The reduction of CO2 emissions is a global challenge that affects many sectors, including the water industry. Desalination technology, which converts seawater or brackish water into fresh water, is a potential solution to water scarcity, especially in coastal areas. However, desalination also has its environmental and high energy consumption challenges.

It is realistic to think that desalination can also follow the reduction of carbon emissions while remaining safe? One straight way to reduce the carbon footprint of desalination is to use decarbonated energy sources, such as renewable energy or nuclear power, to power the desalination plants. This would reduce the dependence on fossil fuels and lower the emissions of CO2 and other Green House Gases. According to a review of greenhouse gas emissions and estimation tools for water reuse and desalination systems, reverse osmosis (RO) technologies powered by renewable energy have lower CO2 emissions than thermal desalination technologies powered by fossil fuels. For example, the carbon footprint of seawater RO desalination powered by solar photovoltaic (PV) energy was estimated to be 0.4 kg CO2 eq/m3, while the carbon footprint of multi-stage flash (MSF) desalination powered by natural gas was estimated to be 6.7 kg CO2 eq/m3.

The main benefit of using a decarbonated energy would be to mitigate the effects on climate change and contribute to the global efforts to limit the global warming to 1.5°C above pre-industrial levels. This would probably enhance the sustainability and resilience of the water supply systems, while reducing the vulnerability to fluctuations in fossil fuel prices as well its availability.

Still, and a priori, the use of decarbonated energy for desalination may also entail some challenges, such as higher capital costs, technical feasibility, integration with the grid, intermittency of some renewable sources, installation security…etc

What to expect on the cost side? The desalination cost operations may vary depending on the type of energy source, the desalination technology, the location of course, and the scale of the plant. We may reasonably estimate that the energy cost accounting for the total operational cost of desalination is ranging from 44% to 77%. Therefore, using a decarbonated energy may affect the operational cost depending on the cost of electricity generation from the different sources. For example, according to a study by the International Renewable Energy Agency (IRENA), the levelized cost of electricity (LCOE) from solar PV was estimated to be 0.05–0.10 USD/kWh in 2020, while the LCOE from natural gas was estimated to be 0.04–0.14 USD/kWh in the same year. This suggests that using solar PV energy for desalination’s operation may be competitive or slightly cheaper even than using natural gas in some cases. However, other factors, such as subsidies, taxes, tariffs, and externalities, may also influence the operational cost of desalination using decarbonated energy.

We could observe the last 15 years that the production’s cost of renewable energy depends on the availability/quality of natural resources, the type and scale of the technologies used, the level of competition and innovation in the market, as well as the policies and regulations that affect the financing and operation of renewable energy projects. The geographic location of a renewable energy project can influence all these factors, as different regions may have different resource potentials, technology preferences, market conditions, and policy frameworks. Therefore, the production cost of renewable energy can vary significantly across different locations, and sometimes even within the same country or region.

Does it mean that the future desalination projects should already include a renewable energy supply on site, dependent of the site owner?

We may answer “likely yes” at least to secure the supply of this -basic life ingredient- which is water… to citizens even in tensed geopolitical moments during which could exist the temptation to use water scarcity as a political influential instrument.

Developed in R&D labs in the earlies 2000, Will “fully autonomous desalination plants” become the norm in 20 to 30 years from now? Or will the dependency to fossil fuel remains, offering to decision maker the unique sarcastic choice of “CO2 or Water” to an ever-growing earth population?

Feel free to brainstorm and express your own views.

Posted by Dr. Lagref Jean-Jacques