Improving coal dumps with ... grass

Thanks to the roots of four to five meters long, vetiver grass is a giant net that holds and improves soil for coal dumps.

After measures such as lowering the slope of waste dumps, screwing concrete slopes (slopes of waste dumps), Vietnam National Coal and Mineral Industries Group (TKV) has used solutions to grow vetiver grass to improve the environment at the yards. coal discharge.

Natural concrete screw grid

Vetiver grass is cultivated in Chinh Bac disposal site, Nui Beo Coal Joint Stock Company.Photo: Q.Huy.

Mr. Vu Manh Hung, Standing Deputy Director of Mineral Coal Group said: "Each year the coal industry emits about 150 million tons of rock and soil, the few are used for leveling and construction, the rest are collected at the yards. waste dumps up to 300m high (Nam Deo Nai beach), these artificial mountain blocks can 'move', landslide at any time when flooding.

In August 2006, Nam Deo Nai disposal site buried a 2-km long ditch and a number of houses and mineral coal took more than two years to overcome the consequences of the incident, with losses of over VND 7 billion. Other concentrated waste dumps such as Deo Nai, Duong Huy, Ha Tu and Coc Sau are also overloaded and dangerous for people living around.

According to Master Tran Mien, TKV Environment Board, measures such as lowering the slope of waste dumps, screwing concrete to reinforce slopes (slopes of waste dumps) have not brought about many economic and environmental benefits. Therefore, for a long time, Vietnam Coal and Mineral Industries Group (TKV) cooked for a solution to improve the new coal dump.

Master Mien added that the idea of ​​growing vetiver grass to improve coal dumps comes from the research and experience of some countries that have applied as Australia, America, South Africa, Spain. These countries grow vertiver grass for the improvement of waste dumps for coal, gold and bauxite mining . and bring high efficiency.

Previously, Vietnam planted vetiver grass in the Mekong Delta area to embank flood-prone residential routes, fight saline intrusion. With roots up to three to four meters long, penetrating deep into the ground, causing the rock to not erode, wash away, help prevent river bank erosion and dykes.

Mr. Nguyen Van Thanh, Deputy Director of the Department of Industrial Safety and Environmental Engineering (Ministry of Industry and Trade), said growing vetiver grass to improve coal dumping is the latest application of TKV. Grass roots are ingrained into the rock layer, acting as a natural 'beton' net, preventing landslides, clearing soil and improving the environment of coal dumps.

The key to improving coal dumps

According to Mr. Hung, compared to the cost of methods such as lowering the slope of the dumpsite (loading soil and rock layers of waste dumps to lower the height and dangerous slope, avoiding landslides) or screwing concrete nets to hold the soil, it is Costly and unsustainable variables. 'A landfill area of ​​5ha, the amount of soil and rock needed to load about 500,000 m ³ , with the price of 8,000 to 10,000 VND per m ³ of unloaded land, the amount was 5 billion VND, excluding the cost of renovation, embankment and embankment. If you plant vetiver grass, 5ha only takes about 1.25 billion VND (half of the loading and unloading cost), ' Hung said.

One outstanding feature is vetiver grass that is able to survive, and grow well on coal dumps, which other plants cannot survive. 'The method of planting vertiver grass is also simple, living ability is 98% and quite suitable for Vietnamese conditions,' Hung said.

According to Mr. Mien, TKV started planting vetiver grass from October 2007 at high risk landslides such as Coc Sau - Hong Thai, Nam Deo Nai, Ha Tu and Nui Beo. In 2009, TKV accelerated planting 50ha, at new disposal sites such as Dong Tu Bac, Dong Cao Son, Dong Bac Khe Ro, Bac waste dumps, Nam Cao Son and Khe Cham III. 'Due to poor soil deposition, only vetiver roots reach two to four meters in length now, the landfill landslide will be basically controlled. Shortly here, green will return on the landfill, which is the 'dead land' of the former mine ', Mr. Mien is confident.

Vetiver has scientific name is Vetiveria zizanioides (Linn) Nash, belongs to Graminea family (Poaceae), Andropogoneae family, name of Vetiveria derived from Vetiver. According to botanists, Vetiver is a native species of northern India. In Vietnam, Vetiver grass is also called Huong Bai or Huong Lau grass which is grown in Thai Binh and Nghe An.