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Fine soil-like materials (FSLM)

  • Context (DTE): Fine soil-like materials (FSLM) recovered from legacy dumpsites may contain contaminants; therefore, they must be tested before being used in any application.
  • FSLM is produced during the Biomining (bioremediation technique) of waste dumpsites.
  • FSLM is the largest component obtained from landfill mining. It has little or no economic value.
  • FSLM, comprises particles smaller than 6 mm. Fine materials in 4-6 millimetres are called ‘bio-earth’ or ‘good earth’ materials.


  • It uses microorganisms (microbes) to extract metals of economic interest from rock ores or mine waste. It is also used to clean up sites polluted with metals.
  • There are two types of processes involved.
    • Some microbes can oxidise metals, allowing them to dissolve in water (Bio Leaching). For example, iron and copper.
    • For metals not dissolved by the microbes, microbes break down the surrounding minerals, making it easier to recover the metal of interest directly (Bio oxidation). Example, gold
  • The greatest environmental risk related to Biomining is the leakage and treatment of the acidic, metal-rich solution created by the microbes.

Legacy waste

Application of FSLM

  • Soil enricher.
  • Filler material for low-lying areas.
  • Used in road construction.
  • Brick making.


  • As per Central Pollution Control Board guidelines, FSLM must comply with the Fertilizer Control Order standards to be used as a soil enricher. However, in most cases, they do not comply.
  • They are not tested for toxic metals before being used as a filler material.
  • Heavy metal contamination is a significant risk associated with using untested FSLM.
    • Toxic metals (lead, mercury, cadmium, and arsenic) can harm human health.
    • Additionally, heavy metals have the potential to accumulate in plants and animals. This can lead to bioaccumulation.

Way forward

  • The comprehensive “Guidance document for assessment and remediation of contaminated sites in Indiaby MoEFCC serves as a roadmap for tackling the issue.
  • It sets clear boundaries for acceptable levels of heavy metals and toxic contaminants through two key sets of standards (Environmental Quality Standards (EQS) and Threshold Limit Values (TLV)).
  • These standards can be utilised to assess the gainful application of FSLM recovered from landfill waste.
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