Manure Separation: Fine Separation via Centrifuge and Vibrating Screen
alternative practice names:
Centrifuge; Vibrating Screen
Removing solids from manure offers significant management and environmental benefits. Most separation methods rely on differences in particle density or size to divide solids from liquids. While coarse solids are commonly removed on dairy farms, fine solids present a greater challenge. Farms often focus on fine solid removal for two reasons. First, it prepares the liquid fraction for advanced manure treatment or irrigation, reducing the risk of clogging or equipment fouling. Second, it reduces phosphorus-laden fine solids, lowering the risk of phosphorus accumulation in the soil when the liquid is applied.
Centrifuges and vibrating screens are designed to remove smaller, fine particles from a diluted manure stream with lower total solids. These technologies are typically secondary processes used after the initial removal of coarse solids. Adding chemicals like metal salts and polymers (flocculants) can further enhance fine particle separation.
Fine solid-liquid separation results in two outputs:
Fine-separated solids: Although unsuitable for bedding, fine solids concentrate phosphorus, particularly non-soluble forms (~80-90%), and can be dried and applied to land.
Liquid effluent ("tea water"): This liquid contains most of the nitrogen and soluble phosphorous. It can be field applied or further treated.
When used, in what regions in the U.S. is the practice found:
Northwest, West, Upper Midwest, Southwest, Northeast, Southeast
FARM SIZE
When used, typically found on farms of the following sizes:
Over 1000 cows

Practice Benefits
Compatibility with irrigation systems: Removing fine solids from the liquid waste stream improves waste application by reducing clogging in irrigation equipment. This ensures smoother operation of nozzles and decreases maintenance needs due to plugging.
Improved nutrient management: Separating fine solids concentrates phosphorus in the solid fraction, while the liquid fraction retains nearly all soluble nitrogen (ammonium, nitrates, nitrites) and potassium. This allows for more precise nutrient application, with different rates for solid and liquid portions to better match crop needs.
Reduced odors: Fine solids separation technology helps remove solid particles that cause odors, resulting in improved air quality and better neighbor relations.
Prerequisite for advanced manure management technologies: Fine solid removal is essential for advanced manure management technologies such as ultra-filtration and reverse osmosis, which require a clean liquid fraction to operate effectively.

Implementation Insights
Site-specific or Farm-specific requirements

Sand separation: Sand should be removed prior to fine separation to reduce the wear of the separation equipment.
Coarse solid-liquid separation: Typically, coarse solid-liquid separation is performed first to remove the larger particles.
Required Capital Expenditures (CapEx)

Separation technology: Fine-solid-liquid manure separation technologies are generally more costly than coarse separation methods due to their complexity and efficiency. Two common fine separation methods are:
Centrifuge: This technology uses high-speed rotation to create centrifugal forces that separate liquids and solids. The centrifuge typically features a horizontal or vertical cylinder rotating at high velocities, causing the denser solids to move to the cylinder's wall while the liquid remains in the center. An auger, rotating slightly faster than the cylinder, moves the separated solids to a discharge location. Centrifuges are effective at producing low-moisture solids and are particularly efficient at removing phosphorus, but they are usually the most expensive option.
Vibrating screen: This method involves pumping liquid onto a flat, vibrating screen at a controlled rate. The vibration helps prevent clogging by keeping coarse particles out of the fine separation equipment. The screen's mesh size for fine materials is typically smaller than 0.5 mm (0.0197 in). Liquids pass through the screen while the solids are gradually moved to the edges and collected. Vibrating screens are semi-self-cleaning but require a power source.
Enclosed structure: Fine particle separation systems are often housed in an enclosed structure to shield them from weather conditions.
Piping and pumps: Pipes and pumps are necessary for transferring liquid waste between components and storage areas.
Three-phase electric power: Farmers may need to upgrade power source infrastructure to operate the mechanical equipment.
Roof or building enclosure: This may be needed to protect the equipment and store solids in cold weather until they can be moved to other storage facilities or utilized.
Required Operational Expenditures (OpEx)

Skilled labor: Workers must monitor performance to ensure efficient operation, prevent clogging, and address issues before they lead to damage or system backups. Skilled technicians are also needed to adjust the equipment and resolve performance problems.
Equipment maintenance: Regular cleaning and lubrication keeps the equipment in optimal working condition. This includes replacing screens and other components according to the manufacturer's recommendations to ensure reliable operation.
Energy costs: The power consumption for fine separation equipment is generally higher than other separation methods, leading to increased electricity expenses.
Solids management: Following separation, solids' storage capacity can be limited. Routine removal and transportation of solids are necessary, requiring additional time and labor to move them to storage or utilization sites.
Chemicals: Costs for chemicals that enhance separation efficiency, if used, should also be factored in.
Implementation Considerations

