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Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 39
https://doi.org/10.20896/saci.v7i1.395
© 2019 Mukherjee and Pahari. This is an Open Access article distributed under the terms of the Creative Commons
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SPECIAL ARTICLE OPEN ACCESS
Underground and Opencast Coal Mining Methods in India: A Comparative
Assessment
Sourav Mukherjee†* and Dr Deb Prakash PahariÎ
Abstract
Coal is one of the most essential resources of a country. It is widely used for power generation and
as a raw material in the industries. India ranks third in coal production. However, the country has to
import coal in order to meet the rising demand for coal. In India, coal mining is conducted using
two methods: underground and opencast methods. The underground method is suitable for
extraction of deeper coal seams, whereas opencast method is suitable for shallow coal seams.
However, due to less production cost, mechanisation, and less wastage, opencast method
dominates in India (93.26% of the total production in the financial year 2016-17). Underground coal
production in India shows a declining trend, and several underground mines are closed every year.
However, 60% of the total coal production in the world is from underground mines, whereas in India
it constitutes only 6.74% in the financial year 2016-17. Thus, underground coal production in India
is declining. Due to the large scale extraction of near-surface coal resources by opencast mining,
near-surface coal resources will be depleted in future.
Moreover, opencast mining has several environmental impacts, which is ignored keeping in view
the colossal coal demand of the country. Thus, coal production in India is facing a crisis concerning
the production method, environmental impacts and future demand for coal. With this background,
this paper has been prepared on the basis of data collected from reports, research papers, and
articles. Here, we make an attempt to compare both the mining methods with respect to
advantages, disadvantages, environmental impact and feasibility. We also discuss the current and
future trends of coal production using both the mining methods. Measures to sustain coal
production in India are discussed in the conclusion part.
Keywords: Coal Mining, Underground Mining, Opencast Mining, Environmental Impact, Coal
Demand, India
† Research Scholar (UGC-SRF), Dept. of Geography, The University of Burdwan, Burdwan: 713104, West Bengal, India
*Corresponding Author, Email: mukherjee824@gmail.com
Î Scientific Officer, Dept. of Geography, The University of Burdwan, Burdwan: 713104, West,
Bengal, India. Email :debprakashpahari@gmail.com
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 40
Introduction
Coal, as a conventional source of energy, plays a
very vital role in the overall economic
development of a country. Coal plays a critical
role in our economy, as 45% of the total energy
consumption in India is met by coal (Energy
Statistics, 2017). Indian economy is facing
massive energy demand due to the rising growth
of population, industry and other
infrastructures. Coal-based power plants meet a
major portion of this total energy demand in the
country. It is also a major driving force for the
industrial revolution, and still, it contributes to
the industrial sector as a significant source of
energy and raw material. A major consumer of
coal in India is the thermal power sector, steel,
cement, sponge-iron, aluminium, fly ash bricks,
paper, textile, and other small industries.
Development of an industrial unit or industrial
agglomeration depends on the availability of
coal to a large extent. Coal is also used as a
source of fuel in households. Countries like India,
where the availability of petroleum is deficient
and confined, coal plays a vital role in overall
economic development. The importance of coal
is not only confined in the energy sector but the
more significant role it plays in the economy of
the country (Coal Vision, 2030a).
The Government of India targeted 1.5 BT of coal
production by financial year (FY) 2020 (Tongia,
2016a). Demand for coal in power plants in India
is increasing at a faster rate since the 1970s
(Chikkatur, 2008a). India ranks third in coal
production with a total production of 657.868
million tonnes (Coal Directory of India, 2016-
17a). Though India ranks third in coal
production, the gap between demand and
supply is so vast that, India has to import coal to
meet the rising demand. The gap between
supply and demand for coal was 89.913 million
tonnes during the FY 2016-17 (Coal Directory of
India, 2016-17b). Demand for coal in India as a
source of energy will increase up to 2030 and
maybe beyond that (Coal Vision, 2030b). In FY
2016-17, India imported 41.644 million tonnes of
coking coal and 149.309 million tonnes of non-
coking coal. Thus, coal production in India
witnessed a massive demand, and domestic
production is not sufficient to meet the rising
demand. Against this background, the central
objective of this research is:
To present a conceptual background
about the OC and UG mining methods in
India.
To make a comparative assessment of
significant advantages, disadvantages
and environmental impacts of both UG
and OC mining methods in the Indian
scenario.
To analyse the overall problems, and
suggest suitable measures.
Methodology
As far as the methodology of this research is
concerned, it is mainly based on various
secondary data sources such as reports, papers,
and articles. Reports about coal production in
India were collected from online sources. To
analyse the impacts of OC and UG mining
methods on the environment, different papers
and articles were studied. Past production and
current trend of coal production in India was
obtained from Provisional Coal Statistics (2012-
13 to 2016-17), Coal Directory of India (2007-08
to 2016-17d), Coal Vision 2030 by Stakeholders’
consultation and Indian Coal and Lignite
Resources-2017, published by Geological Survey
of India have been used to analyse the scenario
of coal mining in India.
