By Dr. Piyush Rai, Honorary Advisor to Pozhat,
Professor & Head, Department of Mining Engineering, IIT-BHU
Exponential increase in coal production and productivity levels need over emphasis through gigantic and expansive coal project outlays, positive outlook towards adoption of rampantly evolving fore-front technologies, research, innovation and designs etc, on one hand and sustainability of mining operations vis-à-vis growing environmental concerns, as the by-product of increased coal production, on the other hand. In this light, the key sustainability issues related to environmental challenges faced by the coal industry in various stages of coal mining operation chain and the possibilities to overcome these challenges in light of emerging technologies are discussed in the present paper.
Although India is producing over 700 Mte of coal annually and it ranks as second largest coal producer globally, there still exists a huge gap between the demand and supply of coal. The huge demand is unlikely to stop in foreseeable future. This is primarily attributable to abundance of this fossil fuel in India, availability of very limited resources and reserves of oil and natural gas and several limitations being faced by renewable and nuclear energy resources in contributing to the energy sector in our country. In addition to the power generation (almost 58%), the coal is an essential raw material for Steel, Cement, Fertilizer, Ceramics, Chemical, Paper and a plethora of MSME industries. Given this situation, coal has been and shall remain “King” in catering to the energy needs of our nation in near as well as distant future. Therefore, Coal mining in India needs to be accelerated in view of ambitious projects, such as “Make in India”, “Made in India” leading to an “Atmanirbhar” India as immaculately envisaged by our Hon’ble Prime Minister.
A noteworthy point, although India as second largest coal producer in world, with a population of about 1.39 Billion (estimated growth rate 0.91% approx.), produced almost 720 Mte (2020-21), China, the world’s largest producer with population of 1.44 Billion(estimated growth rate of below 0.5% approx), has over 5-times higher coal production. This indicates insufficient energy production, which, in turn, distinctly reveals poor per capita energy usage in industrial, commercial, manufacturing and domestic sectors of India. This state is alarming for a growing Indian economy and needs to be viewed and reviewed utmost seriously as is being done by the Govt. of India. Boost in energy sector by massive impetus on expansion of coal projects and also by enhancing the capacity utilization of the existing projects is absolutely crucial for propelling Indian economy.
Exponential increase in coal production and productivity levels need over emphasis through gigantic and expansive coal project outlays, positive outlook towards adoption of rampantly evolving fore-front technologies, research, innovation and designs etc. with proper cognizance to operator’s Safety Health and Environmental (SHE) issues.
Nevertheless, the emphasis on coal production on one hand and serious concern on Net Zero for creating a Carbon Neutral environment on the other hand, has made the industry, academia and researcher very sensitive and overtly conscious about the sustainability of coal mining. In the current and evolving perspective, the ecological imbalances as the by-product of coal mining need to be addressed vociferously by adopting befitting technologies and state-of-art remediation and curative measures to protect the environment in order to make the coal mining more responsible and sustainable in the years ahead, especially in view of energy security needs of our Nation. In this light, the current paper targets the emphasis on the existing gap areas, which need to be addressed to by the Indian coal industry in its quest for sustainability, with environmentally friendly mining tools, techniques and gadgets, in the forthcoming years.
2.0 Goals and Scope of Sustainable and Responsible Mining
Sustainable and responsible Mining aims at fostering innovation, best practices and intelligent solutions to deliver acceptable results across the entire value chain of mining life cycle in its different stages, commencing from the mineral discovery and culminating to the delivery of finished products. The sustainable mining entails the preparation of pragmatic plans prepared after a rigorous internal and external engagement, in-depth understanding and critical assessment of challenges and opportunities in terms of short- and long- range perspective. It necessitates the clear understanding of long-term impacts of mining activities before, during and after the mining operations with especial thrust on environmental, economic, and social dimensions. Sustainable mining practices must accomplish the sacred goals in the different stages of the mining life cycle, as illustrated in Fig. 1.
Fig. 1: Goals of Sustainable Mining Practices Vis-à-vis the Mining Life Cycle
Furthermore, scopes of sustainable mining practices in each stage of the mining life cycle are discernible in the Fig. 2.
Fig. 2: Scopes of Activity in Various Stages of Mining Life Cycle
It is quite evident from the Figs. 1 and 2 that not only the exploration, feasibility, design, planning, construction, exploitation and mineral processing are important, but equally and rather, more important, are the mine closure and post-mining land use planning and its precise implementation. The scope of land use encompasses the restoration of not only the degraded land but it must also be looked into as a measure to restore the complete eco-system (inclusive of biodiversity), with due cognizance to the air, water, noise dust, waste, aesthetic and socio-cultural changes. Effective implementation of this understanding shall establish a long way not only in protecting the environment, ecosystem, public health, public perception and changing the attitude and mindset of people and government towards the mining industry.
