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 90-100°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 farm’s animal population and also
to the efficiency of the anaerobic digester. The HEI Bio ’Lec digester is far more efficient than conventional technology because  Bio ’Lec biogas production (600 Btu/cubic foot) reaches 42% conversion vs only 20 – 26% with conventional technology. Typically:

Animal Units (AU) CONVENTIONAL Bio ’Lec
5000 Head – Finishers 650 50 kW 100 kW
1000 Head – Sow – Farrow to Finish 1300 100 kW 200 kW


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

Sow Operation – (Positive payback from electricity produced, zero electricity bill)
Finisher Operation – (Positive payback from electricity produced, zero electricity bill)

Typical Treatment

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




Capital Cost

Operating Cost

Tax Credits

Low Capital Cost  

Low Operating Cost


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




Capital Cost



Energy Cost


Net pay back possible $20,000/year

15000 Head Finisher or 5000 Sow Facility




Capital Cost



Energy Cost


Net pay back possibly $60,000/year

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