Following the Nutrients
Nutrients must go someplace
Nutrients found in manure enter into the air, water, and soil, where they are utilized in natural processes. However, in excess these nutrients are a form of pollution. Managing and minimizing the impact of excess nutrients to the environment can be accomplished at the farm level and at the regional level using anaerobic digesters and nutrient management systems.
What is anaerobic digestion?
An anaerobic digester uses microbes in an oxygen free environment to break down manure. This process is a phase or step process, beginning with a complex nutrient material, like manure, and heat as inputs into the system. The manure first goes through a liquefaction phase, and then through a gasification phase, in which methane forming bacteria act upon the manure creating biogases. The result of this process is an output of biogases, methane and carbon dioxide and a low odor, nutrient rich liquid.
How do digesters manage nutrients?
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 nutrient loads. To accomplish nutrient removal, added technologies are necessary.
On the farm and off
A regional anaerobic digester facility has the ability to service several farms in a region. Regional systems are more focused on actually removing nutrients from manure and other organic material through multiple strategies that combine anaerobic digestion with wastewater treatment. The products, containing the nutrients, can then be marketed to and utilized by other industries. Regional systems provide small scale farms or larger operations the opportunity to sustainably operate an anaerobic digester in sequence with additional technologies that enable better management of nutrients. These systems likely seek to integrate nutrient credit, energy credit, and carbon credit generation into their business model as a part of the economy of operation.