Chemical use: Chemicals should be used according to manufacturer recommendations. Thorough chemical analysis and testing can be completed before equipment selections. Chemicals and equipment need to work together to meet the incoming solids and desired outgoing solids requirement. Overusing chemicals can be corrosive to equipment and can affect nutrient uptake and plant growth after land application.
Financial Considerations and Revenue Streams
FEDERAL COST-SHARE PROGRAM
Funding is available for this practice through USDA's Natural Resources Conservation Service (NRCS) Environmental Quality Incentives Program (EQIP).
Related EQIP Practice Standard: Waste Sepration Facility (632).
Notes:
Check with the local NRCS office on payment rates and crop rotations relevant to your location.
To quality for EQIP funds, the dairy is required to obtain a Comprehensive Nutrient Management Plan (CNMP) to guide practice implementation.
Additional Resources
► See the Newtrient Solutions Catalog to learn more about Centrifuges and related solution providers.
Article: Solid-Liquid Manure Separation (Livestock and Poultry Environmental Learning Community)
Article: Solid-Liquid Separation of Animal Manure and Wastewater (Texas A&M University)
Report: Assessment of Phosphorus Extraction from B.C. Dairy Manure Using a Centrifuge (Hallbar Consulting)
Review: Centrisys Decanter Centrifuge Technology (Newtrient)
Webinar: Decanter Centrifuge (Newtrient)

Environmental Impacts
MAY REDUCE FARM GREENHOUSE GAS FOOTPRINT
Little scientific research directly evaluates the practice's impact on a farm's greenhouse gas (GHG) footprint. However, the removal of coarse and fine manure solids from liquid/slurry manure storage lowers the amount of organic matter and carbon available for methanogenesis, resulting in lower methane production potential. When separated manure solids are stored in predominantly aerobic conditions, emissions of ammonia and nitrous oxide may increase;¹ however, by eliminating the anaerobic conditions required for methane production, methane emissions are significantly reduced.
See research highlights below:
Fangueiro et al. (2008) found that separate storage of the liquid and solid fractions reduced CH₄ emissions by approximately 35% compared to the raw manure.
Aguirre-Villegas et al. (2019) showed that solid-liquid separation alone could reduce GHG emission by up to 38% and that centrifugation was more effective than screw presses at separating solids.
IMPROVES WATER QUALITY
Fine solid separation systems help farmers reduce the risks of nutrient run-off and leaching associated with nutrient overapplication. By separating the phosphorous-rich manure solids from the nitrogen-rich liquid fraction, farmers can apply different fractions at different rates to better match crop demands.
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¹Amon et al. (2006) found that solid-liquid separation increased total NH₃ and N₂O emissions from storage and application by 77% and 19%, respectively. Conversely, Hao et al. (2015) observed no significant difference in N₂O emissions between separated liquids from unprocessed manure and reported that the separated solids showed lower N₂O emissions than unprocessed manure in terms of the percentage of N applied. Neerackal et al. (2015) also found no significant difference in NH₃ emissions between raw manure and separated liquids.
REFerences

Alignment with FARM Program
FARM Environmental Stewardship (ES) V2-V3 Alignment
FARM ES allows for users to specify their solid liquid separation in the manure section. FARM ES Version 3 offers an expanded list of solid liquid separators including; sand lane/gravity lane, settling basin, weeping wall, roller press, belt press, sloped screen, screw press, rotary screen or a custom solid liquid separator.
Contents
We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights.
We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights.
Removing solids from manure offers significant management and environmental benefits. Most separation methods rely on differences in particle density or size to divide solids from liquids. While coarse solids are commonly removed on dairy farms, fine solids present a greater challenge. Farms often focus on fine solid removal for two reasons. First, it prepares the liquid fraction for advanced manure treatment or irrigation, reducing the risk of clogging or equipment fouling. Second, it reduces phosphorus-laden fine solids, lowering the risk of phosphorus accumulation in the soil when the liquid is applied.
Centrifuges and vibrating screens are designed to remove smaller, fine particles from a diluted manure stream with lower total solids. These technologies are typically secondary processes used after the initial removal of coarse solids. Adding chemicals like metal salts and polymers (flocculants) can further enhance fine particle separation.
Fine solid-liquid separation results in two outputs:
Fine-separated solids: Although unsuitable for bedding, fine solids concentrate phosphorus, particularly non-soluble forms (~80-90%), and can be dried and applied to land.
Liquid effluent ("tea water"): This liquid contains most of the nitrogen and soluble phosphorous. It can be field applied or further treated.
Practices and technologies
Manure Separation: Fine Separation via Centrifuge and Vibrating Screen
alternative practice name:
Centrifuge; Vibrating Screen