Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. One of the end products is biogas, which is combusted to generate electricity and heat, or can be processed into renewable natural gas and transportation fuels. A range of anaerobic digestion technologies are converting livestock manure, municipal wastewater solids, food waste, high strength industrial wastewater and residuals, fats, oils and grease (FOG), and various other organic waste streams into biogas, 24 hours a day, 7 days a week. Separated digested solids can be composted, utilized for dairy bedding, directly applied to cropland or converted into other products. Nutrients in the liquid stream are used in agriculture as fertilizer.
TDigester Technologies Many different anaerobic digester systems are commercially available. The following is an overview based on organic waste stream type (manure, municipal wastewater treatment, industrial wastewater treatment and municipal solid waste): Manure: Anaerobic digestion systems for livestock manure operate to reduce methane emissions, odors, pathogens and weed seeds and produce biogas. They fall into four general categories: Covered anaerobic lagoon digester: Sealed with flexible cover, with methane recovered and piped to the combustion device. Some systems use a single cell for combined digestion and storage. Plug flow digester: Long, narrow concrete tank with a rigid or flexible cover. The tank is built partially or fully below grade to limit the demand for supplemental heat. Plug flow digesters are used at dairy operations that collect manure by scraping. Complete mix digester: Enclosed, heated tank with a mechanical, hydraulic, or gas mixing system. Complete mix digesters work best when there is some dilution of the excreted manure with water (e.g., milking center wastewater). Dry Digestion: Upright, silo-style digesters made of concrete and steel with rigid cover. Dry digesters operate at 20 to 42 percent total solids, which allows them to combine high dry matter manure and crop residuals with very dilute liquid manures or co-substrates.
Using reliable, cost effective and energy efficient blower for aeration are with an integral flow management system and enter the biological treatment stage where it is aerated with fine bubble membrane diffuser. The continuous supply of oxygen together with the incoming food source encourage microorganism to grow on the surface of the submerged media, convening the waste water in to CO2 and water in the process.