Coal Mining Methods in Major Coal Producing
Countries
Presently, 60% of the total coal production in the
world is extracted through the UG method (The
Coal Resource: A Comprehensive Overview of
Coal, 2009)
In the United States, surface mining contributed
66% of the total production in 2015 (Coal Mining
in the United States, 2018). Further, in Australia,
77% of the total black coal production is
extracted by surface mining (Mitra and Saydam,
2012a). The scenario of coal mining for Russia is
not very different, where opencast mining
contributes 60% of the total production (Slivyak
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 41
& Podosenova, 2013). Further, 90% of the total
hard coal production in Poland continues to
come from Longwall mining.
1
In Ukraine,
underground mining accounts for 99% of the
total coal production (Coal Mine Methane
Recovery in Ukraine, 2002).
In developed countries, using advanced
technologies majority of the coal is extracted by
UG method except for Australia, where
advanced technology and low-cost
environment-friendly production method helps
to increase the OC productivity (Mitra and
Saydam, 2012b).
In developing countries opencast method is
more popular due to high productivity, lower
cost of production and application of large
mining equipment. Coal production in
Kazakhstan through surface mining was 73% in
1990, which increased to 89% in the year 2000
(Kazakhstani GHG Emissions Inventory from Coal
Mining and Road Transportation, 2002).
However, in the current times, the total
extraction of coal in Kazakhstan is estimated at
85%, which is retrieved through the OC method
(Oprisan, 2011). Most of the mines in Brazil are
opencast.
2
In China, 95% of the total coal
production is extracted through the UG method.
(Kishore, 2018a). Skilled human resource and
advanced technology along with the investment
in the underground mining sector are the
reasons behind the large UG coal production in
China (Kishore, 2018b) In South Africa OC and
UG method contributes 49 % and 51% of the
total production (Munnik, 2010). Thus, the OC
method of production is dominating in most of
the developing countries like Kazakhstan, Brazil
and India.
Present Status of Coal Mining in India
As stated above in India, coal is mined using both
the methods: UG and OC method. However, the
majority of the coal extracted in India is through
the OC method, and it constitutes, 93.26% of the
total coal production in the country (Coal
Directory of India, 2016-17c). The share of the
OC method of coal production has increased
over the years. Less expenditure and wastage is
the reason behind the dominance of OC mining
technique. During the time of nationalisation of
the coal mining industry in 1973, the total coal
production was only 75 million tonnes per year,
and the share of OC mining was only 20 % (Ghose
& Majee, 2001a). In the FY 1998-99, the
production of coal in India was 228.747 million
tonnes (77.15%) from OC mines whereas, 67.761
million tonne (22.85%) from UG mines (Coal
Directory of India, 1998-99c).
Figure 1: Coal Production from opencast mines in India (FY 1998-99 to 2016-17)
Source: Coal Directory of India, FY 1998-99 to 2016-17
1
Eurocoal. Available at:
https://euracoal.eu/info/country-profiles/poland/
(accessed on 02 September 2018)
2
Source: BRAZIL Market Overview: Mining Equipment
and Supplies. Available at https://build.export.gov/build/
(accessed on 2 September 2018)
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 42
Figure 2: Coal Production from UG mines in India (FY 1998-99 to 2016-17)
Source: Coal Directory of India, FY 1998-99 to 2016-17
During the FY 2007-08, the coal production
through the OC method was only 398.182 million
tonnes, which increased to 613.518 million
tonnes with a total increase of 54.07% in the FY
2016-17 (Figure 1). Furthermore, the coal
production through the UG method was only
58.90 million tonnes in the FY 2007-08, and it
further, decreased to 44.350 million tonnes in
the FY 2016-17 with a total 24.70% decrease.
Thus, the UG method of coal production is
decreasing in share, and the production through
OC coal mining method has increased over the
years (Figures 1 & 2).
A worldwide average of coal production from OC
mining is 40%.
3
However, in India, OC method of
coal mining constitute more than 90% of the
total production, and the share is increasing at a
faster rate over the years (Figure 3).
Choice of mining method depends on various
factors such as geological condition (depth, size,
type, and quality of deposit), technological
development and level of mechanisation.
Besides these factors, production cost along with
selling price, environmental and social aspects
are also significant that should be taken into
consideration before mining. These factors
indeed determine the differences between
resources and reserve of coal (Zehirov, 2017a).
OC method is generally chosen for shallow coal
seams, while UG method is chosen for deeper
coal seams. It is apparent from Figures 4 and 5,
that production from the OC coal mines
demonstrates rapid growth over the years,
whereas production from the UG mines shows
negative growth over the years (Figure 1).
