COSTS ASSOCIATED WITH DIGESTION SYSTEM INSTALLATION

The obvious questions asked when considering digestion systems are:

  1. What will be the capital cost?

  2. The operating costs?, and,

  3. How well will the system fit into the current operation?

System Capital Cost Ranges

Prices vary with system design and components, location, contractors and suppliers. This table provides approximate costs for a relatively simple effective system style currently employed successfully in a variety of locations in the US. There are more exotic approaches, with correspondingly higher initial capital outlays.

Facility Size Cost Range*+

500 cows,
1000 sow farrow to finish, 5000 finishing hogs
2500 sow farrow to wean

 $250,000-300,000

1000 cows,
1500 sow farrow to finish, 10,000 finishing hogs,
5000 sow farrow to wean

 $300,000-$350,000

2000 cows,
2500 sow farrow to finish,
15,000 finishing hogs,
8000 sow farrow to wean

 $450,000-$500,000

* These estimates are for digestion systems with Engine Generators, reduce prices by 1/3 if no genset is to be installed
+ These estimates do not include solids separation, increase value by $35,000-$45,000 if solids separation is to be included

System Operating and Maintenance Costs

Digestion systems with cogeneration will cost about $0.015/kWh generated to operate. This includes all engine generator and digester daily and intermediate expenses. This is about 5% of the initial capital costs.

Digestion systems without cogeneration will require minimum daily attention, and about the equivalent 5% of the initial capital cost in short and long term maintenance.

If solids separation is to be part of the system, operation and maintenance will cost between $0.50 and $1.50 per cubic yard of solids recovered. If solids separation is not to be included, the producer will have to consider the cost of lagoon cleaning.

Fitting the Digestion System into the Existing Facility

The least cost approach to digestion system installation is to use existing equipment to the largest extent possible. Under nearly all circumstances, existing equipment may be used and the costs cited above reduced.  Production facilities may have existing manure pits, pumps, separators, and buildings. Cost of constructions will be lower in those cases.  One notable exception is that existing standby power gensets may not be used.

Biogas collected in the digester may be piped to an engine attached to a generator. This engine will have to be purchased, as standby generators are almost all not continuous duty nor built for this type medium Btu gas. Engine and generator controls will have to be special ordered.

Mixing digestion system produced electricity into the farm system is as simple as connecting to the main switch buss bar.

Mixing digestion system produced hot water from the engine into the farm system will be as simple as installing heat exchangers.

Copyright ENVIRONOMICS  11/03/99


 Last updated February 28, 2005.