A Novel Multiple Staged Leachbed Digestion System for the Treatment of Dry-lot Feedlot and Dairy Manures

A multiple staged digestion system capable of digesting drylot manures is currently under development. The system is currently being validated at the pilot scale with three 1.5 cubic meter batch reactors. The system shows promise with various animal manure wastes as well as other common waste products. The first stage of the process is a dry digestion leachbed process in which the hydrolysis of solid waste products is optimized. The liquid leachate produced by the first stage is then transferred to a storage tank where the leachate is accumulated before use in the last stage. The last stage is optimized for methanogenesis and consists of a high rate methane reactor. 

What Have We Learned?

This configuration of system components lends itself to a variety of potential advantages for regional digestion of animal wastes. Wastes of various solids contents can be segregated into the appropriate reactors, with high solids wastes placed in the first stage, moderate solids in the second stage, and primarily soluble wastes can be sent straight to the last stage. This inherent substrate flexibility could enable the construction of regional digesters capable of treating a wide array of wastes. As the solid wastes are dry digested dewatering at the end of the process is less challenging and leads the production of a high nutrient content soil amendment. 

Future Plans

 Plans are currently in the works to begin scaling this pilot system to build a 100-500kw on farm digester system. 


Lucas Loetscher  lloetscher@gmail.com   Colorado State University

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

Grid Soil Sampling to Guide Manure Application

Why Consider Grid Sampling for Manure Application?

Grid soil sampling for phosphorus and potassium can identify areas in fields with nutrient deficiencies and other areas with sufficient or excess nutrients. Nutrient maps can be used to define areas for manure application or exclusion, using supplemental fertilizer where manure is not applied or does not meet the crop requirements. The overall effect is to increase the fertilizer-replacement value of the manure, conserving its use for nutrient deficient fields and field areas. Related: LPELC Manure Nutrient Management

Each of the case studies was conducted on a Minnesota farm and presents the method to:

  • determine crop nutrient needs
  • create manure application and exclusion zones from nutrient maps
  • estimate the value of manure under whole-field vs zoned application, and
  • evaluate practices to reduce off-site soil and nutrient loss for the specific field analyzed.


The case studies do not discuss variable rate manure application, but do assume capability for supplemental fertilizer application, with or without variable rates.

For More Information


Les Everett, Agronomist, University of Minnesota Water Resources Center evere003@umn.edu

Process for Recovery of Phosphorus from Solid Manure

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Why Study Phosphorus Recovery?

Land application of manure in regions with intense confined livestock and poultry production is an environmental concern when land is limiting because it promotes soil phosphorus (P) surplus and potential pollution of water resources. A net accumulation of soil P results from the disproportion between lower nitrogen (N) and P ratio (N:P) in animal manure and the higher N:P ratio in harvested crops. Although manure can be moved off the farm, its transportation becomes less economical with increasing distances from the source. Thus, management alternatives to land application are needed to resolve agronomic P imbalances for more effective recycling of manure P.

Litter washed solids residue – Low P content

What Did We Do?

A treatment process, called “quick wash”, was developed for extraction and recovery of P from poultry litter and animal manure solids. In the quick wash process, P is selectively extracted from solid manure or poultry litter by using mineral or organic acid solutions. Following, P is recovered by addition of liquid lime and an organic poly-electrolyte to the liquid extract to form a calcium-containing P precipitate. The quick wash process generates two products: 1) washed solid residue, and 2) concentrated recovered P material.

What Have We Learned?

Recovered concentrated P material

The quick wash process selectively removes up to 80 % of the phosphorus from manure solids while leaving most of the nitrogen in the washed litter residue. Consequently, the washed solid residue has a more balanced N:P ratio for crop production and environmentally safe for land application. The concentrated  P recovered materials contained more than 90% of its phosphorus in plant available form. The use of recovered P can provide a recycled P source for use as crop fertilizer while minimizing manure P losses into the environment from confined animal production.

Future Plans

USDA granted an exclusive license of the invention to Renewable Nutrients, LLC (Pinehurst, NC); a centralized plant for treating poultry litter is planned to be built and operated by Renewable Nutrients in the Mid-Atlantic region.


