Western Power calculates its greenhouse emissions annually in accordance with the National Greenhouse & Energy Reporting Act.
Emission sources fall within two major categories, those being Scope 1 or direct emissions (for example, through burning fuel) and Scope 2 or indirect losses from the consumption of electricity. Scope 2 emissions are considered indirect as the emissions are produced at upstream at power station facilities.
Reportable emissions include the six greenhouse gases covered under the Kyoto Protocol, those being carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). By convention and for comparability, all emission sources are reported in carbon dioxide equivalents (CO2-e).
In 2008/9, we emitted a total of 982,546 t CO2-e comprised of 22,473 t CO2-e Scope 1and 960,073 t CO2-e Scope 2 emissions (Figure 1).
Emissions were dominated by carbon dioxide (18,669 t CO2-e), with 423 t CO2-e of methane, 253 t CO2-e of nitrous oxide and 2,927 t CO2-e of sulphur hexafluoride (Figure 2).
Figure 1: Greenhouse gas emissions by scope
Figure 2: Greenhouse gas emissions by gas (Scope 1)
Direct emissions were predominantly due to fuels consumed for transport (17,145 t CO2-e) and in mobile generators (1,437 t CO2-e) along with fugitive emissions of SF6 (2,927 t CO2-e), an insulating gas used in electrical switchgear. Smaller sources include onsite disposal of wastewater and consumption of liquid fuels, natural gas and acetylene in stationary plant and forklifts.
Indirect emissions included 14,867 t CO2-e from electricity purchases and 945,206 t CO2-e from network losses, commonly referred to as line losses. Network losses represent electricity (energy) lost, mainly as heat during transmission and distribution and electricity used in network infrastructure. In 2008-9, losses equalled 6.73% of electricity sent-out on the network, which equates to 96.2% of our total emissions.
Figures 3 & 4 below illustrate the contribution of various emission sources
Figure 3: Proportion of emissions by source
Figure 4: Greenhouse gas emissions by source (network losses removed)
In the past year, Scope 1 emissions have increased by 3,644 t CO2-e largely due to increased fuel consumption by the vehicle fleet & stationary plant (up 525,000 L), however emissions from mobile generators decreased due to a reduced requirement to support the network during faults, maintenance and peak demand. Figure 5 below, compares Scope 1, Scope 2 and total emissions for the past three years.
Scope 2 emissions grew by 45,510 t CO2-e in 2008-9. This largely resulted from line losses (up 41,632 t CO2-e) due to an increase in electricity being sent across the network (up to 16,300 GWh) and a slight increase in the percentage lost (from 6.54% to 6.73%). Future trends in scope 2 emissions will be dependant on network augmentation, customer energy demand and the fuel mix of grid connected generators.
Figure 5: Trends in greenhouse gas emissions
Note: figures presented are in accordance with Western Power’s 2008-9: National Greenhouse & Energy Report. These represent updated figures from those included in the 2009 Annual Report. Figures for prior years were calculated as part of the Greenhouse Challenge Plus program.
Page update on 19 January 2010
