Research Article
Difference between the Predicted Value of the Design Stage and the Definitive Value after the Completion of Construction in Infrastructure LCA
2013 Volume 9 Issue 1 Pages 13-19
Details
2013 Volume 9 Issue 1 Pages 13-19
Objective. The National Institute for Land and Infrastructure Management (NILIM), in cooperation with the Japan Society of Civil Engineers (JSCE), developed a Life Cycle Assessment (LCA) method for infrastructures from FY2008 to FY2010. The objective of this LCA method is to quantitatively evaluate and calculate the environmental impact of infrastructure development with regard to factors such as CO2 emission, waste disposal, and use of natural resources. In order to apply CO2 emission data estimated with this LCA method to decision-making, we must first determine the difference between the predicted value (at the design stage) and the definitive value (after the completion of construction).
Results and Discussion. The difference between the predicted value and the definitive value is due to (1) changes in the types and quantities of construction material and the machinery specified in the design documents, and (2) updating the environmental load units during the construction process. To examine (1), CO2 emissions were calculated on the basis of seven design documents. These documents focused on roads, bridges, tunnels, etc. The results of the calculations showed the following: 1) the predictive value is likely to range between 76% and 164%; 2) the main factors responsible for fluctuations in the predictive value are transportation distance and type of construction machinery; 3) excluding the influence of transportation distance and type of construction machinery, the predictive value is likely to range between 87% and 108%. Regarding (2), we think that the value of the environmental load units of concrete, iron, and asphalt may vary drastically.
Conclusions. This study showed that differences exist between predicted values and definitive values in the LCA method for infrastructures. When making decisions based on a predicted value, we must take this difference sufficiently into account.
