DIGESTION SYSTEM BENEFITS

Digestion systems offer potential economic and non-economic benefits. Actual benefits will vary from farm to farm. Whereas properly designed anaerobic lagoons may provide similar results; a heated digester is remarkably smaller and will permit treatment year around with predictable recovery of usable products. Digesters are often a better investment than a lagoon over the long term life of the structure.

Economic

Digestion systems may both directly and indirectly enhance revenues of the production facility.

1)      Direct Economic Benefits

Several ways a digestion system may directly impact the facility are:

  • A system, which includes equipment to convert biogas to electricity, and hot water, may sell electricity directly to utilities; gas or hot water may also be sold.
  • A system, which includes equipment to remove suspended solids from the liquid, may sell digested fiber.
  • Digestion systems will greatly reduce the viability of seeds found in the waste stream. Consequently, there is the potential less herbicide will need to be purchased.
  • Though the market is not developed to date, there is speculation that waste managers treating certain waste streams may eventually be able to sell pollution credits; current discussion focuses on sale of CO2 credits associated with combustion of manure derived methane which would otherwise have been emitted to the atmosphere.
  • Through the assistance of a tax specialist system ownership may be structured to permit sale of certain tax benefits associated with system installation.

2)      Indirect Economic Benefits

The greatest potential indirect economic benefit is the reduction in risk of the facility being subject to legal action and forced outright closure. Digestion systems, properly designed and operated, significantly reduce the odors associated with manure management.

Even if electricity or hot water are not directly sold:

  • Digestion systems with biogas conversion equipment (boilers, engine generator sets) have the potential to replace purchased electricity and fuel.

  • Recovered digested solids may be used for animal bedding, offsetting the cost of bedding purchase.

  • System using solids separation equipment will reduce lagoon or storage cleaning costs.

  • Because digested manure is biologically stable, the design size (and capital cost) of the storage facility will correspondingly be greatly reduced.

  • While the research has not been completed in the US, research in other countries indicates manure stream nutrient availability and plant uptake may be improved with digestion. Fertilizer purchases are expected to be reduced and crop yields possibly improved.

  • The pumpability of digested liquid is greatly improved.

Non-Economic

Staff as well as neighbors would prefer to not deal with odors associated with manure management. In digestion, compounds, which usually produce odors, are greatly reduced. Pathogenic organism are greatly reduced, most more than 90%, many more than 95%, a few only 50% or more (note: they are not to be considered eliminated).

Copyright ENVIRONOMICS 11/03/99

 


Last updated February 28, 2005.