Orange County NC Website
Browse       Search
<br /> Comprehensive Review of <br /> S olid W aste Collection and Disposal Options <br /> <br /> <br />v2.1 169 10/22/12 <br />Exhibit 12 -8. Basic Autoclave Process <br /> <br /> <br /> <br />12.4.2 Biological <br />There are two types of biological processes being utilized for WC. These include the anaerobic <br />and aerobic process technologies. The following paragraphs briefly describe these technologies. <br />12.4.2.1 Anaerobic Process <br />Anaerobic digestion is the bacterial breakdown of organic materials in the absence of oxygen. <br />This biological process produces a gas, sometimes called biogas, principally composed of <br />methane and carbon dioxide. The anaerobic process is often used to treat organic wastes other <br />than nonsegregated MSW, and that is where it is used the most. This anaerobic process is used <br />to digest sewage sludge (i.e., biosolids – produced from treated sanitary sewage), yard <br />vegetation, agricultural wastes (both animal and plant) and some industrial waste sludge. The <br />number of plants processing these materials is currently in the thousands worldwide. <br /> <br />The anaerobic digestion process occurs in three steps: <br /> <br />1. Decomposition of plant or animal matter by bacteria into molecules such as sugar. <br />2. Conversion of decomposed matter to organic acids. <br />3. Organic acid conversion to methane gas. <br /> <br />Depending on the waste feedstock and the system design, biogas is typically 55 to 75% methane. <br />A basic anaerobic process is shown in Exhibit 12-9. <br /> <br /> <br /> <br />