Anaerobic Treatment of Swine and Dairy Waste

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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.



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 NutrientsIf 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.


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.

Contaminants Flushed Wastewater After Solids Separation After Biological Treatment % Removal
COD 20,000-50,000 mg/l 1000-2000 mg/l 100-500 mg/l 99%


500-1000 mg/l 400-600 mg/l 10-40 mg/l 98%
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. ExpansionIncrease production capacity and profits without increasing
    the existing storage basin.
  4. Eliminate OdorEliminates spraying of anaerobic waste.
  5. Irrigation EquipmentWith 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
  • 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 90-100°F) 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.

5000 Head – Finishers 50 KW Continuously
1000 Head – Sow –
Farrow to Finish
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

Typical Operating Cost

Sow Operation (Positive payback
from electricity produced, zero electricity
Finisher Operation (Positive payback
from electricity produced, zero electricity

Typical Treatment

Treatment Influent Treatment Effluent Reduction
Organic Matter 20,000 mg/l 250 mg/l 99%
Nitrogen 600 mg/l 25 mg/l 97%

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

Aerobic Anaerobic
Capital Cost Low Capital Cost
Operating Cost Low Operating Cost
Tax Credits Available
Ammonia Nitrogen Concentration Reduced Nitrogen Concentration Reduced
Electricity Consumes Produces
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

Aerobic Anaerobic
Capital Cost $100,000 $200,000
Energy Cost $5,000/year Net pay back possible $20,000/year

15000 Head Finisher or 5000 Sow Facility

Aerobic Anaerobic
Capital Cost $150,000 $280,000
Energy Cost $15,000/year Net pay back possibly $60,000/year

© Hoffland Environmental Inc, 2012