Faced with the growing risk of water shortages (see upcoming article on water scarcity), Morocco has adapted its national water management plan through the National Program for Drinking Water Supply and Irrigation (PNAEPI) for 2020-2027.
To increase the water supply, the program not only calls for the construction of 20 new dams, but also several desalination plants. By reducing the amount of salt present in salt water (and the brackish water), desalination is used to obtain fresh water for domestic, agricultural or industrial use.
Desalination is a promising technology for harnessing the water of Morocco's long coastline. But will it be enough to eliminate the risk of water shortages?
Ambitious plans for 2030
Desalination is not a new process in Morocco, with the first units having been built as early as the 1970s in Boujdour and Tarfaya. Since then, half a dozen plants have been built (see map), with a total desalination capacity of 100,000 cubic meters per day. Future projects are far more ambitious: between 3 and 20 desalination plants are due to be built by 2030. The largest of these, in Casablanca, will have a seawater desalination capacity of 300,000 cubic meters per day. This additional freshwater reserve would more than meet the daily needs of 4.57 million Casablancans, i.e. 365,000 cubic meters (based on 80 liters per day, reference daily domestic consumption of an inhabitant of the city of Casablanca in 2014).
The shortage of drinking water in the country's largest city thus seems to have been resolved, but at what price?
the triple cost of desalination
Removing salt from seawater is not as easy as it sounds. Desalinating seawater is a complex and costly process, in energy, financial and environmental terms, whatever the process used. It can be carried out using two types of process: thermal, by distillation for example, or membrane-based, which requires less energy; reverse osmosis being the most common membrane-based process. In Morocco, reverse osmosis is most likely to be the preferred process for future plants, according to the Moroccan government. ONEE Here's an estimate of the triple cost of seawater desalination.
For more technical details on the various desalination processes, a detailed description can be found in some of the following publications articles scientists.
Energy costs: a 13 % increase in our energy bill
The figure: 4-6 kWh/m3
Take Casablanca, for example. Assuming that all drinking water will come from the region's future desalination plant, more than 117 kWh of electricity would be required to cover the entire annual drinking water needs of a single Casablanca resident, i.e. 13 % of its current electricity consumption. For the whole of Casablanca, this is equivalent to 535 GWh.
For agricultural use, desalinated water requirements are much higher: 4,000 to 6,000 cubic meters per hectare each year. Considering the 19.000 hectares where watermelon was grown in 2021, and at a rate of 6000 cubic meters of water per hectare per year, desalinating this quantity of water would require almost 456 GWh of electricity.
Financial cost: desalination a reasonable solution for drinking water and rare crops
The figure: 0.45-2.51 $/m3 (average over 5 countries) - 0.9$-10 dhs/m3 (Morocco)
The cost of producing a cubic metre of desalinated water varies widely, depending on the initial investment, plant capacity and energy costs. The cost quoted in dollars is based on a economic study for several countries, although Morocco is not one of them. In Morocco, this cost would be significantly reduced by the low cost of electricity, at nearly 10 dirhams per cubic metre .
However, it would still be higher than the price of farmers' current subscriptions to public suppliers of water for irrigation (the Offices Régionaux de Mise en Valeur Agricole and the Agence des Bassins Hydrauliques), not exceeding 1 dirham per cubic metre . Irrigating with desalinated water would then be an economic aberration in many agricultural sectors, with the exception of those with very high added value, such as strawberry .
Environmental costs: towards a significant increase in Morocco's emissions
The figure: 0.4-6.7 kg CO2eq/m3
Greenhouse gas (GHG) emissions linked to desalination are essentially generated by the electricity needed to operate the plant. They therefore depend on the electrical requirements of the process used and the energy mix of the country concerned. A study has nevertheless been able to estimate a carbon cost range for reverse osmosis desalination. In Morocco, where almost 80% of electricity production comes from fossil fuel combustion (coal, oil or gas), the carbon footprint of desalination approaches (under current conditions) the upper limit of this estimate. GHG emissions linked to the irrigation of 19,000 hectares of watermelons could reach 684 kt CO2eq / year, increasing national emissions from the agricultural sector by 4.5%.
In addition to the carbon cost of desalination, there is also the environmental cost - more difficult to quantify - of the brine (water with a high salt concentration) discharged by each plant, containing chemical residues (copper, chlorine). For each liter of desalinated water, a desalination plant must discharge 1.5 liters brine . The common practice is to discharge them directly into the ocean. This has a detrimental impact on the local ocean ecosystem, as it increases salt concentration and introduces toxic compounds. However, there are several alternatives to direct ocean disposal exist .
far from a miracle solution, one lever among many
Clearly, to secure water supplies, the government's strategy cannot rely solely on a process as energy-intensive as desalination. The PNAEPI also plans to develop wastewater treatment and reuse, notably for watering urban green spaces. A next step could be to follow the example set by other countries around the Mediterranean, by extending the use of recycled wastewater to agricultural irrigation.
But that's not enough, because agriculture represents 85% of water consumption in Morocco, and the water used in agriculture can hardly be recycled. Solving Morocco's water shortage will therefore involve maximizing freshwater resources (through desalination in particular), but also and above all optimizing its use, particularly in agriculture. A number of levers are available: agroforestry, covered cropping, less water-hungry varieties, underground drip irrigation... [more on these issues soon].
Article by Kenza Himmich and Ali Hatimy