Bangladesh has discovered the biggest ever limestone mine in Naogaon whose commercial production could completely cut the country's reliance on import of the key ingredient for cement.

The mine is spread over a 50-square kilometre area in Tajpur of Badalgachhi upazila.

It might take two years for the mine to go into commercial production, Nasrul Hamid, state minister for power, energy and mineral resources, told reporters at the secretariat yesterday.

The mine would meet the local demand for limestone, which is imported mainly by local manufacturers for producing cement.

Bangladesh would no longer need to import limestone, and it would save Tk 1,000 crore a year, Hamid said.

State-run Geological Survey of Bangladesh (GSB) discovered the mine after drilling 2,270 feet into the surface.

Limestone was found at a depth of 2,214 feet, and its presence was so far traced down to 2,285 feet with a thickness of 71 feet.

Given that this thickness remains the same over the 50-square km area, the deposits would hit 50-100 billion tonnes, said GSB Director General Md Nehal Uddin.

“It is a major discovery,” he told The Daily Star. 

“We have to conduct further study, and see the local demand and the mining cost.”

The quarry could be explored through underground mining and the technology needed for that is available. It would be commercially viable as there is local demand for limestone, he said.

Bangladesh now imports 18 lakh tonnes of limestone a year. 

GSB engineers started drilling the mine on February 20 and found limestone a few days ago.

“Once we extracted limestone from there, we informed the government about the discovery,” said Nehal Uddin.

GSB officials said they would drill another 1,500 feet into the ground.

The deposits at the new field might easily surpass that of Joypurhat field, which holds a reserve of around 100 million tonnes of limestone, according to the GSB. 

But the government didn't go for extraction from the Joypurhat mine discovered in 2012 though preparations were made to that end, said a GSB official.

Bangladesh now depends on import for limestone, which is used for producing cement.

“Once we successfully start commercial production, we will not only be able to meet the domestic demand, but also have a surplus,” said Nehal Uddin.

The GSB relied on its own workforce and technology for the discovery and the project cost was about Tk 70-80 lakh, he said.

Limestone is used as a building material, aggregate for the base of road, white pigment or filler in products such as toothpaste or paint and chemical feedstock for the production of lime.

Clinker, an essential component of cement, is made from limestone. It plays the most vital role in ensuring the strength and quality of cement.

Bangladesh imports about 24 million tonnes of raw materials a year for the cement sector. And of those, 70 percent is clinker, said Alamgir Kabir, vice president of Bangladesh Cement Manufacturers Association.

The materials come mainly from Vietnam, Thailand, China, Japan, Indonesia and Iran.

“The discovery of limestone mines alone would not bring any benefits. We have to extract it,” said Kabir.

At present, only two cement manufacturers -- Lafarge Surma Cement Ltd and state-run Chhatak Cement Factory Ltd -- produce clinker at their plants by importing limestone from India.