抄録
Objective. Results of life cycle assessment on infrastructure include large uncertainty because of its long lifetime and the difficulty of scenario setting. This study aims to propose an “environmental assets management method” for managing such uncertainties with the LCA on infrastructure, and especially explains the treatment of time.
Results and Discussion. Several problems have been pointed out for the “lifetime method”, which fixes lifetime of objective goods or service, and total amount of the environmental load during lifetime is evaluated (normally carried out for LCA). It is difficult to set the maintenance technology or situation in long term use of the transport system and it is one of the main factors of uncertainty. Instead of the lifetime method, the “discount rate method” in which the amounts of environmental loads occurring in the future are discounted is proposed. However, it is also difficult to scientifically determine a value of discount rate that can be applied to CO2 emissions calculation. “Environmental assets management” as an alternative framework for assessment in which emissions calculation. “Environmental assets management” as an alternative framework for assessment in which cash flow method, the rates of return for cases are analyzed, in which an up-front investment produces a benefit in the future, such as in real estate or securities. An environmental yield rate (EYR) indicator determines whether it is possible to recover the “investment for environmental improvement”. A method for examining when and what to invest is described. The method can analyze: 1) when to renew after entering service stage, 2) the timing to start the objective project, 3) what to provide.
Conclusions. The methodology is applied to provision project of the light rail transit (LRT) and some other modes. It is concluded that the temporal environmental assets management method enables us to evaluate various types of “investment for environmental improvement in the future” projects without setting the lifetime or the discount rate. Also, since the unit of index is either [years] or [%], it is possible to compare projects with completely different scales and types.