Figure 3: Percentage of a Share of OC and UG Mines in India.
Source: Coal Directory of India, FY 1998-99 to 2016-17
3
Will privatisation help the cause of coal
industry? The Asian Age . Available at
https://www.asianage.com (accessed on 2 September
2018).
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 43
Figure 4: Percentage of Growth of UG Method of Coal Production in India.
Source: Coal Directory of India, FY 1998-99 to 2016-17
Figure 5: Percentage of Growth of OC Method of Coal Production in India.
Source: Coal Directory of India, FY 1998-99 to 2016-17
Currently, India has 476 mines in operation,
among which, 236 are UG mines, 215 are OC,
and 25 mines are mixed in nature (Figure 6).
However, the percentage of a number of OC
mines is only 45.16%, whereas it accounts for
93.26 % of the total production (Coal India
Directory, 2016-17). 70% of the total coal
resource in India is extractable by UG mining
method, whereas UG mines constitute less than
10% of the overall production (Raghavan, 2014).
Figure 6: Type and Number of Mines under CIL.
Source: Coal Directory of India, FY 2016-17
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 44
Underground Method of Coal Mining
UG mining method is the oldest method of coal
mining, where coal is extracted by making a
tunnel into the earth surface. Tunnels and
horizontal shafts are made in order to extract the
coal. Thus, a network of tunnels is formed in the
underground. As already stated, UG coal mining
method is dominating over the OC method in the
world, as more than 60% of the total coal
production in the world is extracted from UG
mines. However, in India, only 6.74 % of the
overall coal production is from UG mines (Coal
Directory of India, 2016-17e).
UG mining has evolved from the pick and shovel
method to the modern mechanised Longwall
technology. In India, 90% of the total UG coal
production is produced by the Board and Pillar's
method, and the rest is extracted by the
Longwall mining method. (Mishra et al., 2013b).
Board and Pillar's method is the most common
method of UG mining. In this method, a series of
pillars are made to support the roof while the
coal is extracted between these pillars. Board
and Pillar's mining method is more suitable for
shallower coal seams, where the pressure of
overlying materials are low so that the pillars are
able to support the roof. However, the recovery
of coal is low (60%) compared to the Longwall
method (Das Sharma, 2009a).
Table 1: Production in UG Coal Production in India by Different Methods
Mining
Methods
Conventional
Board and
Pillar's
Mechanical
Board and
Pillar's
Conventional
Longwall
Method
Mechanical
Longwall
Method
Other
Methods
Total
Production
in Million
Tonnes
1.123
34.241
0.126
2.616
6.244
44.350
Percentage
2.5
77.2
0.3
5.9
14.1
100
Source: Coal Directory of India, FY 2016-17
In Longwall mining method, self-advancing
hydraulic roof supporters, coal shearing
machine, and a conveyor, which is parallel to the
face of coal are used to extract the coal. In this
method, within a long corridor in one side, steel
supporters support the roof, while the other side
involves in coal cutting. With each cutting, the
coal cutter is forwarded to the excavated space.
After the full removal of coal, the roof is allowed
to collapse.
Longwall mining method has an advantage over
the Board and Pillar's method because it allows
greater extraction of coal, and it also requires
less human resource compared to the Board and
Pillar's method. The main drawback of the
Longwall mining method is that the cost for
installing machinery used in Longwall method is
very high, which is not feasible for small UG
mines. In India, as the majority of the UG mines
are small in size, so the application of Longwall
mining technology is not economically
profitable.
The total coal production from UG mines in India
is only 79.7 % by Board and Pillar's method,
whereas it is 6.2 % by Longwall method (Table 1).
Thus, most of the UG mines in India operated by
Board and Pillar's method have low productivity.
Therefore the production from UG mining is
steadily decreasing over the years compared to
the OC mining (Figure 4).
Recently, CIL has closed 40 UG mines because
these mines had failed to make profits and
contributed only 10 % of the total output by Coal
India Limited (CIL) but employees a huge labour
force (The Economic Times, March 30, 2018).
Most of the UG mines in India belongs to the
colonial period. Due to inadequate technology
and lesser mechanisation, most of the UG mines
in India operates in a traditional manner
involving more labour force.
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 45
Major Advantages of Underground Coal
Mining Method
Lesser Environmental Impacts: UG mines are
operated over a smaller area, and it affects a
small area compared to the OC method. Thus, it
causes less deforestation, less topsoil removal,
lesser impact on the ecosystem of surrounding
areas than the OC method. In UG mines,
generation of dust is limited within the UG
environment; and in the surface, it emits a lesser
amount of dust compared to the OC mines. Thus,
UG mines have a lesser environmental impact
when compared to that of the OC method. This
observation bear resonance to the observation
as reported by Banerjee and Mistri (2019) in
their research on the impact of Barjora colliery
area of Bankura district, West Bengal on
diversification of rural livelihoods. UG method is
useful for densely populated areas or
ecologically sensitive areas, where the
extraction of coal by the OC method can
seriously affect the environment. UG mining is
also suitable for forest areas, where the OC
method requires the conversion of forest land.