Ariel A. Szogi, Research Soil Scientist, USDA-ARS Coastal Plains Soil, Water, and Plant Research Center,  Florence, SC. ariel.szogi@ars.usda.gov

Ariel A. Szogi, Matias B. Vanotti, Patrick G. Hunt – USDA-ARS Coastal Plains Soil, Water, and Plant Rsearch Center,  Florence, SC.

Additional Information



Szogi, A.A., Vanotti, M.B., Hunt, P.G., 2008. Process for removing and recovering phosphorus from animal waste. U.S. Patent and Trademark Office Application Serial No. 12/026,346.

Szogi, A.A., Vanotti, M.B., and Hunt, P.G. 2008. Phosphorus recovery from poultry litter. Trans. ASABE 51(5):1727-1734.

Szogi, A.A. and Vanotti, M.B., 2009. Prospects for phosphorus recovery from poultry litter. Bioresour. Technol. 100(22):5461-5465.

Szogi, A.A., Bauer, P.J., and Vanotti, M.B. Fertilizer effectiveness of phosphorus recovered from broiler litter. Agron. J. 102(2):723-727. 2010.


This work is part of USDA-ARS National Program 214: Agricultural and Industrial Byproducts; ARS Project 6657-13630-005-00D “Innovative Bioresource Management Technologies for Enhanced Environmental Quality and Value Optimization.”

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

Solid Manure Sampling Procedures

Developing a nutrient management plan depends on testing manure for nutrient content. Your manure test results are only as good as your sample. This page outlines recommended ways to sample solid manure from open feedlots.

Sample During Loading

The recommended sampling for solid manure is to sample while loading the spreader. Sampling the manure pack in a barn directly has been shown to result in very variable results and is not recommended. Take at least 5 samples during the process of loading several spreader loads and save them in a bucket. When all of the samples are collected, thoroughly mix the samples and take a subsample from this to fill the lab manure test container.

Sample Manure During Spreading

Spread a tarp or sheet of plastic in the field and spread manure over this with the manure spreader. Do this in several locations and with several loads of manure. Collect the manure from the tarp or plastic sheet in a bucket. Mix the manure collected from different locations and spreaders, and take a subsample from this to fill the lab manure test container. This procedure is usually only practical for more solid manures.

Photo courtesy USDA NRCS

Sampling Daily Haul Manure

Place a 5 gallon bucket under the barn cleaner 4 or 5 times while loading the spreader. When all of the samples are collected, thoroughly mix the samples and take a subsample from this to fill the lab manure test container. Repeat this several times throughout the year to determine variability over time.

Sampling Manure in a Poultry House

Collect 8-10 samples from throughout the house to the depth of the litter to be removed. Samples near feeders and waterers can be very different. Collect samples from these areas proportional to the space they occupy in the house. When all of the samples are collected, thoroughly mix the samples and take a subsample from this to fill the lab manure test container. A sample taken while loading the spreader or during spreading is likely to be a more representative sample.

Sampling Stockpiled Litter

Take 10 samples from different locations around the pile at least 18 inches below the surface. When all of the samples are collected, thoroughly mix the samples and take a subsample from this to fill the lab manure test container. Large diameter auger bit and portable drill or soil sampler can be used to access manure deep within pile.

Taking a sample from a manure stockpile Taking representative sample from all subsamples mixed together in a bucket

Sampling stockpiled manure. Picture Source: Manure Testing for Nutrient Content

Sampling Manure from an Open Lot

These videos were produced by the Iowa Learning Farms project.

Sampling Stockpiled and Composted Manure

Related Web Pages

Overview of Manure Testing

Page Authors: Douglas Beegle, Penn State University and John Peters, University of Wisconsin

Calibrating Solid Manure Application Equipment

Why should you calibrate solid manure spreaders? Simple, because you should know how much manure was applied to your fields. Combined with a manure testing program, you can calculate the amount of manure nutrients that were applied. This can save money on commercial fertilizer purchases AND improve water quality. Related: Calibrating liquid manure spreaders and irrigation equipment.

What Can Cause Manure Application Rates to Change?

