GS Paper: GS3

Why in the News?

INS Arnala, the first Anti-Submarine Warfare Shallow Water Craft (ASW-SWC), was officially commissioned into the Eastern Naval Command at the Naval Dockyard, Visakhapatnam.

About INS Arnala:

What is it: INS Arnala is the first Anti-Submarine Warfare Shallow Water Craft (ASW-SWC) commissioned into the Eastern Naval Command on June 18, 2025, at Visakhapatnam.
Behind the name: It is named after the historic Arnala Fort near Vasai, Maharashtra.
Development: The vessel was designed by Garden Reach Shipbuilders & Engineers (GRSE) and built in partnership with L&T Shipbuilders under a Public-Private Partnership (PPP) model.
Project: It marks the beginning of the induction of 16 ASW-SWC class ships, aimed at enhancing India’s shallow water anti-submarine capabilities.

Key Features:

Propulsion: 77.6 metres long; first Indian Navy warship powered by a Diesel Engine-Waterjet combination.
Indigenous Content: Over 80% indigenous systems, with contributions from BEL, L&T, Mahindra Defence, and over 55 MSMEs.
Arsenal: Equipped with a single centreline rocket launcher, lightweight torpedoes, anti-torpedo decoys, and mine-laying systems.
Sensor Suite: Incorporates Hull-Mounted Sonar (Abhay), Low-Frequency Variable Depth Sonar (LFVDS), and Underwater Acoustic Communication System (UWACS).
Multi-role Capability: Designed for ASW operations, Search and Rescue (SAR), low-intensity maritime operations, and subsurface surveillance in shallow coastal waters.

Significance:

Strategic Defence Upgrade: Replaces ageing Abhay-class corvettes and significantly strengthens India’s anti-submarine warfare posture.
Enhanced Coastal Security: Ideal for detecting midget submarines and Unmanned Underwater Vehicles (UUVs) in waters less than 30 metres deep, where larger warships struggle to operate.
Make-in-India Milestone: Demonstrates India’s growing self-reliance in defence manufacturing and contributes to the Aatmanirbhar Bharat initiative.

[UPSC 2016] Which one of the following is the best description of ‘INS Astradharini’, that was in the news recently?

Options: (a) Amphibious warfare ship (b) Nuclear-powered submarine (c) Torpedo launch and recovery vessel* (d) Nuclear-powered aircraft carrier

June 20, 2025

Why in the News?

SEBI has introduced key regulatory relaxations to ease IPO norms and incentivize startups to shift their legal base back to India through reverse-flipping.

About Reverse-Flipping:

Reverse-flipping refers to the process by which Indian startups that were earlier incorporated abroad shift their domicile back to India, making India their legal and operational headquarters.
It allows Indian companies to access domestic capital markets, reduce compliance complexity, and align with the evolving global tax and regulatory environment.
This shift helps startups tap Indian stock exchanges, reduce reliance on foreign jurisdictions, and benefit from a favorable Indian regulatory ecosystem.

Types of Reverse-Flipping

Share Swap Arrangement:

- In this structure, shareholders of the foreign parent company exchange their shares for shares in the Indian subsidiary.
- This process may trigger capital gains tax under the Income Tax Act, 1961, especially for Indian shareholders.

Inbound Merger (Cross-Border Merger):

- The foreign parent company merges with its Indian subsidiary, with the Indian entity becoming the surviving legal structure.
- If all conditions under the Foreign Exchange Management Act (FEMA), the Companies Act, 2013, and National Company Law Tribunal (NCLT) are met, this merger route can be tax-neutral.

Key Features:

Domestic Listing Access: Startups gain access to Indian IPO markets and valuations.
Simplified Compliance: Reduced legal and regulatory complications from operating across jurisdictions.
Investor Incentives: SEBI now allows foreign venture funds and AIFs to be counted towards minimum promoter contribution in public issues.
ESOP Relaxation: SEBI has allowed promoters/founders to retain Employee Stock Option Plans (ESOPs) granted one year prior to the filing of the Draft Red Herring Prospectus (DRHP).
Capital Market Boost: The move supports India’s goal to become a global startup and financial hub by encouraging reverse-flipping.
Tax & Legal Alignment: Shifting domicile can help startups comply better with Indian tax and business laws.

