The safe bet of underground mining

In the face of coal's challenges, its underground mining can prove to be a promising and environmentally conscious path to safeguarding India's energy future

India’s energy landscape is shifting shape dramatically. The transition towards renewable energy (RE) sources, led by solar and wind, is racing ahead energetically. Green hydrogen, pumped storage hydropower, gravity storage, and energy storage systems are also competing in this transformative race. Keeping in sight India’s nationally determined contribution (NDC) commitment to reducing carbon emission intensity, the collective aim is to eventually cast aside polluting fossil fuels. Coal, therefore, is in the crosshairs.

This shift towards green energy pathways is welcome for climate change considerations. But, there is one major bump. Coal is the keystone among India’s diversified energy fuels.

RE sources are vying hard for a big slice of India’s energy pie. In the current fiscal year until October, RE generation sprinted with a 15.7 billion units (BU) year-on-year jump to 139.76 BU. Yet, this represents a mere 13.36 per cent of the country’s total generation of 1,045.85 BU and trails coal-based generation of 732.09 BU by 5.24 times.

The NITI Aayog and independent international agencies estimate that coal’s use in India will peak by 2030, and will remain at that level for another decade. This is despite India experiencing the fastest RE capacity growth among major economies of the world. While RE is expected to increase at the expense of coal, the overall energy demand is also expanding. This effectively means that the quantum of coal required will increase, even though its percentage in the energy share will shrink.

If India is to meet its NDC commitment, there are two options. Cut down coal’s use drastically or mine it in an environment-friendly manner. The former is well-nigh impossible, as expunging coal at this juncture poses a peril to the country’s energy sector. The viable option is to mine coal in an environmentally responsible manner. In this, underground (UG) mining plays a catalytic role with several distinctive advantages over the opencast (OC) method. It is environmentally cleaner, minimally invasive on land, circumvents displacing large swathes of forest cover and land acquisition, and prevents its degradation. Agricultural land is left undisturbed, and, importantly, it is society-friendly because it does not dislocate people en masse, necessitating rehabilitation and resettlement. Traditional livelihoods are not lost. UG coal is qualitatively superior and helps reduce imports of higher grades of coal. Indian coal extraction is predominantly OC driven. In 2022, of the total 8.5 BT coal produced world over, UG accounted for around 55 per cent. In a sharp contrast, India’s UG output was merely 4 per cent. But, it has not always been so.

For the first decade since the formation of Coal India Limited (CIL) in 1975, the company that spearheads the country’s coal production, UG coal held sway over OC. The scales tilted in favour of OC for the first time in FY85 when the OC production of 70.3 million tonnes (MTs) eclipsed 60.5 MTs of UG. Since then it had been an unrecoverable downhill tumble for UG mining. During the past 38 years while CIL’s OC production expanded by 9.64 times to 677.7 MTs ending FY23, UG output contracted by 57.8 per cent to 25.5 MTs.

The reasons for this fall were loss-incurring production, a longer gestation period, a lack of skilled labour, unavailability of indigenous equipment makers, and departmental production cost being high. It is a logistical and statistical impossibility now to catch up with the global average but CIL has drawn up an aspirational plan to quadruple its UG production to 100 MTs by FY 2030. Admittedly, the company has to tread through a minefield of challenges to achieve it. Yet, it is doable with a focused policy framework and the availability of environmentally friendly mass production technologies. Standardisation of mining equipment to boost domestic manufacturing and advancing Make in India is another fillip to the process.  

What makes UG mining workable now is well-trained skilled operators, outsourcing to contractors, efficient mine developers and operators, and proliferation of mass production technologies. This includes operationally flexible continuous miners suitable for Indian coal seams, the punch entry method for extraction of UG coal at low cost through existing infrastructure, deployment of high wall machines that bypass land acquisition and rehabilitation and resettlement issues. Paste fill technology is another advantage.

In contrast to conventional sand stowing, fly ash is used to fill mine voids in UG mines. While mining can proceed without disturbing surface contours, the menace of fly ash disposal is also taken care of. An estimation of mining activity-wise emissions of PM10 from OC and UG mines for 1 MT of coal produced was undertaken by the Central Mine Planning & Design Institute, the consultancy arm of CIL, and United States Environmental Protection Agency. It revealed that the pollution load from OC mines was 226.81 tonnes annually, while the same was 0.823 tonnes per year for UG mine. PM10 refers to particulate matter with diameters of 10 micrometres or less. Around 52 per cent of total load in OC mines was estimated to be on account of overburden removal and associated steps, which is not applicable in UG mines. Comparatively Co2 equivalent emissions in UG mining are lower by around 24 per cent than OC. For 100 MTs of coal produced through UG, Co2 emissions are relatively down by 2.4 MTs. 

Experience dictates that UG mining has no impact on water pollution, ambient noise levels are significantly lower, and it leaves surface features and fertile topsoil intact. The costs for a just transition, ensuring fair and inclusive growth, are considerably lower for UG mines than for OC mines.

Self-reliance in energy security is key for development in the present geopolitical scenario. In India, coal has the potential to provide the  highest indigenous resource base among other energy sources. Indian coal reserves stand at 361 BT, of which 170 BT are in the proven category. UG mining helps extract these reserves with minimal environmental impact and supplement OC output.

The positive steps taken in the UG journey will pave the way for larger strides in the future.

The writers are, respectively, chairman and director (technical), Coal India Ltd. The views are personal