Least-Cost Replacement Planning for Modular Construction of Landfills

Abstract

The scheduling and economies of scale for municipal landfill liner and leachate-collection system construction are commonly neglected in policy and planning studies, but are shown to significantly affect the economics of landfilling and, thus, integrated solid-waste-management systems. Economic methods for estimating least-cost landfill module sizes and construction schedules are presented. The principal findings are twofold: (1) modular or phased development significantly reduces the discounted cost of landfilling; and (2) for disposal rates less than about 1,000 tons/day, discounted liner and leachate-collection system cost is highly sensitive to the module service life, even with modest economies of scale. This second result indicates that 46% of the nation's landfills, which receive 58% of the nation's waste, may benefit from least-cost module replacement planning, especially as improved source reduction and recycling efforts further reduce disposal rates. The least-cost module replacement interval is fairly robust to uncertainties in waste-to-cover ratio and specific weight of wastes. A case study compares landfill cost reductions from least-cost modular development and from delay of current landfill closure and replacement due to a 25% reduction in landfill disposal rate.