April, 1997 . Volume 20, Number 3
April, 1997 . Volume 20, Number 3
You have been exposed, I'm certain, to considerable information about the potential advantages of adding microbial phytase to swine rations. One of the big advantages is the reduction in phosphorus supplementation required in the rations. Since supplemental phosphorus is one of the higher cost inclusions in swine feeds, this reduces total ration costs.
Another advantage is the reduced phosphorus excretion in the manure. Although current
waste management plan requirements are nitrogen-based, phosphorus-based
plans (P-based WMP) may be required in the future. Consequently,
a reduction in phosphorus excretion should reduce receiving land
acreage and total manure disposal costs.
This potential to reduce manure disposal costs was studied and reported in the 1994-96 Virginia Tech Livestock and Poultry Research Report. In this study, the investigators (Minkang Zhu, Darrell Bosch, and E.T. Kornegay) generated a representative feeder-to-finisher swine operation based on the Duplin County (NC) Swine Database, which covers about 22% of all the swine farms in that county. Although this farm does not actually exist, it was designed to represent typical feeder-to-finish operations.
This farm includes 6 houses with an average total inventory of 4,958 hogs. Receiving land for swine manure totalled 51.2 acres. This included 8.7 acres pasture and 42.5 acres cropland, including 18.9 acres corn and 23.6 acres bermuda grass hay. Controlled grazing by cattle is done on 64% of the pasture and is overseeded with small grain in the winter.
Using a P-based WMP, four scenarios were studied in which phytase was assumed to reduce phosphorus excretion by 10, 20, 30 and 40%. These were compared to a scenario where no phytase was used with 0 reduction in P excretion. These scenarios were compared, in turn, to requirements in a N-based WMP.
The results show that under the N-based WMP, net returns to 51.2 acres used to receive effluent
are -$10,905, a loss of $213 per acre (Table 1). Under the P-based
WMP there are over 2 million gallons of surplus effluent and 41.6
acres must be leased. Net returns the fall further to -$24,705.
Increasing acreage from 51.2 acres to 92.8 acres causes an increase
in the total production cost of $20,786 while total receipts from
crops sold increase only $6,987, a decrease in net returns of
$13,800. Losses increase because (1) the representative swine
farm has to pay $3,558 for supplemental commercial nitrogen on
land receiving effluent and (2) losses are incurred on an additional
41.6 acres of leased land. The potential advantage of using phytase
was estimated and outlined in Table 2.
The authors summarized their study by stating that, based on a P-based WMP, the use of phytase reduces P excreted and increases the application rate, which: (1) increases the effluent application per acre; (2) reduces the cost of supplemental commercial N per acre; and (3) reduces the cost of leasing land and production cost on leased land.
| WMP Scenario | Reduction in P | Surplus Effluent | Land Leased | Net Returntd | Estimated Value of Phytase | |
| per Farm | per Hog | |||||
| Units | % | gallon | acre | $ | $ | $ |
| N-based | 0 | 0 | 0 | (10,905) | . | . |
| P-based | 0 | 2,061,860 | 41.6 | (24,705) | . | . |
| 10 | 1,780,282 | 32.4 | (22,621) | 2,084 | 0.21 | |
| 20 | 1,428,309 | 23.1 | (20,526) | 4,179 | 0.42 | |
| 30 | 975,772 | 13.8 | (18,398) | 6,307 | 0.64 | |
| 40 | 372,390 | 4.5 | (16,213) | 8,492 | 0.86 | |
| Note: An inventory of 4,958 hogs and two groups per year of production on the representative farm are assumed for estimating value of phytase per hog. |
||||||
| Estimated reduction in P excreted, % | |||||||||||||||||||||||||||||||
| Estimated supplemental phytase, U/kg | |||||||||||||||||||||||||||||||
| Phytase for 540 lb feed (perhog), U | |||||||||||||||||||||||||||||||
| Phytase cost per hog, ¢b | | Estimated P savings per hog, ¢c
| Estimated P disposal cost per hog, ¢d
| Estimated advantage for phytase, ¢
| aBased on estimated body weight of 180 lb and a
feed to gain ratio of 3:0 (540lb) feed per hog. |
bBased on a phytase price of $1.36 per pound.
