Manure Composting: The Science Behind Faster, More Valuable Compost

Composting manure is one of the oldest tricks in agriculture, and one of the most misunderstood. 

Most operations that compost manure are doing it for the same reason: to turn a bulky, variable byproduct into something more stable and easier to handle. Fewer are getting the full nutrient value out of the process. That gap between “composting manure” and “composting manure well” comes down to biology, and understanding it is the difference between a pile that breaks down on its own schedule and one that breaks down on yours.

Whether you’re running a static pile behind a dairy barn, a turned windrow at a larger operation, or managing poultry litter between flocks, the underlying science is the same. What changes is how that science plays out in your specific system, and that’s worth understanding before you decide how much time, turning, or input a compost program actually needs.

What Happens When Manure Composts

Manure composting is, at its core, a controlled version of decomposition. Whether it’s dairy bedding, hog waste, or poultry litter, manure is a mix of undigested organic material and animal waste, and both are various forms of organic carbon. That carbon can show up as lignin, cellulose, or hemicellulose depending on the bedding and the animal’s diet, and none of it is available to a plant until something breaks it down.

Bacteria and fungi work through the pile, converting carbon-bound material into stable organic matter and, eventually, plant-available nutrients. This is the same basic manure process that governs residue breakdown in a field: it’s not a separate category of science, it’s the same detritusphere activity that breaks down crop stubble, just working on a different starting material. There’s a reason manure looks nothing like the compost that comes out the other end six months later: biology doing its job. 

A pile isn’t just manure sitting around waiting to become inert. It’s an active worksite, with a population of bacteria and fungi doing real, measurable work on a schedule that depends on how well-supported they are. 

Two piles started on the same day, from the same source material, can finish weeks apart depending on nothing more than how well that biology was supported along the way.

The Microbiology Behind the Pile

Two microbial populations drive manure composting, and they do different jobs. 

Aerobic bacteria need oxygen and are responsible for cycling nutrients, they’re the reason a well-turned, well-aerated pile heats up and breaks down quickly. 

Anaerobic bacteria work in low-oxygen pockets deeper in the pile and are largely responsible for breaking down the denser, solid material that aerobic activity alone won’t touch.

A compost system that only supports aerobic activity will cycle nutrients from the material it can reach, but dense clumps and solid material will linger. A system that leans anaerobic will break down solids over time but won’t cycle nutrients as efficiently. The goal isn’t to pick one, it’s to support both, which is largely a function of moisture, temperature, and available food for the microbial population already living in the pile.

Windrow vs. Static Pile: Does Method Matter?

Most manure composting happens one of two ways: a static pile that sits largely undisturbed, or a windrow that gets turned on a regular schedule. 

Turning introduces oxygen back into the pile, which favors aerobic activity and tends to speed up the overall process, that’s why larger operations with the equipment to turn windrows regularly often see faster, more uniform composting.

Static piles lean more heavily on passive airflow and whatever aerobic activity can happen near the surface, while anaerobic activity dominates deeper in the pile. That’s a perfectly workable system, it just tends to take longer and can compost less evenly, with the outer layers finishing well before the core. Neither method changes the underlying biology at play, it just changes how much help that biology gets.

Poultry Litter: A Different Starting Point

Poultry litter management deserves its own mention, because litter composts differently than dairy or hog manure. 

Litter is typically drier and has a different bedding ratio (often wood shavings, rice hulls, or similar low-moisture bedding) mixed with a nutrient-dense manure source. That combination tends to run hotter and can compost faster than wetter manure systems, but it also means moisture management works in the opposite direction: instead of managing excess liquid, you’re often managing enough moisture to keep microbial activity going at all. A litter pile that’s too dry can look composted on the surface while remaining largely unprocessed underneath.

Litter also tends to accumulate between flocks on a predictable schedule, which makes it a good candidate for a consistent composting routine rather than a one-off pile. Operations that compost litter between every flock, rather than letting it build up over multiple cycles, generally see more uniform breakdown and an easier time managing pile size.

Poultry manure is also nutrient-dense relative to its volume, which is part of why it shows up so often in field trial data. In one Brazil field trial using chicken manure, PhycoTerra alone gained 30% biomass improvement, chicken manure alone gained 36%, and the two combined reached 44%, all versus grower standard. That’s a useful data point for anyone managing poultry litter: the raw material already carries real value, and biology is what determines how much of it gets used.

