Exploring material stock efficiency of municipal water and sewage infrastructures in China

Abstract

Abstract A secured supply of clean water and sanitation relies on material- and capital-intensive municipal infrastructures, and thus requires a large quantity of material stocks. Major infrastructures sustaining the municipal water cycle from water supply to sewage management in China were probed for the period 1980–2050. The infrastructures proliferated rapidly in Chinese cities during the past three decades. The annual water supply capacity climbed from 11 to 100 km3, the sewage treatment capacity soared from 1.1 to 50 km3. To meet the demand of increasing urbanization, these infrastructures may have to more than doubly expand by 2050. Up to 3.3 gigatonnes (Gt) of construction materials, including 170 megatonnes (Mt) iron and steel and nearly 400 Mt cement (approximate to 10% of the global steel and cement production per annum), may be used to build up the infrastructure stocks. An indicator of material stock efficiency was devised to estimate potential and practical services per material stocks in the infrastructures can provide. Key findings include: (i) The conventional network-based water and sewage infrastructures might perform a declining material stock efficiency over the long run. (ii) The stock-based efficiency of the municipal infrastructures decreased by 25% from its peak in the early 1990s. It is driven down by the fact that pipe networks and sewage facilities are more material-intensive and usually developed behind water works. (iii) Nearly a half of the water supply capacity and 20% of the sewage treatment capacity were underutilized, leading to an evident gap between the potential and practical efficiency. The gap can be minimized by improving the utilization of the infrastructure's installed capacity.