It is very consequential to re-affirm the importance of Net Zero vis-à-vis sustainability of mining industry. The recent directive by the Ministry of Coal, Govt. of India is to boost the production and productivity from the CIL in order to reach the annual target of 1 billion tones by 2023-24. In accordance, the CIL has ambitious expansive plans with an outlay of approximately Rs. 1.25 Lac Crores to meet the slated target of coal production by 2023-24. Four Coal India subsidiaries, namely, MCL, SECL, CCL and ECL are likely to invest around Rs. 3400 crores in around 14 major projects to enhance the coal production capacity by over 100 Million tonnes per annum. This capacity expansion necessarily entails huge energy consumption, both diesel and electric, in the entire value chain of production operations. Therefore, there is an emergent need to gear up for the momentum from the beginning in order to follow an integrated and holistic approach from viewpoint of conservation of environment, especially in view of emerging concerns on carbon foot prints, their minimization and culmination to net zero in India by the year 2070, as per Glasgow summit and agreements. The Green House Gas Emissions (GHGEs), dust (especially PM 2.5 and PM 10), noise etc. again become critical components.
In this light, it is of paramount importance that the aggressively evolving technology must be seamlessly intertwined at relevant operational points in order to reap the fullest benefits for accomplishment of cherished goals of sustainable and responsible mining.
3.0 Methods, Concepts and Technological interventions for Sustainable Mining
Apart from focusing on various conventional methods, practices and techniques, to bring forth a few like; replenishing native soils and grasses, cleaning excess waste, proper waste removal, site inspections, replanting trees and restoration of natural forestry, choosing environmentally friendly mining operations and methods, implementing green mining technologies, reducing and reusing waste, re-evaluating the cut-off grades, increased use of in-pit crushing and conveying System, angle conveyors including high angle conveyors, redesigning open cast mines to reduce haul distances (wherever possible), on-line dust suppression techniques, improvements in operation and design of diesel engines, use of electric vehicles (wherever possible), deployment of large sized equipment- drills, shovels, dumpers, draglines etc., creation of impermeable tailing dams and pond, effective treatment of acid mine water, mill tailings, extraction of REE from acid mine water, effective and regulatory shut down of illegal mining etc., some of the latest technological developments are being elaborated (in view of their game changing potential and relevance in the emerging and evolving technological scenario) as follows:
Application of Surface Miners: Surface miners have been working in Indian surface coal mines with higher productivity and environmental benefits. Their use has been attaining increased acceptance, especially in those mining areas where breakage by drilling and blasting is either operationally or cost prohibited. For instance in the Gevra project of SECL almost 66 % of the coal production is attributed to the surface miners. Currently, 135 surface miners are working deployed in 36 OCPs of CIL. The surface miners although not as versatile as the D&B , wherever they can be optimally deployed the success rate has been laudable. Besides overcoming a host of blasting nuisances in and around the blasting area, nearby habitation sites the surface miners are readily vulnerable to selective mining of coal. Furthermore contiguous and/or multiple thinner and inferior coal seams which were unworkable by conventional drilling and blasting system, get readily extractable, which, in turn, has converted the existing coal resources into reserves, thereby increasing the total coal reserves. Overall production cost by the surface miners is reduced. Nevertheless, the hardness and gradient of the coal seam are constraining factors with surface miners.
Overland Conveying Systems (OLCS) : Handling and transportation of millions of tones of broken rock and/or coal to their deposition/end use sites by fleet of trucks is a common practice in surface coal mines. The challenges posed by difficult terrains, weather conditions, road conditions, fugitive and dust emissions, down and maintenance time, idling time due to queuing at loading and disposal site, poor overall efficiency and most importantly the public distress in the mining areas due to frequent plying of trucks with their fugitive and dust emission levels, deterioration and ruining of public roads more than offset the merits of truck transportation system that are largely economical owing to the fleet of trucks being much cheaper to purchase. While the cost benefit aspect may appear to be cheaper initially, in the long range perspective on evaluating the direct and indirect cost elements and the efficiency of truck transport system, the initial hypothesis may appear much more expensive being inefficient and environmentally unsustainable. Given this the Overland Conveyor System (OLCS) besides a plethora of technical and operational merits, are much more superior in terms of their environmentally sustainable features and merits embedded therein. The OLCS of Sasan Power Limited,Reliance, Singrauli, is India’s largest Eco-friendly OLCS for transportation of coal. It is a single flight, securely covered conveyor belt without any transfer point en-route. Therefore, it minimizes fugitive, dust and noise emission during the transportation of coal from the coal mine to the power plant. As such, it does not cause social distress, which, in turn, makes it much more attractive and environmentally sustainable. This OLC System has been designed to carry coal at 4500 TPH capacity with belt speed of 5.6 m/s and belt width of 1800mm. The system is highly durable and robust for long, speedy, noiseless and continuous handling operations.
