Composting turns dairy and feedlot manure into a drier, lighter, more stable material that is easier to store, haul, sell or reuse as bedding. It works when the manure is blended with enough carbon and structure to reach a starting carbon to nitrogen ratio of roughly 20:1 to 40:1 and 40 to 60% moisture, and when the pile is held hot long enough to reduce pathogens and weed seeds. The facility itself has to fit the farm’s nutrient management plan and local water and air rules.

Key takeaways

• The U.S. EPA says composting livestock manure reduces odors, kills pathogens, reduces bulk and stabilizes the manure for easier handling, and that compost costs less to transport than fresh manure.
• Manure is nitrogen rich: Cornell lists it at 5 to 25:1 carbon to nitrogen. Bedding, straw or wood has to bring the blend up, or nitrogen leaves as ammonia.
• NRCS Conservation Practice Standard 317 (Composting Facility) is the design reference for on-farm sites. Land application of the compost is planned under standard 590 (Nutrient Management).
• Time and temperature targets depend on the end use: bedding, the farm’s own fields, organic crops, or produce covered by the FDA produce safety rule.
• In California’s San Joaquin Valley, Rule 4565 sets VOC mitigation measures for sites that compost manure, with tiers at 20,000 and 100,000 wet tons a year.
• Composting moves nutrients into a form that can leave the farm. It does not make phosphorus disappear, so the nutrient plan still has to balance.

Why compost manure at all

The EPA’s Uses of Manure page sets out the case. Composting livestock manure reduces odors, kills disease-causing agents, reduces bulk and stabilizes the manure for easier handling. Compost can be applied more evenly and with better control than manure. Because it holds less water, it is cheaper to transport and worth more per load, so it can reach buyers farther from the farm. EPA also notes that compost sales can remove excess nutrients from farms that cannot use all of their manure nutrients on their own land.

There is a trade-off. EPA points out that the nitrogen in compost is not as readily available to plants as the nitrogen in fresh manure. A dairy that relies on manure nitrogen for its forage crops should compost the surplus, not the whole stream.

Manure as a feedstock: characteristics that matter

Manure is not one material. Pen scrapings, bedded pack and separated solids behave differently in a pile.

• Carbon to nitrogen ratio. Cornell Waste Management Institute lists manure at 5 to 25:1, depending on species and how much bedding is mixed in. Cornell describes about 30:1 as ideal and notes that below it nitrogen is supplied in excess and is lost as ammonia gas.
• Moisture. Cornell’s compost physics notes put the optimum at 50 to 60%. Measure it: wet manure needs separation, drying or dry amendment, and dry-lot manure in an arid season may need water.
• Structure. Fine, wet manure packs tightly. Without coarse particles there is no path for air.
• Weed seeds and pathogens. Manure can carry both, and both are reasons to manage temperature carefully.

Building the recipe: carbon and bulking

The NRCS national standard puts it plainly: developing a recipe is a balancing act, because both the carbon to nitrogen ratio and the moisture of the individual materials have to land in range. It directs operators to keep a dependable source of high-carbon material on hand, to add bulking material as needed for aeration, and to plan for salvaging slowly degrading bulking material at the end of the cycle.

Common carbon and bulking sources on a dairy or feedlot:

• Used bedding. Straw, shavings or sawdust already mixed into the manure. Cornell lists straw at 40 to 100:1 and wood chips or sawdust at 100 to 500:1.
• Spoiled hay, feed refusals and crop residues.
• Ground wood or yard trimmings brought in from off the farm. NRCS notes that standard 633 (Waste Recycling) may be used when nonagricultural byproducts are included. Ask your state agencies whether importing material changes the site’s permit status.
• Screened overs recycled from finished batches.

Test the manure and each amendment for moisture, carbon and nitrogen, calculate a blend, then check it by hand for structure. Our list of compost feedstocks gives the typical ranges.

