Fertilizer Value of Swine Manure: A Comparison of Lagoons and

Deep Pit Slurry Systems

John P. Chastain, Ph.D.Professor and Extension Agricultural Engineer

Waste to Worth Conference, Seattle, Washington

The Westin Seattle Hotel • March 30 – April 3, 2015

Introduction Most modern swine facilities in

NC, SC, and other Southern states use under-slat flush or re-charge pits to remove manure from buildings.

Such systems required large volumes of water to operate.

Recycled liquids are used due to large volumes needed.

Recycling liquids requires adequate treatment.

Treatment needed to reduce solids, ammonium content, and to provide adequate storage time for pathogen reduction.

Treatment lagoons are typically used to provide treated water to recycle through the buildings (≈ 0.5% TS or 99.5% water).

So in the South treatment lagoons and recycle systems typically go together.

Several changes have occurred since 2000. New and expanded regulations that make

expanding or siting new swine farms much more difficult.

Increase in construction cost of clay or synthetically lined lagoons.

Increase in grain prices. Increase in grain transpiration costs. Increase in fertilizer costs.

Prices of Nitrogen (USDA-ERS, 2013)

P2O5 & K2O Prices (USDA-ERS, 2013)

Between 2002 and 2012… Nitrogen prices have increased by a factor of

2.6 Phosphate prices up by a factor of 2.8 Potassium prices up by a factor of 4.0 Price instability Common for fertilizer costs to contribute 30%

to 40% of the cost to produce grain

Result…Companies are considering deep pit barns

Easier to locate under regulatory requirements Reduce risk during high rainfall i.e. hurricanes! Conserve plant nutrients in swine manure Use manure nutrients to produce more grain to

feed swine Reduce transportation costs of grain from

Midwest Promote integration of swine and grain

production

Objective To compare the fertilizer value of the manure

produced from swine finishing barns that use a liquid manure handling with a treatment lagoon, and swine finishing barns that store manure below slotted floors in pits.

Compare the realized economic value of manure if manure is spread based on agronomic rates for N versus P2O5.

Assumptions for the Comparison Corn yield of 160 bu/ac Agronomic rates (CAMM Program Manual chapter 5 &

and EC-476, available at clemson.edu): 1.2 lb N / Bu × 160 Bu/ac = 192 lb N/ac 0.52 lb P2O5 / Bu = 83 lb P2O5 / ac

1.2 lb K2O / Bu = 192 lb K2O /ac

Part of the P2O5 and K2O will come from what already exists in the soil.

Variation in soil-test values not included.

Prices Used in Calculations

Ammonium Nitrate - $0.71 per lb of N P2O5 - $0.69 /lb

K2O - $0.50 / lb

Definitions Inventory value – the total value of N, P2O5,

and K2O in the manure without regard for plant utilization.

Realized economic value – the total value of N, P2O5, and K2O in land applied manure that does not exceed the agronomic need of the crop. That is, over applied nutrients are not given any value for the current crop.

Case 1. Four 880 swine finishing houses that use a single treatment lagoon. Number of Hog Spaces = 3520

Lagoon water nutrients and volume 3520 finishing hog-spaces

Ammonium-N: 3.1 lb/1,000 gal (ATAN = 0.80) Organic-N: 0.9 lb/1,000 gal (mf = 0.60) Plant Available N = PAN: 3.0 lb/1,000 gal P2O5: 2.0 lb/1,000 gal K2O: 4.9 lb/1,000 gal Moisture: 99.63% Volume = 2,432,320 gal / year, or 691 gal/hog-space/year or 89.6 ac-in / year.

Annual Nutrient Production from Lagoon Water

3.0 lb PAN/1,000 gal x 2,432,320 gal/yr

= 7,297 lb PAN/yr

2.0 lb P2O5 /1,000 gal x 2,432,320 gal/yr

= 4,865 lb P2O5 /yr

4.9 lb K2O /1,000 gal x 2,432,320 gal/yr

= 11,918 lb K2O /yr

Fertilizer Inventory Value – Lagoon Water

7,297 lb PAN/yr x $0.71/lb N = $5,181/yr

4,865 lb P2O5 /yr x $0.69 / lb P2O5 = $3,357/yr

11,918 lb K2O/yr x $0.50 lb K2O = $5,959/yr

(Higher than normal K2O content maybe solubilized from sludge .)

Total Inventory Value = $14,497 per year or $4.12 / hog-space / year.

Area of corn that can be fertilized based on agronomic rate for nitrogen using lagoon water.

PAN to Spread ÷ N Demand = Acres Needed For our 4-house swine lagoon example:

7,297 lb PAN/yr ÷ 192 lb N/ac = 38 ac / year.

Liquid application rate = 64,008 gal/ac

or 2.36 ac-in

Not much if you are a grain producer!

How much P2O5 is applied if we apply lagoon water based on N? We will spread 4,865 lb P2O5 /yr along with

the N. Spreadable acres = 38 P2O5 rate = 4,865 lb P2O5 /yr ÷ 38 ac

= 128 lb P2O5 /ac

The 160 bu/ac corn only needs 83 lb P2O5 /ac

Excess of 45 lb P2O5 /ac or 54% over application.

