13
$\begingroup$

Several companies are offering a service to turn ashes of human remains into diamonds. Does anyone know any details about the chemical aspects of the process?

I have no idea, but suspect that the ashes are composed mostly of phosphates and oxides. Where does the carbon hide? Any carbonate would have decomposed at the creation temperature. Or does the cremation chamber has such a high $\ce{CO2}$ partial pressure that $\ce{CO2}$ from burners is captured by the $\ce{CaO}$?

How is the carbon then extracted?

Also, diamond is normally made out of graphite, which agrees with a statement on the LifeGem website.

Let's assume they can squeeze out a little $\ce{CO2}$ by heating the ashes in an oxygen stream. Then they concentrate the $\ce{CO2}$ on a molecular sieve, use the Sabatier reaction to create $\ce{CH4}$ which they decompose on a hot metal wire. Then they dissolve that in acid and get a little bit of powder rich in $sp^2$ bonds and similar to graphite. Could one make diamonds out of that?

On the other hand, the page mentioned above states that they first extract the carbon and then turn it into graphite. How do you turn a few mg of fine carbon powder into graphite?

$\endgroup$
  • $\begingroup$ Welcome to chemistry.SE! If you had any questions about the policies of our community, you can ‎visit the help center or take a ‎‎tour of the website.‎ || Well done! This question is really thought through! $\endgroup$ – M.A.R. Mar 8 '15 at 13:44
6
$\begingroup$

According to US published patent application 20030017932 "Cremeting; filtering carbon particles; sublimation; polishing"

The preferred process for collection begins with the oven operator positioning the body in the oven so that the head and chest area are not positioned directly underneath the main burner. This can be accomplished by positioning the body to the left or right side of the main burner, or positioning the body so that the legs and feet are underneath the main burner rather than the head and torso. Positioning the body in this manner assures that carbon will remain in the body's head area. The carbon can then be gathered by hand, or by using a metal shovel or scoop, or the like.

So, in this technique (or proposed technique) the idea is to not let the normal cremation process occur, which would change much of the carbon to CO2. It seems more like pyrolysis to charcoal.

They go on to say:

Another alternative embodiment for carbon collection involves collecting carbon from pulverized cremated remains. These remains consist mostly of ash, but depending on how the cremation was performed, there may be traces of carbon particles mixed in with the ashes. The remains can be placed in a vacuum induction furnace. The furnace is heated to 2000 degrees centigrade in a vacuum ranging from 30 toir to 500 torr. Chlorine gas is injected into the furnace, and reacts with the impurities to form chlorides. The impurities leave the carbon in the form of chloride gases, and are filtered as they exit the furnace.

For more possible methods read this and other patent applications such as US20040031434.

In another alternative embodiment of the invention, the remains can be cremated conventionally, mixed with additional carbon from another source, and purified as described above. It is contemplated that, using this technique, a gem containing at least some of the original carbon from the cremated remains can be prepared, even if the amount of carbon present in the remains alone is insufficient to make a gemstone of desired size or type.

There is no way to say what actually occurs at a particular company, unless someone has first hand knowledge, which I don't.

$\endgroup$
  • $\begingroup$ That is one creepy patent. 'The resulting synthetic gem quality crystal comprising carbon from a vertebrate has a unique character to it, because it specifically relates to the vertebrate which supplied at least a portion of the carbon for the gem.' I found that LifeGem uses ashes and doesn't depend on this 'special' carbonization process lifegem.com/secondary/lifegemfaq2006.aspx#previouslycremated $\endgroup$ – guest Mar 9 '15 at 1:36
  • $\begingroup$ LIFEGEM is a registered trademark of International Research and Recovery Corporation. The patent application is assigned to the same corporation. The inventors are CEOs of the corporation. google.com/finance?cid=11437443 $\endgroup$ – DavePhD Mar 9 '15 at 7:54
  • $\begingroup$ That makes me wonder if they have a problem getting carbon out of the ashes. The homepage says that normal ashes are ok. Here is a more detailed chemical analysis, unfortunately they didn't look at carbon. scattering-ashes.co.uk/general/… $\endgroup$ – guest Mar 11 '15 at 3:01
  • $\begingroup$ But do they say what percent of the carbon is from the person? If they aren't saying, then it could be only a small fraction. You may find this report interesting cremationdiamondreport.com/LifeGems.html $\endgroup$ – DavePhD Mar 11 '15 at 11:55
3
$\begingroup$

Let's assume they can squeeze out a little CO2 by heating the ashes in an oxygen stream. Then they concentrate the CO2 on a molecular sieve, use the Sabatier reaction to create CH4 which they decompose on a hot metal wire. Then they dissolve that in acid and get a little bit of powder rich in sp2 bonds and similar to graphite. Could one make diamonds out of that?

You ask good questions about how $\ce{CO2}$ is obtained. But if there is a way to get $\ce{CO2}$, I doubt methanation is done en route to graphite. At elevated temperatures, direct reduction of $\ce{CO2}$ to graphite can be accomplished by many metals.

I don't know if it used in the ashes-to-diamonds industry, but in sample preparation for accelerator mass spectrometry, $\ce{CO2}$ is converted to graphite routinely. Here is one paper from the 1980s, which uses finely divided magnesium at 550 °C to reduce carbon dioxide to elemental carbon.

On the other hand, the page mentioned above states that they first extract the carbon and then turn it into graphite. How do you turn a few mg of fine carbon powder into graphite?

A much later report from Lawrence Livermore National laboratory uses zinc for the same purpose, and shows that their protocol is usable on only a few mg of carbon. (Note since they are interested in analytical applications, their protocol is extremely rigorous/tedious, but I would guess that for diamond manufacturing applications this level of rigor would not be required.)

$\endgroup$
  • 1
    $\begingroup$ Interesting LLNL report, thank you. I wasn't aware that CO2 could be reduced to graphite at such low temperatures. The iron catalyst can then be used as a matrix for the diamond synthesis. $\endgroup$ – guest Mar 9 '15 at 1:45
0
$\begingroup$

The simple answer is that the ashes of organic material contain large amounts of sodium carbonate, potassium carbonate and calcium carbonate (along with the respective oxides).

Add a few drops of some acid, and you've got the carbon dioxide.

$\endgroup$
  • $\begingroup$ He specifically mentions that carbonates would decompose at those temperatures to make $\ce{CO2}$ and metal oxides. If you're going to say that is incorrect, shouldn't you back that up with evidence/a reference of some sort? $\endgroup$ – SendersReagent Apr 15 '16 at 0:46
  • $\begingroup$ Those carbonates do not decompose significantly until > 1000 K. $\endgroup$ – Karl Apr 15 '16 at 1:02
  • $\begingroup$ See this. $\endgroup$ – SendersReagent Apr 15 '16 at 1:30
  • $\begingroup$ I cite (emphasis from me): "... can reach temperatures of 2,000 degrees Fahrenheit (1093 degrees Celsius) $\endgroup$ – Karl Apr 15 '16 at 8:46
  • $\begingroup$ Yep. If the can reach 1350K, I don't think regularly reaching > 1000K is unlikely. $\endgroup$ – SendersReagent Apr 15 '16 at 9:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.