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.

Biomining 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.

Application of FSLM

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

Issues

• 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 India” by 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.