> MEED's January 2021 Agenda also includes: Carving a path to net-zero

The UAE’s target to reach net-zero carbon emissions by 2050 requires important and brave decisions. Abu Dhabi’s plan to gradually retire all thermal power plants as part of its energy transition is an example of this.

As announced by Sultan al-Jaber, UAE minister of industry and advanced technology, the process will start in January whereby nuclear and renewable energy plants will gradually replace thermal cogeneration plants in Abu Dhabi.

Water desalination

But all sectors and industries in the UAE need to take responsibility for the 2050 net-zero carbon emissions target. The water sector, for example, has the potential to achieve or surpass this target.

Meeting this goal requires replacing existing thermal desalination plants in Abu Dhabi, which have a combined capacity of 750 million imperial gallons a day (MIGD), with reverse osmosis (RO)-based water treatment plants.

Today’s existing MSF or MED-based plants in Abu Dhabi lock in approximately 3GW of inherent additional fuel to the cogeneration plants. These plants, when converted into seawater reverse osmosis (SWRO) facilities, will require merely 400MW to 500MW of electric power.  

In addition, these plants can run on solar and clean power, rather than fossil fuels, supplied through the grid.

This move alone can reduce the carbon emissions of Abu Dhabi’s water desalination sector by 15 million tonnes of CO2 a year.

The reduced emissions rate is roughly equivalent to the work that a forest of 500 million adult trees would do in sequestering CO2 from the atmosphere 

State utility Dubai Electricity & Water Authority maintains 450 MIGD in thermal desalination and Sharjah Electricity & Water Authority maintains another 40 MIGD. Converting these facilities can unlock another 2GW of fossil fuel-based power and reduce the CO2 emission by another 10 million tonnes of CO2 a year.

Moving away from the traditional concept of steady water generation mainly dictated by the lack of storage can also lead to a new SWRO fleet that can operate in a more sustainable manner: producing more when excess power is available in the grid from solar PV systems and less when the grid is in peak mode. 

Modular SWRO schemes enable utilities to take advantage of the modularity and flexibility of RO technology to produce more – and consequently absorb more energy –  during the off-peak period.

In the same manner, it is possible to reduce the capacity during the network demand peak period in order to alleviate demand on the network.

This approach can aid the desalination industry in reaching net-zero carbon emissions sooner than the set 2050 target, and with minimal additional investment.

One of the biggest paradoxes in today’s wastewater treatment plant approach is the incredibly high amount that is dissipated in the process of “killing” the residual energy of the wastewater treatment streams.

Today’s installed wastewater treatment plants across the GCC have an energy footprint of 0.7 to 1 kWh a cubic metre (cm) of treated water. Furthermore, the largest part of the treated effluent is discharged to the sea whereas the energy footprint could be negative (-0.1 kWh/cm) if the treated sewage effluent (TSE) is used to expand forestry.

Carving a path to net-zero

Greening wastewater 

The next generation of wastewater treatment plants are envisaged as “cradle to cradle”. This implies water processing and energy generation plants where wastewater is upcycled to fresh water and energy from the wastewater stream is recovered rather than dissipated.

Countries in Europe and the US are increasingly adopting this process.

According to this scheme, energy is generated rather than dissipated by the wastewater treatment plant and carbon is stored in sludge that can be reused.

Carbon will be further absorbed by forests and other greenery that can be grown using tertiary treated water, the majority of which is currently discharged to the sea. 

Considering that the UAE produces an average of about 1 billion cubic metres of TSE annually, approximately 500 million trees could be planted that in turn would also help the industry achieve net-zero carbon emissions much earlier than 2050.