Solid spreaders can have poor uniformity if operated improperly, so proper operation and calibration of these types of systems are critical. The system needs to be recalibrated if any of the following are changed:

  • Tractor speed
  • Gate opening (and spinner settings for spinner spreaders)
  • RPM
  • Width of spread
  • Manure characteristics
  • Wind
  • Slope
  • Operator (experience and consistency)

It is helpful to know the capacity and setting ranges available with solid spreaders. Solid spreader capacity is noted in the manufacturer’s specifications and may be listed in tons, cubic feet or cubic yards. Capacity is normally listed in struck level (flush with top of unit) height but may also be rated in “heaped” load.

This video shows how tarps that are laid out and manure spread on them can be collected and weighed. it was produced with smaller farms in mind, but the concepts and procedures apply to equipment of all sizes. Produced by: Rutgers University Cooperative Extension.

What Are the Steps in Calibrating Solid Manure Spreaders?

This video shows a process for weighing the  manure spreader and measuring the area over which manure was applied. The worksheet referenced is Know How Much You Haul Produced by the University of Wisconsin Cooperative Extension.

Tarp Method

Normally calibration of solid spreaders will involve collecting the discharged manure in a tarp to determine application rate and collecting manure in a series of pans laid across the travel path to assess spread pattern, uniformity and to adjust pass width. Click on the following link for an illustration of the procedure for this method. (Source: Rick Koeslch, University of Nebraska). Manure density is normally determined to allow conversion from volume to weight (e.g. tons) applied.

Weighing the Spreader

If manure spreader capacity can be weighed, then the only field measurements required are distance traveled to empty the spreader and width of spread pattern (or distance you move laterally with each pass through the field). From that information, a fairly simple estimate of application rate can be made.

Moisture content of manure has a large impact on manure density and actual spreader capacity. When calibrating, it is important to correctly interpret the nutrient analysis reports provided by the analytical lab. Some analyses report manure nutrient concentration at the moisture content submitted. Other analysis reports may give the nutrient analysis at a moisture content that is different than either the sampled material or the material to be applied. For accurate calibration, match moisture content of manure samples with moisture content of the manure being spread.

Adjustments to achieve the proper application rate and uniformity include adjusting travel speed, gate openings and hammer clearance, and adjusting spinners for spinner spreaders. Narrowing the effective width (pass distance) generally increases application uniformity but also increases application rate.

Types of Solid Manure Application Equipment

Manure is generally handled as a solid at a solids content of 20% or more. Solid manure spreaders come in various types. Spinner spreaders use spinning disks at the rear of the unit to propel the manure, box spreaders use a paddle and/or auger to discharge manure from the rear of the unit, and side discharge spreaders typically use augers and flailing hammers to “throw” the manure out the side of the unit. Spinner spreaders are used to apply poultry litter and are widely used as commercial fertilizer applicators. Side discharge units can handle materials with a wide range of moisture contents. Rear discharge spreaders are commonly used with scraped manure solids from open lots and manures with significant bedding.

Recommended Educational Resources

Author: Garry Grabow, North Carolina State University
Reviewers: Marsha Mathews, University of California-Davis, Rick Koelsch, University of Nebraska, Doug Beegle, Pennsylvania State University

Solid Manure Collection and Handling Systems

Solid manure is typically generated in systems where bedding is added to manure to absorb moisture and enhance environmental conditions in the production area. Solid manure can also result from drying conditions such as occur on the surface of a beef feedlot. Solid manure storage and handling is typically more forthright than liquid or slurry manure systems.

Solid Manure Collection

Solid manure is usually collected using scrapers, box scrapers, blades, front-end or skid-steer loaders or similar devices. Equipment sizes range from small blades suitable for tractors of 50 hp or less to large bucket loaders mounted on dedicated power units for operations generating large volumes of manure.

Solid Manure Handling

Solid manure is typically handled, transferred or transported in box-type vehicles (truck-mounted or pull-type) equipped with drag or apron chains to unload the material. Additionally, some type of fragmentation devices such as beaters, spinner plates or flails are usually employed at the unloading point to chop and spread the manure as it discharges from the vehicle. In some cases, large piston pumps or paddle-type barn cleaners are used to transfer solid manure from a production area to a manure storage area.

For more information, visit the Solid Manure Application Equipment page.