Thus, the environmental impact is much lower in
UG mining when compared to OC mining.
Extraction of Deeper Coal Seams: Extraction of
coal seams with greater depth is more suitable
with the UG method. Rapid and large-scale
extraction of shallow coal seams by OC mining
method causes depletion of near-surface coal
resources of India. Thus to maintain the current
rate of production and to meet the future coal
demand extraction of deep coal seams is
necessary. Extraction of coal seams with greater
depth is more suitable and economically feasible
with UG mining method.
Can Avoid the Problem of Land Acquisition: UG
mining method is operated over a smaller area
as compared to the OC method. Thus, the land
requirement in UG mining is much smaller when
compared to OC mining. UG mining also has a
lesser impact on the surrounding environment
as it is operated within a smaller area. Thus,
problems of land acquisition, displacement, etc.
can be avoided through UG method. After the
extraction is over, the productivity of land can be
maintained through UG mining method.
Lesser Waste Generation: UG mines generates a
lesser amount of waste materials compared to
the OC mines. It has a lesser impact on the
surface than the OC method. It does not create
any anthropogenic landforms such as mine pit
and mine dump like OC mining. The only
deformation that takes place due to UG mining
is subsidence. UG mines have a much smaller
footprint on surface land as compared to the OC
mines.
Involve Greater Manpower: In developing
countries, UG mines involves more labour force
than OC mines due to lesser mechanisation. As a
result, it creates more job opportunities for the
local people than the OC mines.
Adverse Environmental impact of Underground
Coal Mining Method
UG mines affect the environment in various
ways. UG coal mines are exposed to the risk of
roof subsidence, mine fire, explosion, emission
of toxic gases (Mkpuma et al., 2015). The impact
of UG mines on the surrounding are following:
changes in land use and land cover; seismicity
due to blasting; emission of dust into the
atmosphere, and other socio-economic
problems like illegal coal mining and unsocial
activities within coal mining region (Goswami,
2013a).
In the UG mines, after the extraction is over the
strata is allowed to collapse, which puts a severe
impact on surface topography (Wagner &
Schumann, 1991). With subsidence in sub-
surface, surface land also subside. Subsidence
affects the surrounding structures like the
ground, agricultural land, irrigation network,
transport lines and others (Li et al., 2016). Land
subsidence and damages of property and other
infrastructures is the significant impact of UG
mining.
UG coal mines also affect the groundwater of the
mining area. Over exploitation of groundwater
and dewatering within the UG mines affect the
groundwater regime (Table 2). Subsidence of
land also damaged the aquifer (Goswami,
2013b). Thus, water contained within the aquifer
may penetrate deep below as a result of
subsidence. Sometimes, the water that
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 46
discharged from UG mines has high hardness
due to the presence of Sulphate and Chloride,
which are not suitable for drinking or bathing
(Tiwary, 2001a). Thus, the quality of both surface
and subsurface water gets degraded by
wastewater discharged from the UG mines.
Emission of Methane gas from UG coal mines is
another impact of UG mining on the
environment. The deeper the mine, the higher
the amount of methane emission. Methane is
also responsible for underground mine fire.
UG mines are prone to accidents, and most of
them take place due to two main reasons; either
faulty engineering structure within tunnels or
due to the exposure to flammable methane or
coal dust (Das Sharma, 2009b).
Workers of UG coal mines are also exposed to
the risk of lungs disease due to the exposure to
underground coal dust. A study by Bhelkar et al.,
(2015a) shows that the moribund condition is
prevalent more in UG coal mines (65.7%) when
compared to OC mines (54.4%). Their study also
reveals that coal miners in UG mines also open
to the risk of various respiratory diseases, and
backache, skin disease, tuberculosis and others.
Table 2: Impact of UG Mining
Activity within the UG mines
Impact
Depillaring and Blasting.
Land Subsidence and Damages to
Property and Infrastructures.
Dewatering
Over exploitation of Groundwater.
Subsidence in Surface and sub-surface.
Damages to the Aquifer.
Drilling, Blasting, Loading, and Transportation.
Pollution of Land, Water, and
Atmosphere.
Unhealthy Underground Environment and Dust
Generation during Blasting and Extraction.
Health Issues to Mine Workers.
