Welcome     Mission     History     Location     Contact Us     Iowa DNR    
Geology and Water
Data Resources

< An Introduction to Hogs in Iowa

Red ball iconAn Introduction to Hogs in Iowa

L.S. Seigley and D.J. Quade


Recent Trends

Iowa leads the nation in hog production, with 12.2 million hogs on hand as of December 1, 1996 (Sands and Holden, 1997). This represents 22% of the nation’s hogs. Iowa is followed in hog production by North Carolina and Illinois. During the past several years, Iowa’s share of all hogs marketed in the U.S. has ranged from 22 to 27% of the total (Otto and Lawrence, 1993). At both the national and state level, pork production has become more concentrated, with fewer farms owning more of the hogs. Figure 1 shows the number of farms with hogs in Iowa and the number of hogs per farm. The number of farms raising hogs has declined from 90,000 in 1970 to 18,000 in 1996, an 80% decline. At the same time, the number of hogs per farm has increased from 180 to 778, an increase of 332%. This trend has resulted in a rapid expansion of facilities with more than 1,000 head of hogs and a decline in the number of facilities raising smaller numbers of hogs.



Figure 1. Number of farms in Iowa with hogs and the number of hogs per farm in Iowa for the period 1970 through 1996.


During this time, the number of construction permits issued by the Iowa Department of Natural Resources (IDNR) for confinement operations increased from an average of less than 10 permits annually during most of the 1980s to 170 being permitted in 1994 (Agena, 1998). Along with the increase in permits came concerns from the public over the social, economic, and environmental issues surrounding the rapid increase of these confinement facilities. Specific issues of concern included surface water and groundwater contamination, odor, and state versus local control of regulating these facilities. The following provides some perspective on the Iowa hog industry.


Permitting Process in Iowa

The IDNR administers the state’s animal waste control program. Iowa’s current Animal Feeding Operations rules are found in Chapter 65 of the Environmental Protection Commission Section 567 of the Iowa Administrative Code and are summarized in IDNR (1992). DNR rules define a confinement feeding operation as a totally roofed animal feeding operation in which wastes are stored or removed as a liquid or semi-liquid.

Over the years, changes have been made to Iowa’s laws and rules that impact confinement operations. In 1995, House File 519 required submittal of a manure management plan that identifies land where manure is to be applied, and requires that total nitrogen application of fields receiving manure not exceed crop nitrogen needs. It also prohibited IDNR from issuing additional permits to operations that have an enforcement action pending or to any person who has been classified as a habitual violator (three-strikes provision) (Agena, 1998).

In 1996, revisions to the Chapter 65 Animal Feeding Operations rules included specific design and construction standards (i.e., identifying and removing tile lines in the vicinity of anaerobic lagoons or earthen basins), established restrictions on the use of spray irrigation, and placed greater responsibilities on the site engineer to supervise critical points of construction (Agena, 1998). Manure storage basins and lagoons are constructed from available native materials and are designed to limit seepage to no more than 1/16 inch/day.


Distribution of Permitted Hog Confinement Facilities

Figure 2 shows the distribution and size, by landform region, of permitted hog confinement facilities in Iowa. These facilities represent only those that required a permit from the IDNR and were permitted from 1987 through December 1997. The number of hogs at each site is based on the live animal weight divided by 150 pounds. As of December 1997, there were 670 permitted hog confinement operations (HCOs) in Iowa. This number represents less than 4% of farms in Iowa with hogs. Approximately 308 of the 670 permitted sites (46%) are located on the Des Moines Lobe in north-central Iowa; 94 of these units (31%) contain more than 4,166 hogs. An estimated 1.5 million hogs reside in permitted sites on the Des Moines Lobe, and one-sixth of these (250,000) reside in HCOs with more than 13,333 hogs. (Note: These statistics are based on the permitted animal confinement operations database maintained by IDNR.)



Figure 2. Map shows the distribution and size, by landform region, of the permitted hog confinement facilities. The facilities represent only those sites that required a permit from the IDNR and were permitted from 1987 through December 1997. The number of hogs at each site is based on the live animal weight divided by 150 pounds. (Source: Iowa Department of Natural Resources.)


