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Solid Waste and Life-Cycle Assessment Resources

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Workshops
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2017 Sardinia Symposium Life-Cycle Data Quality and Accessibility (slides below)
Life cycle assessment (LCA) frequently relies on disparate and heterogeneous data sources, thus, data quality information is needed to evaluate the reliability of a study. Data indicators are case-dependent, and data quality assessment of these indicators is often non-transparent and subjective. Transparency can be enhanced by adapting the data quality indicators to the characteristics of the technical domain of interest. Data quality and documentation is important both for the researcher carrying out the study to be able to interpret the results correctly, and data quality indicators are also important for the reader of a study to evaluate the quality of the results, and to determine how well the results can be transferred to other areas with similar technologies, waste materials and systems.
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1. Introduction to Data Quality

2. Data Transparency

3. Data Representativeness

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2017 WASTECON - ISWA World Congress (slides below)

Proper management of solid waste is essential to minimize risks to human health and the environment. Solid waste management (SWM) is a highly visible and potentially high-impact target for enhancing environmental sustainability. However, there are numerous competing alternatives for increasing environmental sustainability such as, recycling, energy recovery, and organics treatment. These potential alternatives must be systematically evaluated to ensure that SWM strategies cost-effectively protect human health and the environment. Life-cycle assessment (LCA) provides the necessary systematic framework for estimating the environmental impacts associated with alternative SWM processes and systems. Life-cycle process models that estimate emissions and resource use from solid waste unit processes (e.g., collection, composting, landfills) form the foundation of SWM LCAs. We are proposing a half-day workshop to describe and discuss the state-of-the-art for modeling solid waste processes and to identify key research needs and areas for potential improvement. Each session will include a presentation on the state-of-the-art for a given process as well as time for questions, comments, and discussion. Discussion topics include modeling of waste-to-energy combustion, composting, anaerobic digestion, landfills, and uncertainty management.

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1. Introduction

2. AD and Composting

3. Landfill

4. Material Recovery and Reprocessing

5. Waste-to-Energy Combustion

6. Integrated Assessment Case Studies

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2015 Sardinia Symposium Life-Cycle Modeling Workshop (slides below)

There are many alternatives for the management of solid waste including recycling, biological treatment, thermal treatment and landfill disposal.  In many cases, solid waste management systems include the use of several of these processes.  Solid waste life-cycle assessment models are often used to evaluate the environmental consequences of various waste management strategies.  The foundation of every life-cycle analysis is the development and use of process models to estimate the emissions from solid waste unit processes.  The objective of this workshop was to describe the state-of-the-art for the modeling of the solid waste processes and to identify opportunities for improvement and the need for additional research.   The first part of each session was used to explain the state-of-the-art for a given solid waste process model and the remainder of the time will be devoted to input and discussion.  The full day Workshop  included discussions on the modeling of collection, material recovery facilities, combustion, offsets from remanufacturing, composting, anaerobic digestion, landfills and management of uncertainty.

 
  1. Introduction

  2. Collection

  3. Material Recovery Facilities

  4. Waste Combustion

  5. Remanufacturing and System Interaction

  6. Composting

  7. Anaerobic Digestion

  8. Bioresidue Use-On-Land

  9. Landfill

  10. Ucertainty and Sensitivity Analysis

 
 
 
Presentations and Videos
Check out our YouTube Channel
 
Why Life-Cycle Modeling for Solid Waste Management?

Life-cycle assessment (LCA) is widely used to estimate the environmental and economic impacts associated with products, processes, and systems. Numerous tools and models have been developed to address the unique challenges associated with solid waste management (SWM) processes and systems. LCA is a unique and powerful tool for SWM and can answer questions such as:

 

• Is it better to compost, anaerobically digest, burn, or landfill food waste?

• What are the costs associated with:

  o reducing environmental impacts from solid waste processes or systems?

  o making alternative SWM decisions (e.g. implementing combustion or recycling)

• What are the net environmental implications of recycling?

• What process(es) in the solid waste system lead to the most emissions?