Flooding, Subsidence, and Outgassing within the UG
Mines
Accidents and Deaths of Mine
Workers
Source: Prepared by the Authors
Opencast Method of Coal Mining
Choosing the appropriate mining method for
extraction of coal depends on several factors,
and the OC method is generally chosen when the
coal deposit is large, and the seams are located
near the surface. OC mining or open pit mining is
a surface mining technique where overlying rock
and soil materials (overburdens) are removed to
extract the underlying coal strata. As, the
overlying materials also called as overburden
piled up near the mining site hence, overburden
dump, spoil tips and other anthropogenic
landforms are formed. Excavated area formed a
pit, which is known as mine pit. Thus, the OC
mining method is liable for the change in
topography. OC mining method is dominating in
India because of its more accessible mode of
extraction, a higher rate of production, safety
concern and the higher scope for applying
modern technology for augmented production
(Ghose & Majee, 2001b).
OC mines are operated over a larger area, and it
uses modern, efficient and large equipment like
overburden is removed by draglines, power
shovels, bucket wheel excavators and conveyors
are also used in this regard. Large trucks are used
for the transportation of coal. Other equipment
includes pick-up cars, site-mixing truck,
bulldozers, scrapers, graders, water spray trucks
and others. Loose and less resistant overburden
is removed using bucket wheel excavators (Das
Sharma, 2009c).
An essential aspect of OC mining is that the cost
associated with the removal of overburden,
which determines the profit of the mines. The
depth of coal seams controls the amount of
overburden to be removed. Coal seams with the
greater depth require to remove a large amount
of overburden, and the production cost of coal
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 47
are higher. Nature of overburden is also crucial
because hard and resistant overburden (for
example, boulders,) requires blasting using
efficient technology, which further increases the
production cost. Here, the concept of Stripping
Ratio is critical. Stripping Ratio is calculated in
the following way:-
Stripping Ratio = Unit Waste/ Unit ore cost of
stripping overburden (Coal Directory of India,
2016-17f)
Higher stripping ratio indicates a higher cost for
overburden removal. Stripping Ratio for OC
mines in India is increasing at a faster rate, and
with the increasing Stripping Ratio, the
production cost has also been increasing for the
OC mines (Coal Vision, 2030c).
Table 3: Overburden Removal by Subsidiaries under CIL, SCCL and Different Sectors of India.
Company Name
Overburden Removal
(million tonnes)
Production (million
tonnes)
Stripping Ratio
Eastern Coalfields
Limited
124.637
32.390
3.85
Bharat Coking Coal
Limited
131.215
35.358
3.71
Central Coalfields
Limited
102.630
66.310
1.55
Northern Coalfields
Limited
324.136
84.096
3.85
Western Coalfields
Limited
166.142
40.264
4.13
South Eastern
Coalfield Limited
174.588
120.131
1.45
Mahanadi Coalfields
Limited
123.342
138.193
0.89
North Eastern
Coalfields
5.676
0.597
9.51
Total Coal India
Limited
1156.569
522.663
2.21
Singareni Collieries
Company Limited
312.636
51.821
6.03
Others Public
23.779
9.45
2.51
Private
124.394
29.584
4.56
India
1617.378
613.518
2.65
Source: Coal Directory of India, 2016-17
Stripping ratio of 2:1 to 4:1 is very common in the
mines while the stripping ratio greater than 6:1
makes the extraction unprofitable depending on
the ore extracted (Das Sharma, 2009d). From
Table 3, it is seen that the stripping ratio of India
is 2.67 for the year 2016-17, whereas in the FY
1998-99 it was 2.09. This indicates that the
stripping ratio is gradually increasing over the
years. Stripping ratio is also high for Eastern
Coalfield Limited (3.85), Bharat Coking Coal
Limited (3.71), Northern Coalfield Limited (3.85),
Western Coalfield Limited (4.13), The Singareni
Collieries Company Limited (6.03). This indicates
that cost for extraction of coal is high within
these subsidiaries of CIL and SCCL. As more the
near surface coal resources will be depleted, the
stripping ratio will increase in future to extract
the deeper coal seams. Thus, waste generation
will also increase in future, and after a certain
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 48
level, higher stripping ratio will make the
extraction unprofitable.
Output Per Man shift (OMS) is another measure
which is used to measure the efficiency and
productivity of mine or particular mining
method. It gives an idea about the efficiency and
feasibility of a particular mining method (Coal
Directory of India, 2016-17g). This is the simple
ratio between input and output of mines). The
higher value of OMS indicates the efficiency of
mine, whereas the lower value indicates the
unprofitable condition in mines. From Figure 6,
it is seen that the OMS under CIL for OC mines
increases from 5.52 in FY 1998-99 to 15.00 in FY
2016-17 with a three-fold increase, whereas for
UG mines, OMS shows prolonged growth: 0.59 in
FY 1998-99 into 0.8 in FY 2016-17 (Figure 6).
