Constraints of coal miningPublished by MAC on 2007-05-05
Constraints of coal mining
Badrul Imam, The Daily Star, Bangladesh
5th May 2007
The recent death of a British mining expert inside the Barapukuria coal mine has rekindled the question of safely in the mine. On the morning of April 26, Albert Davies, a mine ventilation expert died inside the roadway tunnel at a depth of 450 meters while he was on a routine check-up of the ventilation system along with his colleague, Nicholas Woodburn. Apparently, the two experts were at a place where the temperature and humidity were very high. While Albert, aged 62, who could not stand the suffocating environment for long, collapsed to the ground and died, the 24 year old Nick, also suffering from suffocation, could somehow reach the point to call the rescue workers.
Most of the energy experts believe that there is no option for Bangladesh other than mining its coal for power generation, because the future power demand cannot be met from gas-based power plants as the gas reserve is too limited to run for long. This seems to be well understood by the policy makers, who are contemplating using coal-based plants for future power generation. At present, the only coal-based power plant (250MW) in the country is in operation near Barapukuria coal mine, which feeds the plant. Since the accidental closure of one production face of Barapukuria coal mine about a year ago, production rate is about 1500 tons per day instead of 3300 tons a day (or 1 million ton a year) originally planned from two faces.
The Barapukuria underground coal mine in Dinajpur district has now gone through a period of 8 years of construction and one year of production. During this period, three labourers and one expert died underground by accident. Although, the fatality rate is insignificant compared to some ill-fated mines around the world, there have been several major accidents which severely affected the infrastructure and economy of the project.
On the other hand, a plan to establish an open-pit mine in nearby Phulbari was aborted last year in the wake of mass protest by the local people. Five persons were shot dead by the law enforcing agency. Since then, coal mining has been hotly debated in many forums around the country. Although there is merit in these debates, scientific judgment must play a role in such deliberations.
Which mining method would be appropriate has to be judged from the view-point of environment, safety, and economics. The following points highlight the issues that matter most while considering mining prospects and problems in Bangladesh.
1) What makes coal mining in Bangladesh much more difficult compared to its counterpart across the border in West Bengal in India is the presence of a thick (about 100 meter), loose, water-bearing sandy layer (aquifer) above the coal deposit.
a) In the case of Barapukuria underground mine, this water-bearing layer poses problems of shaft sinking as well as water flooding. In 1997, the mine was totally flooded with water from this layer, for which mine construction work was suspended for a year.
b) In case of an open-pit mine this water layer will fill the mine pit if the water is not continuously pumped out throughout the period of mining. Such long-term pumping will lower the groundwater table in the surrounding land mass and habitat, and desertification may set in.
2) a) In the Barapukuria underground mine high heat flow in certain areas (southern part) raised the temperature in the tunnels very high. In addition, high rate of water discharge from quarried coal in the above situation makes the environment excessively humid. This gives a perfect recipe for heat stroke and suffocation, most likely faced by the two British experts, one of whom died on April 26. The working condition in such hot and humid environment is often inhumane.
A second problem in Barapukuria is poisonous CO gas emission due to spontaneous combustion. A production face (1110) had to be closed and sealed, with million dollar worth of equipment trapped inside, due to the CO gas emission in September 2005. A little amount of CO gas can kill a person; however the above incident, luckily, did not cause any death.
Roof fall is another problem in Barapukuria, by which the death of three persons was reported on three occasions during mine construction. A fourth aspect of all underground mines is the risk of methane gas explosion, which may kill a good number of people at a time. However, laboratory analysis rated Barapukuria coal as low to medium risk in this respect.
b) In case of an open pit mine the above factors are non- issues, but during monsoon, torrential rain may cause large scale land slide related to pit slope instability. This, along with water logging problem would render coal mining almost impossible. Pit slope will be particularly vulnerable to landslide in the loose water bearing sand layer which has slippery clay interbeds.
3) a) In the Barapukuria underground coal mining area small scale subsidence has been noticed in the surface which has affected a few village houses (wall cracking) and crop fields. The social impact of such events are contained by compensation to the affected people.
b) In case of an open-pit mine eviction, resettlement of a very large number of people is essential. The amount of loss of cultivable land is very high as well. The population density in Bangladesh is about 1000 per sq.km. compared to 350 in India, or less than 10 in Australia where large scale open-pit mines operate. This is probably the most important point raised by the opponents of open-pit mine in Bangladesh.
4)a) In underground Barapukuria mine, expected recovery of coal is 20%. All of it is planned to be used in the country.
b) In case of open-pit mine, recovery is expected to be as high as 95%. A major part of it is expected to be exported by the foreign company which would run the mine; Bangladesh presently is not capable of running an open-pit mine.
Conclusion: The above point to the constraints of coal mining in Bangladesh, irrespective of the mining method adopted -- underground or open-pit. The lesson is that one cannot be too aggressive in mining coal in Bangladesh because of the difficult geological setting, environmental effects and large scale social (resettlement) problems. One has to be cautious and conservative, rather slow and steady in extracting coal from under this soil. The national coal policy which is about to be announced shortly is reportedly contemplating to produce coal at a rate 20 million tons a year within 10 years, and 40 million tons per year within 20 years. This requires more than one large scale open-pit mine. Such a plan may definitely be referred to as aggressive.
The policy makers must consider the inherent ground level problems -- geologic, environmental and social -- before contemplating such aggressive coal policy.
Dr Badrul Imam is Professor, Geology Department, Dhaka University.