Lessons Learned from this Project |
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Cost Estimate
The cost estimate for this project was under $500,000. The actual cost to date has been over $1,000,000. Obtain realistic cost estimates and include plans for exigencies.
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Cover
The digester was designed with a hard top to collect the gas at 12 inches of water column pressure to push gas into the compressor. The greater the pressure the more difficulties there are in sealing a digester. Digesters operating at high pressures should be pressure tested as part of the startup procedure. Use proven technologies to seal digesters. Separate any equipment as much as possible from gas sources.
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Environment
Power generation problems at this site are due to the corrosive environment. Carefully analyze your facility design to limit potential adverse impacts on equipment.
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Heating system
The heating system had several flaws. The heat balance of the digester system is vital. Designs need to address the heat recovery from the biogas, methods to heat the incoming manure, and correct estimates of the maintenance heat needed to maintain a constant temperature in all weather conditions.
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Site Drainage
Drains to control the water table around the digester to prevent buoyancy of the empty digester and to control heat loss were not designed. All in ground structures should have drainage systems in the backfill to reduce heat loss and prevent floatation.
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