OMS for SCCL also shows a similar result, OMS
for OC mines under SCCL was only 3.92 in
FY1998-99, whereas in FY 2016-17 it is 13.85 as
compared to the UG mines, which stands at 0.75
in FY 1998-99 to 1.1 in FY 2016-17. Thus, the
productivity and efficiency of UG mines are
much lower than the OC mines, and the
technology or efficiency of UG mines does not
show any significant progress. Low OMS for UC
mines is due to constraints in size, human
resource, and technology within the UG mines.
Indeed, OC mines have more efficient
technology and higher productivity than the UG
mines. Thus, the share of production of OC
mines is increasing over the years, whereas the
share of UG production shows a decreasing
trend (Figures 4 and 5).
Figure 6: Output Per Man Shift (OMS) of UG and OC mining methods under CIL.
Source: Coal Directory of India (FY1998-99 to 2016-17)
Advantages of Opencast Method of Coal Mining
Extraction of coal over a large area: OC mining
method is useful for extraction of shallow coal
seams that spread over horizontally and situated
over a larger area. Removal of overlying
materials exposed the underlying coal seams
and helped to extract the underlying coal strata.
Therefore, it recovers a more significant amount
of coal than UG method.
Less wastage: Wastage of coal is less in the OC
method as compared to the UG method. In UG
mining method, the amount of coal wastage is
high during blasting, excavation, extraction,
transportation within the mines, whereas, in OC
mines, full exposure of the coal seams and
application of modern and sophisticated mining
techniques reduces the amount of coal wastage.
The benefit of using modern and large
machinery: OC mines provides more enormous
scope for applying modern, large and efficient
machinery, which saves the labour cost and
time. Due to the full exposure of coal strata,
installation and operating the machinery is
natural in OC mines when compared to the UG
mines. Equipment used in UG mines are
expensive and can be used only for mining,
whereas OC mining equipment can also be used
for building construction (Yamatomi & Okubo,
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 49
2009). With modern equipment productivity and
production cost is less in OC mines as compare
to UG mines. Blasting, excavation, extraction,
and transportation of coal are rather easy in OC
mines, as it is operated above ground.
Less production cost of coal compared to the
UG mining: UG mining method is more
expensive than the OC method. Use of large and
heavy machinery helps to recover a more
considerable amount of coal in OC Mines. As a
result, the production cost is much low in the OC
method as compared to UG mining.
Lesser Risk of Accidents: OC mines have a lesser
risk of accidents as compared to the UG mines.
OC mining has a less hazardous environment for
workers (Zehirov, 2017b).
Adverse Environmental Impact of Opencast
Coal Mining
Though the OC method of coal mining is more
economical than UG method, OC coal mines
have a more significant impact on the
environment than UG mines. OC mines are
responsible for environmental degradation. OC
mines destroyed the land and associated
ecosystem, forest, displaced people and affected
the environment (Garada, 2015). Destruction of
forest and agricultural land, discharge of
wastewater are the main adverse impacts of OC
mining on the environment. (Chitade & Katyar,
2010). Discharge of wastewater and pollutants
changes the habitat pattern and leads to change
in the soil, air, and water quality (Baruah et al.,
2016).
The problem of land acquisition is much more
prevalent in OC mines. As the OC mines
developed over a larger area, therefore it
acquires much more land than the UG mines. OC
mines required more space than UG mines for
the parking of the heavy vehicles,
transportation, dumping, storing the coal. Land
in OC mines is also used for staff residences,
official buildings, workshops and other mundane
purposes. Furthermore, a buffer area of empty
spaces should be maintained outside the OC
mines in order to prevent the environmental
degradations like spreading of dust, reducing the
impact of blasting, construction of catchment
drains, sediments walls and others. Thus, the
problem of land acquisition creates many
complexities for the OC mines.
The topography of the mining site is also
changed through the process of OC coal mining;
as the formation of artificial landforms like mine
pits, overburden dump changes the relief,
altitude, and slope of the mining site. With these
changes in the mining site, natural geomorphic
processes also change. Landscape change and
formation of anthropogenic landforms is the
most devastating impact of OC coal mining. OC
mining method not only disrupts the natural
topography, but it also alters the natural
geomorphic processes of erosion and
sedimentation.
The problem of land degradation is another
major impact of OC mines. After the extraction is
over or in certain situations, if the near surface
coal seams are exploited, the OC mines are
abandoned. However, in abandoned OC mines,
the mining sites are left without backfilling or
restoring the topography of the mining site.
Thus, the land lost its productivity and leads to
land degradation (Table 4).
Currently, OC coal mining is responsible for land
degradation due to massive waste generation at
a very fast rate, and this indicates that backfilling
the OC mines is necessary and very important.
However, presently no such steps have been
taken for backfilling the OC mines.
