The combined wastes are sent to a nutrient recovery unit to make organic ammonia fertilizer (which otherwise would be made with natural gas), and extract potassium and phosphorus, leaving compost clean enough to be used as animal bedding. The ammonia fertilizer can be injected below-ground to the roots of growing plants, instead of applied at the surface as manure traditionally has been.
This process eliminates run-off from animal wastes that traditionally would be used as fertilizer, and in a way that surpasses Environmental Protection Agency requirements.
How does it work?
Manure is brought to the digester either through pipes or in trucks. Anaerobic digestion occurs when groups of bacteria work in stages to break down the manure. Three types of bacteria work in sequence to convert manure into biogas:
- Stage one: One bacteria type reduces the manure to fatty acids.
- Stage two: Another bacteria type reduces the fatty acids to acetic acid.
- Stage three: The third bacteria type turns the acetic acid into bio-methane gas.
At the end of this biochemical process, the leftovers enter a nutrient recovery unit that uses what is left to produce natural fertilizers that can be sold to local farmers to enrich the soil for corn and other crops. These fertilizers replace costly, fossil fuel-based fertilizers and are virtually odorless, pathogen-free, and most importantly, environmentally friendly.
No wonder the workers at our anerobic digester wear labels on their hardhats reading "Bug Whisperer."