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50 Shades of Brown

Posted on June 6th, 2019

Fig. 1. This map shows the human waste equivalent of the people, hogs, laying chickens, turkeys, and dairy and beef cattle the city or state that relates to it with its human population only. Reflected is an average of N, P and TS waste.

Some of you may recall the map from a previous blog post titled “Iowa’s Real Population” that quantified the amount of fecal waste generated by Iowa’s people and livestock. I then related that to the equivalent human population of various places around the U.S. and world (Fig. 1 at right).

Since that time, some folks have been asking me what Iowa looks like relative to other states in this regard, so here goes.

First, my method. I harvested livestock population data for each U.S. state from the recently updated Census of Agriculture using the NASS Quickstats website (1). These animal populations were queried: beef cattle, dairy cattle, hogs, laying chickens, food chickens (broilers) and turkeys. I looked at reference values for the amount of nitrogen, phosphorus, and total solids generated by each type of animal (2), and converted that to a human equivalent. 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.

In “Iowa’s Real Population”, I had an FEP for Iowa of 134 million. With the updated USDA data, it’s now 168 million. The number of people commenting on that map following the blog post took me by surprise and actually was a little unnerving, causing me to fear that I had over-calculated. So these updated numbers were a relief.

Anyway, after I divided that number (168 million) by Iowa’s area, and did the same for every other state, Table 1 resulted. So just to ensure clarity, in Iowa we are generating as much fecal waste in every square mile as 2979 people. 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. That’s how much fecal waste we are generating.

Table 1: Fecal Equivalent Population (FEP) per square mile of U.S. states.

Now it must be said that some other states do have a lot of livestock animals. The tiny state of Delaware (2nd on the FEP/square mile list) has 52 million chickens; the huge state of Texas has 12.5 million beef cattle and 170 million chickens. Arkansas has more than 200 million poultry birds, although their 930,000 beef cattle still produce more waste than the poultry.

The hog manure generated in Iowa floats our state to the top of the FEP/square mile list. Iowa is home to one out of every three U.S. hogs, with 23 million residing here at any given moment, a number that has increased by 64% since 2002.

In only six states are human beings the top fecal producer, these all on the east coast except for Alaska. Figure 2 shows the animal producing the most fecal material in each  state; for simplicity purposes, the chicken in the map represents the total of all poultry birds (layers, broilers, turkeys).

Fig. 2 Largest generator of fecal waste in U.S. states.

So how does Iowa relate to our bordering states? Actual human and animal populations, and the human equivalent in fecal waste, are shown in Figure 3. Out of the seven states (IA, MN, SD, NE, MO, IL, and WI), Iowa is 1st in hogs, 2nd in poultry, 3rd in beef cattle, 3rd in dairy cattle, 5th in people, smallest (7th) in land area, and of course first in generated fecal waste, both in total and on a per area basis. Note that Illinois has by far the most people, but produces the smallest amount of fecal waste.

Fig. 3. 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.

So what does it mean for us? We clearly have a lot of crop area to apply that manure, and 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. Manure fertilization also presents a lot more uncertainty to the farmer when it comes to precisely determining the necessary amounts commensurate to crop needs. This is why watersheds with dense livestock populations tend to have higher stream nitrate levels (3, 4, 5). I covered many of these topics in previous posts (link, link, link).

I also want to say that we should not ignore that livestock production has a very real beneficial effect for rural Iowa’s economy—transportation, equipment, construction, and meat packing are just a few of the industries that benefit. Read Art Cullen’s book if you don’t believe me.

But if you think our meat appetite comes without profound environmental consequences, read Elizabeth Kolbert (for the record, I am not a vegetarian). In the modern era, the biomass contained within our bodies outweighs that of Earth’s wild mammals 8:1, and when we add in our domesticated food animals, that ratio jumps to 23:1. Imagine what this last ratio must be for Iowa. It’s got to be staggering. Not much of Iowa, America, or Earth for that matter, remains untouched by the feet and the crap of human beings and our horde of animals.

I’ll finish here on a tangent by saying that I get a fair number of comments relating to the blog that fall somewhere along the spectrum of 1) courteous envy that I am able to post my thoughts; 2) astonishment that I would do so; and finally 3) “Do you still work there?” I’m always consciously guarding against sounding pretentious, and I proceed on here at the risk of doing that.

First and foremost, I am trying to put credible (and almost always publicly-available) information and data into an understandable context. In my view, to do that effectively requires adding a perspective. So yes, I add perspective, most often my own.

Secondly and lastly, I worry about the current state of affairs if people are astonished by the mere existence of this type of expression. I can hardly believe we have gotten to this place. I firmly believe that if we are to solve problems, we all ought to be able to talk about them openly, especially when they involve things we hold in common like our lakes, streams, air and wildlife. End.

  3. Khanal, S., R.P. Anex, B.K. Gelder, and C.F. Wolter. 2014. Nitrogen balance in Iowa and the implications of corn-stover harvesting. Agriculture, Ecosystems & Environment183: 21-30.
  4. Jackson, L.L., D.R. Keeney and E.M. Gilbert. 2000. Swine manure management plans in north-central Iowa: Nutrient loading and policy implications. Journal of Soil and Water Conservation, 55: 205-212.
  5. Jones, C.S., Drake, C.W., Hruby, C.E., Schilling, K.E. and Wolter, C.F., 2018. Livestock manure driving stream nitrate. Ambio, pp.1-11.
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24 Responses

  1. Laura L Jackson says:

    I’m glad you are commenting not only on the nutrient imbalance here, but also the oppression, real and imagined, when it comes to speaking of these things. We have to sustain that sense of astonishment even though the censorship has been going on a long time.

