Following the Nutrients: Farm Scale to Regional Scale
Nutrients Must Go Somewhere
Nutrients in manure enter into the air, water, and soil, causing nutrient pollution. Managing and minimizing the effects nutrients have on ecosystems can be accomplished at the farm level as well as at the regional level through use of anaerobic digesters and nutrient management systems.
What is Anaerobic Digestion?
An anaerobic digester uses microbes in an oxygen-free environment to break down manure into biogases and a nutrient rich liquid. This process is a phase or step process, beginning with a complex nutrient material, like manure, and heat as inputs to the system. The manure first goes through a liquefaction phase where the manure is acted upon, and simplified by acid forming bacteria. Second, the liquefied manure goes through a gasification phase in which methane forming bacteria act upon the manure creating biogases. The result of this process is an output of the biogases methane and carbon dioxide, a low odor, heat, and nutrient rich liquid.
Are Nutrients Better Managed Using Anaerobic Digesters?
Anaerobic digesters reduce foul odors associated with manure, produce biogas that is utilized in electricity production, stabilizes volatile manure compounds, and improves the storing and handling characteristics of manure. Anaerobic digesters do not eliminate or reduce nutrients loads.
On the Farm and Off
A regional anaerobic digester facility can service several farms in proximity to one another. Regional systems are more focused on actually eliminating nutrients from manure and other organic materials through multiple strategies combining anaerobic digestion, water treatment, and marketing and export of nutrients for utilization in other industries. Regional systems provide small scale farms or larger operations that lack the expertise to sustainably operate an anaerobic digester the ability to better manage nutrients. Operating a regional facility is logistically complex, expensive, and increases the amount of stakeholders that must be involved.