Mine water from OC mine generally contains a
high level of total suspended solids, total
dissolve solids, heavy metals, hardness,
Sulphate, oil, grease, Nitrate and pollute the
water regime if it is discharged without proper
treatment. (Tiwary, 2001b). Wastewater
discharged from the OC mines degrade the
quality of both surface and sub-surface water.
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 50
Table 4: Adverse Environmental Impact of OC Coal Mining.
Type of
Impacts
Activity within OC Mine
Adverse Impacts
Impact on
Land
Excavation and dumping.
Alteration of topography
Closure of OC mine without proper
restoration of topography.
Land Degradation and land use, land cover
change.
Excavation and dumping.
Removal of topsoil.
Spreading of pollutants from mine.
Contamination of soil.
Excavation and dumping.
Deforestation.
Impact on
Water
Excavation and dumping.
Degeneration of rivers and alteration of
geomorphic properties of watersheds.
Discharge of wastewater and runoff
from the mine during rainfall.
Acid mine drainage and contamination of
surface and sub-surface water.
Erosion of mine dump.
Sedimentation within the river bed.
Dewatering within the mine and
overexploitation of groundwater.
Lowering the groundwater table.
Impact on
Air
Blasting, drilling, excavation,
transportation etc.
Generation of dust, reduction of the
visibility, particularly in the winter season.
Blasting, drilling, excavation, and
dumping.
Emission of gases and other pollutants in
the atmosphere.
Impact on
the
Ecosystem
Excavation and dumping and related
landscape alteration.
Destruction of local ecosystem and habitat
of species.
Socio-
Economic
Impact
Blasting, drilling, excavation,
transportation etc.
Noise pollution
Excavation and dumping.
Destruction of agricultural land.
Excavation and dumping.
Displacement of people and land loss,
damages of infrastructures, social
instability, and unrest.
Dust generation and pollution.
Health issues of local people and mine
workers.
Blasting.
Damages of infrastructures.
Source: Computed by the Authors
Blasting, waste removal, extraction,
transportation generates a large amount of dust
in OC mining areas. Agricultural land,
households, institutions, roads, water bodies
etc. are surrounded by dust from the OC mines.
Dust particles also reduce visibility and put a
negative impact on the surroundings. People
living in the OC mining areas are suffering from
lungs diseases like tuberculosis (Bhelkar et al.,
2015b).
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 51
Conclusion
Mining of coal in India started from the colonial
period, and after the independence of India,
there is a great reluctance among the
government to renovate the coal mining
industry. Due to lack of infrastructure and
technological constraints, extraction of coal
seams with greater depth is not possible always.
UG mining is more appropriate techniques for
coal seams with greater depth. However, in the
present scenario, the UG mining methods
constitute only a small portion (6.74% in 2016-
17) of overall coal production in India. Mining
authorities, whether public or private sector is
emphasising on OC mining technique, which is
more economical mining method. However, 57%
of the CIL extractable coal resource is situated in
the forest areas, where regulatory approvals
may get more regulated in future and making it
challenging to open OC mines in forest areas
(Fernandes & Sanzillo, 2013b).
Over-extraction of surface coal seams by OC
method of mining will exhaust the near surface
coal seams in future. Moreover, to reduce the
production cost, environmental aspects and
sustainable measures were neglected in the
arena of OC mining. Thus, OC mining is degrading
the environment in various part of the country.
Due to the unprofitable condition and lack of
modern technology, environmental impacts by
OC mines in India is much higher when
compared to the other countries. Allowing the
private sector in the OC mining sector is making
the situation more complicated. Private OC
mines are more concerned with profit rather
than taking environmental measures. OC mines
in India should be more concerned with
environmental impacts. Therefore, provision of
sediment wall, catchment drains to entrap
sediments, afforestation programme, backfilling
of mines, processing of wastewater, dust
suppression from wastewater and minimising
the impacts on land, water and ecosystem are
much required in OC mines of India. OC mining
authorities in India should promote sustainable
mining measures.
Extraction of deeper coal seams with OC mining
method may not be feasible due to the higher
Stripping Ratio. Thus, in order to maintain the
current rate of production, and to meet the
demand for coal in the future, more emphasis
should be given on UG mining. Introduction of
modern technology and efficient equipment is
much needed in UG mining. Therefore,
application of Longwall mining can help to
increase the production from UG mines, and it
will also help to reduce the production cost.
Longwall mining technique has an advantage
over the traditional Board and Pillar's method
because it has facilities for more recovery of coal
in the strata and helps to increase productivity.
Half of the total production of Coal India Limited
(CIL) is from 15 mines which are OC mines and
other 452 mines constitute 50 % of the total
production (Coal Vision, 2030d). Thus small scale
mining operation does not become feasible for
modernisation. In respect of UG mines, 87 %
among them are either semi-mechanised or
operated in a old-fashioned (manual) way (Coal
Vision, 2030e).
