Energy and Water Are Closely Intertwined
10 min read
“Energy is thirsty”, wrote the in one of its commentaries. Water is used in the generation of to cool plants, in the extraction of fossil fuels, in oil refining and also in the irrigation of crops for the production of biofuels. Sustainable management of this water is essential, at a time when the planet's “water stress” is already being exacerbated by population growth and the effects of .
© AFP - Shale gas drilling site in Shandong province, China.
Distinction Between Withdrawal and Consumption
Humans withdraw vast quantities of water for various purposes. The majority of this water (two-thirds of the total) is used by agriculture. Next come drinking water and water for industrial operations. As estimated by the International Energy Agency (IEA), energy‑related activities require 10% of the total volume of water used by humans. But this proportion is set to increase between now and 2040.
When talking about water, it is important to understand the difference between “withdrawal” and “consumption”.
In the first case, water is withdrawn from a natural source and then released back into that source either without treatment, after being used for cooling at a power plant, for example, or with treatment, if the water quality has been affected.
Consumption, on the other hand, is defined as taking water from a natural environment and reinjecting it into a basin, where it evaporates into the subsoil without being recovered. In this case, the water disappears from the natural environment from which it came.
However, certain processes actually result in the production of water, such as oil and gas extraction in which water present in subsurface formations is brought to the surface. The volume of “produced water” is typically greater than that of the oil or gas recovered.
The difference between the volumes of water withdrawn and consumed varies widely depending on the industry.
For example, producing electricity from fossil fuels or nuclear power requires massive quantities of water to be withdrawn: almost 300 billion cubic meters in 2021, of which 95% of water is returned to the natural source. The difference is mainly due to evaporation.
The production of sources ( , oil, gas, biofuels) requires less water ( less than 60 billion cubic meters) but returns less than half. Overall, primary energy production can thus be said to “consume” a higher proportion of water than power generation.
How Is the Water Used?
Hydro: Hydropower plants neither withdraw nor consume water, save for evaporation from barrier lakes. They extract energy from the water flowing through them, without altering it.
: Hot water from deep aquifers is used to produce steam. Once cooled, the water is reinjected into the ground, making geothermal a closed loop system with relatively little water loss.
Thermal: Thermal power plants need water to cool the steam that drives the turbines generating the electricity.
Nuclear plants withdraw the most water, from rivers or the sea. Water is kept in a secondary circuit isolated from the reactor and is returned to nature after being cooled to a temperature that will not affect the ecosystem.
As by far the most common type of power plant worldwide, coal-fired plants are those that use the most water.
Concentrated solar power plants, which use parabolic troughs to capture from the sun, are also water-intensive, which is problematic as they are often located in arid or semi-arid regions.
Wind and photovoltaic: These two industries consume very little water, save for that required to produce solar cells, which must be washed using ultra-pure water, generally flowing in a closed system.
Biofuels: As they are plant-based, producing biofuels requires large quantities of water for irrigation purposes, outdoing coal, oil, and gas.
What About Oil and Gas?
The oil and gas industries use water at different stages in their processes, especially during well . However, the production process itself is particularly water-intensive. When the pressure in well. If the pressure falls, the operators inject water into (or “flood”) the reservoir to push the oil or gas toward the surface from underneath.
Over time, the oil field passes its peak or “matures”, and produces both oil and water, the latter coming from the reservoir itself and from the flooding. On a global average, an oil well produces one of oil for three barrels of water, but a mature well can produce as much as ten barrels of water for one barrel of oil. Certain oil companies even specialize in managing end-of-life fields, which can produce up to 96% water.
Taken from rivers or aquifers for operations or directly from the sea for platforms, flood water must be treated before it can be injected. The sulfates must be filtered out, as they could affect the permeability of the reservoir, and oxygen must be removed to prevent and the growth of . The fluid recovered from the well, known as “produced water”, takes the form of an emulsion of water droplets in oil and is of very poor quality, often corrosive. It must be treated before being reinjected into the ground or discharged into the natural environment.
Shale Gas and Oil Sands
, or “fracking”, is a process used to recover and gas that requires large quantities of water in its early stages. A high-pressure of water is used to create cracks in the source rock to release methane. The water flows through the , mixing with the groundwater, and can be partly recovered. Although extremely water‑intensive at the outset, the process’s requirements subsequently dwindle.
For producers, the challenge lies in managing the large tailings ponds into which the water used to wash the sands is deposited. More than 90% of the water can be recycled but the ponds take decades to dry up, leaving the non-volatile content behind. These sometimes massive structures can have an impact on local ecosystems.
Downstream Operations: Refining
Refineries need water for the initial processing of , steam production and cooling circuits. Process water is treated using physical and chemical processes, such as settling and , or biological methods, which use microorganisms to consume the dissolved hydrocarbons. Major savings have been made in terms of the quantity of water used in the industry: according to IFP Énergies Nouvelles (IFPEN), the average consumption of a refinery has fallen from several cubic meters per metric ton of crude in the 1980s to between 200 and 800 liters per metric ton today.
Water Withdrawal and Consumption Statistics (2021 - Source: IEA)
| Industry | Water withdrawals (In billions of cubic meters) | Water consumption (In billions of cubic meters) |
| Electricity generation | 308 | 16,2 |
| 230
| 16,2
|
| 189,6 | 16,2 |
| 12,1 | 1 |
| Primary energy production | 59,5 | 36,3 |
| 21,7 | 18,8 |
| 37,8 | 17,5 |
| Total | 367,5 | 52,5 |
The energy sector is responsible for 10% of global water withdrawals. However, given the rate at which water is returned to the natural environment, energy-related consumption represents just 3% of the total.
According to the French Ministry of
, in 2021, 30 billion m3 of freshwater were withdrawn in France for human use (excluding hydroelectric production). 48% is used to cool power plants, 18.5% to supply drinking water networks, 17% to supply navigation canals, 9% for agriculture and 7.5% for other economic activities.
Sources:
Energy Sufficiency and Efficiency
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