Manure Storage

The most common methods of manure storage in Iowa are formed tanks (concrete or steel), earthen basins, or anaerobic lagoons. The storage unit size depends on the amount of waste generated. The volume of waste generated varies on the type and weight of the animal, the feed that is being consumed, and the frequency of feeding. A 150-pound hog generates an average of 10.5 pounds of manure per day (ISUE, 1994a). The nitrogen and phosphorus content of animal manure is proportional to the solids content.

An anaerobic lagoon is an uncovered earthen impoundment, designed and operated to provide both long-term storage and partial treatment of animal wastes from a confinement feeding operation. The animal manure is treated with water which creates a greater volume of waste. Anaerobic lagoons are designed to reduce the nutrient content of manure through bacterial action. Methane, carbon dioxide, ammonia and hydrogen sulfide are by-products of this bacterial action. There are two common types of anaerobic lagoons in Iowa: single-stage and multi-stage (ISUE, 1994b). In multi-stage lagoons, the effluent produced in the first cell is transferred to the secondary cells, where further biological treatment occurs. In a single-stage lagoon, no secondary treatment occurs. The IDNR rules require that a portion of the wastes be removed from the lagoon and disposed of by land application at least once annually. Liquid from the lagoon is land applied while the sludge remains at the bottom of the lagoon. The nutrient content of the manure is less than for an earthen basin, therefore a greater volume of manure can be applied per acre relative to an earthen basin.

An earthen basin is an uncovered impoundment designed and operated to provide short-term storage of wastes from a confinement feeding operation. Basins are not designed to provide treatment of the animal waste. Unlike lagoons, a minimal amount of water is added to basins. The IDNR requires that all wastes be removed from the basin at least two times a year and disposed of by land application. By design, earthen basins hold six to eight months of waste production and minimize the loss of nutrients in the manure. Before manure from a basin can be applied, the solids that have settled to the bottom of the basin are agitated to provide a uniform consistency to the manure. Manure from an earthen basin requires a greater land base for application because of the high nutrient content of the manure relative to a lagoon. The cost to dispose of the manure from a basin is higher compared to that of a lagoon. As a safety measure, both basins and lagoons can be filled to within no less than two feet of the top of the structure in order to maintain a minimum of a two-foot freeboard.

Total nitrogen values vary for manure stored in an earthen basin versus an earthen lagoon. It is estimated that during a one-year storage period of manure in a lagoon, 60-70% of the nitrogen is lost from the manure and 80% of the phosphorus remains at the bottom of the lagoon as sludge (ISUE, 1994a). As a general rule of thumb, hog manure stored in an earthen basin has a nutrient value of 36 pounds N/1,000 gallon of liquid manure compared to 3 pounds N/1,000 gallons of liquid manure stored in an earthen lagoon (MidWest Plan Service, 1985). Construction costs and the time required to manage a lagoon are high compared to an earthen basin, whereas, the land required to apply the manure and the cost involved in disposing of the manure are low for the lagoon relative to an earthen basin.



Agena, U., 1998, Overview and status of state programs regulating animal feeding operations, in Proceedings from Watershed Partnerships: Protecting our Water Resources, January 20-21, 1998, Ames, Iowa, p. 47-51.

Iowa Department of Natural Resources, 1992, Environmental regulations and guidelines for animal feeding operations in Iowa: Des Moines, 18 p.

Iowa State University Extension, 1994a, Manure management in the 90s: Conference proceedings.

Iowa State University Extension, 1994b, Design and management of anaerobic lagoons in Iowa for animal manure storage and treatment, AE-3089, October 1994, 10 p.

MidWest Plan Service, 1985, Livestock waste facilities handbook: Iowa State University, Ames, IA, 109 p.

Otto, D. and Lawrence, J., 1993, Economic importance of Iowa’s pork industry: Iowa State University Extension, Ames, IA, 16 p.

Sands, J.K., and Holden, H.R., 1997, 1997 Iowa agricultural statistics: Iowa Agricultural Statistics, USDA-National Agricultural Statistics Service, and the Iowa Farm Bureau, Des Moines, IA, 131 p.

Guidebook for field trip to the Kirkwood Community College Animal Confinement Facility, conducted as part of the Sixth National Nonpoint-Source Monitoring Workshop, September 21, 1998, Cedar Rapids, IA, p. 1-4.