain the minimum temperature, you probably shouldn’t be composing dairy at home. 

Add the dairy to the right spot

Typically, the center of the compost pile is the hottest spot. Using a thermometer at home can help you keep track of this and make sure it’s true. Dairy should be buried at the center of the pile to give it the most direct access to heat and help it break down as quickly as possible. 

Know what to avoid

Although all dairy is generally filled with vitamins, minerals, and nutrients that would be beneficial to compost piles, not all dairy products can be added to compost. While cheese scraps (minus wax wrappers) and yogurt are fine, it’s best to avoid adding liquids like milk. Butter is also a no-no because it’s so high in fat it will decompose so slowly that it’s likely to throw off the efficiency of the entire pile as it spreads. Cottage cheese, like yogurt, can be fine to add. Just make sure you’re balancing out the added moisture with plenty of browns. 

Pre-process with Mill

The Mill food recycler will turn dairy like leftover cheese and yogurt, along with all your other food scraps, into dry grounds that can be mixed in with your garden soil or added to your compost pile. Because the dairy gets dried and ground, it won’t attract pests or other uninvited guests. Just like city and backyard composting, milk and butter shouldn’t be included in Mill, but pretty much all other dairy is fair game.

Can you compost dairy through a city-run composting program? 

Most city-run composting programs accept most forms of dairy. However, just like with home composting, you shouldn’t include things like liquid milk in your compost collection bin (powdered milk is fine). Make sure to check your municipal compost organizations for information about what is and is not accepted, and double-check if there are different guidelines for pickup versus drop-off operations.  

While major cities like Los Angeles, Chicago, and New York City all accept dairy in their pick-up composting programs, New York doesn’t allow food scraps, including dairy, to be included at its drop-off sites. You can check your local sanitation department website for specific information to help you make sure you’re following the guidelines in your area. 

Sources:

1. New York City Department of Sanitation: “Food Scrap Drop-Off.” https://www.nyc.gov/site/dsny/collection/residents/food-scrap-drop-off.page

2. Science Direct: “Milk Lipids.” https://www.sciencedirect.com/topics/food-science/milk-lipids