Land Application of Separated Effluent from Swine Slurry

The Livestock and Urban Waste Research (LUW) Team has developed a successful manure treatment system that couples polymer-assisted separation of liquid manure with composting. This solid-liquid separation of raw swine manure makes it possible to reuse the solid fraction with a high nitrogen and phosphorus content separately from the liquid fraction with a low solids and low phosphorus content. Separation consistently removes more than 90 percent of the solids and approximately 90 percent of phosphorus from liquid manure. The solids fraction is composted, producing a value-added coproduct that can be sold off-farm or transported longer distances for cropland application. The separated effluent is stored in holding tanks for subsequent land application. This direct utilization of the liquid fraction is advantageous because it is simple, has a low application cost, and allows for direct use of nitrogen. Most importantly, this adaptive management technology changes the nitrogen:phosphorous (N:P) ratio thereby minimizing environmental concerns regarding phosphorous contamination.

Land Application of Separated Effluent

The separated effluent, which makes up 90 percent of the raw slurry volume, is transferred to a slurry store® tank where it is aerated before being land applied using center pivot or subsurface irrigation. Because the total solids have been reduced by over 98 percent in the effluent, clogging in irrigation equipment and piping is not a concern. Additionally, no odor problems have been associated with the use of separated effluent even with above ground irrigation systems.

BMPs for Irrigating Separated Effluent

Both the composted biosolids and the separated effluent provide a comparable alternative to using inorganic fertilizers for crop production.

Characteristics of Slurry,
Effluent and Biosolids (Year 1)
Item % Solids % N %P N:P
RS 1.3 0.19 0.05 3.8:1
SE 0.4 0.08a 0.004 20.0:1
BS 10.4 0.9 0.64 1.4:1
a0.09% in irrigant
Characteristics of Slurry,
Effluent and Biosolids (Year 2)
Item % Solids % N %P N:P
RS 0.82 0.11 0.02 5.5:1
SE-B 0.39 0.07 0.006 12:1
SE-MS 0.37 0.06 0.006 10:1
BS-B 9.33 0.55 0.35 1.6:1
BS-MS 0.77 0.65 0.43 1.5:1
Compost Characteristics
% K
% Solids
RS = Raw Slurry
SE = Separated Effluent
SE-B = Separated Effluent from belt press
SE-MS = Separated Effluent from microscreen
BS = Biosolids
BS-B = Biosolids from belt press
BS-MS = Biosolids from microscreen
% Solids = Percent solids
% N = Percent Nitrogen
% P = Percent Phosphorus
% K = Percent Potassium
% Ca = Percent Calcium
N:P = Ratio of Nitrogen to Phosphorus

Land Application of Separated Biosolids

slurry tankThe biosolids, which make up two - 10 percent of the raw slurry volume, are collected, composted and then land applied.

BMPs for Land Application of Biosolids

BMPs for Land Application of Composted Biosolids

  1. Obtain nutrient analysis (NPK) of compost
  2. Apply based on % P concentration
  3. Applying based on % N concentration will result in over applying P
  4. Apply based on % dry matter of compost
  5. Do not apply just prior to or during a rain to avoid runoff or leaching
  6. Soil incorporation immediately after surface broadcast is recommended to reduce odor and loss of N
  7. Apply based on % dry matter of biosolids

Separation Costs

Total separation costs, including equipment, labor, polymer and fuel, come in at less than 1.0¢ per gallon of raw slurry.

Separation Costsa
Equipment $100,000  
Labor $15:hour .35/.34¢ SE/RS
Polymerb $1.60:lb .14/.13¢ SE/RS
Fuel $2.10:gal .15/.14¢ SE/RS
Main 2%:year .08/.07¢ SE/RS
Depr. (15yr) 6.7%:year .27/.25¢ SE/RS
acosts reflect 2007 prices
b560 mg:gal SE, 510 mg:gal RS
Separation/Application Cost (¢:g)a
Item Separation Irrigation Total
RS 0.90 0.10 1.0
SE 0.99 0.10 1.09
RS Direct Injection= 0.70-1.70
acosts reflect 2007 prices

Slurry separation provides an efficient and cost effective system for managing the odor and nutrient overload associated with swine manure while improving animal welfare, reducing non-point source pollution concerns, and providing a source of beneficial soil amendments for crop production.


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University of Illinois at Urbana Champaign College of Agricultural Consumer & Environmental Sciences University of Illinois Extension