What Slows the Process Down

If composting were purely a matter of time, every pile would finish on the same schedule. A few variables consistently determine how fast (or how incompletely) a pile breaks down:

#1: Moisture

Microbial activity needs water to function, roughly the consistency of a wrung-out sponge is the general target for an active pile. Piles that are too dry stall out because the bacteria and fungi doing the work simply can’t stay active. Piles that are too wet can go anaerobic in ways that slow overall breakdown, create odor issues, and lead to handling problems down the line.

#2: Temperature

Composting is a biological process, and biology has a temperature range it prefers. An actively composting pile generates its own heat as microbial activity increases, which is part of why internal pile temperature is often used as a rough indicator of how active the process actually is. Piles in cold climates or cold seasons break down more slowly no matter how well everything else is managed, which is worth planning around rather than fighting.

#3: Food Source 

This is the one most operations overlook. Microbes need more than carbon to work efficiently, they need a readily available food source to stay active and multiply. Without it, the native bacteria and fungi already present in the pile are working with limited resources, and breakdown happens much slower than it could if all bacteria and fungi were active.

#4: Source Material 

What the animal ate and what bedding was used both affect the carbon-to-nitrogen ratio of the starting material, which in turn affects how quickly biology can work through it. 

A pile with too much carbon relative to nitrogen (excess bedding, for example) tends to break down slowly. Too little carbon relative to nitrogen can lead to nitrogen loss and odor. 

Ruminant manure (cattle, dairy) tends to be more broken down already, since ruminants digest fiber more thoroughly. Non-ruminant manure (hogs, poultry) often carries a “hotter,” less-processed nutrient load with different composting behavior.

Signs Your Compost Is Actually Working

A pile that’s genuinely active will typically run warmer at its core than the surrounding air, sometimes noticeably so. Volume will visibly reduce over time as material breaks down and settles. The strong ammonia or raw-manure smell common in fresh material should fade as decomposition progresses, replaced by a more neutral, earthy smell. 

Finished compost tends to be darker, crumblier, and more uniform in texture than the material that went in, with the original bedding largely unrecognizable.

A pile that isn’t heating up, isn’t losing volume, or still smells like raw manure months in usually isn’t lacking time, it’s lacking one of the four factors above.

Feeding the Microbiome to Speed Things Up

Once you understand that composting speed is a biology problem, the fix becomes straightforward: feed the biology. 

This is where a product like PhycoTerra® fits into a composting program. Adding it to a compost pile provides an immediate, balanced food source for the bacteria and fungi already present, which increases their abundance and activity. 

In side-by-side testing, compost treated with PhycoTerra showed a measurable increase in bacterial (CFU) counts over untreated compost, with activity peaking around 22 days after application. 

The goal isn’t to replace what’s naturally happening in the pile, it’s to remove the bottleneck that’s slowing it down.

What Faster Composting Actually Gets You

None of this matters if it doesn’t translate into something usable in the field. In PhycoTerra trials, treated manure has shown up to 32% more NPK availability and increases organic matter compared to untreated manure.* That’s the practical payoff of a faster, more complete composting process. 

More of what’s already in the pile ends up plant-available instead of staying locked behind carbon.

The application itself doesn’t require a separate process or new equipment. Inoculating a compost pile fits into the same handling routine most operations already have, whether that’s a static pile, a turned windrow, or a poultry litter house. The biology does the rest, on a timeline that’s easier to plan a season around instead of guessing at.

Composting manure well isn’t about waiting longer. It’s about giving the microbes already doing the work what they need to do it faster, and getting more usable fertility out of the same pile as a result. For an operation managing dairy bedding, hog waste, or litter between flocks, that’s the difference between compost as a disposal problem and compost as a genuine fertility asset.

This year, PhycoTerra is also offering a Manure Value Initiative program for manure programs looking to shape the future of the manure industry, and try our product. Follow the link to learn how you could get a 70% rebate on your product cost. 

*Percentages based on PhycoTerra field and laboratory trial results. Individual results are not guaranteed and may vary by operation.