Note:

Employee Stock Option Plans (ESOPs) are structured benefit schemes that grant employees the right to purchase shares of their company at a predetermined price—known as the exercise price—after completing a specific period.

[UPSC 2025] Consider the following statements:

Statement I: As regards returns from an investment in a company, generally, bondholders are considered to be relatively at lower risk than stockholders.

Statement II: Bondholders are lenders to a company whereas stockholders are its owners.

Statement III: For repayment purpose, bondholders are prioritized over stockholders by a company.

Which one of the following is correct in respect of the above statements?

(a) Both Statement II and Statement III are correct and both of them explain Statement I *

(b) Both Statement I and Statement II are correct and Statement I explains Statement II

(d) Neither Statement II nor Statement III is correct

June 20, 2025

PM-WANI Scheme

Why in the News?

The TRAI ordered that public Wi-Fi hotspot operators under PM-WANI programme should not be charged more than twice what a residential broadband user paid for setting up a hotspot.

What is the PM WANI Scheme?

Overview: PM Modi launched the Prime Minister Wi-Fi Access Network Interface (PM WANI) in December 2020.
Nodal agency: It is an initiative under the Department of Telecommunications (DoT).
Objective: To democratize internet access, particularly in remote and underserved areas.
Goals: It takes forward the goal of the National Digital Communications Policy, 2018 (NDCP) of creating a robust digital communications infrastructure.
Implementation: Leverages Public Data Offices (PDOs) established in public spaces like railway stations, banks, post offices, and more. Users can access the internet via Wi-Fi at these locations without requiring a SIM card.
PM-WANI ecosystem consists of four parts:

1. Public Data Office (PDO): It establishes the Wi-Fi Hotspots and provides internet access to users
2. Public Data Office Aggregator (PDOA): It provides authorisation and accounting services to PDOs.
3. App Provider: It displays the available hotspots in the phone’s proximity.
4. Central Registry: This overseen by the Centre for Development of Telematics maintains details of App Providers, PDOs, and PDOAs.

How to Utilize PM WANI?

- To access PM WANI services, users must install the Data PM WANI app on their smartphones.
- Through the app, users can connect to nearby public Wi-Fi PDOs.
- This application facilitates seamless connectivity to PM-WANI-compliant Wi-Fi hotspots, empowering users to access broadband services conveniently.

Role of Public Data Offices (PDOs):

The PM-WANI scheme includes a provision for establishing Public Data Offices (PDOs) by rural entrepreneurs in remote regions.
These PDOs procure internet bandwidth from telecom service providers or ISPs to offer Wi-Fi services at minimal charges.
This model enables individuals to access the internet even in areas with limited or no data connectivity.

[2018] Which of the following is/are the aim/aims of “Digital India” Plan of the Government of India?

Formation of India’s own Internet companies like China did.
Establish a policy framework to encourage overseas multinational corporations that collect Big Data to build their large data centres within our national geographical boundaries.
Connect many of our villages to the Internet and bring Wi-Fi to many of our school, public places and major tourists.

Select the correct answer using the codes given below:

(a) 1 and 2 only

(b) 3 only

(d) 1, 2 and 3

June 19, 2025

Rice reveals surprise ability to adapt to cold faster than evolution

Why in the News?

In a major study, scientists proved that cold exposure in rice plants can cause changes that improve stress tolerance and are inherited by the next five generations, supporting Lamarck’s old theory.

What was Lamarck’s theory of acquired characteristics?

This idea was formally presented by Jean-Baptiste Lamarck in 1809, and it was one of the earliest theories of evolution. When the traits developed during an organism’s lifetime due to use, disuse, or environmental influence could be inherited by its offspring. Eg: A giraffe stretching its neck to reach higher leaves would result in its offspring having longer necks.

How did later scientific discoveries challenge it?

Weismann’s Tail-Cutting Experiment: August Weismann demonstrated that acquired traits are not inherited by cutting the tails of mice for five generations, yet their offspring were still born with tails.
Mendel’s Laws of Heredity: Gregor Mendel showed that traits are inherited through stable units (genes) passed unchanged from parents to offspring, rather than traits acquired during life. Eg: In pea plants, traits like flower colour were inherited predictably, regardless of environmental changes.
Discovery of DNA and Mutations: The discovery of DNA as the genetic material and that mutations cause heritable changes explained inheritance scientifically, without relying on acquired characteristics. Eg: Genetic disorders like sickle cell anemia are caused by specific DNA mutations, not by environmental use or disuse.

