Economic Considerations for Beef Manure Management Systems
Charles D. Fulhage and Donald L. Pfost
Agricultural Engineering Extension
Manure can be a valuable resource in a crop production system. Manure contains the macronutrients nitrogen (N), phosphorus (P), and potassium (K) and also contains numerous micronutrients. The nutrient value of manure for crop production depends on the site-specific reserve of plant available soil nutrients, the nutrient concentrations in manure, and the nutrient demands of the crop. In many areas of Missouri, soil levels of P and most micronutrients are already at adequate levels. In some soils, K is also adequate for crop production. Where soil has adequate levels of P, K, and micronutrients, there is little or no economic value associated with these elements in applied manure. Nitrogen is always needed for production of nonleguminous crops (e.g., corn, small grains and grass pasture), and when correctly managed, the N in manure is valuable. For legumes (e.g., alfalfa and soybeans) the N in manure is of little economic value because these crops are able to convert N in the air to plant-available N.
However, when manure is applied to legumes, these plants can make use of the plant-available N instead of producing their own N. Thus, application to legumes can be an environmentally benign way to make use of manure N. The value of the nutrients in manure also depends on the value of alternative sources, mostly commercial fertilizers.
Most of the beef manure produced in Missouri is dropped on pastures. The purpose of this guide is to compare the economics of three systems for collecting, storing, and transporting beef manure from confined feeding operations and applying it to the land. The three systems are solid manure systems, slurry systems (with injection into the soil) and lagoon systems in which the effluent is applied using a traveling gun (and not incorporated). Value will only be based on the N, P and K added to the soil from the application of manure and no value assigned to other benefits of adding manure, such as increased organic matter.
If the added N, P and K are needed for crop production, they have value. If the nutrients are not needed, they have no value. Each landowner or operator will have to consider the soil tests and the manure nutrient tests to determine the value of the N, P and K in the manure for each field being considered. There are two main driving forces at work when manure use is considered. One is "on farm" profitability, and the other is the negative "downstream" effects. At times, economic and environmental quality goals are competing.
Manure management systems commonly used in Missouri are the solid, slurry (liquid tank) and lagoon. Solid systems have been the traditional way to handle feedlot manure. A common practice is to scrape lots with a box scraper and load manure spreaders with a front-end loader.
Slurry systems, sometimes used for feeding cattle on slatted floors over pits in a barn, allow the maximum recovery of the manure nutrients for crop production. Slurry (liquid tank) systems are often used for livestock when a lagoon is not economical or feasible because of unfavorable soil types or geological considerations. Operations may switch from a solid system to a slurry or lagoon system to reduce labor, to improve water quality and to fix other problems. To be practical, each of these systems must minimize the amount of excess (runoff) water being transported to the field by tank wagons.
Lagoon systems are favored by large livestock operations because labor and investment costs are minimized and a flushing system can be used to collect and transport waste to the lagoon. Flush systems can be used in a confinement barn. In beef units, flushing under slotted floors, through 3- to 4-feet-wide open gutters, and in flumes spaced 12 to 14 feet apart, has been used. These systems normally use an irrigation system with pump, pipe and traveling gun to transport and spread the waste. Hose-fed, tractor-mounted injectors are becoming more common in Missouri, usually operated by custom applicators. These applicators can be equipped for variable-rate, site-specific application using GPS and flow meters.
Slurry (liquid tank) and lagoon systems were studied statewide in Missouri several years ago because they were the most likely alternatives to upgrade dairy manure operations. Data were used to project waste management system costs associated with dairy operations ranging in size from 100 to 1,000 cows. Because the solid system is best suited to herds of less than 100 cows, it was not analyzed.
Manure Distribution Cost Analyzer
Ray Massey, an MU Commercial Agriculture Program agricultural economist, has developed a computer program for estimating the cost of land application of manure with dry spreaders or liquid tank wagons. The program, Manure Distribution Cost Analyzer, is a Microsoft Excel spreadsheet and is available at http://agebb.missouri.edu/mgt/ under Farm Management. A spreadsheet titled Fertilizer Value of Manure Analyzer, agebb.missouri.edu/download/university/manrvalu.exe is also downloadable from the Agricultural Electronic Bulletin Board.
This publication presents information for three sizes of beef feeding operations with average animal weights of 1,000 pounds, as follows: 150 head, 300 head and 600 head using lagoon, slurry and solid manure systems.
Lagoon-gutter flush system
Lagoon size is based on a 365-day storage capacity with 100 percent of the manure going into the lagoon. Land required for spreading the effluent is based on 195 pounds of nitrogen per acre for corn production with 165 pounds per acre from manure and 30 pounds per acre from the previous soybean crop.
The lagoon system is assumed to hire a custom irrigation system at $70 per hour. Other components are assumed to be owned. Major expenditures include the cost of a slatted floor and shallow flush pits for a beef-feeding confinement barn and constructing the lagoon. The estimated costs include a clay lagoon seal compacted by a sheepsfoot roller. Other equipment includes the water storage tanks for flushing gutters and the electric pump and pipe needed to recycle water from the lagoon to the flush tanks.
The irrigation system includes a traveling gun irrigator that will distribute 1 acre-inch (27,154 gallons) of effluent per hour (or about 450 gallons per minute (gpm)). A custom operator provides everything except "equipment check labor." The livestock operation is responsible for properly operating the equipment.
