Highlights
-90% China’s coastal cities face water scarcity & desal capacity to grow from 0.77mn cum to 3.0mn cum by 2020
-Desal uses 4x the energy needed for wastewater reuse
-China should prioritize investments in lower-cost and more sustainable water sources such as efficiency & reuse

Desalination gaining attention in China

In fast-urbanizing China, nearly 90 percent of coastal cities face some degree of water scarcity and roughly 300 million rural residents lack access to clean water.

Desal target = 3 million m³ daily by 2020

To quench the country’s chronic thirst, the Chinese government has turned to desalination, aiming to produce as much as 3 million cubic meters of desalinated water daily by 2020, up from today’s 0.77 million cubic meter.

Desalination consuming more energy

However, a World Resources Institute (WRI) analysis shows that China’s desalination strategy would consume an enormous amount of energy, causing other problems such as increased greenhouse gas emission and air pollution, and would cost more than most cities can afford.

WRI analysis shows China’s desal strategy’s need for an enormous amount power  would cost more than most cities can afford

The cities of Qingdao and Tianjin – where per capita water availability is only 12 percent and 7 percent of the national average, respectively – have both commissioned desalination plants. Qingdao’s desalination plant was constructed by the Spanish company, Abengoa, in 2010, and is said to produce 100,000 cubic meters of drinking water per day for 500,000 people (roughly 25% of downtown’s population in Qingdao). Tianjin is home to the Beijiang and Dagang desalination plants, which together are expected to account for a third of China’s 1.5-2 million-ton capacity by 2015.

But desalination’s high-energy demand and steep CAPEX and operational cost challenge it as a sustainable environmental and economic  water supply approach. WRI conducted an analysis that looked at the different energy requirements for producing drinking water from various sources in Qingdao.

Desal plants consume 4 kWh/m³ of freshwater produced, while wastewater reuse requires <1 kWh/m³ 

On average, desalination plants consume 4 kilowatt-hours per cubic meter of freshwater produced, while wastewater reuse requires less than 1 kilowatt-hour of power to process the same volume and same quality of water.

The price of energy accounts for as much as half of annual operating costs, making the cost of operation of desalination plants prone to price volatility in energy markets.

Figure below shows that desalination consumes roughly 10 times more energy than required to extract and process local surface water in Qingdao, largely owing to the energy intensive reverse osmosis (RO) process to remove the salts. WRI’s research indicates that reclaimed wastewater requires much less energy and expense compared to desalination and long-distance water transfers from the Yangtze River.

In China, coal is the dominant energy source, accounting for approximately 79 percent of the total electricity produced in 2012. Therefore, consuming greater amounts of desalinated water would simultaneously increase greenhouse gas emissions. For example, 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.

Desalination should not be prioritized as the primary water sources for a city

Some countries, such as the United Kingdom and Australia have developed strategies to deal with the high cost and high energy demands of desalination technology. The United Kingdom, which opened its first large-scale desalination plant in 2010 with a capacity to supply water to up to 1 million people, only plans to supply desalinated water to the public in emergencies, such as droughts. During periods when it is not is use, it also doesn’t demand costly energy or emit GHGs and air pollutants.

UK & Australia’s experiences show that desalinated water should only be used as a backup source, and renewable energies could be used to power the desal plants

Australia, on the other hand, has looked to renewable energy to power the desalination plant. For example, the Perth Seawater Desalination Plant reduces greenhouse gas emissions by utilizing electricity generated by a wind farm.

Until desalination technology becomes more energy efficient, it should only be used as a backup source of water in China. Continuous government investment in complementary technology, such as renewable energy sources and energy recovery technologies, is also essential to reduce greenhouse gas emissions in desalination.

Water efficiency investments & wastewater reuse should be prioritized

Most important, to help alleviate water stress in China, other, lower-cost, and more environmentally sustainable water sources – such as water efficiency investments and wastewater re-use – should be thoroughly investigated first and prioritized in China’s water resources planning.