There are many estimates. We think the most credible is a 2016 USDA report estimating that U.S. farmed animals produced approximately 1.23 billion tons (about 2.5 trillion pounds) of manure in 2012.[1] This report is based on information from the 2012 U.S. Census of Agriculture and makes detailed assumptions about animal weights, lifecycles, and amounts of manure per species.
These researchers have been making estimates for many years. Their earlier findings were in a similar range. At 5-year intervals from 1982 through 2007 (following the Census of Ag 5-year cycle) each yearly total was estimated in the range of 1.2 to 1.3 billion tons.[2]
Extrapolating from their analysis by using animal inventory figures from the 2022 Census of Ag, it is probable that the total amount of manure in 2022 was close to 1.23 billion tons, perhaps just slightly higher.[3]
Gollehon, N. R., et al., (2016). Estimates of recoverable and non-recoverable manure nutrients based on the census of agriculture—2012 results. USDA Natural Resources Conservation Services, Washington, DC, table 2, p. 9. [“In 2012, livestock on farms in the US produced about 1.23 billion tons of manure, wet-weight as excreted (table 2).” All values include both urine and feces. Exact total is 1,230,064,000 tons. Includes some animal species not raised for food, including horses, but only if raised on operations that meet the definition of a farm.]
Gollehon, N. R., et al., (2016), table A-2, p. 29. [1982 = 1,242,807; 1987 = 1,183,999; 1992 = 1,189,001; 1997 = 1,237,922; 2002 = 1,284,073; 2007= 1,310,719; 2012 = 1,230,064 (in 1,000 tons)] See also, Kellogg, R. L., et al., (2014). Estimates of recoverable and non-recoverable manure nutrients based on the census of agriculture. United States Department of Agriculture Natural Resources Conservation Service.
Based on changes in farmed animal inventories from 2012 to 2022, there would be little predicted change, given the slight decreases in cattle inventory offset by much larger percentage increases in pig and chicken inventories. There was likely some increase in average animal size, possibly offset by decreases in amounts of animal manure per AU due to dietary changes. Cattle (2012) 89,994,614 (2022) 87,954,742 = 2.3% decrease; Milk Cows (2012) 9,252,272 (2022) 9,309,855 = .6% increase; Hogs and Pigs (2012) 66,026,785 (2022) 73,817,751 = 11.8% increase; Broilers (2012) 1,506,276,846 (2022) 1,737,674,957 = 15.4% increase; Egg-Laying Hens (2012) 350,715,978 (2022) 388,509,039 = 10.8% increase. [USDA (2024) 2022 Census of Agriculture, United States, Vol 1, Part 51, AC-22-A-51]
In 2012, manure produced on factory farms totaled ~740 million tons (1.5 trillion pounds), or about 60% of all manure produced. This 2016 USDA report estimates the amount of manure produced on AFOs, or animal feeding operations.[1] AFOs are defined by housing “confined” animals.
The other 40% of total manure is mostly produced by cattle, calves, and milk cows grazing on pasture.
Gollehon, N. R., et al., (2016). Estimates of recoverable and non-recoverable manure nutrients based on the census of agriculture—2012 results. USDA Natural Resources Conservation Services, Washington, DC, table 2, p. 9. [“The AFO farm types produced the majority of the manure—60 percent of the total manure produced.” All values include both urine and feces. Total manure generated from “All AFOs” = 742,133,000 tons or 1.48 trillion pounds.]
Our best estimate for this ratio is about 6 to 1; animals raised for food in the U.S. generate about 6 times as much manure as the nation’s entire human population.[1,2]
Although this ratio has been estimated many times by federal agencies and other organizations, we are not aware of a reasonably recent and accurate reported ratio. The ratio has sometimes been reported as 130 to 1, due to an error in a 1997 congressional report.[3] In 2005, the EPA reported it as “somewhere between 3 and 20 times.”[4] In 2013, the EPA’s estimate was 13 to 1, based on data from 1992.[5]
Using Gollehon’s figure of 1.23 billion tons for total animal manure and 1,215 pounds per year (3.33 pounds per day) for human waste (urine and feces). 1,215 x 313,831,000 (U.S. population in 2012) = 381,304,665,000 pounds, or 190,652,333 tons. 1,230,064,000 tons /190,652,333 tons = 6.45
Our best estimate for human waste volume (3.33 pounds per day) is an average of 3 sources: (a) Rose, C., et al.(2015). The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology. Critical Reviews in Environmental Science and Technology, 45(17), 1827–1879 [3.44 lbs.] (b) U.S. EPA (2003) National Pollutant Discharge Elimination System permit regulation and effluent limitation guidelines and standards for concentrated animal feeding operations (CAFOs). Fed Reg, 68, 7175-7274. [2.84 lbs.] (c) U.S. GAO (2008) Concentrated Animal Feeding Operations: EPA Needs More Information and a Clearly Defined Strategy to Protect Air and Water Quality from Pollutants of Concern, GAO-08-944, p. 58. [3.72 lbs.]
