Can You Compost Bones? Here’s the Nitty-Gritty

If you have your own backyard compost, you might be wondering, can you compost bones? Animal bones from food waste fall under a “gray” area in the composting world. Many composting guides don’t recommend composting animal products for fear of attracting pests and creating strong odors. (This is especially true if you have a small, uncovered compost pile.) However, you can safely compost bones IF you take a few preliminary steps first, namely: boil the bones to remove excess meat, oven bake (to turn the bones brittle), and crush.

We were curious as to how to compost bones as we have our own backyard compost bin. We were recently given a cooked goose (which of course had leftover bones). We conducted our own experiment which we’ll share with you below.

Read on to learn how to safely add bones to a backyard compost without creating a huge stink.

Why most people don’t recommend composting bones

If you take a look at most home composting guides, most don’t recommend adding animal byproducts including meat, dairy, and bones to the average compost.

For example, the U.S. Environmental Protection Agency (EPA) does not recommend composting meat, bones, fish bones, and animal scraps as it may, “create odor problems and attract pests such as rodents and flies.” 

This is mostly true: adding meat and bones to the average backyard compost pile may create more trouble than it’s worth.

This is because many backyard composts are of the “passive” variety meaning you add a variety of food scraps once in a while, and let it sit while nature runs its course.

If you happen to have a passive compost, it’s most likely a “cold” compost which means the pile’s overall temperature remains cool, and the rate of decomposition is slower. If you add bones to this type of compost pile, the bones will take a long time to decompose (maybe years!), and in the meantime, could cause quite a stink.

If this applies to the type of compost you have at home, pause before adding bones to the pile.

On the other hand, the University of Georgia says, “Items such as red meat, bones and small amounts of paper are acceptable, but they take longer to decompose. Add red meat and bones to only a well-controlled compost pile to avoid attracting vermin, pests and insects to partially decomposed meat scraps.”

So, if you have a thriving, hot compost pile, the rate of decomposition is much quicker. You’re probably adding new compostable material frequently, and regularly turning the pile which helps to aerate, mix, and break down components quickly.

With hot composting, it’s safer to add bones. But, they’ll still take a long time to fully decompose before you can use your batch of finished compost.

So, to breakdown bones more quickly, it’s important to take a few extra steps first which we’ll explain below.

Takeaway: Don’t add bones or meat scraps to a compost (especially if you have a cold or passive compost heap), before first taking a few extra steps—see below. Bones may create a strong odor, attract unwanted backyard pests, and just take a very long time to decompose.

Why compost bones?

If you haven’t jumped on the composting bandwagon yet, now’s the time to do so. Food waste is a huge problem. Composting not only diverts waste from landfills, it also creates a nutrient-rich soil amendment for your garden.

Besides, instead of spending money on buying bone meal which acts as a natural fertilizer, you can simply learn to compost leftover bones by grinding them up first. 

Bones are a source of calcium, carbonate, collagen, and phosphate. 

In particular, raw bone meal provides a source of nitrogen. (While bones also contain phosphorous, most of it is not soluble.) According to Alabama A & M & Auburn Universities, steamed bone meal increases the amount of available soluble phosphorous for plants (but slightly decreases the amount of nitrogen available). Steamed bone meal contains about 20 percent calcium.

In the composting world, nitrogen acts as a source of nutrients for the microorganisms and other helpful insects in a compost pile.

Calcium carbonate helps to build strong cells in plants and is a vital part in healthy cell development in plants. All in all, bones provide an excellent source of nutrition for plants.

What kinds of bones can you compost?

Many different types of animal bones can be composted (provided you prepare the bones first which we’ll cover in the next section).

• Beef bones
• Chicken bones
• Fish bones
• Pork bones
• Wild game bones

Can you compost bones? Yes, here’s how

Will composting bones attract unwanted critters like flies and beetles (and potentially ruin an otherwise healthy compost heap)? We decided to test out this method on some leftover goose bones. 

(While we used goose bones, we later tried this with leftover pork bones which also worked).

In a nutshell, the process involves boiling the bones with water until they became soft enough to break apart easily. Then, we baked them at 400 degrees Fahrenheit for about 30 minutes. After baking, we crushed the bones into smaller pieces using a mallet.

When you pre-process bones before adding to a compost, it makes them unattractive to pests. You’re essentially cleaning the bones and crushing them into small pieces. This helps by removing any leftover meat, cartilage, and seasoning (which would make a tasty snack for backyard critters), and breaking into small pieces to speed up decomposition.

You’ll need:

• Large stockpot and wooden spoon
• Baking sheet
• Something to crush the dried bones with such as a mallet, rolling pin, or mortar and pestle

Let’s get started!

Step 1: Boil the bones

This first step involves boiling the bones to soften them; this also helps to clean them by removing any leftover meat, cartilage and flavoring.

As you may know, store-bought bone broth sells for a pretty penny at farmer’s markets and grocery stores. It’s a nutritious stock that’s brimming with collagen. Why not make your own broth while you’re at it?