 

 
Introduction to Life-Cycle Assessment
Life-cycle assessment (LCA) is a systematic framework for estimating the environmental emissions and impacts associated with a product, process, or system. LCA is an iterative process that consists of four primary stages: (1) Goal and Scope Definition, (2) Life-Cycle Inventory (LCI), (3) Life-Cycle Impact Assessment (LCIA), and (4) Interpretation and Improvement. The Goal and Scope Definition stage defines the purpose of the LCA, the product or system to be assessed (i.e., a functional unit), and the environmental emissions and impacts to be considered. The LCI calculates all of the input and output flows of mass and energy for each process in the system, and the LCIA characterizes the environmental impacts associated with the emissions and mass flows calculated in the LCI (e.g., global warming potential from CO2, CH4, and N2O). Finally the Interpretation and Improvement stage reviews the results of the LCA and ensures that each of the stages are consistent with each other (e.g., the analysis matches the purpose defined in the Goal and Scope Definition) and identifies potential areas for improvement in a process or system.
 
 
 
 
Life-Cycle Modeling of Solid Waste Systems and Processes in SWOLF
Solid waste management (SWM) requires the coordination of numerous interrelated processes from collection through separation, treatment, and final disposal. The operation and performance of each process affects the performance of each downstream process. For example, how well a generator separates yard wastes will affect the performance and contamination at the composting facility as well as the generation methane at the landfill. SWM systems also interact with energy systems through the use and production of electricity and fuel. Each of these interrelated processes must be considered to understand the full life-cycle impacts of SWM processes, systems, and policy choices. 
 
 
 
 
 
 
 
 
 
Collection Process Modeling
Solid waste collection is a primary contributor to cost, emissions, and fossil fuel use associated with solid waste management (SWM). A collection process model was developed as part of the Solid Waste Optimization Life-cycle Framework (SWOLF). The collection model can be used within SWOLF or as a stand-alone tool to represent user-defined collection schemes. Using data to represent a site-specific scenario, the model determines total energy consumption, emissions and cost per ton of waste collected. Input parameters were developed from an empirical data set gathered from observation of collection activities and from operational data obtained from industry and government. A dataset developed from empirical values was used in a validation analysis to predict fuel consumption and compare the model-generated values with operational observations. The validation analysis was used to demonstrate the model functionality, provide sample scenario comparisons, and illustrate model sensitivity to select inputs.
 
 
 
 
 
Composting Process Modeling
Composting is a method of biological treatment for organic components of municipal solid waste (MSW) (e.g., food and yard wastes). Composting involves the aerobic biodegradation and stabilization of organic materials into a useful soil amendment material. Composting process models were developed as part of the Solid Waste Optimization Life-cycle Framework (SWOLF) for windrows, aerated static piles, GORE cover systems, and in-vessel composting processes. Using empirical energy consumption and performance data to represent a set of common composting technologies, the model estimates emissions directly associated with compost processing as well as benefits associated with avoided fertilizer or peat use.  This presentation provides an overview of the composting process model, key inputs, and illustrative results.
 
 
 
 
 
 

Anaerobic Digestion Process Modeling
Anaerobic digestion (AD) is process for treatment of readily degradable organic components of municipal solid waste (MSW) (e.g., food and yard wastes). The AD process involves biodegradation of organic materials and collection of the produced biogas for energy recovery.  In addition to energy, a useful soil amendment that can avoid the use of fertilizers or peat is also produced. An AD process model was developed as part of the Solid Waste Optimization Life-cycle Framework (SWOLF). Using empirical performance data to represent a site-specific scenario, the model estimates biogas and resulting energy production, tracks solids and water through the user-specified process configurations, and calculates energy and material inputs required.  This presentation provides an overview of the AD process model, including its capabilities and limitations, and illustrative results. 
 