How did Mendel’s work and DNA discovery change heredity understanding?

Introduction of Stable Hereditary Units: Mendel’s experiments introduced the concept of “genes” as stable, particulate units of inheritance passed from parents to offspring. Eg: Mendel’s pea plant experiments showed traits like seed shape and flower color followed predictable patterns.
Law of Segregation and Independent Assortment: Mendel proposed that alleles segregate independently, ensuring genetic variation without influence from acquired traits. Eg: A plant with one tall and one short gene could pass either to its offspring, not a mix of the two.
DNA Identified as Genetic Material: Later discoveries identified DNA as the carrier of genetic information, solidifying the molecular basis of heredity. Eg: Avery, MacLeod, and McCarty’s experiments in 1944 showed that DNA—not proteins—was responsible for heredity.
Mutation Explained Heritable Variation: The understanding that mutations in DNA cause changes in traits clarified how new heritable variations arise. Eg: Mutations in the hemoglobin gene lead to sickle cell anemia, a heritable disorder.
Disproved Lamarckian Inheritance: These findings rejected the idea that characteristics acquired during life could be inherited, as proposed by Lamarck. Eg: A bodybuilder’s muscular physique isn’t passed to their children genetically.

Why is the Cell study on cold-tolerant rice significant?

Proof of Heritable Epigenetic Change Induced by Environment: The study demonstrated that cold exposure triggered an epigenetic modification (methylation) in rice plants, which was inherited for five generations. Eg: Rice plants exposed to cold passed on improved cold tolerance without any DNA sequence change.
Reinforced the Role of Epigenetics in Evolution: It showed that gene expression can be regulated by epigenetic marks rather than genetic mutations, suggesting Lamarck’s idea of environmental inheritance has merit. Eg: The ACT1 gene stayed active in cold-tolerant rice due to the absence of a methylation tag, helping them survive cold stress.
New Direction for Crop Improvement and Climate Resilience: The findings open doors for non-genetic crop adaptation methods to deal with climate change. Eg: Epigenetically trained rice varieties could be developed to withstand colder environments, improving food security.

What are the steps taken by the Indian Government?

Multigenerational Cold-Stress Breeding: Researchers implemented a directional selection process over multiple generations by exposing rice to cold during the vulnerable meiotic stage, breeding for improved cold resistance. Eg: After three generations, they developed rice lines with stable cold tolerance that persisted for at least five generations.
Epigenetic Mapping and Editing of the ACT1 Promoter: Through multi-omics analysis, scientists identified hypomethylation at the ACT1 promoter as the molecular basis for cold adaptation. They then used precision DNA methylation editing to confirm that removing methyl tags restored cold tolerance.

Way forward:

Incorporate Epigenetic Breeding in National Crop Improvement Programs: Government research bodies and agricultural universities should integrate epigenetic trait selection and editing into mainstream breeding to develop climate-resilient varieties, especially for stress-prone regions.
Strengthen Investment in Multi-Generational Stress Trials: Increase funding for long-term, controlled environment trials to identify and stabilize heritable epigenetic traitsacross major crops, ensuring sustainable food security under climate change.

Mains PYQ:

[UPSC 2019] How can biotechnology improve the living standards of farmers?

Linkage: The core of the article reveals a novel mechanism for plant adaptation—epigenetic inheritance of cold tolerance in rice plants. This scientific breakthrough, falling under the broad umbrella of biotechnology, demonstrates a potential pathway to develop crops that can adapt to challenging environmental conditions (like cold stress) more rapidly than through traditional breeding or genetic modification.

June 18, 2025

What is Project Vishnu?

Why in the News?

India is set to test the Extended Trajectory-Long Duration Hypersonic Cruise Missile (ET-LDHCM), an advanced hypersonic missile developed by DRDO under the secretive Project Vishnu.

What is Project Vishnu?

Overview: Project Vishnu is a top-secret initiative by India’s Defence Research and Development Organisation (DRDO) to develop hypersonic missile technologies.
Strategic Purpose: The project aims to enhance India’s strategic deterrence by delivering high-speed missiles capable of both conventional and nuclear roles.
Focus: It is specifically designed to counter threats from China and Pakistan, reinforcing regional strike capability.
Platform Flexibility: A core feature is multi-platform deployment, allowing the missile to be launched from land, air, and naval systems.
Integrated Technologies: It brings together scramjet propulsion, materials science, and precision guidance into a single hypersonic weapons system.
Doctrinal Alignment: It reflects India’s shift toward technology-driven warfare and supports its credible minimum deterrence doctrine.

