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Structural Path Analysis a tool for informed decision-making towards TBL sustainability

A Structural Path Analysis "unravels" TBL impacts into single contributing supply paths. It gives extensive detail of the impact of a sectors or companys activities, in TBL terms. It allows investigating the location of impacts within the supply chain. In the case of a company, the control over the input procurement process then provides the possibility of substituting impact-intensive suppliers with more sustainable suppliers.

The table below shows a selection of top-ranking structural paths for the example of greenhouse gas emissions from the Australian business management sector. The Structural Path Analysis computer algorithm developed at the University of Sydney covers the entire upstream supply chain (see the boundary problem). Many more indicators can be analysed in this manner. The Structural Path Analysis of this sector is in terms of greenhouse gas emissions, and is expressed in units of grams of CO2-equivalent per $ of output.

In the table below, each path is be characterised by a line, consisting of

  1. a description of the path
  2. the path value (in this case the greenhouse gas impact in grams of CO2-equivalent per $ of final output of business management services),
  3. the path order (that is, from which upstream supply layer the path originates),
  4. the path coverage, that is, the relative contribution (in %) to the total TBL impact of the sector.
For example,
  • the structural path 'Black coal > Electricity' describes the emission of seam gases (mostly methane) from black coal mines that supply power plants that supply the business management sector with electricity.
  • the path value is 2.1g CO2-e per $ of final output of business management services.
  • the path is of second order, that is originates from production layer 2, that is from a supplier (mine) of a supplier (power plant), and
  • constitutes a coverage of 0.68% of the total greenhouse gas impact of the business management sector.

In the example of the Australian business management sector, rank 1 represents emissions from power plants supplying the sector with electricity. Rank 2 are the sectors own emissions from fuel use in buildings and cars. Rank 3 are emissions from planes carrying the sectors employees. Rank 4 are emissions from power plants supplying electricity to business services such as typing, copying or mailing, for the business management sector. There are more paths that relate to emissions associated with electricity for suppliers of the business management sector: these are for entertainment (rank 5, restaurants, hotels, venues), communication (rank 6), electric pumps of water suppliers (rank 7), technical services (rank 10), travel and storage agencies (rank 14), and so on. Rank 8 are (non-energy, methane) emissions from water treatment processes on the sites of water suppliers to the sector. Rank 9 are seam gases (mostly methane) that emerge from coal seams in mines that supply power plants that supply the sector with electricity. Rank 11, 13, 24, 25, and 27 represent energy use, venting and flaring in the fuel refining and distribution sector that makes the fuels used by business management firms. Paths 15 and 22 are of third order, and describe the (non-energy) emissions from land use changes associated with growing conifers for paper and printing for business management services. Rank 19 describes CO2 emitted during the chemical reduction of limestone and dolomite to lime used by the water supply industry (for pH control and sewage sludge stabilisation). Thousands of paths up to 10th and higher order can be identified using this technique.

For further information please contact

Dr Arne Geschke
ISA, School of Physics A28
The University of Sydney NSW 2006
+61 (0)2 9036-7505
arne.geschke@sydney.edu.au