GHGEs, Environmental Considerations vis-à-vis Intelligent Technology: In light of previous description of the Net Zero vis-à-vis sustainability, the GHGEs and other environmental parameters need to be carefully monitored and analyzed by using state-of-the art techniques, tools and methods. The intelligent and smart monitoring, quantification and analysis of these key parameters shall go a long way in accomplishing the goals of production, productivity, cost economics, on one hand and sustainability of mining projects on the other hand in our quest for “Green mining”. Apart from active mining faces and mining operations in the active mining areas, the haul roads, the crusher points, coal handling plants, railway sidings, waste dumps etc. must be considered as suitable sites for monitoring and remediation by generating suitable KPIs for evaluation. Towards this, state-of- the art application of sensor based drones, digitization of data gather, high resolution cameras, dashboard systems could be effectively utilized for smart monitoring and providing the MIS. The information and data so gathered could be aptly synthesized, analyzed and interpreted by use of a number of Artificial Intelligence (AI) techniques, such as big data analytics, Machine learning, deep learning, advanced statistical techniques etc.. The results of gathered data and its analysis could be disseminated by use of sensor based IIOTs, on the Android phones, as well.
Mine Depth Related Issues: As the mines get deeper the ventilation, water management system and safety of operation shall be confronted. Close monitoring of operational and operator’s safety and health issues is warranted thereof. Water appears to be a big deal in the future. Process technology where we use less water, reuse of water, as well as dealing with mine water may be interesting and challenging too. Also, in deeper mines static as well as dynamic loading on deep pit and dump slopes would be important. To be handled with adequate caution. Impact assessment of blasting fumes and dust generation potential due to blasting vibrations from the active benches and loose waste dumps and their dispersion pattern need to be monitored properly, especially when the mines are going deeper and clearance of dust and fumes has been posing immense challenge from deeper horizons. On-line monitoring, water sprinkling and analysis of dust dispersion patterns need to be done by state-of-the art techniques.
Waste to wealth: This area has recently received significant attention in view of the noble idea of reducing, reusing and recycling the waste generated in any process or technology so aptly propounded by our Hon’ble Prime Minister. The idea and motivation holds very laudable potential to provide huge revenue to the coal industry by using the waste generated in mining operations. OB waste is already being used to generate sandstone, it could also be thought of and researched properly for use (after suitably crushing and sizing) in making embankments, pavements, reinforcing mine haul roads etc. Similarly, the byproducts from coal washing plants, such as ash, tailings, burnt oil etc., could be reused within the mining industry itself in a closed loop. Waste such as ash, tar and burnt furnace oil from the nearby TPPs also offer tremendous reuse potential in mining loop itself. Additionally, very low grade coal, as a by-product in higher grade coal mining, could be converted into graphene and nano-particles for energy storage. The use of oxygen storage in graphene and nano-particles needs to be explored. REE and heavy metal extraction, acid mine water neutralization, bricks manufacturing from ash need especial mention here.
Clean Coal Technologies (CCT): Clean coal technologies need not be restricted to washing coal and concurrently harnessing the value from the washery rejects. It is now imperative to tap the deep seated and/or low grade coal resources that have merit to be become reserves. To meet this end, although lot of prospecting and exploration in underway in various coal fields, still lot more serious impetus needs to be given to tap the techno-economic and techno-commercial extraction of Abandoned Mine Methane (AMM), Coal Mine Methane (CMM), Coal Bed Methane (CBM), extraction of coal by primary/in-situ gasification methods. The resource and reserve characterization for these CCTs need to be done in a coherent and organized manner by bringing a host of agencies and institutions together on a workable platform. Surface coal gasification is considered as cleaner option as compared to burning of coal in the TPPs. The surface gasification (aka secondary gasification) largely depends on the chemical properties of coal. Syn Gas produced from the surface coal gasification has multiple usages, namely, for producing Synthetic Natural Gas (SNG), energy fuel (methanol & ethanol), production of urea for fertilizers and production of some important chemicals etc.
Sustainability of mining operations in general, and surface coal mining operations, in particular gain much greater significance and have become much more imperative with exponentially rising demand of coal to meet the energy security of our nation. To increase our impetus on sustainable mining, it is essential to critically view the sustainability at each stage of the mining life cycle. Accordingly, in addition to continuing the conventional methods practices and techniques of tackling the environmental issues, it is of paramount importance that the aggressively evolving technology must be seamlessly intertwined at relevant operational points in order to reap the fullest benefits for accomplishment of cherished goals of sustainable and responsible mining. This ought to cater to the energy security needs of our nation on one hand and make our coal mining industry very contemporary, environmentally sustainable and responsible in the global perspective, on the other hand.