Technology Description Cost per Hog Finished Complete mix digester Anaerobic digestion in an enclosed concrete or metal vessel that captures methane and reduces ammonia emissions. $3.99 Constructed wetlands Reduces nitrogen and phosphorus from waste stream by passing waste through a specially constructed basin that contains water, soil and selected plants. -$0.35 Covered ambient digester Anaerobic digestion in a covered lagoon that captures methane and reduces ammonia emissions. $2.39 Solids ecoreactor A system that dewaters liquid waste as it passes through a shallow holding pond.  Biosolids accumulate in the ponds and are dried and sold as compost. $2.87 Upflow biofiltration system Wastewater is treated aerobically by passing through an aerated tower where the organic matter is digested by bacteria growing on plastic media and reduces nitrogen.  $5.21 Nutritional Approaches to Reducing Hog Waste and Odors Phytase supplement Phytase is an enzyme that breaks down the phytate molecule in feed so that more of the phosphorus is taken up by the pig.   Phytase can reduce phosphorus excretions by 25 to 50 percent. $0.36 - $0.72 Mixing feedstuffs and synthetic amino acids Reducing the dietary protein by mixing feedstuffs and using synthetic amino acids can reduce nitrogen excretions. $1.80 - $3.60

Notes:
1) All cost estimates are for adding alternative technologies to existing hog operations.
2) Spray irrigation costs were estimated to be $1.65 per hog for all systems.
3) Taxes and insurance were included in cost estimates and assumed to be one percent of the total capital costs for the system.
4) Returns from value added products were calculated and factored into total net costs when information was available.
5) Costs for solids ecoreactor were based on a 5,000-head finishing farm.  So costs may be slightly different for 4,000-head finishing farm.

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