About the ET-LDHC Hypersonic Missile:

Overview: It is the flagship missile system under Project Vishnu.
Speed and Range: It reaches Mach 8 (~11,000 km/h) and has a strike range of 1,500 km, making it nearly impossible to intercept with current defence systems.
Payload Versatility: It can carry 1,000–2,000 kg of conventional or nuclear warheads, allowing mission-specific configurations.
Propulsion: Powered by an indigenously developed scramjet engine, it uses atmospheric oxygen for combustion, improving fuel efficiency and endurance.
Strike Capabilities: With evasive manoeuvrability and a flat trajectory, the missile is ideal for deep-penetration and precision attacks.
Next-Gen Materials: It is built from materials that withstand 2,000°C+ temperatures, ensuring oxidation resistance and structural integrity.
Launch Platforms: The missile is compatible with land systems, fighter jets, and naval vessels, offering operational flexibility.

[UPSC 2024] Consider the following statements:

1. Ballistic missiles are jet-propelled at subsonic speeds throughout their flights, while cruise missiles are rocket-powered only in the initial phase of flight.

2. Agni-V is a medium-range supersonic cruise missile, while BrahMos is a solid-fuelled intercontinental ballistic missile.

Which of the statements given above is/are correct?

Options: (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 *

June 18, 2025

First Assembly of the International Big Cat Alliance (IBCA)

Why in the News?

The first Assembly of the International Big Cat Alliance (IBCA) was held on June 16, 2025, in New Delhi, with the Union Environment Minister presiding over the session.

About the International Big Cat Alliance (IBCA)

Overview: It is a multi-country, multi-agency alliance of 95 countries, both range and non-range, dedicated to the conservation of big cats and their habitats.
Launch: Proposed by PM Modi in 2019, the alliance was officially launched in April 2023 to mark Project Tiger’s 50th anniversary.
Conservation Focus: IBCA seeks to protect and restore populations of 7 big cats: tiger, lion, leopard, snow leopard, cheetah, jaguar, and puma.
Core Functions: The alliance works through advocacy, knowledge exchange, promotion of eco-tourism, and resource mobilisation.
Conflict Resolution: It aims to reduce human-wildlife conflict and restore degraded habitats critical to big cat survival.
Global Participation: IBCA brings together 95 range countries from:
- Asia: India, China, Nepal, Pakistan, Iran
- Africa: Kenya, Congo, Ghana
- Americas: Brazil, Ecuador, United States
- Europe/Central Asia: Russia, Kazakhstan
Members: Bhutan, Eswatini, Cambodia, Guinea, India, Liberia, Nicaragua, Somalia and Suriname have deposited an instrument of ratification.
Institutional Structure: It is governed by a General Assembly, an elected Council, and a secretariat led by a Secretary-General.
Permanent Base: The ratification of the headquarters agreement has enabled IBCA to set up its permanent headquarters in India.

India’s Role:

Species Richness: India is home to 5 of the 7 big cats—the tiger, lion, leopard, snow leopard, and cheetah—and holds 70% of the world’s tiger population.
Funding Commitment: The Indian government has committed ₹150 crore (2023–2028) and is attracting additional global contributions to support the alliance’s goals.
Conservation Leadership: India plays a leading global role in big cat protection, setting benchmarks in wildlife conservation and ecological stewardship.

[UPSC 2024] Consider the following statements:

1. Lions do not have a particular breeding season.

2. Unlike most other big cats, cheetahs do not roar.

3. Unlike male lions, male leopards do not proclaim their territory by scent marking.

Which of the statements given above are correct?

(a) 1 and 2 only * (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 2

June 18, 2025

PRASHAD Scheme

Why in the News?

The long-awaited Chamundi Hills development project in Karnataka is finally gaining momentum under the Pilgrimage Rejuvenation and Spiritual Heritage Augmentation Drive (PRASHAD) scheme.

