Sciencemadness Discussion Board

Urea to Ammonia using urease

vanBassum - 5-10-2023 at 23:56

Hello,

Let me start off by saying that my knowledge of bio is just about enough to keep myself alive. So please bear with me. :D

Every so often I have the urge to try and make nitric / nitrates. Last time I made platinum on quartz wool and used a pump to bubble air through an ammonia solution. That worked, but doesn't seem very economical or practical. While I was looking around for possible candidates to convert into nitrates, urea seems to be the most economical. Problem is, I need to convert the urea to ammonia. I have looked into thermal decomposition and a process called eU2A that uses electrolysis. When using these methods, I soon found that the output of ammonia isn't steady enough to leave it running for a couple of hours.

While searching the internet, I found that urea could be hydrolyzed to ammonia using an enzyme called urease. Apparently, this enzyme is found in watermelon seeds. My idea is to get a watermelon and just try it out. (I mean, they are delicious, so win-win.) As a first test, I was thinking of just crushing up some seeds and put them in a solution of water and urea. Then I hope to smell ammonia after a bit. If this works, I just pump air through the solution, driving the ammonia / air mixture through the catalyst. I assume you need quite a lot to get a decent production of ammonia. I was thinking of filling a 25L bottle. As a very nice bonus, the urea is converted into ammonia and CO2, so there won't be any products left after the urea is depleted. It might be possible to just keep feeding the reaction more urea.


Now for my questions:
- Has anybody got experience using urease?
- How many seeds would I need per liter?
- Could the urease be isolated from the seeds?
- What concentrations of urea do I need?
- Is this a viable idea?

Sources:
- eU2A: https://iopscience.iop.org/article/10.1149/2.0041510eel
- Urease: https://microbiologyinfo.com/urease-test-principle-media-pro...

Alkoholvergiftung - 6-10-2023 at 04:10

I ve only read that before ww1 an Factory in Yokohama worked with urease and urin. They made ammonia in worth of 140Mark (that was an lot worth) a day. The urease was form soya beans. Maybe you finde more with google.

UC235 - 6-10-2023 at 20:40

Enzymes don't really work like that. They're generally quite slow relative to lab chemistry, they tend to die when their solutions are bubbled (physical denaturation at the air/water interface), and typically require buffer solutions with pH control for activity. Without pH control, formation of ammonia will rapidly raise pH and the enzyme stops working. It may even irreversibly denature it but that is enzyme specific

Tsjerk - 7-10-2023 at 09:08

Not to mention the effect of concentration of the product often effects the enzyme activity. When the concentration of ammonia/ammonia salts becomes too high activity will drop.

khlor - 23-6-2024 at 08:58

I am not sure if it helps or if you are still on this project, but... here is my take on it, since in a not so near future I myself will be performing experiments with a somewhat similar goal. so here is my shot:

Instead of bothering with enzymes which are slow and difficult to keep, why not do it with bacteria, I mean, there are plenty of bacteria that do convert urea to ammonia, it is easy to take care of it and easy to scale up, as well as readily available from what I could gather, since it can be found almost anywhere on the ground and air. I do believe that going this rout is far more feasible than dealing with enzymes.

please understand that I am not an expert, nor I did this before, just someone who does experiments on my spare time and I just happened to find this thread.

best regards!
Khlor Ag.

Alkoholvergiftung - 23-6-2024 at 10:56

Problem with Bacterias is Ammonia poisening. Ammonia oxidizing Bacterias life from ammonia but got poisenend if ammonia solution has more than 1,5%. I think the same is for the Urea decompusers.

khlor - 29-6-2024 at 13:30
Quote: Originally posted by Alkoholvergiftung  
Problem with Bacterias is Ammonia poisening. Ammonia oxidizing Bacterias life from ammonia but got poisenend if ammonia solution has more than 1,5%. I think the same is for the Urea decompusers.


I see, that makes sense, an embarassing oversight on my part. though, since you mention that, I believe it could still be used to make ammonia salts which are easier to process into ammonia than urea, using an acid buffer solution to react with the ammonia as it is formed something like HCl, H2SO4 in low enough concentrations as not to upset the bacteria and then adding it continuously dropwise to keep enough acid to react with the newly formed ammonia but not so much as to acidify the solution. however I don't know what would the maximum ammonia salts concentration the solution could hold before it started affecting the bacteria.

just a theory I cooked up as I read your post, I know it is done in the industry to produce other goods and it is also done in the human body to keep pH equilibrium so it could work on a bio-reactor even though it would be at the cost of simplicity(increasing complexity)

pesco - 22-12-2024 at 11:33


If your goal are nitrates look at my post over here -> https://www.sciencemadness.org/whisper/viewthread.php?tid=16...


From experience with working with pure enzymes back at uni and bit afterwards I know it is often difficult, slow and expensive.

Boffis - 26-8-2025 at 06:19

Before the Haber process came along ammonia was prepared from urine or sewage by adding burnt lime (calcium oxide) and distilling off the liberated ammonia.

Urea + calcium oxide = ammonia + calcium carbonate + heat

The latter helped the distillation process no end I suspect. Slaked lime also works but more external heat is required. This process looks a lot more amateur friendly given that both reactant are readily available in most places and dirt cheap.