How much K2O is applied if we apply lagoon water based on N?

We will spread 11,918 lb K2O/yr along with the N

Spreadable acres = 38 K2O rate = 11,918 lb K2O/yr ÷ 38 ac

= 314 lb K2O /ac

The 160 bu/ac corn needs 192 lb K2O/ac

Excess is 122 lb K2O /ac or an excess of 64%

Realized economic value of the lagoon water for application based on N

Nitrogen: 192 lb N/ac × $0.71/lb N = $136.32/ac P2O5 : 83 lb N/ac × $0.69 / lb P2O5 = $57.27/ac K2O: 192 lb K2O/ac × $0.50 / lb K2O = $96.00/ac Total value from lagoon water = $289.59/ac Value of wasted P2O5 = 45 lb P2O5 /ac × $0.69 / lb P2O5

= $31.05/ac Value of wasted K2O = 122 lb K2O /ac × $0.50 / lb

P2O5 = $61.00/ac

What percentage of lagoon water value was realized? ($289.59 / $381.64) × 100 = 76%

Area of corn that can be fertilized based on agronomic rate for P2O5 using lagoon water.

P2O5 to Spread ÷ P2O5 Demand = Acres Needed

For our 4-house swine farm example:4,865 lb P2O5 /yr ÷ 83 lb P2O5/ac = 59 ac / yr

17 ac/hog-spaceNeed 1.55 times more corn land if lagoon water

is spread based on P2O5 rate (59 ac vs. 38 ac).

Liquid application rate = 41,226 gal/ac

or 1.52 ac-in

How much N is applied if we apply lagoon water based on P2O5?

We will spread 7,297 lb PAN/yr along with the P2O5

Spreadable acres = 59 N rate = 7,297 lb PAN/yr ÷ 59 ac

= 124 lb N /ac

Calculation of additional N Needs Fert. N = (N-rate needed) – (N manure credit) Fert. N = 192 lb N/ac - 124 lb PAN/ac

= 68 lb N/acre. Lagoon water saved 65% on N cost. Allows more efficient use of N to grow the

crop by including a second application of N to provide optimal yield.

How much K2O is applied if we apply lagoon water based on P2O5?

We will spread 11,918 lb K2O/yr along with

the P2O5

Spreadable acres = 59

K2O rate = 11,918 lb K2O/yr ÷ 59 ac

= 202 lb K2O /ac

The corn needs 192 lb K2O/ac

Over by only 10 lb K2O /ac.

Realized economic value of the lagoon water for application based on P2O5.

Spread to provide 83 lb P2O5/ac ($0.69/lb) Nitrogen applied = 124 lb PAN/ac ($0.71/lb), and K2O applied = 192 lb P2O5/ac ($0.50/lb). Total value from lagoon water = $241.31/ac Value of wasted K2O = 10 lb/ac × $0.50/lb = $5.00/ac

Only 2% nutrients wasted – 98% utilization. Need to add 68 lb N/ac at optimal time.

Summary: Value of Lagoon Water for 160 bu/ac corn – 4 houses Spread based on N: 76% realized economic

value: lagoon water was worth $11,004/year or $3.13/hog-space/year.

Spread based on P2O5: 98% realized economic value: lagoon water was worth $14,237/year or $4.04/hog-space/year.

Now we need to consider the sludge. We will look at the value on an annual basis.

Lagoon sludge nutrients and volume for a 4 house finishing farm - 3520 hog-spaces

Ammonium-N: 6.1 lb/1,000 gal Organic-N: 15.5 lb/1,000 gal (mf = 0.36)

PAN – incorp.: 10.5 lb/1,000 gal (ATAN = 0.80) PAN – injected: 11.7 lb/1,000 gal (ATAN = 1.0) P2O5: 47.3 lb/1,000 gal K2O: 6.3 lb/1,000 gal Moisture: 90.0% Volume = 58 gal/hog-space/year (new ASABE Standard) Annual Volume = 204,160 gal of sludge/year (10% TS)

Direct Injection Minimizes N Losses and Odor Emissions

Towed Hose

Tank Type

Annual Sludge Nutrient Production & Value using direct injection – 3520 hog-spaces

11.7 lb PAN/1,000 gal × 204,160 gal sludge/year = 2,389 lb PAN/yr × $0.71/lb = $1,696/yr

47.3 lb P2O5 /1,000 gal × 204,160 gal sludge/year

= 9,657 lb P2O5 /yr × $0.69/lb = $6,663/yr

6.3 lb K2O /1,000 gal × 204,160 gal sludge/year

= 1,286 lb K2O /yr × $0.50/lb = $643/yr

Sludge is best used as a P fertilizer and is worth $9,002/year or $2.56/hog-space/year.

