A Staff Report from the Straight Dope Science Advisory Board

Do hens produce more poop than they do eggs?

March 3, 2006

Dear Straight Dope:

I have a friend in San Francisco who recently received a live chick as a pet. He keeps it in a rabbit cage, and believes that it is worth keeping for the eggs it will eventually lay. Having raised chickens while growing up in Oregon, and having shoveled more than my share of chicken droppings, I know them to be primarily poo-machines, laying eggs only as an afterthought. Apart from the city code issues involved, I don't think keeping a single chicken in the city is worth the feed, mess, or (most importantly) sheer volume of crap he'll be dealing with in exchange for the two or three eggs he'll get per week. I promised my friend that I'd help him build a coop if I'm wrong, but I'm betting that a chicken produces more poop in a year, by volume, than eggs. Am I right about this, or should I start buying chicken wire?

Don't think I'm obsessed with poop. However, for reasons having purely to do with scientific interest, this is a subject I happen to know a lot about.

The first comment my ladyfriend made upon reading your question was, "He should make sure of the gender of the chick, because if it's a male chick, I can tell you right now that the ratio of eggs to waste is going to be fairly poor." But assuming that you're dealing with a future hen here, you're really asking two questions--first, how much waste relative to eggs is produced, and second, whether it's economical to raise your own chickens for eggs. Both are difficult questions to answer, especially the second one, because there's such a wide variety of chickens and eggs. So I'll try to stick to some generalities in my assumptions, especially in terms of the overall economics.

First, let's define chicken waste. Chickens don't just produce droppings, they also have soiled straw and bedding material (such as sawdust), uneaten and spoiled feed, feathers, broken eggshells, and other items that must be disposed of regularly to keep their cages clean. This combined waste is often referred to as "chicken litter," and it can accumulate fairly quickly in a large operation. According to the National Resource, Agriculture, and Engineering Service (NRAES), broiler hen litter production is said to be approximately 1.25 tons per 1,000 birds brought to market. Laying hens, the ones used for egg production, produce even more. The University of Georgia College of Agricultural & Environmental Sciences estimates that each laying hen produces about 20-30 pounds of litter per year.

According to the USDA, in 2003-2004 a laying hen produced an average of 259.5 eggs per year--call it 260. For simplicity we'll assume the eggs are either "large" or "extra large" as defined by the USDA, large eggs weighing a minimum of 24 ounces per dozen and extra large 27 ounces per dozen. Given 260 eggs per year, we have a minimum egg production of 32.5 to 36.6 pounds per year.

If we take the highest estimate of chicken litter (30 pounds per hen per year) and the lowest estimate of egg production (32.5 pounds per hen per year), we have an egg-to-litter ratio of 1.08:1, which is close, but still more egg than poop. But that's on the basis of weight, and you asked about volume. Estimates of poultry litter density vary, but one resource which tested the effectiveness of poultry litter spreader trucks in Arkansas gave an average value of 32.7 pounds per cubic foot. So assuming 30 pounds of litter per year, we have 0.92 cubic feet of litter per year per hen. Now taking our figures of 32.5 to 36.6 pounds of eggs per year, and assuming an egg density of about 1.05 that of water (in other words, about 65.5 pounds per cubic foot), we have from 0.50 to 0.56 cubic feet of eggs produced per year. In other words, on a volumetric basis, the chicken probably does produce more waste than eggs.

Turning now to egg economics, I'm mainly going to consider the cost of operating and maintaining the henhouse. I'll ignore capital costs, electricity for heating, the initial cost of the hens, spoiled/dropped eggs, hen mortality, veterinary bills, inoculations, and so forth. I'm going to assume a single-year basis, as the chickens won't keep laying forever, and they will need replacing. I'm going to assume we're running a New Age chicken coop where hens that stop laying aren't put to death, but rather are allowed to live--not because I'm a great humanitarian, but so I don't have to calculate the value of their meat (which I've been told is not that good from a 3 year-old hen, but I digress). What I'll consider is litter disposal or sales, feed cost, and egg sales. In other words, feed goes in, eggs and litter go out.

Generally litter costs money to get rid of. However, for a large operation that can find the right market, litter has value, since it's rich in nitrogen, phosphate, and potash, all of which make for excellent fertilizer. The value of breeder hen litter has been estimated at $19.67 per ton. Subtracting transportation costs (from $8 to $14 per ton, according to the University of Georgia), this leaves a potential benefit of between $5.67 and $11.67 per ton. As a practical matter, even large-scale operations have difficulty finding markets for their waste (thus leading them to explore other options, such as pyrolysis of litter into fuel oil, landfilling, and incineration). But assuming one could net $11.67 per ton of litter, and assuming 30 pounds of litter per hen per year, the net benefit is $0.175 per hen per year. Alternatively, a small operation could use the litter as fertilizer, result in a disposal cost of zero. If you can't sell the waste or use it in any other way, then you'll likely end up paying trucking costs ($8 to $14 per ton) plus a tipping fee of perhaps $10 per ton. This works out to $18 to $24 per ton, and with each hen producing 20-30 pounds of waste per year, a cost of as much as $0.36 per hen per year.

