Waste-to-energy in Dubai
Tim Clarke, CEO of Dubai Waste Management Company (DWMC), talks to The Energy Year about how the company reflects the larger ambitions of the UAE, how waste is transformed into energy and how efficient the process is. DWMC operates an energy from waste (EfW) centre capable of producing 215 MW of electricity continuously.
How does the Dubai Waste Management Company reflect the larger ambitions of the UAE?
There is an obvious issue globally with the way waste generated by human society is being managed. Although some places in the past decades, such as Europe, have engaged in partial circular economic models, when it comes to waste recycling, many countries have not.
There are different steps in the circular approach to waste, including the five Rs: reduce, reuse, repurpose, recycle, recover. Ultimately you should aim to incorporate these five aspects. Here in Dubai, however, the practice is not mature, and the mechanism that Dubai Municipality has decided to focus on in the short term is the recovery of energy and metals from waste.
Currently, almost all solid municipal waste generated by the city of Dubai is sent to landfills, which is neither sustainable nor does it feed any value back into the economic system of the city. As part of the ESG strategies laid out by the UAE and the government of Dubai, the goal is “zero to landfill” by 2030.
That is where the DWMC comes into play. We’ll be the main contributor to that effort. Once fully operational, 45% of the solid municipal waste generated by Dubai will be processed through our facility and transformed into electricity that will be partly utilised by Dubai Municipality, with the balance being resold via Dubai Municipality to DEWA [Dubai Electricity and Water Authority].
Can you guide us through the process of the transformation from waste to energy?
The system is configured for the process to take 24 hours from the waste collection to the utilisation of the generated electricity. The waste is collected and delivered to our facility without any pre-processing. We have a discharge bunker with a capacity of 25,000 tonnes, and it will take about 5,500 tonnes of waste daily, which equals 1.9 million tonnes per year.
The bunker is fully automated and ventilated to avoid any odours or emissions. Grab cranes within the bunker move the waste to the back to allow incoming waste to be delivered, and they also mix the waste together to obtain a homogeneous distribution of moistness and calorific value before it enters the boiler.
At the back, the cranes put the waste in the hoppers, which automatically level and feed the waste into the five boilers. These boilers are the largest ones you can currently build with existing technology. 15 cubic metres of waste is pushed in every 15 seconds. It takes about four minutes for the waste to cross the grate and be completely consumed. The end products are ashes and incombustibles, which are further processed.
As for electricity generation, the hot gases produced from the combustion process will pass through the boiler and create steam as it heats the water, which, like any other steam-power generation system, will generate pressure and drive a single turbine to create 215 MW of electricity continuously.
How efficient is the whole transformation process?
Regarding thermodynamics, our efficiency level cannot be improved with the equipment we have. Our boiler combustion system produces steam at 434 degrees Celsius and 80 bars of pressure, which allows us to transform 34% of the energy contained within the waste into useful electricity.
Other aspects of our facility make it a state-of-the-art recycling plant. The water for the boiler feed is created from the recycling of the waste freshwater outfall from the adjacent sewage treatment plant. The ashes are taken to a pre-maturation area to dry, and we are then able to extract the various ferrous and non-ferrous metals that are contained in the ash.
Furthermore, the remaining materials – ash, stones and other incombustibles – are to be recycled into construction materials for the municipality to use. All the hot waste gases that are emitted during the process are also filtered to retrieve pollutants such as sulphur dioxide, nitrous oxide, heavy metals and dust.
Effectively everything that comes into the plant is intended to be recycled in some way, apart from the flue gas treatment residue, for which there is currently no economically viable recycling process. Even the electricity required to power the operations within the plant itself is produced from the waste.
Can you provide further details about the construction of the plant and the stakeholders involved?
The construction of the plant started back in 2020. The project was initiated on the demand of the Dubai Municipality and organised under an SPV that includes Hitachi Zosen Inova Ag, BeSix NV, Tech Group and Itochu; and the Emirati companies Dubai Holding Investments and Dubal Holdings who together own 51% of the company.
The overall value of the project is USD 1.1 billion, and the plant is expected to be commissioned in July 2024, with the stakeholders operating under a 35-year Concession contract. Due to the nature of the partnership and the scope of the project, we comply with the most stringent safety and environmental standards, which replicate the European Emissions Standards.
All the contracts regarding the EPC works and financing were put in place by DWMC to meet the needs of DM as the waste supplier and the shareholders in terms of the return on investment.
The plant is being constructed in two blocks and we are currently commissioning the first block, which comprises the steam turbine, the air condenser, the first two boilers and the balance of plant. We will burn the first waste on the 4th of May, and from late July on, we will be processing 2,000 tonnes of waste per day, rising to 5,500 tonnes per day as we approach the plant’s completion in July 2024.
What insight into the future scalability of circular economic projects does this facility demonstrate?
The DWMC operates as an SPV that is focused entirely on this one plant. However, our shareholders are closely monitoring the project and are most definitely looking forward to building more of these waste management facilities in the Middle East.
There are other developers with projects underway. The Sharjah plant is currently being commissioned, and in Abu Dhabi a tender has been announced. Other Middle Eastern countries are looking to launch tenders for the construction of similar facilities.
In terms of economic viability, size and capacity, these plants will most likely not be larger than the one we have in Dubai. In Europe we actually see these plants on a smaller scale, depending on the city and the economic viability of transporting and transforming the waste. The available gate fee for waste and the electricity tariff available dictate the economic viability of a project in any given location.
At DWMC we have surrounded ourselves with quality, talented people. The technology we use and the efficiency with which we work make this project a milestone for the region.