LANDFILL GAS PIPELINE PROJECT REQUIRES AGGRESSIVE SCHEDULE TO ACHIEVE SIGNIFICANT ENERGY SAVINGS FOR MILORGANITE® PRODUCTION

摘要

The Milwaukee Metropolitan Sewerage District (MMSD), located in Milwaukee, Wisconsin, pioneered the beneficial conversion of wastewater sludge, or biosolids, into a soil amendment marketed as a product named Milorganite®. As is common in most wastewater treatment facilities, the biosolids are wasted from the treatment process in liquid form followed by a thickening process. The thickened sludge is then dried further and stabilized using heat. MMSD currently uses natural gas to provide the heat to dry the biosolids and produce the Milorganite® product. Natural gas is used to drive turbine generators for power production at the plant. The waste heat from the turbines is also used in the Milorganite® process.In 2008, natural gas prices hit record highs, and MMSD and their contract operator, Veolia Water Milwaukee (VWM), realized that alternative sources of energy were needed to reduce the dependence on natural gas and the vulnerability to huge increases in operating costs. A viable source of alternative fuel was identified at the Emerald Park Landfill. MMSD estimates that the use of landfill gas (LFG) will save the ratepayers $148 million over 20 years. LFG is the byproduct of the decomposition of municipal solid waste in anaerobic conditions in capped landfills. Although LFG is used in many locations for either power generation or heat production, the majority of LFG is burned, or flared, at the landfill. When LFG is used beneficially, however, it is usually on site or piped to a facility located a short distance away. Unfortunately, in this case, the Emerald Park Landfill is located over 17 miles away from the Jones Island Water Reclamation Facility (JIWRF) where the Milorganite® is produced.This paper will review the challenges presented by the project, including planning, designing, and constructing a pipeline from the landfill to the WRF; meeting the regulatory and permitting requirements; and satisfying the contract requirement to have gas flowing by January 1, 2011 (18 months from Design Notice to Proceed).Specifics include maximizing the use of available data in terms of GIS mapping; coordination with several concurrent road improvement projects in multiple jurisdictions; avoidance of historic, cultural, and environmental resources, including threatened and endangered species habitats; and establishing design and operational parameters to qualify for low pressure transmission status in the gas pipeline regulatory environment.Other potential time and cost savings measures are also described. These include bidding strategies and advance procurement of pipe materials, as well as evaluation of the use of an existing, mothballed, steel petroleum pipeline. This existing pipeline would reduce the length of new construction by 25 percent and eliminate impacts to the most heavily developed residential area along the route. Condition assessment of the existing pipeline and gas quality parameters are discussed in terms of using the steel pipeline as is or whether it must be sliplined.