Digester Gas Powers Energy Conservation at Baltimore's Back River WWTP

Performance contracting provided the City of Baltimore and the Back River Wastewater Treatment Plant with the expertise and guaranteed savings to warrant implementation of a significant digester gas utilization system as well as other energy saving facility improvements.The Back River process for wastewater treatment results in digested solids and methane gas, a good portion of which was burned off with flares up to 20 feet in the air visible from the surrounding area. The new cogeneration process will clean and utilize essentially all of the methane gas burned on-site and use it, thus reducing the need for flares. Some gas will be used in existing boilers and heaters, and the rest will run the generators that produce electricity. This process will reduce the city's purchase of electrical power by 1.4 million annually and effectively utilize the methane gas produced at Back River.The savings resulting from reducing the amount of electricity purchased was sufficient to pay for the capital cost of the new facilities and other benefits including:Annual reduction of 19.4 million kWh of purchased electricity for plant operations.14 million over ten years in energy savings and plant improvement projects.Annual reduction of 12.9 million pounds of carbon monoxide and 7.7 grams of nitrogen oxide from electric power plantsThe following is a description of a unique process used to develop, implement, and finance the project.