About the PRASHAD Scheme:

Launch: It was launched in 2014–15 by the Ministry of Tourism.
Core Objective: It aims to revitalize pilgrimage sites and develop spiritual tourism infrastructure across India.
Scope and Mission: In 2017, PRASHAD was upgraded to a National Mission, integrating features of the HRIDAY scheme to create a unified heritage and spiritual site development model.
Cultural Focus: The scheme emphasises cultural preservation, community involvement, and promoting both domestic and international spiritual tourism.

Implementation:

- Executing Agencies: Projects are executed by state-level agencies appointed by the respective state or union territory governments.
- Funding Model: The scheme offers 100% central financial assistance for eligible infrastructure and development components.
- Public-Private Support: It encourages Corporate Social Responsibility (CSR) contributions and Public-Private Partnerships (PPP) to expand sustainability and local ownership.
- Centre-State Collaboration: Implementation is designed to ensure close cooperation between central and state governments while respecting local cultural and religious traditions.

Key Features:

Infrastructure Development: Roads, drinking water, sanitation, solid waste management, lighting, and public conveniences at pilgrimage sites.
Connectivity Enhancement: Improved rail, road, and air links to facilitate easier access for pilgrims.
Pilgrim Facilities: Creation of accommodation, food courts, wayfinding systems, and security measures for safe and hygienic pilgrimages.
Cultural Conservation: Restoration of temples, monuments, ghats, and sacred lakes; integration of cultural traditions in tourism.
Community Empowerment: Skill training for locals, development of tourism-linked jobs, and stakeholder participation in project design and operation.
Sustainability Focus: Use of eco-friendly technologies, green energy, and promotion of responsible tourism to reduce environmental impact.

[UPSC 2022] The Prime Minister recently inaugurated the new Circuit House near Somnath Temple at Veraval. Which of the following statements are correct regarding Somnath Temple?

1. Somnath Temple is one of the Jyotirlinga shrines.

2. A description of Somnath Temple was given by Al-Biruni.

3. Pran Pratishtha of Somnath Temple (installation of the present day temple) was done by President S. Radhakrishnan.

Select the correct answer using the code given below:

Options: (a) 1 and 2 only * (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3

June 17, 2025

Ocean Darkening: A New Ecological Crisis

Why in the News?

A new study from the University of Plymouth has revealed that over 21% of the global ocean has significantly darkened in the last two decades.

What is Ocean Darkening?

Ocean darkening refers to the reduction in sunlight penetration into the ocean’s upper layers, known as the photic zone (up to 200 meters deep), where sunlight drives photosynthesis and supports marine biodiversity.
This process is measured using the diffuse attenuation coefficient (Kd 490), which tracks how quickly light diminishes as it passes through seawater.
The photic zone is essential for phytoplankton productivity, oxygen generation, marine food chains, and the regulation of global climate.

Recent Report Citing Ocean Darkening:

A new study by researchers from the University of Plymouth, published in 2024, titled “Darkening of the Global Ocean”, revealed that 21% of the global ocean has significantly darkened from 2003 to 2022.
Key findings:
- 9% of the ocean saw a drop of more than 50 meters in light penetration—equal to the area of Africa.
- 2.6% experienced a loss exceeding 100 meters in photic depth.
Affected Region: The study found the Arctic, Antarctic, Gulf Stream, and North Sea among the worst affected regions.
Causes:
- Algal blooms from nutrient runoff in coastal areas.
- Warming seas, altered plankton dynamics, and changing ocean currents in open ocean zones.

Implications of Ocean Darkening:

Ecosystem Disruption: Light-dependent species, such as Calanus copepods, are being pushed into shallower zones, increasing predation and competition.
Loss of Habitat: The shrinkage of the photic zone could be one of the largest marine habitat losses ever, affecting fish stocks and biodiversity.
Climate Feedback Loop: Reduced photosynthesis in oceans could weaken the ocean’s role in carbon sequestration and oxygen production, worsening climate change.
Threat to Global Fisheries: The contraction of productive zones affects fish populations, jeopardising fisheries and food security.
Scientific Concern: Researchers warn that this hidden crisis could fundamentally alter marine ecosystems if not urgently addressed.

[UPSC 2025] With reference to the planet Earth, consider the following statements:

I. Rain forests produce more oxygen than that produced by oceans. II. Marine phytoplankton and photosynthetic bacteria produce about 50% of the world’s oxygen. III. Well-oxygenated surface water contains several folds higher oxygen than that in atmospheric air.

