What Is AD ?
Anaerobic digestion (AD) is the process by which organic material is broken down (digested) by microscopic organisms, in the absence of oxygen. The human digestive system is a familiar example of the AD process. AD produces biogas (primarily methane and carbon dioxide), a stabilized solid and a liquid. The micro-organisms create biogas/bioenergy by means of a four step biological conversion process, as illustrated.
The Anaerobic Digestion Process
The Biogas Advantage
Renewable energy can be defined as energy produced from a resource that is replaced rapidly by a natural process. The resource is available directly from the greater environment and cannot be expected to be depleted by humans. This definition leads to the five categories of renewable energy sources. They are wind, solar, water, geothermal and biomass. AD is classified as a biomass form. All five forms have significant benefit to our society with the inclusion of each in the energy supply mix in North America. The key is to develop these differing solutions keeping in mind that each has a fit and value that is vastly different from the other.
Biomass generated renewable energy using AD is unique when compared to the other forms. Biogas is continuously produced from organics that are found everywhere in our communities, everyday. You don't have to locate in a high wind resource area and wait for the wind to blow, or wait for the sun to shine, or be near large water sources, or drill a hole in a high heat sink area.
An added benefit is the bioenergy is produced in the community, for consumption within. In addition, biogas is flexible and can be used to create multiple forms of bioenergy. The wind, sun and water produce electricity. Geothermal can produce electricity and heat. Biogas can be used to produce electricity, heat, pipeline grade gas and a liquid fuel.
These benefits translate into significant added value. AD can help solve two problems with the implementation of a single action---the need to produce renewable energy is achieved while eliminating harmful climate change emissions created by current waste management practices. An added value is that another goal can be supported - the need to maximize the diversion of waste from landfill.
And every person can contribute, everywhere, because we all generate organic waste and that will never change because we all need to fuel ourselves, everyday.