End products of Compost (for Gardening)

[HikingViking]

I have a question concerning the end products of compost (in gardening). Not just a general answer, but a specific answer from an organic chemistry point of view concerning a theoretical list of materials that an organic chemist would recognize as end products of compost. That is, if you separated the end components of finished compost into small "piles", what would they be?

 

In my example, one creates a compost pile for gardening containing the perfect amount of nitrogen and carbon containing materials from straw, cow manure, vegetable scraps, fruit waste, biochar, and coffee grounds. Then, bacteria multiply by the trillions, heat up the compost, and run their course. That's followed by fungal activity to further break down the material. After an unspecified time, bacteria no longer can sustain their activity, die off or become inactive. Fungal activity decreases. At this point, what is left? Are there piles of partially broken down lignin strands? Cellulose/glucose? Partially broken down cellulose? What chemicals remain?

 

I apologize if this is not the right sub-forum for this topic. I am trying to understand the end components of compost, and I think only the organic chemistry community would actually be able to understand this. I'm a little tired of hearing the term "black gold".

[studiot]

The compost story is somewhat more complicated than you have presented it, since there is no ideal or one-size-fits-all, but I suggest you start by looking into humic acids and then posting further.

 

Here you will find chemical formulae and explanations galore.

 

https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=humic+acids&gbv=2&oq=humic+acids&gs_l=heirloom-hp.3..0j0i22i30l9.953.3922.0.10234.11.7.0.4.4.0.188.969.0j7.7.0....0...1ac.1.34.heirloom-hp..0.11.1171.-upd4UbOnKA

 

One thing to bear in mind is that organic fertilising material is more acid than soil.

 

This should be a good start, but do come back and expand your discussion, this is a good subject to talk about.

 

[Essay]

Alkanes, alkenes, and polycyclic aromatic hydrocarbons ...oh my!

 

Yes, you're right about the "...piles of partially broken down lignin strands? Cellulose/glucose? Partially broken down cellulose?" ...and along with broken down bacterial and fungal cell walls, which then break down more, into various chemicals such as phenols and furans and ketones and aldehydes, as well as pyrenes, pyrones, and pyrimidines ...and various acids and alcohols or whatever, somewhat depending on conditions and source materials.

 

Humus is the generic word for that pile of chemicals, which result from the decomposition of biomass. So if you search online for "humus" or "humic substances" (and click on images), you should get some good pictures of the various chemical moieties, which make up the black gold ...or Texas Tea. Also search "chromophores" to see what some humic substances look like.

 

And, btw, any "tea" is just a solution of humus. Even the chemicals that we can smell, or see as smoke, would be hard to distinguish from the "humic substances" originating from decomposition, if those smell or smoke chemicals were found in the soil.

 

The book, "An Introduction to Organic Geochemistry" should explain everything you want to know. But in the end, you'll notice how, whether by slow bio-geological processes, or by fast pyrolytic or burning processes, the end products are very similar or often the same, chemically.

 

"An Introduction to Organic Geochemistry explores the fate of organic matter of all types, biogenic and man-made, in the Earth System."

and it "...investigates the variety of pathways and biogeochemical transformations that carbon compounds can experience over a range of time scales and in different environments."

...beginning, of course, with decomposition.

 

Good luck, and glad to hear that you're using biochar! Biochar will help with the retention of humus, reducing offgassing from the more rapid decomposition processes, which then improves the compost's moisture regulating properties and reduces leaching from the compost. In several ways, it seems to me that biochar is essentially just solidified, or dehydrated, humus.

 

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