  2. […] 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 […]

  3. David Kirchman says:

    Your calculations are great in helping to visualize the problem. I see my state has the dubious honor of being second only to Iowa in FEP per area, which I smell every time I cycle around here.

    • cjones says:

      Thanks for this comment, and for reading the blog. At least the flat terrain in DE is good for biking i suppose.

  4. […] Chris Jones updated some details about the population and fecal waste issues. Please follow this link for his post 50 Shades of […]

  5. […] size, and Iowa ranks first in the nation for waste creation, Jones writes in a blog he’s titled “50 Shades of Brown.” “Just to ensure clarity, in Iowa, we are generating as much fecal waste in every square mile as […]

  6. Lisa says:

    Imagine if Iowa could turn 75% of all of this manure into clean, potable water!? While at the same time protecting groundwater and regenerating soils with nature’s perfect fertilizer! We’d love to have a conversation about an affordable manure treatment technology that is revolutionizing the livestock’s industry approach to handling animal waste. Producers in 9 other States have already implemented this technology… now let’s bring it to Iowa!

    • Veronica M. Lack says:

      Affordable manure treatment where CAFO liquid manure would be separated by the CAFO Owner, on site, solids separated from Water, and water being returned to drinkable Quality.

  7. […] we are generating as much fecal waste in every square mile as 2,979 people,” Jones wrote in a blog on the university’s […]

  8. John Norwood says:


    This is great stuff. Great minds think alike because I’ve been speaking about our need to think about our animal populations as well! Couple of thoughts/observations about your estimates:

    1) Does your hog space number include sow barns?
    2) The cattle number seems low.
    3) I wonder if its more useful to talk about animal populations in the static sense or as a function of annual production? What many folks don’t understand is the tremendous rate of growth of these animals compared with humans. A hog goes from 0-280 pounds in about 5 months for example. Off the charts for a human.
    4) I’d like to see your work extended to capture the methane potential of our livestock manure and put that in context of something we can understand like powering a natural gas plant of a certain capacity.
    As a Polk County Soil and Water Commissioner, I’d like to talk with you more about how we think about managing all this manure and getting a better handle on the biggest threats. I don’t think it’s nitrogen. It’s pathogens and bacteria. Did you see the Pig Zero article last weekend in the NYT? Pandemics and ineffective drugs are likely our biggest threats to human and animal welfare.

    • cjones says:

      John I will reply to this via email later this week when i have some time. Thank you for reading the blog.–CSJ

  9. Nancy Slach says:

    I think you need to address all of the regulations that farmers have to abide by when applying manure as fertilizer. There is more land that we could be using this natural fertilizer on than there is manure to cover it so farmers need to resort to chemical nitrogen. What about the free range farmers that do not keep their animals out of the creeks and waterways? Just want to hear the rest of the story – your information appears to be a bit slanted. You mention in a couple of sentences how manure is a good fertilizer, but difficult to store…

    • cjones says:

      Thank you for this comment. I am considering a blog post about the regulations. To that end, there is a lot of paperwork for regulated livestock producers, but very little enforcement of actual manure application restrictions. Separation distance requirements are meant to prevent direct discharges to water resources, but the only restriction that could reduce leaching of nitrogen (N) to aquifers and tile drainage is limiting the total amount of N from manure and commercial, and of course we don’t do that. Our and others’ research has shown that in manure-dense watersheds, overall application rates are elevated, sometimes far beyond ISU recommendations.

      Yes there is more land that could be using manure. Just like there is plenty of food to feed the world, the problem is that it is not evenly distributed; similarly we have too much manure in some places and have to rely on commercial fertilizer in others. Commercial fertilizer is still being sold at high rates in counties where there is more than enough manure to supply crop needs. This causes degraded water quality.

      I feel bad that you think the information is slanted. I will say the livestock population data is from USDA and the waste produced by the animals relative to human beings is basically “book” values from the literature. Nobody should be surprised at these numbers. I am always looking for good sources of data and if you have such data i am happy to take a look.

      Thank you for reading the blog.–CSJ

  10. Cindy Hildebrand says:

    I’m not about to get anyone in trouble by offering specifics, but based on many varied conversations I’ve had over the years, there is a lot of self-censorship in this state regarding the environmental impacts of agriculture. People want to protect possibilities for promotions, tenure, getting elected to office, good relationships with rural neighbors, getting hired for new positions, etc. I knew someone who worked at ISU and changed jobs within the university because the person was tired of having to deal with the very touchy university politics of agricultural pollution. If many Iowans believe that it takes courage to be honest about the topics discussed in this blog, I’m not surprised.

  11. […] It amounts to more than four Californias or 53 Iowas. (Thank you, Chris Jones.) […]

  12. Budva Bet says:

    Your calculations are great in helping to visualize the problem. I see my state has the dubious honor of being second only to Iowa in FEP per area, which I smell every time I cycle around here.

  13. cbg clones says:

    nice blog! Thanks for sharing this.

  14. Thanks for sharing this. congrts

  15. tanx nice blog , keep on job

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