What Happens to Ashes After They’re Buried?


Cake values integrity and transparency. We follow a strict editorial process to provide you with the best content possible. We also may earn commission from purchases made through affiliate links. As an Amazon Associate, we earn from qualifying purchases. Learn more in our affiliate disclosure.

If you’re getting ready to cremate a loved one, or you’re preparing your own end-of-life wishes, you may be curious to see how the process works from start to finish. While cremation is a concept that is easy to understand, the process of what happens to the ashes after they are placed in an urn and buried is less known.

Jump ahead to these sections:

Thankfully, the answers for this are simple and straightforward. Should you have a curious loved one preparing their end-of-life plans or want to know for yourself, we explain below what happens with ashes after they’re buried underground. 

Tip: If you want to keep or bury a loved one's ashes in a unique way, you can have them turned into natural cremation stones with Parting Stone.

Can Human Ashes Decompose When They’re Buried?

To understand whether ashes decompose, you first need a little information about how cremation works.

In Western countries like the U.S., the cremation process always occurs in closed furnaces in crematoriums due to environmental concerns. 

» MORE: An online memorial is a perfect ending to honor and celebrate someone's life. Create one for free.

Getting the ashes

First, the body is taken to the crematorium where it is placed inside a furnace with temperatures ranging as high as 1000 degrees Celsius or over 1800 degrees Fahrenheit.

Most modern furnaces in crematoriums have complete control over temperature and spy hole cameras are fitted inside so the operator can ensure the process is occurring as it should. Crematorium operations need to make certain that the body has been completely treated since the process can vary from body to body. 

Human crematoriums can only incinerate one body at a time, unlike pet crematoriums. The body has to be placed in a wooden coffin to enhance the process. The cremation chamber is usually lined with insulation and fire bricks that are replaced from time to time.

Other than the U.S., most countries in the West including the U.K., Germany, and Australia mandate burning a body in a coffin and provide strict guidelines regarding the types of coffins to be used.

Modern techniques have developed another method of cremation that uses chemicals instead of fire to be more environmentally friendly. One such process is called “aquamation.”

The aquamation technique is more suitable for people planning to make memorial diamonds from the ashes of their loved ones since this process preserves more carbon that is ultimately used to create cremation jewelry. This process uses water instead of fire to reduce a body to bones which are then ground to powder and made into “ashes.”

Burying the ashes

Regardless of whether you choose a traditional cremation or aquamation, the end result is still the same. What is left is commonly known as the “cremains,” or the fine powder-like bone fragments left over after a body has undergone the process of cremation.

Bones are not biodegradable so they will not further decompose at this point. Because of this, airtight burial urns that hold ashes can last for centuries and the ashes will remain just as they were the day they were placed into the urn. 

Complete decomposition is only possible for organic material. Bones contain so much calcium that they are similar in composition to a rock. Their heavy calcium makeup is the reason why even when people are buried, a person’s flesh and organs decompose quickly but the skeletal remains can stay as-is in a tomb for centuries. 

It’s important to point out that because of the high pH content in ashes, it’s never a good idea to bury ashes in a garden or under a tree. Since they also contain no nutrients that plants need in order to grow, the ashes can stall or thwart plant growth.

While the concept of planting a memorial tree, flower bed, or garden with the ashes might be a sweet, eco-friendly sentiment, planting with ashes will almost always cause plants more harm than good. 

» MORE: Grief can be lonely. Create space for your community to share memories and tributes with a free online memorial from Cake.

How Long Do Cremated Ashes Last?

Since cremation ashes are mostly made up of bone, and bones are not degradable, the ashes can last as long as a person wants them to. The typical packaging that ashes arrive in after the cremains are sent to a loved one is both air and water-tight. The ashes can then be further protected when stored in an urn purchased for the reason of displaying or burial. 

The burial of ashes is known as internment of ashes. The ceremony is similar to a funeral except it is more efficient, usually taking no more than 45 minutes. If desired, a family can include many of the same ceremonial concepts that a traditional burial has including friends and family to witness the internment and a pastor or priest that says a prayer for the departed. Common elements left out of urn burials include pallbearers and the lowering of the casket.

