CDM News - August 2007 - (Page 10)

Perspective: Harnessing Bioenergy By David L. Parry, Ph.D., P.E., BCEE For utility managers at today’s wastewater treatment plants, rising energy and operating costs are ever-present challenges. Increasing electric and natural gas rates, combined with energy demands, contribute to these escalating costs, while rising oil prices continue to adversely affect transportation expenses, such as biosolids hauling. And at the same time, there is positive, encouraging interest in being “green”—using renewable energy and reducing greenhouse gas emissions—that bodes well for the future of our environment. So how can a utility manager reduce energy costs, while embracing environmental stewardship? One solution is bioenergy. In essence, bioenergy refers to managing the energy associated with biosolids, which includes the residual solids resulting from wastewater treatment. Harnessing biogas for use at wastewater treatment plants reduces greenhouse gases by decreasing a plant’s reliance on purchasing electricity and natural gas to fuel its operations. What is Biogas? Biogas is a byproduct of anaerobic digestion—a proven, safe biological process that has been used for decades, typically at wastewater treatment plants that serve more than 50,000 people. Thickened wastewater solids are heated from 95 to 98 degrees Fahrenheit for about 20 days in the presence of anaerobic micro-organisms that decompose the solids, thus producing stable biosolids and biogas. Biogas is composed of 60 to 65 percent methane and 35 to 40 percent carbon dioxide, with trace amounts of hydrogen sulfide, siloxanes, and particulates, and is saturated with water vapor. As such, it is primarily composed of methane, or natural gas— commonly used for home heating and cooking. Biogas powers a molten carbonate fuel cell at a wastewater treatment plant.

Table of Contents Feed for the Digital Edition of CDM News - August 2007

Contents Envisioning Tomorrow’s Dublin Initiative & Innovation Stabilize Mercury Mines Preserving Old Town Alexandria Taking a Hard Look at Concrete Corrosion Perspective: Harnessing Bioenergy Engineering Better Lives CDM Announces Award-Winning Projects People Highlights

CDM News - August 2007

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