Copyright Anders Damgaard & Morton A. Barlaz, NC State University 1
The Application of Life-Cycle Analysis to Waste Management
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 2
Objective
• Introduction – what is LCA and how is it useful – 4 phases
• Goal and scope defintion• Inventory analysis• Impact assessment• interpretation
– The basis for engineering of plants and systems• mass balances• energy budgets• emission accounts
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 3
Integrated Solid Waste Management Collection Recycling Biological Treatment by Composting and
Anaerobic Digestion Waste-to-Energy (thermal processes) Landfill with or without energy recovery Many alternatives for solid waste
management have some positive aspects– large differences in cost
What is “best” for the environment?
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 4
Integrated Solid Waste Management
Should we recycle ONP instead of waste-to-energy?
Should we make compost or methane out of grass?
Should we recycle to save landfill space if it actually consumes more energy than waste burial?
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 5
Life-Cycle Analysis
How do we even begin to answer these questions and others?– plastic versus disposable diapers– comparison of alternate product delivery systems?
– plastic versus glass packaging– recyclable versus refillable bottles?
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 6
Life-Cycle Analysis
What is it?What can it do?What are the limitations?How to use it to make engineering decisions?
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 7
What Is It?
An objective process to evaluate the environmental burdens associated with a:– product– process– activity
By identifying and quantifying energy and materials used and wastes released to the environment,And to evaluate and implement opportunities to effect environmental improvements.(SETAC Code of Practice, 1991)
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LCA for products
• LCA introduced in product manufacturing in early 1980s
• From “cradle-to-grave”• The approach has been
standardized (ISO 14040-46)• Several models are available
with large databases:– Gabi– SimaPro– Eco-invent (database)
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 9
System boundaries
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 10
LCA- product-waste-interface
• In product LCA the waste is often treated superficially : tons of waste, tons of ash, etc. – when landfilled or burned. Recycling better but not consistently treated
• Containers for milk were the first studies really linking product-LCA with waste - the results varied a lot because of insufficient consistency in boundary issues and large variation in data quality
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 11
LCA- Waste
• LCA introduced in waste management in mid 1990s• Waste LCA is system based, often focusing on a service: e.g.
management of waste from city• From “bin-to-grave” or “curbside to grave”• The waste in itself is often considered a “zero-burden-boundary”
– Waste is the starting point, it exists• LCA on waste management offers a holistic approach to assess
resource issues and emissions in waste management • LCA helps avoid “problem-shifting”• LCA help in decision-making when choosing among alternatives
– Narrow down multiple options to a few for detailed study
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System boundaries 3 – LCA of waste
“Zero burden”
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LCA- 4 phases
• Definition of the goal and scope • Inventory analysis:
Preparing an inventory of inputs and outputs from all processes within the system
• Impact assessment:Using the results of the inventory analysis to prepare environmental impact and resource consumption profiles for the system
• Interpretation of the impact profile and resource consumption
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Elements of LCA
Direct applicatione.g. product development
marketingecolabellingpublic policy making
Goal & scopedefinition
InterpretationInventoryanalysis
Impact assessment
Direct applicatione.g. product development
marketingecolabellingpublic policy making
Direct applicatione.g. product development
marketingecolabellingpublic policy making
Goal & scopedefinition
InterpretationInventoryanalysis
Impact assessment
Goal & scopedefinitionGoal & scopedefinition
InterpretationInterpretationInventoryanalysisInventoryanalysis
Impact assessmentImpact assessment
Ref. ISO 14044
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LCA is an iterative exercise
Interpretation
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Environmental BurdensTypical:
CO2 – fossil vs. biomassNOxSOxEnergy – renewable vs. fossil?particulatesCOhydrocarbonsBODCODHeavy MetalsNutrients - NO3-N, NH3-N, PO4-P
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Carbon Dioxide – fossil, biomass and storage
CO2 is removed from the atmosphere to grow forest products (paper, wood) and agricultural products. When these products decay, the CO2 is returned to the atmosphere. If these products do not decay, then the carbon is considered to have been sequestered.
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 18
Environmental BurdensTypical:
CO2 – fossil vs. biomassNOxSOxEnergy – renewable vs. fossil?particulatesCOhydrocarbonsBODCODHeavy MetalsNutrients - NO3-N, NH3-N, PO4-P
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 19
Environmental BurdensPerhaps Others:
Water consumptionSolid wasteLand useResource consumption
- renewable - a tree- non-renewable - fossil fuel or an element
Cost?
