Material stock disparity and factors affecting stocked material use efficiency of sewer pipelines in Japan

- A novel method for measuring stocked material use efficiencies (SMUE) was evaluated.
- Decomposition analysis was used to ascertain the main drivers of change in the SMUE.
- The SMUE appears to be sensitive mainly to population density and pipeline size.

Service is most often measured with a flow and monetary perspective using indicators such as gross domestic product (GDP) or the value added or income of a particular economic sector. However, infrastructures and therefore the associated material stocks also participate to the service delivery. Our study contributes to this emerging research field through a novel method of measuring stocked material use efficiency (SMUE) of sewerage pipelines in Japan, beyond monetary measures. We estimated the Japanese national and prefectural material stocks (MS) using statistical data and used direct service indicators such as the population with access to sewerage treatment services and the amount of treated wastewater to find the SMUE. Later, decomposition analysis was used to ascertain the main factors influencing SMUE. Results show an MS increase for all prefectures and a doubling of the national MS from 207 million tonnes (Mt) 520 Mt between 1984 and 2012. Material stocks are found mainly associated with population size, the highest populated prefectures Tokyo and Osaka also accounting for the highest material stocks. Concerning SMUE ranging from 4 to 48 m3/ton for a national average of 27 m3/ton, its main determinants are population density and pipeline size. This research promotes greater understanding of our stock use condition and thereby facilitates appropriate stock management.