Which of the statements given above is/are correct?

Options: (a) I and II (b) II only * (c) I and III (d) None of the above statements is correct

June 17, 2025

Rudrastra UAV passes key army trial.

Why in the News?

India advanced its indigenous defence tech with SDAL’s successful trial of the Hybrid VTOL UAV Rudrastra at Pokhran.

Rudrastra UAV passes key army trial.

About Rudrastra:

Rudrastra is an indigenously developed Hybrid Vertical Take-Off and Landing (VTOL) UAV built by Solar Defence and Aerospace Limited (SDAL).
The UAV is engineered for deep-strike capabilities, capable of carrying out precision missions without endangering human soldiers.
It is tailored for anti-personnel roles, with airburst munitions designed to strike targets across hostile borders.
Rudrastra blends rotor-based vertical lift with fixed-wing cruise capability, enhancing deployment across diverse terrains.
It is considered a “stand-off” weapon, enabling missions deep into enemy territory with autonomous return capability.

Key Features:

Hybrid VTOL Design: Can vertically take off and land like a helicopter and cruise like a fixed-wing aircraft, enhancing flexibility.
Extended Range: Demonstrated a total mission range of over 170 km, including loiter time over the target.
Real-Time Surveillance: Maintained a stable video link while covering a 50+ km mission radius.
Precision Strike Capability: Successfully deployed airburst munitions, effective for area damage and anti-personnel use.
Endurance: Achieved a flight endurance of 1.5 hours, ideal for extended ISR or strike operations.
Autonomous Navigation: Returned independently to the launch site after completing the mission.
Made in India: Fully developed by an Indian defence company, supporting indigenous innovation in combat drones.

[UPSC 2025] With reference to Unmanned Aerial Vehicles (UAVs), consider the following statements:

I. All types of UAVs can do vertical landing. II. All types of UAVs can do automated hovering. III. All types of UAVs can use battery only as a source of power supply.

Which of the statements given above are correct?

Options: (a) Only one (b) Only two (c) All the three (d) None*

June 17, 2025

[16th June 2025] The Hindu Op-ed: What are flue gas desulphurisation units?

PYQ Relevance:

[UPSC 2022] Discuss global warming and mention its effects on the global climate. Explain the control measures to bring down the level of greenhouse gases which cause global warming, in the light of the Kyoto Protocol, 1997.

Linkage: SO2 as “one of the major greenhouse gases that cause global warming”. Flue Gas Desulphurisation (FGD) units are designed specifically to remove SO2 emissions from the combustion of fossil fuels. Therefore, FGD units serve as a direct “control measure to bring down the level of greenhouse gases” as addressed by the question.

Mentor’s Comment: India’s top science advisory group has suggested ending the 2015 rule that made it compulsory for all coal-based power plants to install Flue Gas Desulphurisation (FGD) units. This has raised serious concerns because FGDs are key to reducing sulphur dioxide (SO₂) pollution, which causes 15% of India’s PM2.5 levels and leads to breathing problems, environmental damage, and climate change. Although installing FGDs is expensive (₹1.2 crore per MW), experts warn that dropping the plan could harm public health and clean air efforts. Worryingly, only 39 of 537 plants have installed FGDs, and deadlines keep getting pushed back.

Today’s editorial focuses on the analysis of the installation of the Flue Gas Desulphurisation (FGD) units in a thermal power plant. This content is very relevant to GS Paper III (Environment, Science and Technology) Mains.

Let’s learn!

Why in the News?

A group of experts, led by Principal Scientific Advisor Ajay Sood, has recently suggested that India should cancel the 10-year-old rule that requires all coal-based thermal power plants to install Flue Gas Desulphurisation (FGD) units.

Why India should cancel the 10-Year-Old Rule (2015 FGD Mandate)?

High Installation Cost Burden: Installing FGD units costs around ₹1.2 crore per MW, which can significantly raise power generation costs and electricity tariffs. Eg: For 97,000 MW of new capacity, the cost would be about ₹97,000 crore, making power less affordable.
Delayed and Poor Implementation: Despite the 2015 rule, compliance has been dismal—only 39 out of 537 plants had FGDs installed by 2025. Eg: Repeated deadline extensions (up to 2029) show lack of feasibility and institutional capacity.
Limited Local Air Quality Impact in Some Areas: In certain regions, the contribution of SO₂ emissions from TPPs to PM2.5 levels is relatively small. Eg: In Delhi, most air pollution comes from other sources like vehicles and construction, so FGDs at distant plants may offer minimal benefit.