 
 
 
 
 
 
Material Recovery Facility Process Modeling
A process model was developed to estimate the cost, mass of recoverable material, and electricity and fuel demand from material recovery facilities (MRFs) that receive aluminum, ferrous, glass, old corrugated containers (OCC), mixed paper, and several types of plastic (e.g., HDPE, PET).  The model was developed for the Solid Waste Optimization Life-cycle Framework (SWOLF) and includes modules for facilities that process single-stream, dual-stream, and pre-sorted recyclables, as well as mixed waste.  A mass balance is conducted at each piece of separation equipment until all waste is sorted into recovered streams of recyclables and a residual stream.  The mass balance is then combined with representative equipment motor sizes and costs, as well as facility construction costs and lighting demand, to calculate total cost and resource use. The four MRF modules were used with industry data to show differences in energy use and cost across MRF types.
 
 
 
 
 
 
Beneficial Material Reprocessing
After materials are separated in a material recovery facility, they must be reprocessed into useful products. The beneficial recovery of materials via recycling leads to emission offsets due to the avoided production of virgin materials. For example recycling aluminum cans including losses during reprocessing avoids the production of aluminum cans from virgin aluminum ore. The remanufacturing model developed for the Solid Waste Optimization Life-cycle Framework (SWOLF) includes the emissions and energy use associated reprocessing as well as the avoided virgin production emissions. The presentation will discuss recovery of paper, plastic, metals, and glass and show illustrative results.
 
 
 
 
 
 
 
 
 
Thermal Conversion and Waste-to-Energy Process Modeling
Waste-to-energy (WTE) combustion is the primary form of thermal conversion used in solid waste systems. Approximately 12% of U.S. municipal solid waste (MSW) is currently treated in WTE facilities. The WTE process model for the Solid Waste Optimization Life-cycle Framework (SWOLF) considers emissions at a combustion facility as well as generated electricity that avoids grid electricity production. Emission factors for greenhouse gases, criteria pollutants, and metals are calculated. The WTE process model considers the energy content of each material as well as the heat lost to moisture and ash for each material. The WTE process also allows ferrous and non-ferrous metals to be recovered and for bottom ash to be beneficially used. The model, key inputs, and illustrative results are presented. 
 
 
 
 
 
 
 
 
Landfill Process Modeling
The World Bank estimates that 340 million metric tons of municipal solid waste (MSW) are currently landfilled annually (excluding dumps), and this may grow to 570 million metric tons by 2025 due to increases in population, urbanization, and economic development. The U.S. EPA estimates that 135 million metric tons of MSW were disposed in U.S. landfills, which are currently estimated to be the third largest source of anthropogenic methane in the U.S. behind natural gas systems and enteric fermentation. The SWOLF landfill process model estimates the costs and environmental emissions associated with landfill construction, operations, closure, and post-closure including landfill gas and leachate generation and management. Previous life-cycle assessment (LCA) studies have shown that the manner in which landfill gas is managed has the most significant impact on the overall global warming potential (GWP) of a landfill, so the SWOLF landfill process model calculates 100 year temporally averaged collection and oxidation efficiencies associated with each material based on landfill operation. The modeling framework, key inputs, and illustrative results are presented.  Landfills that either flare or utilize the gas beneficially can be represented.
 
 
 
Overview of SWOLF and Illustrative Results
While previous research has applied environmental life-cycle assessment (LCA) to solid waste management (SWM) using formal search techniques, existing models are either not readily generalizable and scalable, or optimize only a single time period and do not consider changes likely to affect SWM over time, such as new policy and technology innovation. The Solid Waste Optimization Life-cycle Framework (SWOLF) presents the first life cycle-based framework to optimize—over multiple time stages—the collection and treatment of all waste materials from curb to final disposal by minimizing cost and environmental impacts, while considering user-defined emissions, waste diversion constraints and future changes in energy and GHG prices. Specifically, the framework allows for the cost of energy and emissions to change over time in response to policy changes (e.g., cap and trade, carbon tax).  The framework considers the use of existing SWM infrastructure as well as the deployment and utilization of new infrastructure.  SWOLF was used to illustrate how a typical suburban U.S. city can proactively and sustainably adapt their SWM system over the next 30 years including potential changes in the energy system.
 
 
 
 
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