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Farms collect and store manure in different ways. For the most part, manure is handled and stored as either solid, slurry, or liquid. The biggest differences are between systems designed for solid manure and those designed for liquid or slurry manure.
Solid manure is approximately 80% (or less) moisture and 20% (or more) solids. It can be stacked into piles and handled with equipment like front-end loaders and box scrapers. Semi-solid manure (around 15% solids) is handled and stored the same as solid manure.
Common examples where farms handle manure as a solid:
- Beef feedlots and dairy farms scrape manure from open earthen lots (Photo 1)
- Broiler (meat chicken) litter is a mix of manure, feathers, and bedding (Photo 2)
- Layer (egg-producing chicken) manure contains feathers but no bedding (Photo 3)
Less common examples where farms handle manure as a solid:
- Bedded pack barns or hoop buildings for beef cattle or pigs
- Compost pack barns for dairy cattle
Photo 1. (Above) Two examples of open earthen lots with beef cattle on the left and dairy cattle on the right.
Photo 2: (Above) Broiler litter being cleaned out of a house (left) and what a similar house looks like when populated with chickens (right). Photos courtesy of Josh Payne, Oklahoma State University.
Photo 3: (Above) Most layer hen houses built recently use belt systems to remove manure. Several cages are stacked on top of each other and a belt in between each tier catches the manure. The belts convey manure to a collection point; manure is taken from the collection point to a separate storage area. Photo courtesy of Robb Meinen, Pennsylvania State University.
Solid Manure Storage
Solid manure is typically stacked or piled in storage areas that may be covered (Photos 4 and 6, below) or uncovered (Photo 5, below) depending on the amount of rainfall or snowmelt an area receives. Farms in arid areas are more likely to manage solid manure storage areas without a roof or cover.
Roofs or covers prevent rain or snowmelt from entering the storage area, but are more expensive to build. If precipitation causes runoff from uncovered solid manure storage areas, the runoff needs to be captured and contained to prevent it from reaching streams, lakes, or other surface water.
Photo 4. (Above) Solid layer hen manure is stored on the ground level of this high-rise layer house. The hens are housed in the upper level and manure falls through slats in the floor. High-rise houses used to be the most common system for layer hens but are gradually being replaced by manure belt systems. Image courtesy of the United Egg Producers.
Photo 5. (Above) The solid manure storage area and handling equipment for a beef feedlot.
Photo 6. (Above) A covered manure storage structure on a poultry farm. Photo courtesy of David Schmidt, University of Minnesota.
Slurry manure is approximately 10-15% solids. It is a very thick liquid that requires pumps for collection and handling. Equipment and structures for handling slurry manure need to be engineered for materials of this consistency.
Common examples where farm collect and handle manure as a slurry:
- Pig manure in deep pit barns
- Dairy manure in scrape (Photo 8, below) or vacuum systems in free stall barns
Less common examples where farms collect and handle manure as a slurry:
- Layer hen farms with scrape systems
- Slatted floor beef buildings with a manure pit
Photo 7. (Above) A slatted floor in a small-scale swine research barn. Slatted floors are part of both slurry and liquid manure collection systems, especially on pig farms. If a deep pit for long-term storage is beneath this floor, the farm handles manure as a slurry. If manure is flushed from beneath the slats to an external storage structure, the farm likely handles manure as a liquid. Photo courtesy of Rick Ulrich, University of Arkansas.
Photo 8: (Above) An automated scraper collecting slurry manure in a freestall dairy barn. Slurry manure can also be collected from barns or feed pads using vacuum tankers. Photo courtesy of Karl Vandevender, University of Arkansas.
Liquid manure has only a small amount of solids (less than 5%). It is very dilute in terms of nutrient content and cannot be hauled long distances because of the cost of hauling large amounts of water. Liquid manure is collected and handled with gravity flow or pumps and is stored in structures called ponds or lagoons.
Common examples where farms handle manure as a liquid:
- Runoff holding ponds for open earthen lots (beef or dairy)
- Pull-plug or flush systems in pig barns
- Flush systems in dairy barns
Less common examples where farms handle manure as a liquid:
- Layer hen farms with flush systems
Slurry and Liquid Manure Storage
Slurry and liquid manure can be stored in earthen pits (Photo 9, below), holding ponds, or treatment lagoons. They can also be stored in above-ground tanks (Photo 10, below) or in concrete structures (Photo 11, below).
Photo 9. (Above) An earthen liquid manure storage structure on a pig farm. Photo courtesy of USDA NRCS.
Photo 10. (Above) The orange arrow points to an above-ground steel manure storage tank.
Photo 11. (Above) The manure storage structure on this dairy farm includes a concrete wall near the barn and ramp for access when removing manure. Photo courtesy of David Schmidt, University of Minnesota.
The video below, produced by the University of Wisconsin, introduces systems for handling and storing liquid and slurry manure. It also discusses safety precautions for these systems and structure. The final section covers the importance of agitation, or mixing, when preparing manure for land application.
Process wastewater is water used by farms, often for cleaning, which comes in contact with animals, manure, or feed. It may also contain chemicals for sanitizing or cleaning a product or surface. This is not considered to be manure, but must be captured and contained and can be stored in the liquid manure storage structure or a separate structure.
