What is Compost?
How facilitated rotting is different than waste management
I recently presented to a group of college students and one of them asked, “I know this might seem like a basic question, but what is compost?” I loved this question and it’s not so basic. This post is my meandering answer.
Facilitated Rotting
Natural things naturally rot, and “composting” is just facilitated rotting. Compost heaps are a way for us to participate in the miraculous act of decomposition. Our participation unlocks the possibility for things to degrade faster and for a particular microbiome to be nurtured (one capable of restoring functionality to our soils).
Unfortunately, large-scale composters don’t usually tap into the latter possibility! But for diy, craft, or boutique composting the magic is in tending to waste and transforming it into something vibrant and restorative - what’s not to love about that? 💫
Compost is a verb (and maybe a place?)
“Compost” is mostly a verb to me, the process or act of participating in decomposition.
e.g. “I like to compost”
It can also be used as a noun to describe the place or heap where facilitated rotting is actively occurring.
e.g. “check out my compost” (points to pile of rotting things).
However, I feel conflicted about also using the word “compost” to refer to the stuff that goes into the compost bin, and the stuff that makes up the end result.
Why? For one, it makes conversations about composting very confusing. Secondly, composting is such a transformative process - what you start and end with are two completely different things that should not be referred to by the same name.
In baking, we don’t call cake “finished batter” or bread “finished dough”. Similarly, there is a huge biochemical difference between the start and end materials of composting.
Useful Terms
Feedstocks or Inputs
Feedstock: this is a useful term for all the various materials that go into a compost pile. For example, food scraps, wood chips, manure, grass clippings, leaves are all examples of different feedstocks.
Inputs: if you want to sound more casual / less industrial, you could easily refer to feedstocks as inputs 😎
Soil Amendment: this is my suggestion for what to call a finished compost material. Perhaps there’s a better term, but this one reflects what I am personally trying to create when I’m composting. Plus, I like that it might give someone pause to consider the quality and effect it might have when applied to soil.
What do you think we should call the end result of composting?
Composting is different than waste management (IMO)
I view compost piles as incubators of beneficial soil microbes. At least, that’s what they ought to be! However, industrial-scale compost facilities aren’t often focused on nurturing decomposition to yield a useful amendment, rather they’re focused on waste management.
The primary business concern for industrial compost facilities is collecting a fee for the drop-off of organic waste which they aim to process and offload as quickly as possible. While this service diverts significant amounts of material from landfills (a good thing!) their interest, typically, is not in making a great soil amendment and yet well-meaning homeowners, gardeners, farmers, and landscapers apply this product to soils by the truckload.
Why industrial composting (typically) doesn’t make for great soil amendments
Industrial compost heaps are technically made up of decomposing natural waste like any other compost pile, so why does the finished product tend to have poorer biological quality?
This can happen for a number of reasons but the main culprits are:
Not having diverse or balanced inputs / feedstocks
whatever is brought to the dump is what gets ground up and put into the pile, it seems impossible to divvy up materials into different feedstock categories as they come in, then recombine them to ensure a diverse mix at balanced ratios of greens:browns:high nitrogen inputs (which would yield a diverse set of microbes)
Allowing compost to get too hot and/or not allowing it to mature at ambient temperature
heat is naturally generated during decomposition and can be used as a tool to kill potential pathogens and weed seeds, but it also kills beneficial organisms which is why a maturation period at ambient temperatures is needed for those organisms to recover; even still a maturation period may not result in a biodiverse soil amendment depending on other factors like feedstocks, moisture and oxygen levels
Poor moisture management - either too wet, too dry, or too inconsistent
to really incubate beneficial microbes, a consistent moisture of 50 - 70% is needed, fluctuating moisture tends to slow down decomposition and the succession of microbial communities
Creating change with genuine inquiries
An easy way to know if an industrial compost product is worth buying is to ask the manufacturer (or even a retailer) a question like, “can you tell me about the biological quality of your product?”
I do this all the time and it’s been really interesting to see how people respond. Most folks don’t know what I’m asking but are willing to engage in conversation about it (this is the work, y’all!)
While at a conference in Oklahoma recently I inquired about biological quality at a booth for a soil yard named Prairie Dirt Solutions, the owner lit up in response to my question and we had an enthusiastic conversation about soil health. She explained they make a slurry of microbial foods (a recipe informed by world renowned soil biologist, Dr. Elaine Ingham) that they apply to their ground-up materials to yield a more biodiverse soil amendment - awesome!
Why isn’t every large-scale composter doing this?
By and large, consumers don’t know to care about the biological quality of compost products, and therefore, most makers stick with the status quo of focusing on a waste management business model rather than concerning themselves with making a more useful soil amendment.
I encourage you to have similar conversations with soil yards near you and to do so from a place of genuine curiosity, not a place of smug superiority. If someone can’t answer the question, that’s okay. The inquiry is mostly an exercise in letting businesses know that quality matters to us as prospective customers, and it just may present an opportunity for a conversation on soil health. 🤎
Are you facilitating any rotting?! I’m planning on moving some of my composting efforts to our community gardens soon - I expect it will be even more enjoyable raising microbes with friends and neighbors :)
Update: We are doing a trial in a large compost yard in CA. The first test was done by inoculating the -1 compost after its 2 weeks of cooking. At 8 days, we were seeing bacteria, protozoa, flagellates and bacteria eating nematodes.
If you have time to come to CA, we will be working for a few more weeks on site. If not, we can converse off line after the next 2 tests are finished and the results are in.
Hi Andie, It would be great to have a conversation with you about what we do to go beyond compost. We aerobically use biologics, themperature and mechanical means to create a liquid slurry soil amendment rich in biologics. The process takes about an hour and we are working to break into the food waste area as we can handle meat, fish, cooked food, spoiled food, yard waste and or field waste. Gary Ailes