S WOLF. Life-Cycle Modeling of Solid Waste Processes and Systems.

Transcription

1 Life-Cycle Modeling of Solid Waste Processes and Systems Jim Levis, PhD Research Assistant Professor Department of Civil, Construction, and Environmental Engineering S WOLF

2 Model Objective Provide a tool and evaluate solid waste system performance (i.e., economical, environmental) while accounting for changes to waste composition and generation, SWM policy, the U.S. energy system, and potential future GHG mitigation policies. Solid Waste Optimization Life-cycle Framework (SWOLF) LCA Model GHG Policy Impact Assessment Model (e.g., Global Warming, Smog Formation) Energy System SWM Process Models Optimizable Integrated SWM System Model Cost Emissions Energy Use Impacts SWM Policy Waste Generation and 2 Composition

3 Solid Waste Systems Material Reprocessing Waste Generation Collection Treatment/ Separation Disposal

4 Solid Waste Systems

5 Solid Waste Management in the U.S Survey of Waste Generation and Disposition in the U.S U.S. EPA MSW Facts and Figures 5

6 Functional Unit The functional unit of LCA s assessing solid waste systems is a mass of generated waste in the area of interest over a specified time period. E.g., mass of MSW generated in Wake County, NC over the next 30 years If performing a static analysis usually 1 ton is the baseline and it is scaled as necessary

7 Waste Generation Sectors Three types of waste generation sectors: Single-family residential (SF) Multi-family residential (MF) Commercial (COM) User creates any number of sectors, and defines the following inputs for each sector: Sector type Population and number of stops (e.g. houses, buildings) Waste generation rate and composition Collection services offered Waste destinations (treatment or disposal facility)

8 Process level life-cycle assessment models form the foundation of this work Process models are developed bottom-up to determine the costs, emissions, and environmental impacts associated with each process in consideration of waste quantities and composition Process models are then linked using mass balance equations to develop full system models Included Processes Collection Transfer stations Material recovery facilities Anaerobic digestion Composting Landfills Material reprocessing Waste-to-energy Process modeling 8

9 Generic process model for cost and life-cycle emissions estimation Incoming Waste Materials (Mg in ) Direct Emissions (kg/mg in ) Equipment Fuel Use (L/Mg in ) User Inputs Generic Process Model Stored Mass (Mg stored / Mg in ) Electricity Use (kwh/mg in ) Transportation Use (kg-km/mg in ) Capital Cost ($/Mg-yr -1 ) Operating Cost ($/Mg in ) Physically Separated Materials (e.g., recyclables, residuals) (Mg out / Mg in ) Biologically/ Chemically Transformed Materials (e.g., ash, compost) (Mg9 out / Mg in ) Process models determine downstream mass flows

10 Integrated SWM system boundaries Gross Emissions Electricity, fuel, and raw material extraction and processing LCA System Boundary Electricity Fuel Raw Materials MSW SWM System Remanufacturing Comingled Single Recyclable Stream Collection MRF Ash WTE Landfill Mixed Waste/ Mixed Residual Waste Collection MRF Generated Electricity Compost Electricity Generation Soil Amendments Avoided Emissions Avoided Emissions Organics Collection Anaerobic Digestion Soil Amendment Composting Landfill Recyclables Remanufacturing Avoided Emissions Gross Emissions 10

11 NERC Electricity Regions 1.08 kg 0.42 kg 0.61 kg 1.07 kg 0.80 kg 0.76 kg National Average 0.71 kg 0.76 kg 0.76 kg

12 GWP (kg CO 2 e/mg Mixed MSW) Effects of Electric Grid Mix on Life-Cycle Emissions kg MRO/HICC/SPP 0.71 kg U.S. Average 0.42 kg NPCC High Med-High Medium Med-Low Low kg FRCC/RFC/SERC/TRE 0.61 kg WECC Landfill WTE

13 Acknowledgments 13