Slurry (liquid storage tank/pit) system
The slurry system is assumed to include a 12-foot deep pit with approximately 180-day storage capacity under a slatted floor in a confinement barn. The equipment cost includes an open-impeller, centrifugal chopper pump used to agitate the slurry in the tank while pumping from storage to tank wagon(s). The tank wagon size varies with herd size; a 4,200-gallon tank wagon pulled by a 190-horsepower tractor for 150 head, a 12,000-gallon tank wagon pulled by a 325 hp tractor for 300 head, and two 12,000-gallon tank wagons pulled by 325 hp tractors for 600 head (to permit waste distribution within a 10-day period during the 180-day storage period). The tank wagons are equipped with injectors to maximize the use of plant nutrients and to minimize runoff and odor problems.
Labor required for loading, hauling and spreading the manure assumes the tractor operator for each tank wagon used to distribute the manure onto the fields will also operate the tractor powering the agitator pump to fill the tank wagon.
Solid manure handling system
The solid system includes a tractor-drawn box scraper for maintaining lot surfaces, a farm tractor with front-end loader for loading a solid manure spreader and a tractor with operator to haul manure to the field(s) for land application. The lot areas are assumed to be sized at 250 square feet per head, and the total area with runoff draining to the holding pond is 400 square feet per head. The holding pond is sized for 365-day storage capacity, and land application of the holding pond effluent is by a custom traveling-gun irrigator.
Manure applied to the land is assumed to have an equivalent fertilizer nutrient value for the replaced commercial fertilizer or for the increased production of plant growth, which is harvested or used by animals.
Fertilizer nutrient availability is shown in Tables 13, 20, 26A and 26B; nitrogen availability is based on data in Tables 14 and 15. For ammonia nitrogen availability, a factor of 0.6 is used for the unincorporated manure applied by the solids spreaders and by irrigation; a factor of 0.95 is used for slurry manure injected by the tank wagon(s).
The investment per animal for the lagoon and slurry systems is roughly equivalent when compared with the investment for the solid handling system, as shown in Table 1 (these data are from Tables 6, 7 and 8).
Likewise, the net annual costs per animal for the lagoon and slurry systems are relatively close to each other when compared with the cost per animal for the solid handling system, as shown in Table 2. (These data are also from Tables 6, 7 and 8). The net annual cost per animal accounts for the fertilizer equivalent value of the plant nutrients in the manure if it is applied to the land and fully used for crop production in lieu of purchased fertilizer.
Table 3 shows the minimum required acres for land application for the three systems based on nitrogen as the limiting nutrient. (These data are from Tables 13, 20, 26A and 26B.) The lagoon system requires considerably less acres than the other two systems.
Table 4 compares annual plant-available nutrients (N, P and K) for the three systems. Less nitrogen is available from the lagoon system because of oxidation, denitrification and dilution. The values for the slurry system are about three to four times greater than the values for the lagoon system. This can be an advantage for lagoon systems if nearby land available for manure disposal is limited. However, there may be a considerable expenditure for disposing of accumulated sludge when the lagoon is closed. The values for the solid system are slightly greater than the values for the lagoon system.
Assumed value of the fertilizer nutrients
$0.30 per pound
$0.20 per pound
$0.15 per pound
Table 5 shows that the cost for pumping a lagoon with owned equipment may be much greater than hiring a custom operator for small operations. However, if custom operators are not available when the lagoon must be pumped, owning equipment may be necessary.
Table 14 illustrates the advantage of prompt incorporation of manure to minimize losses of ammonia-N; 80 percent can be lost in a week without incorporation. In the case of irrigated lagoon effluent, incorporation occurs if the soil is dry enough for the liquid to soak in and the application rate does not exceed the soil infiltration rate.
Table 15 provides data on the availability of N from the organic portion of applied manure. About 50 percent may become available in the year of application, the reminder becoming available at a declining rate over the next few years.
For annual fixed costs and annual operating costs, see Tables 9, 10, 11 and 12 for the lagoon system, Tables 16, 17, 18 and 19 for the liquid manure tank system, and Tables 21, 22, 23, 24 and 25 for the solids system. Tables 27, 28 and 29 provide data and an example for calculating fixed and operating costs for a traveling-gun irrigator.
In Missouri, a confined animal feeding operation (CAFO) with 1,000 or more animal units (for beef, 1,000 or more beef feeders or slaughter animals) is required to obtain an operating permit from the Missouri Department of Natural Resources (DNR). CAFOs with 300 to 999 animal units are encouraged to obtain a letter of approval from DNR for their animal manure management plans. This may cause some operations to upgrade their manure management system. Cost-sharing assistance may be available from the EQIP program administered by the Natural Resources Conservation Service (NRCS). Contact your local NRCS office for details on the EQIP program.
The solids system has much lower initial investment per animal and much lower net cost per animal than either the lagoon or the slurry system.
Even though manure from slurry (liquid tank) systems is more concentrated and valuable than the manure from lagoon systems, the net cost per animal for a slurry system is similar to that for a lagoon system for the three herd sizes considered in this publication.
The slurry system requires a plant filter area about three to four times larger than that for a lagoon system. This can be a major consideration for operations with limited acreage. The solid system requires slightly more land-application area than the lagoon system.
Large feedlot operations with more than 600 animals may benefit from purchasing a traveling-gun irrigator rather than relying on a custom operator charging $70 per hour (Tables 27, 28 and 29 ). However, lack of available labor and management may make hiring a custom irrigation system a better choice, even for the largest of operations.
- USDA-Natural Resources Conservation Service. 1992. Agricultural Waste Management Field Handbook, Part 651. USDA-NRCS, Washington, D.C.