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Raw Materials Extraction Material manufacture Component Manufacture Material processing Module Assembly Product Processing/assembly Use Transport Recycle/

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Presentation on theme: "Raw Materials Extraction Material manufacture Component Manufacture Material processing Module Assembly Product Processing/assembly Use Transport Recycle/"— Presentation transcript:

1 Raw Materials Extraction Material manufacture Component Manufacture Material processing Module Assembly Product Processing/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

2 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 system 2.Life cycle Inventory 3.Life cycle impact assessment (LCIA) 4.Improvement Analysis

3 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

4 Example of system boundary Meth-tert-butyl ether (MTBE) – oxygenate replaced lead in gasoline Compare lead LC to MTBE petroleum extraction refiningdistributionuse Pb LC lead emissions to atmosphere petroleum extraction refiningdistributionuse MTBE LC no lead narrow boundary MTBE leaks into water  carcinogen wider boundary

5 Boundaries cont’d  general 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

6 b) Functional Unit  per kg, m 3, energy unit etc…  determines equivalence between options e.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 lifetimes e.g. plastic bag vs. cloth sack  cloth option may have lower volume but longer lifetime

7 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)

8 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

9 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

10 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)

11 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

12 i. Classification  inputs/outputs are put into relevant environmental impact category, examples of categories below: IMPACTEXAMPLES OF TYPES OF INPUT/OUTPUT Global Warming Potential (GWP)CO 2,H 4,N 2 O, CFCS etc… Ozone Deletingchlorofluorocarbons (CFCs) Human Carcinogensbenzene Acidification NO x, SO x Aquatic Toxicitypesticides Terrestrial ToxicityPCBs Habitat DeteriorationDams Eutrophicationammonia Depletion of Non-renewable Energy

13 GWP Factors (100 yr) Atmospheric Lifetimes (Years) GasAtmospheric LifetimeGWP a Carbon dioxide (CO 2 ) Methane (CH 4 ) b 12±321 Nitrous oxide (N 2 O) HFC ,700 HFC HFC ,800 HFC-134a14.61,300 HFC-143a48.33,800 HFC-152a HFC-227ea36.52,900 HFC-236fa2096,300 HFC-4310mee17.11,300 CF 4 50,0006,500 C2F6C2F6 10,0009,200 C 4 F 10 2,6007,000 C 6 F 14 3,2007,400 SF 6 3,20023,900

14 ii. Characterization  Quantification of impacts for each inventory item  integrates environmental impact with potential (potency) to cause harm  Use potency factors  weighting factors potency factor * inventory value = impact score e.g. GWP of CO 2 = 1, for CH 4 = 21 (100 yr value). So if process produces 20 tonnes/kg of product of CO 2 and CH 4 of 2 tonnes/kg CO 2  20 tonnes/kg product CH 4  42 tonnes/kg product for total of  62 tonnes/kg

15 ii. Characterization cont’d  potency factors must take into account temporal and spatial factors ImpactSpatial ScaleTemporal Scale global warmingglobal10-100s yrs e.g. CH 4 has 20 yr GWP 62 ozone depleteglobal10s yrs smogregional/localhours-days Acid Rainregional/continentalyrs Aquatic Toxicregionalyrs Terrestrial Toxlocalhours-years Habitat Dest.regional/localyrs-10s yrs Eutrophicationregional/localyrs

16 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

17 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

18 Limits to LCA  time  uncertainty in inventory  uncertainty in potency factors  temporal/spatial aggregation of data (i.e. how do we combine data from different locations or seasons?)  Valuation step is subjective


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