The Application of Life-Cycle Analysis to Waste … lca part 1...• In product LCA the waste is...

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Copyright Anders Damgaard & Morton A. Barlaz, NC State University 1

The Application of Life-Cycle Analysis to Waste Management

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

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?

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?

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?

Life-Cycle Analysis

What is it?What can it do?What are the limitations?How to use it to make engineering decisions?

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)

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)

System boundaries

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

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

System boundaries 3 – LCA of waste

“Zero burden”

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

Elements of LCA

Direct applicatione.g. product development

marketingecolabellingpublic policy making

Goal & scopedefinition

InterpretationInventoryanalysis

Impact assessment

Goal & scopedefinition

InterpretationInventoryanalysis

Impact assessment

Goal & scopedefinitionGoal & scopedefinition

InterpretationInterpretationInventoryanalysisInventoryanalysis

Impact assessmentImpact assessment

Ref. ISO 14044

LCA is an iterative exercise

Interpretation

Environmental BurdensTypical:

CO2 – fossil vs. biomassNOxSOxEnergy – renewable vs. fossil?particulatesCOhydrocarbonsBODCODHeavy MetalsNutrients - NO3-N, NH3-N, PO4-P

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.

Environmental BurdensTypical:

CO2 – fossil vs. biomassNOxSOxEnergy – renewable vs. fossil?particulatesCOhydrocarbonsBODCODHeavy MetalsNutrients - NO3-N, NH3-N, PO4-P

Environmental BurdensPerhaps Others:

Water consumptionSolid wasteLand useResource consumption

- renewable - a tree- non-renewable - fossil fuel or an element

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

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

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)

Scope 1: Example on functional unit definition

Waste generationMSW

Incinerator40,000

Mineral waste landfill

40000 tonnes

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

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

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)

Scope 2: System expansion/substitution

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

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

Assessment criteria

• Local impacts:- Land use- Odor- Division of habitats- Radiation- Accidents

• Local toxicity- Stored toxicity- Spoiled groundwater resources

Assessment criteria

Consumption of non-renewable resources:• Oil• Natural gas• Iron• AluminumConsumption of renewable resources:• Forest biomass• Agricultural biomass• Groundwater• Freshwater

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, …?

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

Mass balance (conceptual)

Waste system:

Fuel, water, etc.

Emissionsto atmosphere

Remanufacturing

Use on land

WastewaterEmission to water and soil

Example: Mass balance

Mass balance (conceptual)

Incinerator:

Ancillary products:Lime, act. carbon,water, etc.

Stack emissionsto atmosphere

Bottom ash

APC-residues

Sludge

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

Example: Emission account

Meaning of <0

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

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

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

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.

Collection Activities

environmentalemissions energy

consumption

natural resourcesconsumption

environmentalemissions

energyconsumptionnatural resources

consumption

systemboundary

environmentalemissions

energyconsumptionnatural resources

consumption

systemboundary

Precombustion energy

Copyright Anders Damgaard & Morton A. Barlaz, NC State University 46Copyright Morton A. Barlaz, NC State University

MSW Generation Mixed WasteCollection

Landfill Disposal

A Solid Waste Management Alternative

SWM Alternative 1 - TOTAL

SWM Alternative 2 - TOTAL

• 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

Typical LCIA Outputs

• Global warming• Ecotoxicity• Cancer/Non-cancer chronic health effects

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)

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?”

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)

Phase 3: Assessment criteria

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 jIFQjIPjIP )()()(

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 )()()()()(

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

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

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

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

Landfill Life-Cycle Analysis

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

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

The Application of Life-Cycle Analysis to Waste … lca part 1...• In product LCA the waste is...

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