NRCS practice standard 317 and the nutrient management plan

NRCS defines a composting facility (code 317) as a structure or device to contain and facilitate an aerobic microbial ecosystem for the decomposition of manure, other organic material, or both, into a final product stable enough for storage, on-farm use and application to land. NRCS issues a national standard (the current one is dated September 2020) and each state office adopts its own version, which can be stricter, so get the current text from your state NRCS office. The national standard, linked above, shows what a design has to address:

1. Siting. Outside the 100-year floodplain where possible, at least 50 feet from wells, streams and other water features (the New York version sets 100 feet from wells), with the floor at least 2 feet above the seasonal high water table unless special design features are used.
2. Capacity. Space for active composting, curing and bulking material.
3. Moisture. A water source for dry conditions and a cover where considerable precipitation is likely.
4. Foundation and wastewater. A foundation designed to keep leachate out of groundwater, with any leachate or contaminated runoff collected and conveyed to storage or treatment.
5. Safety. Fire prevention and signage. Bin stack height is limited to 6 feet unless forced aeration is provided.
6. Operation and maintenance plan. A written plan, and a record form covering the date, material added, compost temperature, weather and management actions.

The standard does not cover routine carcass composting (code 316, Animal Mortality Facility) or dry stacking of manure solids (code 313, Waste Storage Facility).

Compost use ties back to the nutrient plan. Standard 317 sends producers to standard 590 (Nutrient Management) for land application of finished compost, and says that compost which is not a stable, pathogen-reduced product should be applied under the criteria for manure solids. For permitted concentrated animal feeding operations, federal rules at 40 CFR 122.42(e) require the permit to include a nutrient management plan, and require large operations to give anyone receiving manure the most current nutrient analysis and to keep transfer records for five years. If compost leaves the farm, record it.

Pathogens and weed seeds: time and temperature by end use

How hot and how long depends on where the compost is going.

End use	Time and temperature	Source
Used on the farm in the same way as manure solids	Above 104°F for 5 days, with at least 4 hours above 131°F	NRCS standard 317
Weed seed kill	Compost needs to reach 145°F	NRCS standard 317
Certified organic crops	Starting carbon to nitrogen ratio of 25:1 to 40:1, then 131 to 170°F for 3 days in an in-vessel or static aerated pile system, or 15 days in a windrow turned at least five times	7 CFR 205.203(c)(2)
Produce covered by the FDA produce safety rule	Aerobic static composting at a minimum of 131°F for 3 consecutive days, or turned composting at 131°F for 15 days with at least five turnings, each followed by adequate curing	21 CFR 112.54

Two cautions from the same NRCS standard. Temperatures above 165°F inhibit composting by destroying thermophilic bacteria. Piles above 185°F need immediate action, generally water and then mixing, to prevent combustion. Probe piles on a schedule and keep the log.

The outer shell of an unturned pile runs cooler than the core. Turning moves that shell inward. A covered or capped aerated pile insulates the surface instead, so more of the cross-section reaches temperature.

Bedding reuse

EPA notes that some dairies buy sawdust, shavings, straw or sand for bedding, that those materials have become more expensive, and that solids recovered from manure through solid-liquid separation, composting or anaerobic digestion can replace them. Citing a Cornell Waste Management Institute report, EPA states that dried manure solids can be used for bedding without adversely affecting herd health. Reuse as bedding is also one of the purposes named in NRCS standard 317.

For a bedding loop, focus on three things: dryness at the stall, a consistent temperature history, and fresh material. Work with the herd veterinarian and track udder health whenever the bedding source changes.

California: SJVAPCD Rule 4565 and other air rules

The San Joaquin Valley air district regulates VOC from manure handling. Rule 4565 (Biosolids, Animal Manure, and Poultry Litter Operations, adopted March 15, 2007) applies to facilities whose throughput consists entirely or in part of biosolids, animal manure or poultry litter and to operators who landfill, land apply, compost or co-compost them.

Check the exemptions first. Facilities subject to the district’s Rule 4570 (Confined Animal Facilities) are exempt from Rule 4565 except for recordkeeping, as are composting sites that take in less than 100 wet tons a year of biosolids, manure and litter combined. Ask the district which rule applies to your operation.