In the FY 2010-11, the Geological Survey of India
(GSI) has explored a total of 115 seams, among
which 79 seams lie below the depth of 150
metres, and 43 seams are below 300 metres
depth. Therefore, UG mining is more efficient to
extract these seams. However, UG mining have
higher production cost and lower productivity as
it extracts only 40-70% of the coal deposit. Thus,
extraction of deeper coal seams can increase the
production cost and market price of coal. The
price of electricity can also increase with that.
Thus, current coal price in India does not permit
for UG mining (Fernandes & Sanzillo, 2013c).
Thus, small and unprofitable mines should
merge to make bigger and profit gaining mines.
Investment is much required in UG mines to
promote modern technology and increase
production. Ignoring the UG mining sector may
affect the future coal production in India, as in
future when near-surface coal resource is
depleted or extraction is carried through OC
method will be unprofitable due to higher
stripping ratio, adopting UG mining will be the
solution. However, in the present scenario, most
of the UG mines are closing every year and the
UG production shows a declining trend. Thus,
Mukherjee and Pahari. Space and Culture, India 2019, 7:1 Page | 52
investment and the opening of new UG mines
are much needed, keeping in view the future
coal demand. Allowing private sectors in the UG
mining sector may be a right solution, as the
private sector will provide investment and
technology for the UG mines and UG mines will
help to sustain the future coal production of
India.
Increasing the import of coal from the other
countries is not a solution to meet the rising coal
demand of India. If coal import increases, the
domestic coal sector may face intense
competition in future. Increasing the import will
also affect the Gross Domestic Product (GDP)
and the economy of India.
In India, selling of raw coal is done by either
through E-auction or through Long-term Fuel
Supply agreement (FSA). Price of Raw coal which
sold under FSAs by CIL is not always reflecting
the market price of the coal in the international
market, while the coal sold under E-Auction
reflect the market price. Therefore, the price of
coal sold under FSAs is much lower than the coal
sold under E-auction (Mishra & Suhag, 2017).
Price of coal should be determined to keep in
view the international price of coal. Giving
subsidies in coal price only cannot save this
sector.
Generation of electricity consumes nearly 75%
of domestic coal production (Chikkatur, 2008b).
Energy demand will increase in the future due to
population growth, industrial expansion, and
infrastructural development. Exploration effort
by CIL is inadequate keeping in view the future
coal demand (Fernandes & Sanzillo, 2013d).
Demand for electricity and coal is so high in the
country that the coal mines are violating
environmental regulation and norms. Therefore,
the main challenge before the government is to
enforce and tighten the existing regulations.
(Chikkatur, 2008c).
Coal conservation and finding alternatives to
coal in the energy sector is much required.
Dependence on coal not only degraded the
environment, but it also affects the economy as
the coal import of India is rising over the years.
Thus, more emphasis should be given to non-
conventional energy sources like solar energy,
wind energy, and atomic power etc. Instead of
heavy dependence on coal government should
take the initiative to popularise the non-
conventional and eco-friendly sources of energy.
Conservation measures of coal should also be
taken keeping in view the future coal demand of
India. Saving electricity and energy, increasing
the use of nonconventional sources of energy is
required in this regard. Also, lower grade coal
should be mixed with superior quality coal for
use in industries. Furthermore, coal wastage
should be reduced during transportation. Coal is
a resource of our country, and we have to realise
rather than understand the value of coal keeping
in view the future coal demand of India and by
this way conservation of this precious resource
is possible.
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Acknowledgements
Both the authors are thankful to the anonymous
reviewers for their contributions and valuable
comments. Authors are also thankful to the
editor of the Journal of Space and Culture, India
for his/ her co-operation and guidance for
publishing the paper.
About the Authors
Sourav Mukherjee has completed his Mastersˈ in
Geography from the Department of Geography,
The University of Burdwan. Presently, he is a
Research Scholar (UGC-SRF) in the same
Department. His foremost research interests are
the fields of Geomorphology (Fluvial),
Environment (hazards), and Application of
Remote Sensing and GIS. He has published four
research papers and one book chapter; and
presented ten papers in National and
International Seminars and Conferences.
Dr Deb Prakash Pahari is the Scientific officer,
Department of Geography, The University of
Burdwan. He completed B.Sc in Geography
(Specialisation: Cartography), M.Sc. in
Geography & Environment Management
(Specialisation: Coastal Geomorphology), and
PhD (Research Topic: Coastal Resort of West
Bengal and Environmental Appraisal). His
foremost research interests are Geomorphology
(coastal), Environment (hazards), Tourism and
Remote Sensing and GIS. He completed 4 (four)
research projects as a co-investigator. He has
published seven research articles in scholarly
books and reputed journals; and presented 18
papers in National and International Seminars
and Conferences.
