Its finding shows that desalination plants — which are expected to meet a significant share of Qingdao’s future water demand — use 10 times more energy than extracting water from local rivers.
Of all the unconventional water sources, the study notes, turning seawater into fresh water is also the most energy-intensive, on average consuming 4 kilowatt-hours per cubic meter of fresh water produced. By contrast, wastewater reuse requires less than 1 kWh of power to process the same volume and produce the same quality of water.
Qingdao is among the most water-stressed Chinese cities, with per-capita water resources only about 12 percent of the national average. The city has already been constructing a desalination plant to meet the water demand for one-quarter of its downtown population. Qingdao also plans to triple its daily desalination water production capacity to 400,000 cubic meters before 2016.
“But desalination’s high-energy demand and steep capital expenditure and operational cost challenge it as a sustainable environmental and economic water supply approach,” the researchers said in the study. “For instance, if all 400,000 cubic meters of Qingdao’s proposed daily desalination capacity were in place, greenhouse gas emissions would increase by 80 percent per cubic meter of water produced.”
The planners’ dilemma
This conflict between resources may not only happen in Qingdao but across the nation. To quench China’s chronic thirst, the government has turned to desalination, aiming to produce as much as 3 million cubic meters of desalinated water daily by 2020, up from 0.9 million cubic meters in 2013.
Zhong Lijin, the research project lead and a senior associate at the World Resources Institute’s Beijing office, said that other Chinese cities are likely to face the same challenge as Qingdao does, because most desalination plants use similar technologies.
“It is a fact that desalination is both energy- and carbon-intensive, but this issue has been largely ignored,” Zhong said.