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The Joint Research Centre (JRC) is the European Commission's science and knowledge service which employs scientists to carry out research in order to provide independent scientific advice and support to EU policy.
However, not all energy sources are equal. There are vast differences in the amount of water required to produce the same amounts of energy from different sources, especially renewables.
Some forms of hydroelectric energy, for example, can consume over 1,000 times more water than wind energy.
The energy sector is one of the largest consumers of water: whether it is for cooling reactors, growing plants for biofuels or evaporated water in hydro energy reservoirs.
The ever-increasing demand for water can lead to severe periods of water scarcity, particularly during the summer.
Water scarcity is a concern, as it leads to disruptions in the power supply of homes and businesses, which could intensify when we shift to water-intensive means of producing energy.
One of the key priorities of the European Commission is to build an energy union that provides European households and businesses with secure, sustainable, competitive and affordable energy.
Firmly committed to keeping its global leadership in tackling global warming, the European Commission aims to make Europe climate neutral by 2050.
To ensure that energy security is guaranteed while sustainability goals are met, policymakers need to pay special attention to the differences between the water needs of energy sources.
Within their new publication in the Environmental Research Letters journal, researchers of the JRC and the University of Twente compiled the most detailed water footprint assessment yet of the EU energy sector.
Water footprints are calculated by estimating the total amount of water used to produce of one unit (terajoule) of energy. It not only measures the consumption of water in rivers, lakes and groundwater, but also the consumption of soil moisture.
According to the researchers’ findings, first generation biofuels and wood have by far the largest water footprint, partly due to their vast consumption of soil moisture.
If we only look at the water consumption from rivers, lakes and groundwater, reservoir hydropower has the largest water footprint, followed by first generation biofuels and wood.
Other renewable energy sources are however on the other end of the water footprint scale. Solar, geothermal, wind and run-of-river hydropower have the smallest water footprints. Non-renewables, such as oil and coal, fall between the two groups of renewables.
The table below shows the average water footprints of the different renewable and non-renewable energy sources, without including soil moisture.
To understand the vast differences in the size of the water footprints of different types of energy, take the following example.
When we include soil moisture, first generation biodiesel uses 137,624,000 litres of water to produce 1 terajoule, the average amount of energy that 50 Europeans consume annually at home.
To generate the same amount of energy, reservoir hydropower consumes 9,114,000 litres of water, while run-of-river hydropower and wind energy would only consume around 1,000 litres.
The authors also compared the water footprints of the energy, food and municipal water supply sectors. Combining the three sectors and including soil moisture consumption, the water footprint of the daily consumption of an average EU citizen is 5,011 litres of water.
Out of this, food consumption is responsible for 3,687 litres per person. An average citizen’s daily energy consumption requires 1,301 litres to produce, while the water footprint of municipal water supply is only 23 litres per person per day.
The illustration below shows the daily water footprint of an average EU citizen’s food, energy and water consumption.
Due to the large reliance of the EU energy and food sectors on imports, water footprint values of energy (1,068 litres per person per day) and food production (2,521 litres per person per day) within the EU are somewhat lower.
As the problem of water scarcity is not only faced by the European Union, imports in the energy sector might not help to strengthen energy security.
This is also true for other imports such as biofuels and wood, which are often produced under conditions of water scarcity.
To ensure that energy security is not compromised by decarbonisation goals, the authors of the article recommend that water-related criteria such as the water footprint be introduced into long-term energy policies.