For composting and co-composting facilities under Rule 4565:

Throughput (wet tons per year)	Requirement
Less than 20,000	Three Class One measures, or two Class One plus one Class Two for active composting
20,000 to less than 100,000	Four Class One measures, or three Class One plus one Class Two for active composting
100,000 or more	Four Class One plus one Class Two for active composting, or two Class One plus Class Two for both active and curing phases

Class One measures are operating practices: daily scraping of mixing and storage areas, at least 5% oxygen in the pile, 40 to 70% moisture, a starting carbon to nitrogen ratio of at least 20:1, and covering piles within 3 hours of each turning with a waterproof cover or 6 inches of finished compost or soil. Class Two measures are engineered controls, such as conducting active composting in an aerated static pile or in-vessel system vented to a control device with at least 80% VOC control by weight, or an approved alternative that demonstrates the same reduction. Records are kept for five years.

Elsewhere in California, the South Coast district’s Rule 1133.2 covers co-composting, which includes mixes with more than 20% manure. Sustainable Generation (SG) reports greater than 95% VOC control in third-party testing of its covered systems, which have been tested against air district rules. As of October 2026, read the current rule text before you design to it.

Choosing a method

Method	Fits when	Does not fit when
Turned windrow	Land is plentiful, the manure is fairly dry, neighbors are distant, and a turner or loader is already on the farm	Rainfall saturates open piles, the site is tight, or an air rule requires engineered control
Aerated static pile, uncovered or capped	Wet manure with good bulking, a wish to cut turning, and power at the pad	Heavy rain or strong odor sensitivity, since the surface is still exposed
Covered aerated static pile	Wet or cold climates, close neighbors, a small footprint, VOC rules, or a product that must document time and temperature	Very small volumes where a simple bin or windrow under standard 317 is enough

Our comparison of windrow, ASP and in-vessel methods goes further. SG’s own systems are covered aerated static piles under a GORE® Cover with positive aeration controlled by oxygen and temperature feedback. Its farm and animal waste page says SG has helped farm operators with design, construction, operation and compliance, and its SG HEAP® System page lists agricultural operations (manure, bedding and mixed feedstocks) among the intended uses, for sites managing 1,000 to 100,000+ tons a year. Our list of compost uses in agriculture covers markets.

FAQ

What carbon to nitrogen ratio should a manure compost mix start at?

Cornell describes about 30:1 as ideal, the NRCS composting facility standard recommends 20:1 to 40:1 for rapid composting, and the USDA organic rule requires 25:1 to 40:1. Manure alone is usually below that, so bedding, straw or wood is added. Lower ratios lose nitrogen as ammonia.

Does composting kill weed seeds in manure?

It can, if the whole pile gets hot enough. The NRCS composting facility standard says compost needs to reach 145°F to adequately kill weed seeds. Seeds survive in cool outer layers, so turning the pile, or insulating its surface with a cover or cap, is what makes the result consistent.

Can composted manure be used as dairy bedding?

Yes. EPA notes that solids recovered from manure through separation, composting or digestion can replace purchased bedding, and cites Cornell research that dried manure solids can be used without adversely affecting herd health. Keep the bedding dry and monitor udder health after any change.

Does SJVAPCD Rule 4565 apply to every dairy that composts?

No. Rule 4565 exempts facilities subject to the district’s confined animal facilities rule (Rule 4570) and sites handling less than 100 wet tons a year of manure, biosolids and litter, apart from recordkeeping. It applies to other operations that compost, land apply or landfill those materials in the San Joaquin Valley. Confirm your status with the district.

Next step

To see how forced aeration and a cover change the process, read how covered aerated static pile composting works. If you want numbers from your own manure and bedding before you design a pad, SG’s pilot and demonstration program lists farms and processors among its uses.

Related guides

• Aerated static pile composting: the complete guide
• Compost process control: oxygen, temperature, moisture and C:N
• Composting digestate: a guide for anaerobic digester operators
• Converting a windrow site to covered ASP
• Compost facility permitting guide

← All commercial composting guides

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