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How Do We Start? Definition of study objective and system
boundaries A framework to rigorously define the product,
process or activity to be studied:– waste sources– waste constituents– solid waste unit operations– remanufacturing processes & energy recovery
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Phase 1: Scope
• The objective of the study – the functional unit• The boundaries of the system and exchanges over boundaries• The assessment criteria to be applied• The time scale of the study• The technologies representing the different processes• Allocation for processes entering into other systems as well
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Functional UnitThe service provided, the function of the system is defined in a way allowing comparison – it defines the objective of the comparison• 1 ton of MSW as generated• 1 ton of MSW set out for collection
• excludes backyard composting, in-house recyclables management
• 1 ton of MSW (or MSW + other) arriving at the landfill• Packaging studies – delivery of 12 oz of juice• Quantity of waste to be managed • Composition of waste • Duration of the waste management service • Quality of the waste management (legal emission limits,
requirements for residual products)
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Scope 1: Example on functional unit definition
Waste generationMSW
Incinerator40,000
Mineral waste landfill
40000 tonnes
Ashes
APC residue
Iron to recycling
Electricity
RDF Plant
Waste generationSludge
14000 tonnes
RDF:Currently shipped for co-combustion
in coal plant
APC landfill
Rest of the waste30.000 tonnes
Landfill
Metal recycling Glass recyclingLandfill of inerts and non useable
RDF waste
Old Incinerator line
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Goal Definition
• The goal definition describes the purpose of the study and the decision process to which it provides environmental decision support
• The goal should be defined as close as possible to the decisions to be made, to the consequences of the decision
• LCA is often used for comparing alternatives– Consequential vs. attributional LCA – Atrributional – average situation– Consequential – marginal changes
• Does a landfill tax in one state decrease landfilling or increase transport across state boundaries with more emissions
• Energy Offsets• Biofuels mandates
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System BoundariesInclude all that is relevant, include only what is relevant. This is an iterative process
Issues to consider:• The infinite nature of the product
system/cut-of-limits• Allocation or system expansion• System expansion:
- Attributional approach (substitution is average)- Consequential approach (substitution is marginal)
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Scope 2: System expansion/substitution
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Assessment criteria
Why are we doing LCA- what do we want to protect?
SETAC Working group on Impact Assessment:Four areas of protection:• human health• ecosystem health• natural resources• man-made materials
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Assessment criteria• Which methodology
– EDIP (Environmental Design of Industrial Products)– TRACI– And many more
• Global impacts:- Global warming- Ozone depletion
• Regional impacts:- Photochemical ozone formation- Acidification- Terrestrial and aquatic eutrophication- Human toxicity- Ecotoxicity
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Assessment criteria
• Local impacts:- Land use- Odor- Division of habitats- Radiation- Accidents
• Local toxicity- Stored toxicity- Spoiled groundwater resources
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Assessment criteria
Consumption of non-renewable resources:• Oil• Natural gas• Iron• AluminumConsumption of renewable resources:• Forest biomass• Agricultural biomass• Groundwater• Freshwater
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Temporal and technological scope
What are the temporal dimensions for the use of the LCA?• requirements on future validity of results• time horizon for impacts and equivalency factors• need for forecasting and trend analysis for key processes taking
place in the future– use stage – emissions from landfills
• Choice of technology for the different processes• average, best available, worst case, …?
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Quantifies resource and energy consumption, and environmental emissions associated with all processes in a system emissions are post-treatment
apply to collection, MRF, landfill, combustion
Will refer to this as:Life-Cycle Inventory (LCI)
II. Inventory Analysis
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Mass balance (conceptual)
Waste system:
Waste
Fuel, water, etc.
Emissionsto atmosphere
Remanufacturing
Use on land
WastewaterEmission to water and soil
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Example: Mass balance
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Mass balance (conceptual)
Incinerator:
Waste
Ancillary products:Lime, act. carbon,water, etc.
Stack emissionsto atmosphere
Bottom ash
APC-residues
Sludge
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Mass balances, energy and emissions
• Mass balance:– All generated waste as well as residues from treatment are kept
track of (nothing forgotten)– All emissions can be conceptually identified by evaluating all
discharges from the waste system, intended or unintended• Energy budgets:
– All energy consumed (fuels, electricity etc.) is known– All energy containing outputs can be utilized
• Emission accounts:– Direct environmental loads can be monitored, assessed and
maybe reduced– Indirect or pre-combustion emissions are included
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Example: Emission account
Meaning of <0
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Remanufacturing
• When recyclables are converted to new products:– resource consumption and emissions are
associated with recyclables collection and remanufacture
– some remanufacture from virgin is avoided and there are implications for resource consumption and emissions
• Combustion is a net producer of energy and this offsets energy produced from utilities
• Landfill gas can also be converted to energy
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Material substitution - processes/crediting
Material recycling:
Processing of recovered materials – A x Saved virgin production
If the reprocessing and the virgin production takes place at the same plant and in the same process then estimation of the GW benefit of recycling is possible and likely to be correct
If the reprocessing takes place at a separate plant (e.g paper mill) there is no direct link between reprocessing and the avoided virgin production
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Example: Energy budget
41Copyright: Anders Damgaard & Morton A. Barlaz, NC State University
The Energy Grid
http://www.eei.org/industry_issues/industry_overview_and_statistics/industry_statistics/index.htm
coal, 48.6
nuclear, 19.4
gas, 21.5
hydro, 5.8
oil, 1.6
renewabale, 2.5
other, 0.6
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ElectricityFruergaard, T., Ekvall, T. & Astrup, T. (2009) Energy use and recovery in waste management andimplications for accounting of greenhouse gases and global warming contributions.
