Anaerobic digesters are biological facilities that turn waste or biofuel crops into biogas. This biogas is then used to create electricity, or cleaned compressed and pumped into the natural gas grid or used to produced a biofuel such as bio-diesel.
When suitable organic material is put into the digester, anaerobic microbes (methanogens) digest the waste and produce mainly methane as a by-product.
The process is able to reduce odors and pathogens in manure and is may make some farms more viable.
Anaerobic digesters carry out the process of anaerobic digestion which is the subject of this web site.
In anaerobic digesters, the aim is usually nowadays to produce methane gas, however the anaerobic digestion facilities may perform dual functions, and also be useful for the manner in which they treat the feedstock. So much so in some cases that they may be considered to be a waste disposal method achieving diversion of waste away from landfill.
It is important to note that this process must always take place in the absence of oxygen. Otherwise, depending on the type of microbes used, the microbes will start producing carbon dioxide and water or will die.
Anaerobic digesters more specifically are airtight tanks that take organic waste such as animal manure and ferment it. By limiting access to any oxygen during the reaction in the digester, the digester uses the microbes in the waste to create the methane and carbon dioxide.
The process may be run as a batch digestion process, which has a distinct sequence of operation from charging the reactor through gas production and ending with the emptying and discharge of the batch at the end of the cycle. On the other hand the digester may be run as a continuous process, in which case the feedstock (usually a waste material) is continually added all the time. In either process, the most critical aspect is the need for a consistent very warm to hot temperature throughout.
Anaerobic digestion was researched scientifically during the 1930’s when it gained academic. It was in doing this basic research that scientists discovered of anaerobic bacteria; these being the microorganisms that carry-out the methane production process.
Organic material or “biomass” is made up from large organic polymers. In order for the bacteria in anaerobic digesters to access the energy potential of the material, these chains must first be broken down into their smaller constituent parts. One of the fundamental problems toward establishing the most efficient biogas digesters is the ability to break up those long chain molecules during the process and quickly enough to allow an economically viable biogas digester.
Anaerobic digesters are very good for the disposal of animal waste and if done correctly the odor of animal waste can also be avoided. Farmers and especially dairy farmers faced with increasing federal and state regulation of the waste are keen to explore the biogas digester as one of their best options to assist them in complying with new farm waste regulations.
More new digesters are being built every year, because they can eliminate many environmental environmental hazards of dairy farms, followed almost as closely by other non-arable farmers.
With the implementation of ever increasing requirements for livestock farmers to store slurry longer before it can be spread on the fields, and the high cost of large slurry storage tanks and lagoons which bring in no income, many people are looking at the potential for building a smaller slurry storage capacity, plus an AD plant. This brings a new income source, and the slurry storage need only be the much smaller volume needed for treatment, plus storm storage.
