Transcript Process LCA Wrap-up - Civil and Environmental Engineering

Introduction to Input-Output
Based LCA
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Structure of a Process-based LCA
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How Research is Done…
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Sitting around in an office, we were
complaining about problems of LCA
methodology.
Realized economic input-output models could
solve boundary and circularity problems.
Then hard work – assembling IO models,
linking to environmental impacts and testing.
Found out later that Leontief and Japanese
researchers had done similar work, although
not directly for environmental life cycle
assessment.
Economic Input-Output
Analysis
Developed by Wassily Leontief (Nobel Prize
in 1973)
 “General interdependency” model: quantifies
the interrelationships among sectors of an
economic system
 Identifies the direct and indirect economic
inputs of purchases
 Can be extended to environmental and
energy analysis
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The Boundary Issue
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Where to set the boundary of the LCA?
“Conventional” LCA: include all processes, but at least
the most important processes if there are time and
financial constraints
In EIO-LCA, the boundary is by definition the entire
economy, recognizing interrelationships among
industrial sectors
In EIO LCA, the products described by a sector are
representing an average product not a specific one
Circularity Effects
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Circularity effects in the economy must be accounted for: cars are made
from steel, steel is made with iron ore, coal, steel machinery, etc. Iron ore
and coal are mined using steel machinery, energy, etc...
R
E
S
O
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C
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S
waste
product
emissions
system
boundary
Building an IO Model
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Divide production economy into sectors (Note:
could extend to households or virtual sectors)
Survey industries: Which sectors do you
purchase goods/services from and how much?
Which sectors do you sell to? (Note: Census of
Manufacturers, Census of Transportation, etc.
every 5 years)
Building an IO Model (II)
Form Input-Output Transactions
Table – Flow of purchases between
sectors.
 Constructed from ‘Make’ and ‘Use’
Table Data – purchases and sales
of particular sectors. (Note: need to
reconcile differing reports of
purchases and sales...)
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Economic Input-Output Model
Input to sectors
Output from sectors
1
2
3
n
Intermediate input I
Va lue added V
Total input X
 Xij + Yi = Xi;
 (Aij*Xj) + Yi =
1
X11
X21
X31
Xn1
I1
V1
X1
2
X12
X22
X32
Xn2
I2
V2
X2
3
X13
X23
X33
Xn3
I3
V3
X3
n
X1n
X2n
X3n
Xnn
In
Vn
Xn
Xi = Xj; using Aij = Xij / Xj
Xi
in vector/matrix notation:
A*X + Y = X =>
Y = [I - A]*X
or X = [I - A]-1*Y
Intermediate
output O
Final
demand Y
Total
output X
O1
O2
O3
On
Y1
Y2
Y3
Yn
X1
X2
X3
Xn
GDP
Building an IO Model (III)
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Sum of Value Added (non-interindustry
purchases) and Final Demand is GDP.
Transactions include intermediate product
purchases and row sum to Total Demand.
From the IO Transactions Model, form the
Technical Requirements matrix by dividing each
column by total sector input – matrix A. Entries
represent direct inter-industry purchases per
dollar of output.
Scale Requirements to Actual
Product
Engine
$20,000
Car:
Steel
Other
Parts
$2500
Engine:
...
$2500 $2000 $1200 $800
$300
Steel
$10
Plastics
$200
$150
...
Aluminum
$10
Example: Requirements for
Car and Engine
Engine
Car:
Steel
0.125 0.1
0.06
Other
Parts
Engine:
0.12
Steel
...
0.04
0.0005
Plastics
0.08
0.06
...
Aluminum
0.004
Using a Requirements
Model
Columns are a ‘production function’
or recipe for making $ 1 of good or
service
 Strictly linear production
relationship – purchases scale
proportionally for desired output.
 Similar to Mass Balance Process
Model – inputs and outputs.
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Mass Balance and IO
Model
Racing
Engine
Steel
Etc.
Car Production
(Motor Vehicle Assembly)
Etc.
Final Demand
Supply Chains from
Requirements Model
Could simulate purchase from
sector of interest and get direct
purchases required.
 Take direct purchases and find their
required purchases – 2 level
indirect purchases.
 Continue to trace out full supply
chain.
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Leontief Results
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Given a desired vector of final demand
(e.g. purchase of a good/service), the
Leontief model gives the vector of sector
outputs needed to produce the final
demand throughout the economy.
For environmental impacts, can multiply
the sector output by the average impact
per unit of output.
Supply Chain Buildup
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First Level: (I + A)Y
Second Level: A(AY)
Multiple Level: X = (I + A + AA + AAA + … )Y
Y: vector of final demand (e.g. $ 20,000 for auto
sector, remainder 0)
I: Identity Matrix (to add Y demand to final
demand vector)
A: Requirements matrix, X: final demand vector
Direct Analysis – Linear
Simultaneous Equations
Production for each sector:
 Xi = ai1 X1 + ai2 X2 + …. + ainXn + Yi
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Set of n linear equations in
unknown X.
 Matrix Expression for Solution:
X(I - A) = Y <==> X = (I - A)-1 Y
 Same as buildup for supply chain!
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Life Cycle Stages
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At each stage, there are some inputs
used and some outputs created that
need to be identified
Example: automobile production
– Direct: smoke from factory
– Indirect: smoke from suppliers’ factories
Effects Specified
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Direct
» Inputs needed for final production of
product (energy, water, etc.)
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Indirect
» ALL inputs needed in supply chain
» e.g. Metal, belts, wiring for engine
» e.g. Copper, plastic to produce wires
» Calculation yields every $ input needed
Recall: Supply Chain Exercise
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See posted spreadsheet
EIO-LCA Implementation
Use the 491 x 491 input-output matrix of
the U.S. economy from 1997
 Augment with sector-level environmental
impact coefficient matrices (R) [effect/$
output from sector]
 Environmental impact calculation:
E = RX = R[I - A]-1 Y
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Data Sources in EIO-LCA (1997)
Data
Latest
Source
Year
Available
Economic input -output matrix
1997
U.S. Dept. of Commerce
Electricity consumption
1997
U.S. Dept. of Commerce
Fuel use
1997
U.S. Dept. of Commerce
Toxic chemical emissions (TRI)
2000
U.S. EPAΥsTRI database
Conventiona l air pollutant emissions
1999
U.S. EPAΥs AIRS database
EIO-LCA Software
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Internet version http://www.eiolca.net/
About 1 million users to date
About 1,500 registered users
– update notices
– other benefits
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First LCA tool completely free on Internet in
full version (not a ‘demo’)