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Is Quality Compost Always Black?

by Marty

Is there actually a way to make compost in a commercial setting so that it doesn’t go anaerobic? Is high quality finished compost always black in color? If not, is the end-product simply dark brown?

Here is the background on my question…

I continue to read what I can on making quality compost for garden use and compost tea. Right or wrong, I have developed this preconceived notion that well-made finished compost takes on a rich, dark black color. This has been confirmed (even though my finished compost fails to ever attain this “dark black” color) by the appearance of a couple of good locally available bagged products, including what I see coming out of our local biosolids composting facility (no, I do not use this for compost tea).

I recently pulled the following book off my shelf to reread – “Adding Biology – For Soil and Hydroponic Systems.” A wonderful book that is
small, concise, and easy to understand. However, there is a strong point made about finished compost that has begun to make me question my preconceived thoughts. It states that black compost is not the result of a successful composting process, but instead is due to a period of anaerobic activity.

It is stated that due to anaerobic conditions, ammonia and hydrogen sulfide are produced which leaves a black residue in the compost. The “blackness” explains many questions that I have had about this whole issue of finished composts. It explains why some of the bagged compost that I have purchased has the light smell of ammonia. It also explains why the biosolid composting facility “smells” of ammonia when I drive by it.

I don’t have the science to back me up but it is hard for me to believe that the center of an active windrow, or static pile, doesn’t run out of oxygen and go anaerobic within hours of turning. If it doesn’t show, I struggle with the basic fundamentals of compost production whether it be massive static piles, windrows, or simply 8 to 10 yard piles like mine. I do want to learn and understand the details. I look forward to anyone’s response.


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Jun 10, 2010
Attempt One – More Responses Wanted!
by: Compost Junkie Dave

Hi Marty,

As you can tell from the title of my response, I would love for others to provide their feedback on this question.

After you posted it, I sent it out to several different sources (e.g. professional composters and various composting forums I belong too). The consensus is this…Quality Compost is, dare I say it…NEVER black. Instead, as you alluded to in your post, and have observed, high quality compost is typically a dark, chocolate brown color.

One of my sources, said that the degree of blackness depends on moisture content, as well as processing temperature history.

After receiving this reply, I took a stroll out to one of our compost piles and made a simple observation (confirming the above comment regarding moisture content). It was an incredibly hot day, so the exterior of the pile was quite dry and indeed a nice chocolate, brown color; however, when I dug my hand into the pile, the compost appeared black. But…the interior of the pile was also a lot more moist than the exterior, thus giving it this darker, almost black, color.

You may also take some interest in the following website about soil humic substances. This was provided by one of the members of the composting forum I belong too. The site is quite technical, but have a look at Number 4 – Properties of Humic Substances.

On the above page you’ll see a color gradient, which does provide some insight into the various colors of compost. The author of the site notes that the major component of soil humic substances (i.e. humus) is humic acid, which is a dark-brown/grey-black color. Since compost describes the end-product of the breakdown of organic matter into humus and other organic substance, we might assume much of composts color comes directly from this humification process (aka the humic acids present in the material).

Just a brief comment on the bagged products being black – I wouldn’t put it past the large commercial suppliers of bagged compost to be adding some sort of dye (or black carbon compound) to their products. Oftentimes, these products are of low quality, and require the dyes to help boost buyer appeal. This may be similar to the dyes used on wood mulches (e.g. red, black, brown). In my opinion, these dyes are masking other “quality-related” issues with the products, and thus we should avoid the use of these dyed mulches in our garden. Okay, I’m starting to rant…

I hope this helps a little. Once again, if anyone else has any comments to add, please share!

Jun 11, 2010
by: Marty

thanks for your comment on my question. that is encouraging. thanks for taking time to answer. would you be able to share with me the composting group/forum that you are part of? i would like to join just to read and follow the threads. that would be greatly appreciated. thanks again.


Jun 11, 2010
Compost Forums
by: Compost Junkie Dave

Hi Marty,

You’re very welcome. Hopefully, we get some other responses in the future.

Here is a link to one of the forums I belong to. A word of warning though…as with most forums, make sure you read between the lines when people provide answers/advice. They may just be promoting their own products and/or websites.

Thanks again for your question. Please keep in touch and Happy Composting!

Dave 🙂

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