Reclamation of mining dumps: Is mining waste suitable for forest restoration?

Prachi Thatte

PhD Candidate, National Centre for Biological Sciences (NCBS)

With 664 million tonnes (Mt) of coal, India was the third largest producer in 2014-15, next to China (3474 Mt) and the USA (924 Mt). The Indian government has announced an ambitious plan to produce 1500 Mt of coal by 2020, at an annual growth rate of almost 20%. In order to meet this target, massive expansion of open cast mines is envisaged. About 80% of India’s coal reserves lie in the central Indian landscape and much of it is under forests. Destruction of forests is inevitable for open-cast mining. Along with deforestation, direct and indirect mining activities change the landscape surrounding the mine. Direct activities include removal of the top soil, followed by excavation of overburden and then coal extraction. Indirect activities include tree felling for constructing roads, houses and other infrastructure, thus increasing the anthropogenic impact on the surrounding landscape.

A coal mine. Photo by Nitin Kirloskar.

Under the Forest Conservation Act, 1980, whenever forest land is diverted for non-forest use, compensatory afforestation (CA) needs to be carried out on an equal amount of non-forest land, or double the amount of degraded forest land. It is usually recommended that CA should be done at the point closest to where diversion is taking place. Mining companies often reclaim the overburden dumps for afforestation. But can these overburden dumps, after reclamation, support similar species of trees which were found in the forest that was cleared? How different are the physical and chemical properties of the dump soil compared to the soil found in the surrounding areas?

In order to answer these questions, Jitendra Ahirwal and Subodh Kumar Maiti from the Indian School of Mines, Dhanbad evaluated the changes in soil properties due to direct and indirect mining activities around Ananta open cast mine in Odisha. They collected soil samples from 5 different sites in 2008:

1. Soil from Sal (Shorea robusta) forest patch- original habitat before the area was mined
2. Reclaimed mine soil (RMS)- While excavating coal from the mine, the overburden (rock and soil which lies above the coal) was dumped in a nearby area. In 2003 these dumps were reclaimed by planting fast growing species of trees such as Acacia and Cassia
3. Mine face topsoil, the uppermost layer of soil which is close to the excavated area
4. Soil from wasteland- Sal forest that was degraded due to human activities
5. Soil from agricultural area (mostly rain-fed paddy cultivation).
   

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