Raw MaterialsExtraction

Material manufacture

Component Manufacture

Material processing Module Assembly

ProductProcessing/assembly

Use

Transport

Recycle/Reuse Disposal

1. Premanufacture

2. Product/Process Manufacture

3. Product Delivery

4. Use

5. Recycle/Reuse/Dispose

waste

energy

waste

energy

raw material

waste

energy

waste

energy

energy

Life cycle Assessment (LCA) purpose is to give quantitative and

qualitative information to identify and prioritize impacts of product/process

Range from very detailed over all life stages to specific part of product life

Four major steps:1. Scope system2. Life cycle Inventory3. Life cycle impact assessment (LCIA)4. Improvement Analysis

1. Scope/Boundary Definition identify product/process/service chose functional unit set temporal/spatial boundaries

a) system boundaries- narrow boundaries less data

collected/analysis required, may miss important impact

- wide boundaries more accurate but may be impractical

Example of system boundaryMeth-tert-butyl ether (MTBE) – oxygenate replaced lead in gasoline

Compare lead LC to MTBE

petroleum extraction

refining distribution usePb LC lead emissionsto atmosphere

petroleum extraction

refining distribution useMTBE LC no lead

narrow boundary

MTBE leaks into water carcinogen

wider boundary

Boundaries cont’dgeneral rule of thumb is common sense

and include any part of LC that accounts for 1-3% of energy use, raw material, wastes or emissions

b) Functional Unit per kg, m3, energy unit etc… determines equivalence between optionse.g. paper vs. plastic bags

- not appropriate to use “number of bags used” as it doesn’t reflect volume/mass bags can hold (e.g. kg)

account for different product lifetimese.g. plastic bag vs. cloth sack cloth option

may have lower volume but longer lifetime

2. Life Cycle Inventory (LCI) material and energy inputs/outputs

quantified

i. Major categories of inputs/outputs

Energy requirements (e.g. MJ/kg)

Feedstock energy (MJ)

Nonfuel raw material use (mass)

Atmospheric emissions (mass)

Wastewater emissions (mass)

Solid Waste (mass)

ii. Co-products- if process produces multiple products

may have to “allocate” wastes/energy use

- usually allocate based on mass but if co-product is a by-product (i.e. wouldn’t be produced unless product was produced) then may weight allocation

iii. Recycled - allocation of input and outputs may be

weighted if the product is made from recycled material (i.e. do include energy that went into original products?)

e.g. Fleece jackets are made of polyethylene tetraphthalate which is from recycled plastics

iv. Quality of Data- direct measurements or engineering

estimates

v. Data Aggregation- Merging of data and scale of analysis- some impacts are global (greenhouse

gas emissions) and some regional (wastewater emissions to water body)

3. LCIA In this step combine overall quantities of

wastes, and raw materials/energy requirements with impacts on the environment

Purpose is to convert inventory data into an estimate of environmental impact

Made up of two steps: classification characterization

i. Classification inputs/outputs are put into relevant environmental

impact category, examples of categories below:IMPACT EXAMPLES OF TYPES

OF INPUT/OUTPUT

Global Warming Potential (GWP) CO2,H4,N2O, CFCS etc…Ozone Deleting chlorofluorocarbons (CFCs)Human Carcinogens benzene

Acidification NOx, SOx

Aquatic Toxicity pesticidesTerrestrial Toxicity PCBsHabitat Deterioration DamsEutrophication ammoniaDepletion of Non-renewable Energy

GWP Factors (100 yr)

Gas Atmospheric Lifetime GWPa

Carbon dioxide (CO2) 50-200 1

Methane (CH4)b 12±3 21

Nitrous oxide (N2O) 120 310

HFC-23 264 11,700

HFC-32 5.6 650

HFC-125 32.6 2,800

HFC-134a 14.6 1,300

HFC-143a 48.3 3,800

HFC-152a 1.5 140

HFC-227ea 36.5 2,900

HFC-236fa 209 6,300

HFC-4310mee 17.1 1,300CF4 50,000 6,500C2F6 10,000 9,200C4F10 2,600 7,000C6F14 3,200 7,400

SF6 3,200 23,900

ii. Characterization Quantification of impacts for each inventory item

integrates environmental impact with potential (potency) to cause harm

Use potency factors weighting factorspotency factor * inventory value = impact score

e.g. GWP of CO2 = 1, for CH4 = 21 (100 yr value). So if process produces 20 tonnes/kg of product of CO2 and CH4 of 2 tonnes/kg

CO2 20 tonnes/kg product

CH4 42 tonnes/kg product for total of 62 tonnes/kg

ii. Characterization cont’d potency factors must take into account temporal

and spatial factors

Impact Spatial Scale Temporal Scaleglobal warming global 10-100s yrs e.g. CH4 has

20 yr GWP 62ozone deplete global 10s yrssmog regional/local hours-daysAcid Rain regional/continental yrsAquatic Toxic regional yrsTerrestrial Tox local hours-yearsHabitat Dest. regional/local yrs-10s yrsEutrophication regional/local yrs

ii. Characterization cont’d Potency factors and weighting factors may

vary according to the method used to determine them (not for GWP as this is universal)

Methods may be based on different criteria: different environmental regulations relative risk different end points

4. Valuation This step involves putting a “value” on the results of

step 3: emissions could be weighted based on legal limits and

aggregation of contaminant in each medium (air, water, soil) OR

combine the “characterization” step and valuation to get a single weighting factor OR

combine the “characterization” step and valuation based on flows of emissions/resources relative to the ability of the environment to absorb waste or provide resources

This step is VERY subjective and often a LCA will be stopped at Step 3

Limits to LCA timeuncertainty in inventoryuncertainty in potency factors temporal/spatial aggregation of data

(i.e. how do we combine data from different locations or seasons?)

Valuation step is subjective