During the industrial revolution, the era of large-scale coal distillation, ammonia was recovered from the "ammonical liquors". This process produced more than enough ammonia and the urine source gradually fell into disuse.

Disruptive - 3-1-2026 at 03:05

Biochemistry is done at low concentrations. If you want to make nitrous and nitric acid from urea using bacteria (biochemistry) the concentrations are going to be very weak. This is mostly due to toxicity issues in the series of reactions. So the reactions are urea -> ammonia -> nitrite -> nitrate, whereby the you are going to have problems stopping at nitrite. The bacteria can be bought in the form of aquarium biofilter quick starter sets. The natural concentrations for the ammonia oxidisung bacteria are under 1 mg/l TAN. Above this a thick biofilm is formed to give the low corresponding concentration at the cell walls. More easily you could take water runoff from a farm or sewage farm. At the end of the day you are going to have to concentrate the nitrate salt.

Back in the bad old days, people wanted to make explosives and that required such acids. The Haber-Bosch process was developed to this end rather than to feed the world. Herr Haber moved up to do poison gas. The ammonia produced was very expensive.

As Boffis has indicated old industrial chemistry is the source for how these chemicals were made economically in the past.

If you really want to understand the biochemistry involved in ammonia oxidation you should go to my post on "Carboxy Exters in Biochemistry - Lets start with the nitrogen cycle".

@Boffis the second Zenodo preprint might be interesting for those with a detailed knowledge of historic industrial chemistry.

Alkoholvergiftung - 3-1-2026 at 05:08

If you make Nitrates 28% of calciumnitrate is the highest concentration of any bacterial made nitrate. For Potassiumnitrate it is 5%. Than why higher Potassiumnitrate concentrations or found in nature ( on the claypot methode the KNO3 was 94% pure ). Capilar forces drag away the nitrate from the bacterias, thats only at the right tempertures. Is it to hot the water evaporates to fast and everything remains in the soil. Is it to cold the transport is to slow. Oh and i found the Patants on making NH3 from trash. It is in german.There are methodes with soya beans descripte in it the methode i mentioned earlier.

Attachment: AmmoniakUrin_all_pages.pdf (240kB)
This file has been downloaded 35 times

Disruptive - 3-1-2026 at 05:56

@Alkoholvergiftung That is an interesting piece of info and luckily I speak German. Of course back then much of the scientific literature was in German, including the hydrogen transfer hypotheis regarding ammonia oxidation by bacteria (there is one german uni with a copy). I will digest the info in good time with the right whisky.

I hope you have got over the festival poisoning (Gift = presents?).

MfG

Alkoholvergiftung - 3-1-2026 at 06:30

Gift = Poison.

To Bad that all synthetic methodes for ammonia are to energy intensiv for DIY.
And all requires to seperate O2 from N2 or the yield are much worse.

If an methode would maybe work in homescale is with Bariummetal i know there was an factory in the US in the early 1930 they used bariummetal and hydrogen after the Bariumhydrid was formed they lid N2 gas ofter the 500-600C host mix and it released ammonia and formed Bariumnitrid than they lit again hydrogen over the nitrid....

Disruptive - 3-1-2026 at 07:35

@Alkoholvergiftung

Gift = Poison = false friend

Apart from the economics, there is also the safety aspect. Heating urea with sodium hydroxide is also not realy DIY chemistry for everyman.

Now if we only had a new chemistry...

Plants take nitrates and make ammonia from it in the reverse of nitrification. The ammonia is then used to make amino acids. So, what if a similar new biochemistry based chemistry is done at biological conditions using electricity? Keine Schapsidee von mir!

p.s. I am fluent in German, but the old scientific text is often in old fonts that make it hard to follow.

Alkoholvergiftung - 3-1-2026 at 09:23

They did this too. They reduced nitrates with zink and acid to ammonia. Sometimes they used H2S gas from the soda wastes. Scientist of that time sayed thats an waste.
Alternative there was the Nithack process or machine he used an fessel filled with water and pressed air inside at 50-100bar. than he did electrolysis with Pt anodes he got Ammoniumnitrate but couldnt concure with ammonia form Nitrolime.
In an old journal they wrote about iron when it rusts it forms with the air ammonium they did an experiment where they had in an secound flask HCL and did colect the NH4Cl. If someone has the time for it :D

bnull - 3-1-2026 at 12:37

Quote: Originally posted by Disruptive  
Now if we only had a new chemistry...

Plants take nitrates and make ammonia from it in the reverse of nitrification. The ammonia is then used to make amino acids. So, what if a similar new biochemistry based chemistry is done at biological conditions using electricity?

Like good old microbial electrosynthesis. I remember reading a review about it some ten years ago, maybe this one https://doi.org/10.1038/nrmicro2422.

Disruptive - 5-1-2026 at 12:49

@Alkoholvergiftung

Moin,

You have shown yourself to be a real oracle in historical chemistry, and you speak German! I have a post on nitrification, and I have just attached something from 1926 in German. The larger document covers "hydrogen transfer theory". Do you know if this was a common assumption/theory in chemistry or "German speaking" chemistry at the time or was it an outlier opinion?

MfG