Life cycle GHG emissions of MSW landfilling versus Incineration: Expected outcomes based on US landfill gas collection regulations.

From a GHG perspective, most LCA studies find incineration (MSWI) to be preferred over landfilling because of high energy recovery offsets. In some studies, however, landfilling results in less greenhouse gases (GHG) emissions than MSWI. We investigated using LCA, the landfill gas (LFG) collection efficiencies and waste composition that led to landfills resulting in less GHG emissions. Then, we explored what theoretical minimum lifetime gas collection efficiencies can be expected when following US LFG regulations. Only landfills with high LFG collection efficiencies (at least 81%) and recovery of methane for energy resulted in less GHG emissions compared to the management of the same waste stream in MSWI; required efficiency increased to 93% without LFG energy recovery. Expected theoretical lifetime LFG collection efficiencies were modeled in the range of 30-80%, with the lower rates associated with landfills having smaller input masses, high decay rates, and low concentrations of nonmethane organic compounds (CNMOC). Our modeling found that only under a limited combination of conditions (e.g., high CNMOC, high waste input rate, low decay rate) could a landfill expect to achieve a LFG collection efficiency as high as 80%, and that this value falls just under the 81-93% collection efficiency threshold needed for a landfill to result in less GHG emissions than MSWI. When exploring the influence of higher oxidation rates, changing decay rates, varying electricity grids, and inclusion of nonferrous metals recovery offsets the collection effciency range needed increased in nearly all cases; the electricity grid and nonferrous metals offsets had the greatest influence.

Moving beyond recycling: Examining steps for local government to integrate sustainable materials management.

Recently, local governments experienced unprecedented challenges to their recycling programs and are looking to alternative forms to meet their sustainability goals. Traditionally, waste management policies focus on using a mass-based recycling rate to promote and measure sustainability, however that metric inadvertently promotes recycling over source reduction. Here, we present a metric which measures a community's greenhouse gas (GHG) and energy use footprints for their consumed and end-of-life material streams. Using materials and waste statistics for Florida as an example, we estimated the consumed and discarded masses of 24 materials in 2018. We developed methods and used existing (i.e., WARM, literature) lifecycle assessment data to measure upstream and end-of-life environmental footprints of these materials. The total upstream footprints were approximately 12 and 10 times larger than the end-of-life GHG emissions and energy use footprints, respectively, indicating the need for sustainable materials management application. Mixed paper, cardboard, mixed construction and demolition (C&D) materials had the largest lifecycle footprints. We then use these data to illustrate a method for local governments to apply the alternative metric referred to as the lifecycle footprint reduction target. We demonstrate this target's application in Florida using a hypothetical 20% footprint reduction and provide approaches which focus on increasing the source reduction and recycling potentials of key materials to meet the target. The approaches included a junk mail ban, food donation mandate, cardboard takeback mandate, and building deconstruction mandate and were evaluated for their feasibility in meeting the target; the building deconstruction and the food donation mandate resulted in the greatest and least progress, respectively, toward meeting the target. These approaches provide local government a baseline for continued progress toward SMM application.Implications: Consumer consumption of manufactured products - the packaging for our food and beverages, the products in our homes and offices, the vehicles we drive, and the buildings we live and work in - ultimately must be discarded at the end of their useful life. It is through the management of residential and commercial solid waste that local governments face the consequences of society's materials consumption. Thus, not surprisingly, materials conservation efforts at the government level focus primarily on efforts to recycle waste and divert these materials from landfill disposal. Here we examine a concept whereby local governments - normally charged with collecting and managing residential and commercial waste, and thus setting waste recycling targets - expand their thinking to include all life cycle phases for the materials consumed and discarded in their jurisdiction. In doing so, local governments can now shift from a waste management to a lifecycle-oriented perspective and expand beyond just managing waste to managing materials.

Characterizing municipal solid waste component densities for use in landfill air space estimates.

Understanding the densities of individual waste materials in landfills as a function of landfill overburden pressure can provide a means to estimate the space occupied by these materials when they are landfilled. A compression device was used to simulate the overburden pressures in a landfill to determine the densities associated with 14 material categories. The materials with the greatest density were food waste, yard waste, and glass, ranging from 1302 to 1865 kg m-3. The lowest density was associated with aluminum and steel/tin cans at 206 and 389 kg m-3, respectively. Some materials did not exhibit a large variation in density when the load increased, indicating that their density was mostly independent of the overburden pressure. The data gathered from this research can be used as lifecycle assessment impact categories, where the functional unit of interest is 1 tonne of a material and the impact is measured as m3 of landfill space occupied.

Replacing Recycling Rates with Life-Cycle Metrics as Government Materials Management Targets.

In Florida, the passing of the Energy, Climate Change, and Economic Security Act of 2008 established a statewide mass-based municipal solid waste recycling rate goal of 75% by 2020. In this study, we describe an alternative approach to tracking performance of materials management systems that incorporates life-cycle thinking. Using both greenhouse gas (GHG) emissions and energy use as life-cycle indicators, we create two different materials management baselines based on a hypothetical 75% recycling rate in Florida in 2008. GHG emission and energy use footprints resulting from various 2020 materials management strategies are compared to these baselines, with the results normalized to the same mass-based 75% recycling rate. For most scenarios, LCI-normalized recycling rates are greater than mass-based recycling rates. Materials management strategies that include recycling of curbside-collected materials such as metal, paper, and plastic result in the largest GHG- and energy-normalized recycling rates. Waste prevention or increase, determined as the net difference in per-person mass discard rate for individual materials, is a major contributor to the life-cycle-normalized recycling rates. The methodology outlined here provides policy makers with one means of transitioning to life-cycle thinking in state and local waste management goal setting and planning.