Authors: Charles Fulhage, University of Missouri and Joe Harner, Kansas State University


Poultry litter contains bedding to create manure mixture with as much as 50% solids.





Solid manure handling equipment should have heavy-duty characteristics and be able to operate in corrosive environments.





Box-type manure spreaders (left) with flails or beaters can handle manure containing large amounts of bedding.
Trucks spreading poultry litter (right) are equipped with spinner plates to spread the manure in a wide swath.


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Images CC 2.5 Charles Fulhage or Joe Harner

Solid Manure Application Equipment

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How is solid manure applied to cropland?

The most common equipment for applying solids to the land is a rear-discharge, box-type spreader equipped with beaters that broadcast the manure over a width of several feet (see Image 1).

Usually, the manure is conveyed to the beaters at the rear by slats attached at each end to a sprocket-driven chain. Some use a powered front end-gate to push the material to the beaters at the rear. To handle semisolid manure, a tight-fitting, closable rear end-gate is required.

Some spreaders have a side discharge; most of these have V-shaped hoppers and feed the material to the discharge with augers. A rotating expeller slings the material out of the discharge port. The application rate is varied by an adjustable gate opening, usually operated by a hydraulic cylinder.

Flail-type spreaders have a semicircular hopper bottom and a rotating shaft with chain-suspended hammers to fling the material from the hopper. The flail-type and the side-discharge spreaders are adapted to both semisolid and solid manure.

Image 1: Broadcasting manure on cropland.

Manure spreaders may be tractor-drawn models or they may be mounted on a truck. Most tractor-drawn spreaders are PTO operated, but some are driven from the ground wheels. Some are hydraulically powered for greater speed variation, especially for the apron drive, to vary the application rate. In the past, spreader capacities varied from about 30 to 400 cubic feet with tractor horsepower requirements ranging from 10 to more than 120.

Recommended Reading About Land application of Manure

Land Application Equipment for Livestock and Poultry Manure Management

Authors: Jon Rausch, Ohio State University and Ted Tyson, Auburn University.

Role of Solid Liquid Separation in Manure Storage

There are benefits for manure storage systems in separating manure into solid and liquid components. Solid-liquid manure separation is also a desirable first step in many systems used for manure treatment (composting, anaerobic digestion, etc.)

Solids Accumulation

Waste solids, particularly those from dairy freestall housing bedding, can accumulate quickly in waste storage ponds. Solids accumulation requires longer, more thorough agitation at pump out time to re-suspend settled solids and special manure solids handling “chopper” pumps for transfer to tanker wagons or waste slurry irrigation systems.

Solids can cause pumping problems, and over time can greatly reduce usable storage pond volume. Serious consideration is usually given to the installation of solids separation equipment between animal housing, particularly dairy freestall barns, and the waste storage pond.

Mechanical separators are typically either rotating or stationary screens and generally remove 20 to 30 percent of the waste solids. These separators require little attention although operation in freezing weather requires special considerations. They produce manure solids that may be easily recycled as bedding or land applied off-farm with solid manure spreaders.

vibrating screen separator conveyor inclined screen separator typical two-cell settling basin

Settling Basins

Properly designed gravity settling basins can remove up to 50 percent of the waste solids but need enough elevation between the barn collection channel bottom and the maximum storage pond liquid surface height for installation of the settling basin and associated minimum 1% slope gravity in/out transfer lines. Gravity settling basins require periodic cleaning out with a tractor front end loader and work best when at least two are constructed side by side to allow alternating use and some manure solids drying out before cleaning.

Separated solids can be handled by conventional manure solids handling equipment. These nutrient-rich solids can be spread on distant fields and pastures as fertilizer and soil amendments, or sold for horticultural uses, with or without composting. Removing solids that retain their nutrients can help reduce nutrient loading on nearby fields, which are often irrigated from storage ponds or lagoons during the periodic pump outs required for proper management.

Related Web Pages

Page Managers: Ted Tyson, Auburn University, tysontw@auburn.edu and Saqib Mukhtar, Texas A&M University, mukhtar@tamu.edu .

