Environmental Impacts of Multi-Storey Buildings Using Different ...

- 73 -Table 6.9: Total GWP of each building’s life cycle for landfilling and reutilisation scenariosBuilding type Landfilling [t CO 2 eq.] Reutilisation [t CO 2 eq.]Concrete 6,794 6,782Steel 6,883 6,567Timber 5,982 6,010Timber + 5,276 5,330The total primary energy use of all four buildings was lower in the reutilisation scenarios, assome energy was generated from wooden materials. It should again be noted that the landfillresults could change in the future if landfill gas capture rates increase, and if energy fromlandfill gas is able to be calculated. The GWP results are more varied than the energy useresults. As with energy, the GWP impacts of the Steel and Concrete buildings are reducedwhen material reutilisation is chosen as an end of life option. However, for the Timber andTimberPlus buildings the results indicate that the benefit as a result of carbon storage inlandfills (landfill scenario) is very slightly greater than the benefit from offsetting emissionsfrom other energy sources (reutilisation scenario).The small difference in both primary energy use and GWP for the Concrete building isbecause concrete is recycled into aggregate which is a very low embodied energy product.The reason that the Steel building fares much better in the reutilisation scenario can beattributed largely to the recycling of steel (avoiding some primary steel, which has a very highembodied energy).The Concrete building has the lowest difference in energy and GWP between the twoscenarios, with the reutilisation scenario showing a 0.5% and 0.2% saving respectively. TheTimberPlus building has the greatest energy saving in the reutilisation scenario, with a 4.2%reduction, because it has a large quantity of wood waste for combustion. The Steel buildinghas the greatest reduction in GWP, with a 4.6% reduction; again this is due to the highembodied energy of steel, which is recycled into other steel products, thus avoidingproduction of a large quantity of virgin steel. The reutilisation scenario for all buildings showsa reduction in total energy, as the energy recovery from combusting the wood has beensubtracted from the total energy use of the buildings.