Now, if you really want to make a proper bone broth, you’ll need to boil bones for hours. However, if you don’t have that much time, boiling the bones anywhere from 30 to 60 minutes (depending on the amount and size of bones) should suffice for cleaning and softening them for composting.

So, here’s what you do:

• Throw those leftover bones into a large stockpot. Fill with enough water to completely covet the bones, and add any herbs, spices or seasonings (optional). I like to throw in leftover vegetable odds and ends which we save in the freezer just for this purpose—to season soup stocks.
• Bring to a boil. Leave at a vigorous boil for 30–60 minutes. Stir occasionally.
• Allow to cool and remove bones.
• Pat dry.

After boiling, the bones should be clean and free of any leftover meat or cartilage. 

Step 2: Bake the bones

The second step involves drying the bones and making them brittle enough to easily crush into smaller pieces. 

• Preheat oven to 400 degrees Fahrenheit (204 degrees Celsius).
• Place bones in a single layer on a baking sheet.
• Bake for approximately one hour (or until bones are completely dry and brittle). Begin checking on the bones after 30 minutes for signs of browning. Depending on the size and amount of bones you have, you may need to bake for longer. Our duck bones were completely dried and brown after 30–40 minutes.
• Remove from oven once dry and allow to cool.

You know the bones are done when they easily crumble and are completely dried.

Step 3: Crush the bones

The main goal here is to avoid leaving big pieces which take longer to decompose. There are a number of ways you can do this. You could use a mortar and pestle if you’re working with smaller bones. Or, you could use a rolling pin.

What we found worked well (and was pretty satisfying!) was using a mallet and smashing them outside.

If you want to take this a step further and grind the bones into a fine powder to make bone meal, you could do that now. If you grind the bones into bone meal, you can add it directly to soil as a natural fertilizer and skip the composting process altogether.

The bottom line: It really doesn’t matter what you use to crush the bones so long as they are all in small pieces. This allows the fragments to break down more quickly in a compost pile.

Step 4: Add to compost

Now that you’ve properly prepared bones by boiling, baking, and crushing them, it’s time to add them to your compost!

When adding something new to a compost pile (especially something that’s more difficult to break down such as bones), it’s best to add to the center of the pile. The middle of a compost pile is where all the action is—the microbes are actively working to break down organic material which heats up the compost and helps break down ingredients more quickly.

So dig a hole in the middle of the compost bin. Add the bone fragments in. Cover with a thick layer of compost. And let the compost naturally work its magic.

Once you’ve processed the bones before adding to a compost, there’s virtually no smell, and little chance of attracting unwelcome critters to your backyard compost.

Depending on how active your compost pile is, the amount of bones you’ve put in, plus the size of the bone fragments, you could easily see decomposition in a matter of months rather than years.

Other ways to compost bones

Let’s say you don’t want to go through all the trouble of boiling, oven baking, and crushing leftover bones. (We don’t blame you.) 

Don’t worry, there are still other options if you don’t want to send your leftover dinner bones to the landfill.

Municipal food composting

If your area has a municipal collection system for food waste, most programs allow for meat and bones in compost. Check your local municipal food compost service to see what items are accepted.

Bokashi composting

A bokashi bin is different than other household composting systems. It breaks down food in an anaerobic (oxygen-free) container and uses inoculated bran as a starter to decompose food via fermentation. You can safely add meat bones to a bokashi bin.

Can you add bones to your worm bin?

If you have a vermicompost, personally I don’t see much point in putting leftover whole bones from dinner in. First, it would take red wigglers ages to break down bone content. Second, as a general rule, it’s best to keep their diet mostly plant-based. Avoid adding in animal products including bones and meat as it may cause a strong odor and attract pests.

If however, you wanted to boil, bake, and crush bones into a fine bone meal, this would be okay in small amounts.

Check out our other articles composting animal products and other tricky household food items:
Can You Compost Shrimp Shells? How Shrimp Shells Help Your Garden
Can You Compost Hair? Here’s What You Need To Know
Can You Compost Dairy Products?
Can You Compost Lemons, Limes, and Other Citrus Fruits?
Can You Compost Vegetable Oil? Here’s What You Need To Know

References

1. United States Environmental Protection Agency (EPA), Composting At Home, https://www.epa.gov/recycle/composting-home. Accessed August 2021.
2. University of Georgia, Food Waste Composting: Institutional and Industrial Application, https://extension.uga.edu/publications/detail.html?number=B1189&title=Food%20Waste%20Composting:%20Institutional%20and%20Industrial%20Application. Accessed August 2021.
3. Britannica, Bone anatomy, Chemical composition and physical properties, https://www.britannica.com/science/bone-anatomy/Chemical-composition-and-physical-properties. Accessed August 2021.
4. Alabama A & M & Auburn Universities, Fertilizing the Organic Garden, https://www.aces.edu/blog/topics/vegetables-lawn-garden/fertilizing-the-organic-garden/. Accessed August 2021.