About this Course

Anaerobic digestion is a natural biological process where microorganisms convert complex carbohydrates into biogas in an oxygen free environment. Anaerobic digestion mineralizes nutrients and reduces odors, which enables farmers to apply digestate (the slurry that is removed from the digester after digestion) in places manure cannot be applied. A growing number of farms are using anaerobic digestion to treat manure as part of a manure management plan.

An anaerobic digester simulates the digestive process of the ruminant animal. Like the ruminant animal, an anaerobic digester uses fermenting bacteria to break down biomass into organic acids. These acids are converted into methane by methanogens. Biogas is typically 60 percent methane and 40 percent carbon dioxide, with some trace gases

Anaerobic bacteria break down complex carbohydrates in the feedstocks into organic acids that are used by methanogens to create biogas and slurry. The biogas is removed to produce natural gas, electricity or heat. The slurry is removed and land applied as a source of nutrients on growing crops or further processed into a filtrate or fiber product. Both present value added opportunities for farmers.

This module provides background information on the anaerobic digestion process, biogas and other products of anaerobic digestion, and on the energy applications of biogas. Possible environmental benefits and concerns associated with anaerobic digestion are described.

Learning Outcomes & Objectives:

• Understand the biological process for producing biogas.
• Discuss anaerobic digester applications for agricultural and wastewater systems, the situations that warrant an on-farm digester and the various digester size options that are available for a producer.
• Describe the uses for digestate and biogas.
• Discuss the environmental benefits and concerns associated with anaerobic digesters.