Each pound of premix supplies 600 U of phytase activity per g or 272,400 U/lb. Thus 1,000
Units of phytase would cost .499¢. |
cBased on P equivalency values (or replacement
value) of 250, 500 or 750 U of phytase equal to one gram of high-quality inorganic
feed-grade P. This would be equal to a .1% reduction in P added from feed-grade
phosphates or 245 g of P per hog. Based on P cost of $.65 per pound of actual P ($234/ton)
or .143¢/g (65¢/454g/lb). |
dThese estimates are taken from data generated in
this report (see Table 1). |
| |||||||||||||||||||||||
Charles Stanislaw
Is Manure a Waste or a Resource?
An economic definition of
a waste is "any product that costs more to apply (utilize)
than it is worth once applied (utilized) is a waste." There
is no question that manure has intrinsic value: it contains nitrogen,
phosphorous, potassium, and other nutrients essential to plant
and animal growth. A problem in utilizing manure (and many other
organic byproducts) is that the nutrients are dilute, they are
mixed together, they are in relative proportions that are inappropriate
for most plant and animal uses, and nutrient content of manure
may vary over time and from sample to sample.
The low concentration of nutrients in manure means that costs of storage, transportation and application of manure are high per pound of nutrient compared to commercial fertilizers or other feed ingredients. A ton of fresh swine manure may contain 12 pounds (0.6%) total N, 9 pounds (0.45%) P2O5, and 9 pounds (0.45%) of K2O. In some cases, the low concentration of nutrients means that the cost of application exceeds the value of the nutrients as fertilizer.
The inappropriate mix of nutrients in manure means that the value of manure in utilization is less than the sum of the value of the nutrients it contains. For example, a bermuda grass hay field receiving 300 pounds N from anaerobic lagoon effluent may utilize 45% of plant available P2O5 (adapted from Barker, 1988). If the manure is spread thinner so that the phosphorous is fully utilized by the crop, the cost of applying the manure increases and usually exceeds the value of the additional phosphorous utilized. In addition, a supplemental application of nitrogen is required to meet plant needs so total application costs may be further increased.
Climate, soils, crop selection and yields, extent of other livestock and poultry
production, and prices for land, labor, feeds and fertilizer all affect the
cost effectiveness of various manure management systems. The
following examples demonstrate costs and revenues of a few swine
manure management systems.
Profitability of Manure Management Systems
Swine manure management systems can have several components including removal from
buildings, storage, treatment, transport, and application. Potential revenue
from manure management systems includes byproduct sales revenue,
revenue from on farm utilization of byproducts, reductions in
swine production costs, and increases in quantity or quality of
hogs produced. Basic costs of manure management systems include
interest and depreciation on the initial investment in facilities,
repairs, property taxes and insurance, electricity and fuel, labor,
and supplies. Additional costs of manure management systems include
record keeping, permitting and compliance, fines and legal fees,
losses of net crop receipts, land clearing and grading.
The following table provides a hypothetical example of manure management costs for a
4800 head finishing operation in North Carolina. The cost estimates are
based on work by Cox (1993) and Roka (1994). Some data used by
Cox and Roka is from 1992 so the following estimates likely understate
current costs.
| Lagoon (45,000 cu.yd.) | ||
| Irrigation (168 ac.in.) | ||
| Land (42 acres) | ||
| Net Receipts from Bermuda Grass Hay (6 tons, $50/ton) | ||
| Total Cost |
The lagoon costs listed above include depreciation and interest on the initial investment
in construction. The irrigation costs include depreciation, interest,
and repairs on the pump, pipe, and traveling gun plus energy and
labor costs. The land cost is interest and property tax on acres
occupied by the lagoon and the sprayfield. The net crop income
is crop revenue minus nonfertilizer costs of producing and raising
the crop. Note that a positive crop income is shown as a negative
number in the cost columns above.
