DIGESTER GAS CLEANING REQUIREMENTS BASED ON END USE

The anaerobic digestion process, used for solids stabilization at municipal wastewater treatment facilities, is a net producer of energy in the form of digester gas that can be used to offset part of the energy requirements for plant operations. However, there are several challenges associated with the use of digester gas as an alternate fuel source. As generated from the digesters, the gas contains several contaminants that can increase the maintenance requirements of the equipment fueled by the gas. A multi-step cleaning process is often called for to improve the gas quality. The capacity requirements and costs of the gas treatment system can depend on several variables, including the quantity of gas treated, the initial concentration of contaminants, and the final concentration of contaminants in the gas to meet the quality requirements for the gas utilization equipment. Not all applications require the gas to be of high quality and there can be significant differences between the gas quality requirements for different gas utilization equipment.The paper provides an overview of the typical problems associated with handling and using digester gas without adequate cleaning, a decision matrix to determine the cleaning requirements based on the end use, and the technologies available for cleaning the gas to meet the specified quality requirements.