Results of spreading lagoon sludge to 160 bu/ac corn based on P2O5

Spread to provide 83 lb P2O5/ac ($0.69/lb) will fertilize 116 acres or 33 ac/hog-space

The volume spread / acre = 1760 gal/acre. Nitrogen applied = 21 lb PAN/ac ($0.71/lb), and K2O applied = 11 lb K2O/ac ($0.50/lb). Total value from sludge = $77.68/ac Provided 27% of fertilizer requirement value. Realized economic value = 100% or $2.56/hog-space

Summary: Realized Value of Lagoon Water + Sludge for 160 bu/ac corn – 3520 hog-spaces

Spread water based on N and sludge based on P2O5

Value of manure = $3.13/hog-space for water + $2.56 for sludge = $5.69 / hog-space.

Spread water and sludge based on P2O5:

Value of manure = $4.08 + $2.56 for sludge = $6.64 / hog-space

Case 2. Four 880 swine finishing houses that use deep slurry pits that provide 1 year of storageNumber of Hog Spaces = 3520

Estimates for Four Deep Pit Swine Barns, 880 pigs /house – 3520 hog spaces

Ammonium-N: 23 lb/1000 gal (ATAN = 1.0) Organic-N: 19 lb/ 1000 gal (mf = 0.60) PAN – Direct injection = 34 lb/1000 gal P2O5: 33 lb/1000 gal K2O: 28 lb/1000 gal Moisture: 92.5% or 7.5% TS Manure prod. = 418,326.5 gal/house/year For 4 houses = 1,673,306 gal/year 475.4 gal/hog-space/yr

Annual Nutrient Production 4 Deep Pit Houses - 3520 hog spaces, direct injection

34 lb PAN/1,000 gal x 1,673,306 gal/year = 56,892 lb PAN/yr

33 lb P2O5 /1,000 gal x 1,673,306 gal/year

= 55,219 lb P2O5 /2yr

28 lb K2O /1,000 gal x 1,673,306 gal/year

= 46,852 lb K2O /yr

Fertilizer inventory value for a 4 house deep pit farm - 3520 hog spaces 56,892 lb PAN/yr × $0.71/lb N = $40,393/yr 55,219 lb P2O5 /yr × $0.69/lb P2O5 = $38,101/yr 46,852 lb K2O/yr × $0.50 lb K2O = $23,426/yr

If you can use all of it effectively the total inventory value is $101,920 per year.

Equal to $28.95 per hog-space per year.

Estimation of spreadable acres based on N requirement for corn fertilized with pit manure

PAN to Spread ÷ N Demand = Acres Needed

For our slurry example:

56,892 lb PAN/yr ÷ 192 lb N/ac = 296 ac / yr,

Or 84.1 acres/1000 hog-space/yr

Still not much for a grain producer!

Resultant application rates for P2O5 & K2O using deep pit manure.

P2O5 rate = 187 lb P2O5 /ac

The corn only needs 83 lb P2O5 /ac without counting soil test

Excess of 104 lb P2O5 /ac

K2O rate = 158 lb K2O /ac

The corn needs 192 lb K2O/ac

Short only 34 lb K2O /ac

Realized economic value deep pit manure for application based on N

Nitrogen: 192 lb N/ac × $0.71/lb N = $136.32/ac

P2O5 : 83 lb /ac × $0.69 / lb P2O5 = $57.27/ac

K2O: 158 lb K2O/ac × $0.50 / lb K2O = $79.00/ac

Total value from manure = $272.59/ac Value of wasted P2O5 = 104 lb P2O5 /ac × $0.69

/ lb P2O5 = $71.76/ac

Realized economic value = $80,687/year or $22.92 / hog-space/yr. – 79%

Results of spreading deep pit manure to 160 bu/ac corn based on P2O5

Spread to provide 83 lb P2O5/ac ($0.69/lb) will fertilize 665 acres – 189 ac/hog-space.

The volume spread / acre = 2516 gal/acre. Nitrogen applied = 86 lb PAN/ac ($0.71/lb), and K2O applied = 70 lb K2O/ac ($0.50/lb). Total value from sludge = $153.33/ac Realized economic value = $101,920/year or

$28.95/hog-space/year – 100%

Calculation of additional N Needs Following Application of Slurry

Fert. N = (N-rate) – (N manure credit) Fert. N = 192 lb N/ac - 86 lb PAN/ac

= 106 lb N/acre. Manure saved 45% on N cost – similar to lagoon

system we get more nutrients per year. Allows more efficient use of N by splitting the

application.

Some take home ideas… Lagoons are needed to provide treated water that

can be used to remove manure from flush or pit-recharge swine buildings.

Lagoon systems were designed to provide treatment with little consideration for the N losses or value of P and K.

Application based on agronomic rates for P2O5 provided the best use of manure for both systems –Realized economic value of 100%.

Some take home ideas…(2) Deep pit slurry systems allow a producer to increase

nutrient value per hog-space from $6.64 to $28.95/hog-space – a factor of 4.3.

Provided about 45% of the plant nutrients needed for corn (160 Bu/ac)

A deep pit swine production unit can support 3.7 times more corn land than a lagoon system –

189 ac/1000 hog-spaces vs. 50 ac/1000 hog- spaces.