An example of the costs and revenues of applying swine anaerobic lagoon effluent to corn is presented below. In this example, the costs of irrigating the effluent are $7,780 while the value of the nutrients used by the corn crop total $4,396. This calculation assumes that all of the N, P, and K required by the crop is provided by the effluent.
| ITEM | |
| Irrigated Volume Plant Available Nitrogen per Acre Inch of Effluent |
|
| Corn Acreage | |
| Corn Yield | |
| Annual Corn Revenue | |
| Annual Corn Costs | |
| Annual Irrigation Costs | |
| Annual Value of N Saved | |
| Annual Value of P Saved | |
| Annual Value of K Saved | |
| Net Income (Loss) |
Where additional cost of transport and application of effluent exceeds the loss in net income, less profitable crops may be produced as part of the manure management system. The net return to land including irrigation costs, crop revenue, and crop costs excluding fertilizer varies directly with yield. Increasing yields allow increased effluent application rates on fewer acres. In one example, net returns to land producing corn with lagoon effluent ranged from -$75 per acre for 75 bu. per acre yields to +$78 per acre for 150 bushel per acre yields. Only half the land area would be required to receive effluent for a 100 bu./acre crop versus what would be required for a 75 bushel per acre crop.
Irrigation cost increases with area to be irrigated although at a decreasing rate.
The dominant factors in irrigation cost calculations developed by
Cox (1993) are volume of liquid to be irrigated and the hours
per acre inch available to complete the irrigation. Irrigating
at a higher rate requires a larger traveling gun, larger pipe,
and more horsepower. Cox's equations assume that the irrigation
system will be devoted solely to the acres included in the calculation.
Lower costs may be achieved by using the same equipment across
additional acreage. Cox's equations suggest that there is little
difference in cost between irrigating 168 acre inches on 38 or
46 acres in a given period of time.
Land cost (the cost of owning land including interest and property tax) increases directly
with the number of acres occupied by the lagoon and the sprayfield.
For example, the annual cost of owning land valued at $800 per
acre may be $64 per acre assuming a 7.5% interest rate and a 0.5%
property tax rate.
The effect of a 25% reduction in the concentration of nitrogen in lagoon effluent may include a 25% reduction in the area of sprayfield required (e.g. $605 per year in the example), some reduction in irrigation costs, and some reduction in net crop income ($264 per year in the previous example).
The effect on irrigation costs is uncertain. If more time is allowed for irrigation on a smaller acreage, a smaller traveling gun will be more economical. If the same volume of effluent must be applied in the same time on a smaller acreage, costs may actually increase slightly with additional labor.
The benefits of a 25% reduction in surplus nutrients may be much larger if the farm is required to reduce nutrient load per acre and has no additional land available for sprayfield. For example, reducing inventory by 25% would cost a 4,800 head finishing operation $27,720 per year (.25 x 2.8 x 4800 x $8.25) Other methods of reducing surplus nutrients to be land applied are likely to be more cost effective.
One measure of the potential value of various improvement in manure management technology is the potential reduction in costs. A 25% reduction in required sprayfield may save $0.025 per hog finished in the hypothetical example above (($605 - $264) / (2.8 x 4800)). The savings may be slightly greater if a more profitable crop can be grown on the released acres or if the land would have been cleared at a cost greater than its productive value (e.g. $1400 versus $800 per acre). Some proposed technologies suggest reduction required acreage by 75%.
A 25% reduction in lagoon capacity would save $0.112 per hog finished and a 25% reduction in the volume irrigated would save $0.128 per hog finished in the example above. Solids separation offers potential for reduced lagoon capacity and reduced sprayfield to the extent that nitrogen concentration in the effluent is reduced. Reduced excess water use and reduced accumulation of rainfall may reduce irrigation requirements. Other alternatives include the use of constructed wetlands or overland flow to reduce the volume that has to be irrigated.
Kelly Zering
Northeast Regional Pork Conference
February 11, 1997
HogHealth
Vol. 6, No. 6