The Magħtab dump should be turned into a recreational park in the next three years but gases will keep being extracted for at least another two decades.
Some 100 million cubic metres of gas have been burnt over the past two years, stripping the gas of its toxic elements before releasing it into the air.
The gas is being collected through 400 steel wells that have been dug throughout the dump. These direct the gas to a €1.5 million oxidiser where it is burnt at temperatures that reach 900°C. "This destroys their toxicity," Resources Minister George Pullicino said.
Last month, the planning authority approved the €24 million rehabilitation of the Magħtab dump, which will be transformed into a green hill having more than 20,000 trees.
Speaking at the launch of the next stage of Magħtab's rehabilitation, which is expected to start in the coming days, Mr Pullicino said that, despite the many wells, some gases were still seeping out of the landfill into the air.
To stop this, the authorities will be covering the 300,000 square metre dump with a mixture of limestone and compost, sealing Magħtab and redirecting the gases to the labyrinth of pipes that take them to the oxidiser.
The sealing process is expected to start in the coming days and Mr Pullicino said this would ensure that no toxic elements were released into the air.
The next step would be covering the whole area with soil and planting trees and flowers.
The cover would also stop contaminated particles from being deposited along the Baħar iċ-Ċagħaq coastline, Mr Pullicino said, adding that no leachate (the liquid that drains from a landfill) was flowing into the sea. Although the gases were being stripped of toxic elements, the smell that has become associated with Magħtab persists in the areas close to the oxidiser. Mr Pullicino said the unpleasant odour was restricted to the area close to the oxidiser and reiterated that, despite the smell, the gases were not a health hazard.
"We need to get rid of the problem over a period of time," Mr Pullicino said. Wasteserv chief executive Vince Magri said the dump should remain a reminder of the repercussions of mismanagement of waste disposal.
An open day will be held at Magħtab on Saturday between 10 a.m. and 3 p.m.
Facts and figures
• €30 million in EU funds will be used to turn the Magħtab, Sant'Antnin and Qortin dumps into leisure areas.
• Eighty per cent of the gases that come out of the Magħtab dump are toxic, the other 20 per cent is methane, being used to operate the regenerative thermal oxidiser.
• Almost 20 million tonnes of waste were dumped in Magħtab since the 1970s. Some 22.6 million tonnes of waste were deposited in 10 dumps since the 1960s.
• Another 1.5 million tonnes of waste were deposited in the Ta' Żwejra and Għallis engineered landfills since 2004.
• Some 700,000 tonnes of rubble were moved from the dump to stabilise the area after it was determined there was a risk that certain areas would collapse, leading to pockets of gas coming out.
• Some areas of the dump reach temperatures of 200°C.
• The 400 steel wells capture 6,000 cubic metres of gases every hour, with 40 million cubic metres being collected and treated every year.