U.S. Senate Committee on Agriculture (1997) Animal Waste Pollution in America: An Emerging Problem. https://p2infohouse.org/ref/16/15459.htm [Calculating annual human waste figure as “80 pounds of solid human waste,” which appears to be a dry waste calculation, compared to wet waste for animals.]
Rogers, S., & Haines, J. (2005). Detecting and mitigating the environmental impact of fecal pathogens originating from confined animal feeding operations, U.S. EPA, Washington, DC, EPA/600/R-06/021, p. 1.
U.S. EPA (2013) Literature Review of Contaminants in Livestock and Poultry Manure and Implications for Water Quality. EPA 820-R-13-002, p. 5, referencing U.S. EPA (1998) Environmental Impacts of Animal Feeding Operations, Appendix IV, pp. A1-A3.
Our best estimate for this ratio is about 4 to 1; animals raised on factory farms in the U.S. generate ~4 times as much manure as the nation’s entire human population.[1,2]
Using Gollehon’s figure of 742 million tons for total manure from AFOs and 1,215 pounds per year (3.33 pounds per day) for human waste (urine and feces). Calculation: 1,215 x 313,831,000 (U.S. population in 2012) = 381,304,665,000 lbs., or 190,652,333 tons. 742,133,000 tons / 190,652,333 tons = 3.89
This ratio is in line with the EPA’s quoted ratio of 3 to 1. [U.S. EPA (2003) National Pollutant Discharge Elimination System permit regulation and effluent limitation guidelines and standards for concentrated animal feeding operations (CAFOs). Fed Reg, 68, 7175] [“USDA estimates that operations that confine livestock and poultry animals generate about 500 million tons of manure annually (as excreted). This compares to EPA estimates of about 150 million tons (wet weight) of human sanitary waste produced annually in the United States, assuming a U.S. population of 285 million and an average waste generation of about 0.518 tons per person per year. By this estimate, all confined animals generate 3 times more raw waste than is generated by humans in the U.S.” at 7180]
Definitions of manure types vary and “lack universal consensus.”[1] Also, it is sometimes unclear whether the stats are referring to all manure, including portions generated on pasture, or only the manure from confined animals on factory farms. Other analyses focus on “recoverable manure,” i.e., amounts that have potential for being applied to crops.
It is possible, too, that a lack of attention from federal agencies reflects some loss of interest in trying to monitor and eventually solve the seemingly intractable problems associated with excess manure on factory farms. In the late 1990’s, 2000’s, and even early 2010’s, the glaring problems of excess nutrients, pathogens, and contaminants from factory farm manure spawned multiple analyses and demands for mitigation.[2-5] After decades of highly problematic manure dispersal, highlighted by the pervasive nutrient pollution damaging U.S. waterways, agencies may have turned their focus to other issues. Lawsuits from environmental non-profits, however, continue to demand their attention.[6,7]
Kleinman, P. J. A., et al., (2022). Envisioning the manureshed: Toward comprehensive integration of modern crop and animal production. Journal of Environmental Quality, 51(4), 481, p. 482. [“Even definitions of animal manure types can be difficult to pin down, as exemplified by the terms “dry,” “liquid,” “slurry,” “solid,” and “semi-solid” that may be defined consistently within certain contexts but lack universal consensus.”]
U.S. Senate Committee on Agriculture (1997) Animal Waste Pollution in America: An Emerging Problem. https://p2infohouse.org/ref/16/15459.htm
Rogers, S., & Haines, J. (2005). Detecting and mitigating the environmental impact of fecal pathogens originating from confined animal feeding operations, U.S. EPA, Washington, DC, EPA/600/R-06/021.
U.S. GAO (2008) Concentrated Animal Feeding Operations: EPA Needs More Information and a Clearly Defined Strategy to Protect Air and Water Quality from Pollutants of Concern, GAO-08-944.
U.S. EPA (2013) Literature Review of Contaminants in Livestock and Poultry Manure and Implications for Water Quality. EPA 820-R-13-002.
Food & Water Watch et al. vs. U.S. EPA, Petition to Adopt a Rebuttable Presumption that Large CAFOs Using Wet Manure Management Systems Actually Discharge Pollutants Under the Clean Water Act, U.S. Court of Appeals, 9th Cir.
For more information on nutrient pollution in waterways, see, Nutrient Pollution and Eutrophication