Costs of Solid Manure Application and Transport

Poultry litter and beef feedlot manure are the most common types of “solid” manure. Separated solids from dairies can also be a source of solid manure. Solid manures must be scraped off the floor of the pen or house where the animals were raised. Scraping and loading onto trucks usually is done with a front end loader. If the manure is not land applied at the time the pens are cleaned, the manure can be stockpiled until needed. Poultry litter, in particular, when stockpiled is stored in covered sheds. The cost of the storage shed is an additional cost to manure loading.

Transport Costs of Solid Manure

As previously mentioned, solid manures are the least expensive to transport because most of the bulk transported is dry organic matter containing fertilizer nutrients (N, P and K). Water has little value in manure and adds a lot of weight that costs money to transport. Often, the manure is loaded into transport trucks that haul it to the receiving field, where it is unloaded and then loaded into an application truck.

Land application of solid manure. CC 2.5 Charles Fulhage or Joe Harner

Land Application of Solid Manure

Land application of dry manures is done with a flail type spreader. The manure, as it comes out of the truck-mounted or tractor-pulled spreader box, is flailed out in small pieces onto the surface of the soil. The spreader box is usually a specialized piece of equipment that can be expensive unless it is used to spread a lot of manure on many acres. If the manure needs to be incorporated into the soil, the cost of disking the manure into the soil could also be considered a cost of manure management.

Transportation Cost Assistance

To encourage appropriate use of the nutrients in manure, several government programs subsidize manure management costs. These programs can help reduce transportation costs, increasing manure value as it is more fully utilized as a soil amendment/fertilizer where it is most needed.

Examples of assistance include:

  • subsidy programs in Oklahoma and Arkansas that assist in moving poultry litter from nutrient sensitive watersheds to nutrient deficient areas;
  • loan guarantees to producers purchasing appropriate manure transportation equipment in Missouri;
  • USDA Environmental Quality Incentives Program (EQIP) that cost shares on certain manure investments depending on the priorities of each individual state.

Potential applicants for assistance programs could contact their local USDA Natural Resources Conservation Service office and state Departments of Agriculture or Environental Quality.

Authors: Ray Massey, University of Missouri and Josh Payne, Oklahoma State University

Page reviewers: Alan Lauver, NRCS and Chandra Theegal, Lousiana State University

Composting Livestock or Poultry Manure

Compost not only describes the completed degradation of a mixture of materials; it also denotes the process that materials undergo before becoming compost. A workable definition for compost is that it is an organic soil conditioner that has been stabilized to a humus like product, is free of viable human and plant pathogens and plant seeds, does not attract insects or vectors, can be handled and stored without nuisance, and is beneficial to the growth of plants. A more useful explanation of the process of composting is the controlled biological process of the decomposition of organic materials into a humus rich product that can be used beneficially as a soil amendment or in erosion control techniques.

Compost is produced through the activity of aerobic microorganisms that require oxygen, moisture and food. These microorganisms generate heat, water vapor and carbon dioxide as they transform raw materials into a compost product. Effective composting begins with a basic knowledge of the material or feedstock properties, the general principles of decomposition and a method for controlling the process.

What Factors Influence Composting?

There are a few feedstock characteristics that are most influential in the composting process. These include carbon to nitrogen ratio (C:N ratio), moisture content, and the size and distribution of the feedstock particles. Raw materials blended to provide a C:N ratio between 25:1 and 30:1 is ideal for active composting, although initial C:N ratios from 20:1 to 40:1 consistently give good composting results.

High quality mature compost

When ratios fall outside this range, odor problems and longer composting times can be the result. Too little moisture, as well as too much moisture, can lead to poor composting conditions and decreased microbial activity. A moisture content ranging between 40-60% usually provides the water levels needed by microbes without saturating the required air pore space within the compost matrix . With regard to particle size distribution, a size of 90 percent cumulative passing through 2 to 3 inch openings usually is sufficient to provide a composting substrate with adequate surface area for microbial degradation and with adequate porosity for the storage of oxygen.

Methods of Manure Composting

Harnessing the natural process of decomposition to best serve a purpose within a set of specific parameters is the basis for composting systems. There are four general composting groups or methods commonly used by the composting industry:

Additional Information About Manure Composting

Author: Jason Governo, University of Georgia