Process-BasedLife Cycle Assessment:

H. Scott Matthews

Civil and Environmental Engineering /

Engineering and Public Policy

Carnegie Mellon University

Admin Issues

• HW #1 due today• Friday Sessions

– And last 2 weeks of February

• HW #2 Out tonight

Simplified LCA procedure in practice

• Draw a process flow diagram• Identify required data• Based on the data quality requirements set,

start to gather data from (1) on-site visit, (2) survey, (3) literatures, (4) model calculation, (5) databases.

• Data validation• Prepare an inventory table

Streamlined LCA

• Reading on website (for today)• Summary, anyone?• Admits there is a “continuum” or

spectrum of needs and requirements when doing LCA– Suggest various boundaries appropriate– Choices of inputs/output/etc ok

LCA patterns of use

• More for larger firms than smaller.• More a tool for a pull strategy than for a push

strategy.• Acceptance substantially vary among countries (more

accepted by developed countries than developing countries).

• LCA started to become a part of the regulatory system in Europe but not in the US.

Source: Frankl&Rubik, 1999

Important applications of LCA perceived by industries

Growing and harvestingcotton

Seed removalPacking in bales

FertiliserPesticides

25 MJ

Pr oduct ion of

polyest er

48 MJ

Pr e-t r eat ment , bleaching, (dyeing), post -t r eat ment

Bleaching agent s, sodium hydrox ide, opt ical

br ight ener, ant i shr inking agent s

30-80 lit er wat er

25- 90 MJ

Reuse0 ,1 * 1 kg

S ewing of unif or m

1 kg

Wash (100x)

2500 lit er wat er1,5 kg washing agent

600 MJ

S pinningSpinning oil

6 MJ

Ext r uding,

cut t ing and packing

7 MJ

Use (100x)I nciner at ion

0 ,8 * 1 kg

Deposit0 ,1 * 1 kg

Dr ying, ir oning,

pr essing (100x)

200 MJ

WeavingSize

20 MJ

S pinningSpinning oil

6 MJ

Ext r act ion of

oil and nat ur al gas

0 ,5 kg 0,5 kg

Credit ingheat & power

19 MJ

Credit ingunif orm

0,1 * 1 kg

Credit ingindoor heat ing

in t ot al 200 MJ

Disposal

Use

Resources and materials

Manufacture

Example of process-flow diagram(aggregated): Source: Hauschild, 2003

Product system of a uniform (cloth)

Example of “required data” table (Inputs and outputs table - part) (source: International Aluminum Institute, 2003)

Example of inventory result (part) (source: International Aluminum Institute, 2003)

Revisit Example - walking through how to use NREL data - Electricity Generation

Data We Have from NREL• Electricity Generation• Anthracite and Bituminous Coal Production and

Combustion• Natural Gas Extraction and Processing• Nat Gas Combustion• Uranium Production and Consumption• Oil Combustion in Power Plants• Petroleum Refining• Biomass combustion in power plants• Rail, truck, etc. transportation

If we want to identify CO2 used to make electricity

• How might we streamline?• And why?• Assumptions?• Validity?

To make 1 kilowatt-hour (kWh) of electricity..

Conversions from Last time..• What is total energy (GJ) required to make electricity?

• Conversions: 1 lb coal ~ 12000 BTU– 1 BTU =1054 Joule; – Gasoline ~ 125000 BTU/gallon– Distillate (e.g., diesel) ~ 135,000 BTU/gallon– Residual ~ 150,000 BTU/gallon– 1 ft^3 of natural gas ~ 1000 BTU– Truck transportation ~2500 BTU/ton-mile

Source: EIA Annual Energy Review, 2006

Draw our Streamlined Process (LCA) Diagram

Some Factors of Interest• Bituminous Coal Combustion

– 2250 lbs CO2 / 1000 lbs coal• Bituminous Coal Production

– 4 lbs methane/1000 lbs coal (Methane = 21x CO2)• Nat gas extraction / processing

– 0.64 lbs methane / 1000 cubic feet gas• Nat gas extraction / processing

– 122 lbs CO2 / 1000 cubic feet gas• Uranium Production

– 1750 lbs CO2 / 1000 lbs Uranium dioxide

Our weighted average

• 1 kWh of electricity requires..– 0.53 lbs coal + 1.82 cu ft gas + 1.4 E-6 lbs

UO2 + (all other fuels)

• CO2 Per kWh: 0.53*(2250+80)/1000 + 1.82*(122+12)/1000 + (1.4 E-6)*1.75– 1.2 + .24 + ~0– 1.45 lbs CO2 / kWh– Comments so far?

Validate: E-GRIDhttp://www.epa.gov/cleanenergy/egrid/index.htm

• Note: Combustion only!• Nat gas: 1.1 lbs/kWh• Coal: 2.2 lbs/kWh• So our overall total given 50% coal,

19% gas should be at least..– 0.5*2.2 + 0.19 * 1.1 = 1.1 + 0.2 = 1.3 lbs

CO2/kWh

Thoughts

• Our streamlined “LCI” of electric generation in the US (with many caveats) quickly approaches the value used by DOE/EPA

• Should we add other types of generation?• Expected effects?• How much is enough? • What does ISO tell us?

Paper vs. Plastic Grocery Sacks: Comparison of Three Studies

Allen & Bakshani

Graedel & Allenby

Ciambrone

PE

60,790 sacks

Energy

[M BTU]

40 40 34

Air pollution [lb] 73 76 59

Paper

30,395 sacks

Energy

[M BTU]

50 49 39

Air pollution [lb] 195 198 49

In-Class Assignment• Suppose you need to choose a new copier for

an office. In a small group:– Define appropriate goals and scope for a life cycle

cost and environmental life cycle assessment.– Define appropriate environmental indicators (e.g.

electricity or energy use).– Define major benefit or cost categories to consider– Develop a set of processes to be considered (i.e.

inputs and outputs identified and estimated).• We will have reports from groups by end of

period.

Example: Copier LCA• In GaBi demo, explore under Processes,

Production, Materials, Metal• Look at steel (3 options)• Can also see plastic, etc options• Double click to see inputs/outputs

– Generally shows normalized impacts for 1kg of output item (eg 1 kg of ABS plastic)

– The data records refer to a process that requires many inputs, and produces 1 kg of ABS plastic (as well as many other outputs)

Complexity

• We’ve been looking at fairly small, streamlined LCI problems

• How does the method scale?