Swine and Dairy
MS-Word Doc: Anaerobic Treatment of Swine and Dairy Waste

Pork and Dairy production wastewater contains high levels of organic contamination, both soluble and insoluble residues, and urea. The wastewater has been drained and stored in large foul smelling anaerobic lagoons containing essentially all of the organic solids and the nitrogen compounds resulting from the urine waste. The anaerobic degradation of the solids creates highly undesirable odors and high levels of nitrogen and nitrogen compounds, which, when distributed over cropland, easily over-nitrify the soil.


Every farm that produces animals must have a tank to store excess water resulting from animal excretion, barn flushing and cleaning and rainwater. Current practice is to store the excess water with the animal waste in an open earthen basin tank that becomes an anaerobic lagoon. When the lagoon is full the excess water is pumped to spray fields and disperse through spray nozzles. The foul smelling gases resulting from the anaerobic microbial action on the stored animal waste is liberated. The airborne foul odor drifts along the ground for miles. The local neighbors are very unhappy and have recently become irate, with this current practice.

Excess Nutrients
If more nutrients (nitrogen) are added to the soil than is consumed by the crops grown, the excess nitrogen will either run-off into the river and streams or percolate into the groundwater. Both results are illegal. Regulatory limits have been placed on the distribution of nitrogen and its compounds relative to the consumption of the cultivated crops.
Under current practices, the large dairy and pork production facilities do not have sufficient land to distribute their collected waste in an agronomically and environmentally sound manner. Excess nitrogen must therefore be removed prior to land application.


Hoffland Environmental, Inc. has developed economical solutions for concentrated animal feed operations (CAFO). The methods can be divided into two different solutions depending upon the size of the operation and climatic conditions. The first method is the HEI Aerobic System, which economically removes the solids from the waste, and maintains aerobic conditions to eliminate the formation of foul odors. An attached diagram details this method. A discussion of benefits follows.

The second method is the HEI Anaerobic System, which collects and contains the waste animal solids in a covered anaerobic digestion basin. By heating and inoculation, an environment is created that permits the microbial culture to rapidly digest the waste solids and produce methane gas as a by-product. The methane gas produced is utilized as an energy source to operate a generator and produce electricity. Thus, the farmer has created a renewable energy resource from an undesirable waste product. The system will produce more electricity then the farm consumes. The excess electricity is sold to the power grid. The remaining liquid after digestion is further treated under aerobic conditions to degrade the remaining low-level waste. A diagram of the systems as well as a discussion of the system merit is following.

Aerobic Solution for Dairy and Swine Waste
  • Odor Free Spray Fields
  • Odor Free Flush Water
  • Denitrification of Ammonia

Hoffland Environmental has developed an economical solution for the pork and dairy producers. HEI will convert your existing lagoon into an efficient bio-digester. First, to limit the biological load on the system, the large solids, feces and undigested food are screened from the wastewater.

HEI's efficient screening and clarification systems removes over 80% of the total solids. The lagoon environment will be customized to create areas that develop specific microbial cultures, which digest the remaining fecal and urine matter, and not only remove the ammonia but also nitrogen. The treated water will be essentially free of odor, ammonia and pathogens such as salmonella.

Problem 1: Odor - Eliminated
The entire system supplied by HEI is free of the traditional anaerobic odor. The screened solids are collected and stored under aerobic conditions and do not have a foul odor. When the excess water is spray irrigated, no odor is present.

Problem 2: Excess Nitrogen - Eliminated
The biological process (patented by HEI) not only removes the animal waste but also biologically removes ammonia and nitrogen. The excess water can be utilized for irrigation through fixed irrigation nozzles. Foul smelling spray fields do not exist.


Flushed Wastewater
After Solids Separation
After Biological Treatment
% Removal
20,000-50,000 mg/l
1000-2000 mg/l
100-500 mg/l
500-1000 mg/l
400-600 mg/l
10-40 mg/l

Treatment Advantages

  1. No Anaerobic Lagoons.
  2. Reduction of Land Area.
    Purchase or lease of additional land to distribute the stored wastewater is not required.
  3. Expansion
    Increase production capacity and profits without increasing the existing storage basin.
  4. Eliminate Odor
    Eliminates spraying of anaerobic waste.
  5. Irrigation Equipment
    With the reduced land area, irrigation equipment may be permanently installed.
    The labor required to move and monitor the irrigation reels will be eliminated.
  6. No Chemicals

Proven Technology

Hoffland Environmental has installed its new technology on a North Carolina Pork Production facility. The unit is a 5000-head farrow to wein facility with an animal mass of 2000 animal units. The facility operates with less than 30 kilowatts of electrical energy.

The net operating cost to the producer is about $0.10 - $0.15 per-weiner pig sold. Translating the technology to a finishing facility, the energy cost would be approximately $0.30 - $0.50 per finisher produced.

Anaerobic Treatment of Swine & Dairy Waste

  • Reduction of Solids Handling
  • Odor Free Environment
  • Odor Free Flush Water
  • Denitrification of Ammonia

Hoffland Environmental, Inc. has developed an efficient, economical covered anaerobic system that not only digests the waste animal solids but also produces sufficient electrical energy to provide a positive payback for the farmer. The waste animal solids are utilized as a renewable energy resource (certain tax credits are available for this type of equipment). The waste solids (reference following diagram) flushed from the production floors are concentrated and transferred to a covered mesophilic (temperature 90-100F) anaerobic digestion basin. The waste solids in the absence of oxygen and cultured under controlled mesophilic conditions, will biologically decompose forming biogas -principally methane gas. The methane is collected, pressurized and used as fuel for an engine/generator to produce electricity. The electricity produced will be adequate to supply all of the electric requirements for the farm plus sell the excess to the power grid. The amount of electricity produced is proportional to the farms animal population, typically.

50 KW Continuously
100 KW Continuously

The waste heat produced by the engine is captured and utilized to heat the digester basin to maintain the desired mesophilic microbial growth. Rapid decomposition of the waste solids occurs in a mesophilic culture. The size of the anaerobic basin is minimal requiring only 10 days retention, usually sized at 20 days for redundancy.

The effluent from the mesophilic digester is transferred to an aerobic basin to remove the remaining organic components and biologically remove the ammonia. The ammonia is biologically nitrified and subsequently denitrified to non-toxic benign nitrogen gas (process patented by HEI).

The effluent from the aerobic basin is stored for reuse or distributed through spray fields without the characteristic anaerobic odor.


  1. Anaerobic odor free operation
  2. Anaerobic odor free spray fields
  3. Excess nitrogen nutrients are removed
  4. No chemicals required
  5. Sufficient electricity is produced for net payback of equipment

Typical Operating Cost

(Positive payback from electricity produced, zero electricity bill)
(Positive payback from electricity produced, zero electricity bill)

Typical Treatment

Treatment Influent
Treatment Effluent
Organic Matter
20,000 mg/l
250 mg/l
600 mg/l
25 mg/l


Hoffland Environmental, Inc. will supply either the Aerobic or the Anaerobic system. The following is a brief comparison of the two processes.

Capital Cost
Low Capital Cost
Operating Cost
Low Operating Cost
Tax Credits
Nitrogen Concentration Reduced
Nitrogen Concentration Reduced
Waste Solids
Solids produced must be stored or distributed daily
Solids flow directly to the digester, no daily labor required

Approximate Cost Excluding Earthwork & Installation

5000 Head Finishing Facility

Energy Cost
Net pay back possible $20,000/year

15000 Head Finisher or 5000 Sow Facility

Energy Cost
Net pay back possibly $60,000/year
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