Bioearth mined from dumpyards may be used to restore degraded land, says Anna University study

Legacy garbage dumpyards may be of some use after all. Bioearth mined from these sites may be used to enhance soil quality in degraded lands, according to a study by Anna University.

Bioearth is a type of fine residual soil that is formed in legacy dumpyards through long-term microbial degradation of organic matter. It constitutes about 30 to 40% of the total waste volume. Two scientific papers on the studies, published earlier this year in Environmental Science and Pollution Research and Stochastic Environmental Research and Risk Assessment, throw light on the physical, chemical and nutrient characteristics of bioearth, besides assessing heavy metal content and related risks.

Carried out by Centre for Environmental Studies of Anna University, the studies analysed multiple samples from 13 dumpsites across Tamil Nadu and found that the bioearth contained nutrients in adequate proportions to support plant growth. Although the presence of heavy metals was a concern, the alkalinity of the bioearth (pH of 7.75 to 8.5) ensured that the solubility of the heavy metals was greatly reduced, thereby limiting their intake by plants and soil organisms, said Saranya Kuppusamy, visiting professor, Centre for Environmental Studies and co-author of the papers.

Only chromium and nickel were found to be marginally over the permissible limits as per Indian standards, Dr. Saranya said, adding that there were remedial measures to ‘immobilise’ or ‘stabilise’ this heavy metal content as well. For example, phyto-remediation that involved planting hyper-accumulating plants to absorb the soluble fraction of heavy metals or use of organic amendments like biochar could be considered.

Both the studies recommended remediation strategies to be developed and implemented before bioearth is used for agricultural or ecological purposes.

S. Kanmani, Head, Department of Civil Engineering and Director-in-charge, Centre for Climate Change and Disaster Management, who is the lead researcher for the study, said that the study results have policy implications for the government, especially in the fields of afforestation, wasteland reclamation and environmental management. She also suggested pilot afforestation trials across diverse climatic zones to collect data on growth performance and soil health recovery.

To this end, a pilot project was undertaken to regenerate a degraded forest area in Madurapakkam near Nanmangalam forest on the outskirts of Chennai using bioearth from the Perungudi dumpyard. The results were stated to be encouraging.

The bioearth study was funded by the Tamil Nadu State Planning Commission under its Tamil Nadu Innovations Initiative (TANII) scheme.

Published - June 07, 2025 11:20 pm IST