sustainability - SUNY College of Environmental Science and Forestry

Sustainability 2011 , 3
1891

known as bottom-up analysis and akin to life-cycle analysis, accounts for the energy inputs and outputs
in a process by aggregating them through the sequential stages of production. Economic input-output
analysis, or top-down analysis, converts economic input-output tables into energy units by multiplying
by sector-specific energy intensity values. A third method is emerging that is a hybrid of both of these
methods. The choice of which method to use is normally made on the basis of where the system
boundary is drawn (see Figure 1 and Figure 2), or by data restrictions.

Figure 1. Biophysical model of the energy-economy system based on Hall et al. [16] (p.38).

The energy system is depicted as a series of processing stages: extraction, processing and

distribution. The economy is split into four sectors: industrial, residential, transport and

public, with associated outputs. The scale of the system boundary may vary along the

process chain dimension.

Figure 2. Production process with increasing levels of analysis by expansion of the system

boundary to include more inputs.

ChemicalBioGeo-

Processes

Sun ResourceEnergyQ UnprocessedExtractedEnergy

EnvironmentalServices

ProcessedEnergy Available forEnergy

Heat, Work

IndustrialSector

Residential,Commercial

Sector

TransportSector

PublicSector

Capital

Labour

ServicesGovt.

OTHER ECONOMIC SECTORS

ExtractionLosses ProcessingLosses DistributionLosses

ConversionLosses Consumption

SYSTEM BOUNDARY 3

SYSTEM BOUNDARY 2

SYSTEM BOUNDARY 1

G