Common types of process wastewater generated on animal farms:
- Egg wash water
- Milking center wash water
Covered Manure Storage
In recent years, the use of covers on manure storage structures has increased. This is especially true for pig farms. Covers are primarily used to address odor concerns, but can also be part of an anaerobic digestion system. Photo 12, below, shows a covered manure storage structure.
Photo 12: (Above) A very small earthen manure storage structure with a cover installed. Most covered manure storage structures are larger than this but look very similar.
Is There Enough Manure Storage Capacity?
The main purpose of manure storage is to contain manure, process wastewater, and contaminated runoff until it can be safely and appropriately applied to crop fields or be used in an alternative manner. Good stewardship of manure storage involves two important steps:
- Designing the facility so it has enough capacity to store manure and process wastewater generated by the farm plus precipitation plus freeboard (margin of safety) during time periods when land application is not possible or appropriate.
- Operating and maintaining the manure storage or treatment facility so that problems can be identified and prevented or corrected before they cause overflows or failures.
There are several considerations when calculating the amount of capacity needed in the manure storage or treatment structure and planning for its operation and maintenance.
Regulatory requirements. For some farms, the minimum amount of storage capacity and freeboard as well as frequency of inspections is prescribed by regulation. Keeping records on design and construction, inspections and findings, maintenance activities, corrections made, and amount of manure or process wastewater in the storage structure is essential to prove the requirements are met.
Cropping system. Manure is not usually applied to fields between planting and harvest for cultivated crops. The amount of time fields are unavailable during the growing season should be factored into the planning for manure storage structures. Hay or pasture fields add some flexibility because manure can be applied more often. But, as with cultivated crops, hay or pasture fields should not have more manure nutrients applied than is agronomically indicated in the nutrient management plan. Farmers who rely on off-site manure transfers to neighboring farms or for other uses should also consider the cropping system or other timing needs of manure recipients and plan their storage period appropriately.
Climate. The design capacity of manure storage will be influenced by the amount of time that manure must be stored during extended time periods that are undesirable for land application. Those include times when soils are frozen, snow-covered, or saturated. Design capacity for uncovered manure storage structures also needs to consider how much rain or snow melt may add to manure levels.
Photo 13. (Above) This collage shows two depth markers in manure storage structures. The concrete structure on the left includes a simple rope (see orange arrow) marked at regular intervals as a way to monitor manure levels. The marker on the right is more elaborate and includes (recommended) a “start pumping” mark (yellow bar extending to the left). The especially important levels a farm manager should know are “start pumping” when the level reaches design capacity and, for some structures, “stop pumping” when it reaches a lower limit. It is also important to know the level to which manure should be pumped/emptied before entering a season where land application is not possible. If a state bans manure application from December 15 until April 1 for example, a farm should know which mark manure levels should be below to ensure enough storage capacity going into that season. Concrete structure image courtesy of Robb Meinen, Pennsylvania State University and metal depth marker image courtesy of Leslie Johnson, University of Nebraska.
Future plans. What are the chances a farm will add more animals in the future? Expanding to 1,500 animals when the manure storage is designed for 1,000 means the structure will fill up faster than originally intended, making unlawful spills or inappropriate land application practices more likely.
Figure 1. A schematic of the different categories of waste and the related volumes that the storage design must accommodate. More than just manure, process wastewater, or open lot runoff needs to be factored into the designed capacity. Anaerobic lagoons require a minimum volume at all times so that the bacteria treating the manure remain present and active. Some minimum storage level also helps keep the bottom sealed by preventing drying and cracking. Storage or treatment structures that do not have a roof or cover also need to hold typical rainfall or snowmelt for the area. Every storage structure storage should be designed and managed to maintain a margin of safety, or freeboard, so that it is never filled to the top. Figure courtesy of University of Missouri Extension via Dr. Charles Fulhage.
Resources On Manure Storage Design and Sizing
- Animal Waste Management Software USDA Natural Resources Conservation Service
- SPAW Model USDA Agricultural Research Service
- LPES Curriculum Lesson 20 – Planning and Evaluation of Manure Storage
- LPES Curriculum Lesson 21 Sizing Manure Storage and Typical Nutrient Characteristics includes several example problems and calculations
- More LPES lessons
Photo 14. (Above) A manure storage structure about to overflow due to recent rainfall. This problem is most common when long winters or extended wet periods in the fall or spring make manure land application difficult or impossible. Managing this risk requires planning ahead as much as possible to prevent it. In this photo, the farm is agitating the manure and getting ready to apply it to a field to lower the manure level in the storage structure. Favorable weather conditions allowed application when field soil conditions were acceptable, or no longer saturated.
- Ag 101 (U.S. Environmental Protection Agency)
- Manure 101 (eXtension)
- Consistency of Manure/Water Mixtures factsheet by Doug Hamilton (Oklahoma State University) explains the differences between solid, slurry, and liquid manure.
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These materials were developed by the Livestock and Poultry Environmental Learning Center (LPELC) with funding from the U.S. Environmental Protection Agency and with input from the Natural Resources Conservation Service, National Cattlemen’s Beef Association, National Milk Producers Federation, National Pork Board, United Egg Producers, and U.S. Poultry and Egg Association.
For questions on these materials, contact Jill Heemstra, firstname.lastname@example.org. All images in this module, unless indicated otherwise, were provided by Jill.
Reviewers: Tetra Tech, Inc.; Joe Harrison, Washington State University; Rick Koelsch, University of Nebraska; and Tom Hebert, Bayard Ridge Group