Probabilistic Resource Recovery of Legacy Waste in Dhapa Landfill: An Approach of Bio-mining in Kolkata

Abstract

Rapid growing competition for resources, increasing price for raw materials, diminishing natural reservoirs for valuable resources and increasing environmental problems make resource extraction from alternative sources as viable option such as Bio-mining. NGT mandated for implementation of Bio-mining of legacy waste throughout the Indian landfills for environmental impact minimization and recovery of 10,000 hectares of urban land that is locked in these dumpsites. The waste generation of Kolkata is around 4500 MT/day which further get accumulated in the major landfill site Dhapa since 1987 which turned into legacy waste. From composition analysis, an estimated recovery of 85-90% of legacy waste is possible. Material balance suggests different components of bio-mining like combustible (5.23%) and non-combustible materials (29.97%), compostable (56.04%), recyclables (0.476%) and residuals (8.642%). Whereas, from sample analysis of 100 kg material in dumpsite, different fraction of components are found as 25-30% non-combustible or C&D materials, 10-15% combustible or RDF materials, 1-2% recyclables, 15-20% bio-earth, 20-30% coarser organic fraction, 5-10% process rejects and 15-25% of evaporated moisture. A comparative analysis have been done with probabilistic data with site specific primary data.  A waste to soil ratio of 40:60 is achieved. Cost estimation of different components along with revenue generation suggests a circularity solution. Recovered legacy waste will be further processed for Incineration/RDF/Co-processing, making of building materials, filling materials, waste plastics to paving blocks, compost processing and landscaping, primarily as a valuable material extraction and energy resource recovery strategy to meet the environmental sustainability towards circular economy. This generic methodology will be applicable to different landfill sites of India where Bio-mining is yet to be implemented.