Monitoring Flow Rates From a Biogas Digester
A biogas digested (or biodigester) breaks down organic matter in an anaerobic biological process that not only decomposes plant and animal matter, but produces biogas (consisting of methane and carbon dioxide). Many types of organic waste products can be used in a biogas digester, including food waste, plant material, and manure from livestock. Anaerobic digestion processes occur naturally in any oxygen free environment, for example when organic matter is buried under the soil, muddy substrates of lakes and dams, or under ocean sediments. They can also occur under more controlled conditions such as those found in a specially designed biodigester or biogas plant. In the latter, organic waste material, such as manure from livestock, is placed into an airtight biodigester together with various kinds of anaerobic bacteria -- bacteria that flourish in an oxygen-free environment. The anaerobic bacteria then start to feed on the organic matter, breaking it down in three phases: 1. Decomposition: the first phase of the anaerobic digestion process consists of the decomposition (or hydrolysis) process. In this process organic plant and animal matter is broken down into smaller molecules (i.e. sugars). 2. Organic Acids: in the second phase, the decomposed material is converted into organic acids. 3. Methane Gas: in the third, and final phase of the anaerobic digestion phase, the organic acids are converted into methane gas. Depending on the biogas systems design, and the type of waste used in the biodigester, biogas typically tends to consist of between 55-75% pure methane. Highly sophisticated biodigester systems can produce biogas that contains more than 95% pure methane. Aerobic digestors are now commercially available and can be used with agricultural organic waste, or to treat industrial and municipal wastewater. In many of these cases unprocessed waste material would typically result in odors and water contamination, whereas anaerobic digestion minimizes odors and problems associated with the disposal of liquid waste, producing biogas that can be used as a fuel for heating or to generate electricity.