Monsoon rain has slowed biomining operations at Delhi’s three largest landfill sites, potentially delaying the Municipal Corporation of Delhi’s (MCD) effort to meet deadlines for clearing decades-old waste from the city’s towering garbage dumps.According to the civic body’s dashboard, the slowdown has been most pronounced at the Okhla landfill, where daily biomining output — which had averaged between 6,000 and 9,000 metric tonnes per day (TPD) — fell to around 650 TPD between August 3 and 11 with several days showing no legacy waste has been lifted. During the same period, around 2,800 TDP of municipal waste continued to arrive at the site daily, offsetting much of the progress.At Bhalswa landfill, daily processing has declined to roughly 1,700 TPD last week, after averaging between the usual 6,000 and 11,500 TPD, according to the MCD dashboard. Around 4,300 TPD of fresh waste is being dumped daily at the landfill. The drop is significant as MCD has set a goal of eliminating both the Okhla and Bhalswa landfill by December.The Ghazipur landfill, the city’s largest, has also fallen short of its target. The MCD has set a daily biomining goal of 7,000 TDP of legacy waste there, but official data shows that only around 1,400 TPD was lifted over the last nine days. Meanwhile, another 2,400 TDP of fresh municipal solid waste are deposited at the site each day.Urban Development Minister Ashish Sood had directed the MCD to ramp up the biomining capacity from 7,000 TPD to 12,000 TPD by July 31 to meet the December 2027 deadline, while on his visit to the Ghazipur landfill site in June.The processBiomining involves excavating legacy waste, biologically treating it and separating recyclable and reusable materials, allowing portions of landfill land to be reclaimed.Officials say the recent rainfall has complicated that process. “Heavy rainfall has made the waste wet. This wet waste gets clogged in the trommels and affects the separation process. The machines have to be cleaned multiple times, making it difficult to meet the output target,” a senior MCD official said.Story continues below this adA civic body official on site, explained the process of biomining. “Biomining is done by using trommels which are large, elevated rotating drums equipped with perforated screens. As excavated legacy waste is fed into the elevated end of the cylinder, the drum slowly rotates, causing the material to tumble and eventually separate.”Biomining relies on trommels — large, rotating, cylindrical screens that separate excavated waste into different categories. As waste becomes saturated with rainwater, it clumps together and sticks inside the machinery, reducing efficiency and requiring repeated cleaning.The sorting process produces three primary streams: inert material, refuse-derived fuel (RDF) and construction and demolition waste.RDF consists largely of combustible material such as non-recyclable plastics, paper and cardboard that can be used as an alternative fuel in cement plants, another MCD official said.Story continues below this adAs per a report submitted by the MCD to the National Green Tribunal in 2025, inert material and construction waste recovered through biomining are transported to low-lying areas in Uttar Pradesh and Haryana for use in proposed industrial and commercial developments.The disruptionOfficials acknowledged that the monsoon regularly disrupts the operation and said contractors are likely to maximise processing before the season begins.“We always advise the contracted firms to achieve their targets before the monsoon arrives because the biomining process slows considerably during this period. If they fail to meet the second-phase deadlines, penalties will be imposed,” another official said.Decades-old problemThe MCD began biomining in 2019 after directions from the National Green Tribunal to scientifically process and remove legacy waste that had accumulated over decades.Story continues below this adThe city’s landfill sites, some of which have been in operation since the 1980s, grew into vast mounds of garbage. Ghazipur, which rises to about 65 m, has become one of the country’s most recognisable landfill mountains.Officials said that a new fresh waste processing plant is being built at Okhla with a daily capacity of 1,400 TPD, which will be completed by October to increase the pace of biomining.According to MCD officials, about 30 of the 62 acres at the Okhla landfill have been reclaimed, while roughly 25 of Bhalswa’s 70 acres have been cleared. At Ghazipur, around 20 acres have been reclaimed, with the second phase of biomining scheduled for completion in September.As of June, the MCD estimated that nearly 100 lakh TPD of legacy waste remained across the three landfill sites. Ghazipur accounted for about 69 lakh TPD, followed by Bhalswa with 18 lakh TPD and Okhla with 12 lakh TPD.