‘Peak pig’ in Iowa leads to a ‘staggering’ amount of shit in the state

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Pigs in a CAFO (concentrated animal feed operation). — photo via the United States Geological Survey, public domain

It’s probably not an accomplishment state officials will want to boast about, but Iowa out-performs the rest of the country when it comes to producing shit. Not “shit” in any metaphorical sense, but literal fecal waste.

Chris Jones, a research engineer and an adjunct associate professor at the University of Iowa, IIHR (UI’s hydroscience and engineering center), has done the math, and published the results on his blog about water quality. Iowa, with a population of 3.2 million, produces more than twice the amount of fecal waste per square mile than California, which has almost 40 million people.

But what’s propelled Iowa to the top of the shit list isn’t people, it’s pigs.

Last year, Iowa hit “peak pig,” with 23.6 million pigs, the most ever recorded in any state. When Iowa set that record in August, North Carolina, the state that ranks second in swine, only had 9.4 million. And pigs, Jones explained on his blog, produce much more waste than humans.

“A feeder pig is about the same size as a human being, but it excretes 3 times as much nitrogen (N), 5 times as much phosphorus (P), and 3.5 times as much solid matter (TS-total solids),” Jones wrote, comparing the fecal output of pigs and people.

Jones used the “reference values for the amount of nitrogen, phosphorus, and total solids generated” by pigs and as well as the other animals that make up most of Iowa’s livestock population, “and converted that to a human equivalent.”

“When I apply the N, P and TS values of the waste from these animals, what would be the equivalent-sized human population that would generate such waste is staggering,” he wrote.

• Iowa hogs: equivalent to 83.7 million people

• Dairy cattle: 8.6 million people

• Beef cattle: 25 million people

• Laying chickens: 15 million people

• Turkeys: 900,000 people

“In total, these five species generate the waste equivalent to that produced by about 134 million people,” Jones estimated.

That was March. Since then the USDA has released updated the data in its Census of Agriculture, and Jones published a new post on Thursday updating his assessment of Iowa’s fecal output.

“With the updated USDA data, it’s now 168 million,” according to Jones.

In his new post, Jones calculated how Iowa’s annual fecal load compares to other states.

“I looked at reference values for the amount of nitrogen, phosphorus, and total solids generated by each type of animal [cattle, hogs and poultry], and converted that to a human equivalent,” Jones explained. “I then added that number to the human population to get a ‘fecal equivalent population,’ which I will call FEP for brevity from here on out. Since US states vary in size from 1545 (Rhode Island) to 665,000 square miles (Alaska), I divided the FEP by the states’ areas to get an FEP density, if you will.”


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Iowa is number one.

Table 1: Fecal Equivalent Population (FEP) per square mile of U.S. states — prepared by Chris Jones.

“[I]n Iowa we are generating as much fecal waste as 2979 people per square mile,” Jones said. “For reference, Iowa City is the 2nd-most densely-populated city in Iowa and has 2775 people per square mile. So imagine an Iowa-sized Iowa City (there’s a conservative nightmare if I ever saw one). That’s how much fecal waste we are generating.”

Jones also created an infographic to show how Iowa compares to its immediate neighbors.

FEP of Iowa and neighboring states. Animal and human populations in Iowa and bordering states, along with the human equivalent fecal waste. Values are in millions. The chicken represents all poultry animals. — prepared by Chris Jones

Iowa has so many pigs, because its home to many industrial hog farms. Last year, the Iowa Policy Project (IPP) reported, “Iowa has more than four times as many large concentrated animal feeding operations (CAFOs) as it did in 2001 and over the last decade has added nearly 500 new or expanded state permitted CAFOs annually — now an estimated 10,000 CAFOs of all sizes.” The vast majority of CAFOs in Iowa raise pigs.

The IPP report listed the environmental problems caused by CAFOs, including “water degradation” due to manure leaks and spills, which “are associated with fish kills, nitrate and ammonia pollution, antibiotics, hormones, bacterial contamination, algae blooms, water quality impairments, closed beaches and are a major contributor to the ‘dead zone’ in the Gulf of Mexico.”

Numerous studies in the last decade also have documented the impact of CAFO air emissions on the health of neighbors, finding significant increases in childhood asthma, adult asthma, airway obstruction, and irritant-linked eye and upper airway symptoms. Other studies have documented negative impacts of CAFO air emissions on mood (more tension, depression, fatigue, confusion and less vigor), other psychosocial measures, and between odor and multiple quality-of-life measures. Several studies now find that property value near animal feeding operations, depending on distance, wind direction and other factors, is depressed 20 to 40 percent.

As Jones notes on his blog, “it must be said that manure is a good fertilizer and can promote healthy soils. Manure has value beyond just the macro-nutrients of nitrogen and phosphorus. The organic carbon contained within the manure is especially beneficial to crops and soils. However, manure is a much more difficult fertilizer to manage compared to synthetic chemical fertilizers, and manure almost always needs to be accumulated and stored for long periods of time before application to crops. This is why watersheds with dense livestock populations tend to have higher stream nitrate levels.”

A report released by IPP in April examined the state’s spending on water quality, and found that funding of the water quality program had peaked in 2009 at over $45 million, before dropping to under $30 million in 2012. Last year, Iowa spent $43 million from the state’s general fund on water quality programs.

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