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Sludge Is Power Utilizing microturbines to produce heat and energy from wastewater treatment plant sludge Diane McDilda, Distributed Energy, March/April 2009. "Wastewater treatment plants are looking for ways to utilize the biogas they produce to generate their own power and heat while reducing their methane emissions. Possibly creating a closed loop, where both the offsite electricity and methane emissions become obsolete. Methane is generated in the anaerobic digester, a solids management system that reduces both the volume and toxicity of sludge. Sludge originates in the plant’s primary and secondary clarifiers, where microorganisms consume bacteria under aerobic conditions and then settle out, respectively. Waste-activated sludge from the secondary clarifier is a slurry, at 2–4% solids, and requires additional treatment or disposal. According to a November 2008 study by BCC Research, the North American and international market for sludge treatment is growing. One method of treating waste-activated sludge is anaerobic digestion, where sludge is processed into methane, carbon dioxide (CO2), and nutrient-laden solids that can be suitable as soil amendments. The EPA estimates that in 2006, wastewater treatment plants produced 4% of the anthropogenic, human-made, methane emissions, generating the equivalent of 23.9 teragrams of carbon dioxide (Tg CO2 Eq) or, in terms of emissions, 23.9 million metric tons of CO2. This level has remained relatively constant since 1990. With respect to methane produced as part of managing waste in the US, wastewater treatment plants fall between landfills that create 125.7 Tg CO2 Eq, and composting that generates 1.6 Tg CO2 Eq annually. With a heating value of 1,000 Btu per cubic foot (Btu/cf) alone, or approximately 600 Btu/cf when mixed with the other components of biogas, biogas can easily be flared to destroy the methane. But flaring doesn’t utilize the potential energy. By employing technologies such as microturbines, plants can harness the energy of biogas while reducing carbon emissions. Microturbines join a cast of other technologies that make use of the thermal and energy benefits of methane, including boilers, reciprocating engines, and fuel cells, with fuel cells and microturbines being the most avant-garde." http://www.distributedenergy.com/march-april-2009/sludge-is-power.aspx -- ********************************************************************** Dr. Ann C. Wilkie Tel: (352)392-8699 Soil and Water Science Department Fax: (352)392-7008 University of Florida-IFAS P.O. Box 110960 E-mail: [log in to unmask] Gainesville, FL 32611-0960 ______________________________________________________________________ Campus location: Environmental Microbiology Laboratory (Bldg. 246). http://campusmap.ufl.edu/ ______________________________________________________________________ BioEnergy and Sustainable Technology Society http://grove.ufl.edu/~bests/ **********************************************************************