What is a Flue Gas Desulphurisation (FGD) unit?

FGD units are devices used in coal-fired thermal power plants (TPPs) to remove sulphur dioxide (SO₂) from flue gas. Flue gas is a byproduct of burning fossil fuels and contains pollutants like SO₂, CO₂, NOx, and particulate matter.
Three common FGD technologies:
- Dry sorbent injection (adds powdered limestone to flue gas).
- Wet limestone treatment (reacts SO₂ with limestone slurry to form gypsum).
- Sea water scrubbing (used near coastal areas).

How does it reduce SO₂ emissions from thermal power plants?

Chemical Neutralisation Reaction: FGD units use alkaline substances like limestone or lime to react with acidic SO₂ in flue gas, converting it into stable, non-toxic compounds. Eg: In wet limestone FGD, SO₂ reacts with limestone slurry to form gypsum (CaSO₄·2H₂O), a harmless industrial byproduct.
Efficient Scrubbing Techniques: Technologies like wet scrubbers or dry sorbent injection physically remove SO₂ from exhaust gases before release into the atmosphere. Eg: Dry sorbent injection sprays powdered lime into the flue gas stream, which binds with SO₂ and is later captured by filters.
Controlled Emission Discharge: FGD ensures that the treated flue gas released into the environment has significantly lower SO₂ levels, complying with environmental norms. Eg: Power plants near coasts use sea water FGD, where sea water absorbs SO₂ and is then treated before being discharged safely.

Why are SO₂ emissions harmful?

Respiratory and Health Issues: Sulphur dioxide (SO₂) irritates the respiratory system, causing problems like asthma, bronchitis, and lung damage, especially in children and the elderly. Eg: Studies in urban industrial areas show a direct link between SO₂ exposure and increased hospital admissions for respiratory illnesses.
Formation of Secondary Particulate Matter (PM2.5): SO₂ reacts in the atmosphere to form fine particulate matter (PM2.5), which can penetrate deep into lungs and enter the bloodstream, posing serious health risks. Eg: According to studies, 80% of PM2.5 from coal combustion is due to secondary particles formed from SO₂.
Contribution to Acid Rain: SO₂ combines with water vapor in the atmosphere to form sulphuric acid, leading to acid rain that damages soil, crops, forests, and aquatic ecosystems. Eg: Regions near coal-fired plants have reported acidic lakes and damaged crops due to acid rain deposition.
Environmental Degradation: High SO₂ levels can corrode buildings, especially monuments made of limestone or marble, and degrade overall air and water quality. Eg: The Taj Mahal has shown signs of yellowing, partly attributed to SO₂-related pollution.
Climate and Visibility Impact: Though SO₂ itself is not a greenhouse gas, it leads to formation of aerosols, affecting cloud formation, reducing visibility, and causing climate imbalance. Eg: In industrial belts, hazy skies and temperature variations are linked to SO₂-derived aerosols.

What is the status of FGD installation in India (2025)?

Low Overall Commissioning: Only about 39 out of 537 thermal power plant units (≈ 19,430 MW capacity) have commissioned FGD systems, representing ~11% of the total required capacity. Eg: Just 13 out of 35 units within 300 km of Delhi have installed FGDs, showing slow progress in high-pollution zones.

Stalled Projects and Delays: Contracts have been awarded for about 238 units (~105,200 MW), and 139 units (~42,847 MW) are still in the tendering stage, but many projects remain stalled. Eg: Some plants, especially near Delhi, may take up to 36 months to complete FGD installation due to regulatory and logistical hurdles.

Repeated Deadline Extensions: Compliance deadlines have been extended multiple times: from 2017 → 2024 → 2026–2029, depending on the location and plant category. Eg: The Ministry of Environment has pushed back deadlines for thermal plants in Delhi NCR without strict justification, raising concerns about enforcement.

Way forward:

Prioritised FGD Installation: Expedite FGD implementation in high-emission and densely populated zones to balance cost and health impact.
Policy and Financial Support: Provide targeted subsidies or incentives to TPPs and integrate FGD costs into long-term tariff planning for smoother adoption.

June 16, 2025