Due to the rising popularity of cremation, you can now choose numerous places for the interment of ashes such as a cemetery, an urn garden, or if you or a family member want the ashes close, the urn can be placed in a special place in the house or a private garden to be displayed or placed underground. 

If placing a burial urn in a garden, it’s essential to choose an urn built to withstand the harsh conditions under the earth. Your best choice is an urn made of sturdy materials such as metals or granite. If you prefer to have a green option, you can choose a biodegradable urn. Just keep in mind that, while the urn might degrade, the ashes will not. It’s best to place a biodegradable urn in a location where you will not plant trees, flowers, or vegetables, since the ashes can harm plants. 

Alternately, you can choose a biodegradable urn that comes with soil amendment so the high pH level from the ashes will be properly balanced out, ensuring a good environment for your plants and trees.

Urns are traditionally stored in a special place in the home of a loved one, in a columbarium, or can be buried at a cemetery. Many funeral homes provide services for any of these options to address the wishes of the deceased or the family. If you’re looking for other more memorable ways to ensure your loved one’s ashes are memorialized, there are numerous services available. 

Lasting services

Since ashes do not degrade, numerous burial alternatives are available to provide a permanent memorial to your loved one using their ashes. One service allows you to send a small portion of your loved one’s ashes in a container into low earth orbit or even into deep space such as the moon and beyond. Once in space, the ashes will forever orbit or explore the galaxy, depending on which option you choose.

Ashes can also be incorporated into cement and concrete of your house to make them a permanent part of your life. Placing the ashes of your loved one into the cornerstone of your home makes for a significant and lasting memorial. Encased in cement, they’ll never degrade and you’ll never have to worry about being separated from them.

If your loved one was passionate about the environment, you can have the ashes incorporated into artificial reefs that are being used to prevent coral reefs from going extinct.

No matter which way you decide to keep the ashes of your loved one close, you can rest assured knowing that they’ll be with you as long as you desire — whether in an urn, a memorial reef, or in a garden. You can even have a memorial diamond created from ashes with a company like Eterneva

If your ultimate desire is to keep your relative close, you can bury their ashes in an urn or place the urn in a special area of honor in your home. If you are looking for something very unique (think a game, a classic car, or instrument of choice), you can custom order an urn from a store like Foreverence. You submit a design idea or sketch, then the company designs and 3D prints your urn, so you get a 100% unique container.

Whether you bury or display the urn that holds your loved one’s ashes, you can’t go wrong. The ashes will never decompose, dissolve, or fade away for as long as you will be alive.

» MORE: Online obituary that is 100% free. Honor a loved one beyond a newspaper.

Choosing Cremation

Whatever you choose to do with the remains of your loved one, the diversity of choices available allows you to make a decision that your loved one would be pleased with.

Whether you decide on cremation or burial, be sure to take care of a person’s ashes in a way that represents the passions, beliefs, and final wishes of your loved one. 


    1. Celestis Writers. “Memorial Spaceflight Experiences.” Experiences, Celestis, 2020. celestis.com/experiences-pricing/
    2. Eternal Reef Writers. “What is an Eternal Reef?” Our Story, Eternal Reefs, 2020. eternalreefs.com/the-eternal-reefs-story/what-is-an-eternal-reef/
    3. Engrave Writers. “Ink Process.” The Process, Engrave Ink, 2020. engraveink.com/
    4. Dyer, Mary. “Planting in Cremation Ashes.” Gardening Tips and Information, Gardening Know How, April 3, 2018. gardeningknowhow.com/garden-how-to/info/cremation-ashes-and-plants.htm#:~:text=Cremation%20ashes%20may%20be%20harmful,be%20leached%20into%20the%20soil.
    5. Atkin, Emily. “The Fight for the Right to be Cremated by Water.” Cremation, The New Republic, June 14, 2018. newrepublic.com/article/148997/fight-right-cremated-water-rise-alkaline-hydrolysis-america



Icons sourced from FlatIcon.