Anaerobic Digestion Technology Certificate Program

About Anaerobic Digestion (AD)

What is it?


Anaerobic digestion (AD) is a process in which organic matter from wet organic wastes (i.e. liquid manure, food processing wastes, etc.) is converted into methane by bacteria in the absence of oxygen. Under typical dairy farm conditions manure is stored in open ponds and applied to fields, where decomposition often occurs under anaerobic conditions. This leads to the natural, open-air production of methane, a greenhouse gas with more than 20 times the warming value of carbon dioxide. By enclosing, controlling and accelerating this natural anaerobic conversion process, not only can the methane be contained, but it can be converted to renewable energy, providing two mechanisms for carbon sequestration and global warming reduction – methane capture/conversion and fossil-fuel energy offset. Add to this climate impact such environmentally advantageous benefits as odor control, solids reduction, pathogen destruction, and air/water protection, not to mention economic revenue from a previously economically-negative aspect of dairy production, manure management, and you have a truly revolutionary farm management tool.

How does it work?

AD Diagram

Organic wastes are loaded into the air-tight anaerobic digester and bacteria break down the waste into three primary components: solids (fiber), biogas (methane and carbon dioxide used to generate electricity), and high-nutrient effluent. These products can be processed further to create even higher value products such as horticultural fiber, refined fuel and non-chemical fertilizer products.

The Future of Anaerobic Digestion

Anaerobic Digestion technology has been in use for several decades but failure rates have been high due primarily to poor operation and maintenance of either the biological AD unit or the associated gas production and energy units. Because of high failure rates, among other challenges, adoption of AD has lagged. However, recently the US government and dairy industry signed a commitment to reduce farm-based greenhouse gas emissions by 25% by 2020, a declaration contingent upon the installation of a large number of digesters. Rural-based trained AD technicians are needed to meet the upcoming demand for operation, repair and maintenance of AD units.