Waste Management & Research, Special Issue , November.
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Collection Activities
environmentalemissions energy
consumption
natural resourcesconsumption
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Collection Activities
environmentalemissions
energyconsumptionnatural resources
consumption
systemboundary
© M.A. Barlaz
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 45
Collection Activities
environmentalemissions
energyconsumptionnatural resources
consumption
systemboundary
© M.A. Barlaz
Precombustion energy
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 46Copyright Morton A. Barlaz, NC State University
46
MSW Generation Mixed WasteCollection
Landfill Disposal
A Solid Waste Management Alternative
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 47
SWM Alternative 1 - TOTAL
SWM Alternative 2 - TOTAL
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• Step 1: Selection of impact categories and classification
• Step 2: Characterization
• Step 3: Normalization
• Step 4: Weighting
• Step 1-2 are mandatory, step 3-4 are voluntary (4 with caution)
III. Impact Assessment 4 Assessment Steps
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Typical LCIA Outputs
• Global warming• Ecotoxicity• Cancer/Non-cancer chronic health effects
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4 assessment steps
• Step 1: Selection of impact categories and classification
• Step 2: Characterization
• Step 3: Normalization
• Step 4: Weighting
• Step 1-2 are mandatory, step 3-4 are voluntary (4 with caution)
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4 assessment steps
Classification: Assignment of emissions to impact categories according to their potential effects
• “What does this emission contribute to?”Characterization: Quantification of contributions to the different
impact categories• “How much does it contribute?”Normalization: Expression of the impact potentials relative to a
reference situation• “Is that much?”Valuation: Ranking, grouping or assignment of weights to the different
impact potentials• “Is it important?”
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Selection and classification of impacts
• Refer to the scope in phase 1:– Do we still find it relevant with the original impact categories
assumed?• Midpoint versus endpoint• What contributes to which categories (software to do this for you)
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Phase 3: Assessment criteria
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Characterization• What is the impact of each substance we chose in the classification
above– e.g. 1 kg of CH4 has a GWP of 25 kg CO2-equivalents (IPCC 4th
assessment report)– These factors are calculated in the methodologies applied, and the
main importance is understanding what each methodology assumes – Calculated via the following two formulas
Q= QuantityIF=Impact factorJ = impact categoryi= substance
iii jIFQjIP )()(
i
iii
i jIFQjIPjIP )()()(
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Characterization• What is the impact of each substance we chose in the classification
above– e.g. 1 kg of CH4 has a GWP of 25 kg CO2-equivalents (IPCC 4th
assessment report)– Calculated via the following two formulas
CO2e kg 260N2O kgCO2e kg298N2O kg 01.0
CH4 kgCO2e kg25CH4 kg 10
f-CO2 kgCO2e kg1f-CO2 kg 7)(
landfillgwpIP
remfgmrfcollectionlandfill gwpIPgwpIPgwpIPgwpIPgwpIP )()()()()(
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Normalization
• A way to put a comparative study on a common scale.• Done by assuming an average release (or consumption) for a
person (e.g., a person equivalent)– e.g. 1 PE wrt. to global warming is 8700 kg CO2-equivalents
• Calculated based on:
)()()(jNRjIPjNIP NIP = Normalized impact
NR = Normalization reference
PE 03.0
PECO2e kg8700
CO2e kg 260)( landfillgwpNIP
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NormalizationComparing across categories• which are the largest environmental impacts?• is it the environmental impact or the resource consumption that is
largest?Reliability control• Is it realistic that the waste treatment contributes as much as this
number of persons?CommunicationThe person equivalent• how large a part of my impact is caused by the waste treatment?The environmental space currently occupied per person
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Weighting of resourcesWeighting expresses the relative scarcity of the resource
Supply horizon (SH): For how many years can the current extraction continue, given the known reserves?
Non-renewable resources:
• reserve: economically exploitable• reserve base: technically exploitable
– The weighting factor is based on the reserve
Known reserves of resource i (per person)Annual consumption of resource i (per person)SH(i) =
950 x 109 mton7.7 x 109 mton/yr
SH(coal) = = 120 years
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4 phase: Interpretation
• Consider goal, scope and results together• Improvement assessment• Sensitivity analysis: Address uncertainty
(boundary choices, incomplete inventories, data uncertainty)• Decision support regarding environmental issues: In real world also
social aspects and economy
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Landfill Life-Cycle Analysis
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Landfill Life-Cycle Analysis
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Limitations
The decisions on what inventory parameters are most critical may be site-specific
– NOx may be more important in some areas of U.S. than others; so too for water consumption
– Multi-criteria decision-making– emissions location: local/global
Similar data across unit operations must be available to do meaningful comparisons
Copyright Anders Damgaard & Morton A. Barlaz, NC State University 64
How Can It Be Applied?
Evaluation of alternate solid waste management strategies Improvement assessment
Guide for product design or product use Present policy makers with sound technical
information in an easily understood format The life-cycle framework offers an opportunity to
present credible information Hopefully, we will be able to use this framework to
bring science and policy together
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