Chicken feed costs again are highly variable--I learned that when I checked prices with several sources online and also called the Farm Co-op near me to. I found that feed cost is often expressed in terms of pounds of feed per pound of egg, and that this cost ranged from $0.17 to $0.25 per dozen eggs. The University of Nebraska Cooperative Extension estimated between $0.222 to $0.227 per dozen using an enzyme-supplemented corn and soy diet--a fairly premium meal. Using $0.225 per dozen as an average estimate, if a hen lays 260 eggs per year, that equates to about $4.88 per hen per year.

According to the USDA, a dozen Grade A white eggs in the carton, as delivered to the store door, cost from $0.6706 to $0.8791 over the period 2000-2004 inclusive. Taking the average price of $0.775 per dozen, this results in a gross sales of $16.79 per hen per year. The final tally of cost/benefit is $16.79 in egg sales, minus $4.88 in feed, and assuming no net cost or benefit for waste, yields $11.91 per year. Looking at some sensitivity analyses, we get:

Hen Economics, per hen-year

Best Case Average Worst Case
Eggs Produced: 260 260 260
Feed Cost: $3.68 $4.88 $5.42
Waste Cost: ($0.18) $0.00 $0.36
Egg Sales: ($19.06) ($16.79) ($14.53)
Total Net (Profit): ($15.56) ($11.91) ($8.75)

. .  . in other words, a net profit ranging from $8.75 to $15.56 per hen-year. These numbers seemed optimistic to me, so I looked for other examples. The Virginia Tech Virginia Cooperative Extension used values of:

  • 264 eggs per hen per year.
  • 3.8 pounds of feed per dozen eggs produced
  • Feed cost of $9.00 per 100 pounds.
  • Egg price of $0.60 per dozen ($0.05 per egg)

. . . resulting in a feed cost of $7.52 in feed per year per hen, an egg production of $13.20 per year, and a net profit of $5.68 per hen-year.

If you want something more detailed, we need to look further, because, as mentioned, neither of these rough estimates includes veterinary costs, capital cost and improvements, utilities, chicken mortality (typically around 9-10% per year) and replacement cost, interest on borrowed funds, etc. The British Columbia Ministry of Agriculture, Food, and Fisheries, however, has a very detailed report, complete with sensitivity analysis, which goes into great detail, including taxes, inspections, labor costs, costs of removing dead chickens, the impact of size distribution on eggs, and even capital costs of the coop. This study shows a net profit of U.S. $0.28 $0.28 per dozen eggs at a sales price of U.S. $2.52 per dozen large eggs. Since they assumed that each hen laid 23.75 dozen eggs per year, this results in a net profit of U.S. $6.73 per hen-year.

The final economic fact to consider  is what some would call "egg snobbery," in that the cost charged for "home grown" or "free range" eggs is often much more than the price at the store. Assessing an average price is difficult, but by doing several web searches I was able to find prices ranging from $3 per dozen to as much as $5 or more per dozen. Using these values in the previous calculations greatly changes the economics, to the point where it would take a lot of additional costs to even fall back to break-even. Labor costs might still make the economics swing back the other way for a small-scale operation, depending on the value you put on your time. However, the people I know who raise chickens for egg sales do it mostly in their spare time as a labor of love, so I'm discounting their labor costs. After all, if they weren't raising the chickens after work, they'd probably be watching a football game, downloading porn, or writing Staff Reports.

References

Clauer, Phillip J., "Estimating The Value Of Domestic Fowl," Small Flock Factsheet, Number 30, Virginia Cooperative Extension.

McMullen, Jennifer; Fasina, Oladiran; Wood, Wes; Feng, YuCheng; Mills, German. "Physical Characteristics of Pellets from Poultry Litter," Paper number 046005, 2004 ASAE Annual Meeting, 2004.

Paulson, Stewart; Hurd, Lawrence; Kermode, Diane Kermode. "Planning for Profit: 5000 Free Range, Organic Layers - Lower Mainland," British Columbia Ministry of Agriculture, Food, and Fisheries, February 2002.

Ritz, Casey W. and Merka, William C., "Maximizing Poultry Manure Utilization Through Nutrient Management Planning," The University of Georgia College of Agricultural & Environmental Sciences, Cooperative Extension Service.

Scheideler, Sheila E. and Abudabos, Alaeldein, "Enzyme Supplementation in Corn/Soy-Based Layer Diets," University of Nebraska Cooperative Extension MP 70, 1997.

United States Department of Agriculture--National Agricultural Statistics Service, "Agricultural Statistics 2005."

United States Standards, Grades, and Weight Classes for Shell Eggs, AMS 56.200 et seq., effective April 6, 1995, United States Department of Agriculture--Agricultural Marketing Service--Poultry Programs.

VanDevender, Karl and Huitink, Gary, "Calibrating Poultry Litter Spreader Trucks," FSA1040-PD-1-03N, University of Arkansas Division of Agriculture--Cooperative Extension Service.

Weaver, W D., Jr. and G. H. Souder, "Feasibility and economics of transporting poultry waste," Proc. 1990 National Poultry Waste Management Symposium, pp.123-129.

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