The Central Pollution Control Board (CPCB) has released guidelines to regulate and repurpose stone slurry from marble and granite processing, aiming to reduce pollution and promote industrial circularity. Measures include lined storage, GPS tracking, mandatory MoUs, and inclusion in Consent to Operate terms.
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Picture Courtesy: DOWNTOEARTH
The Central Pollution Control Board (CPCB) released draft guidelines to promote sustainable utilization of stone slurry.
Stone slurry is a semi-liquid waste produced during the cutting and polishing of natural stones like marble, granite, and limestone.
Composed largely of calcium carbonate (94–98% in some cases), silica, and other minerals, it accounts for nearly 40% of the processed stone volume. The exact chemical composition of stone slurry depends on the parent rock.
In India, particularly Rajasthan, marble and granite units generate 5–6 million tonnes of slurry annually.
Land Degradation: Dumping slurry on open land or agricultural fields reduces soil fertility and water permeability, making land unsuitable for farming.
Water Contamination: Slurry dumped in rivers or streams increases siltation, blocks aquifer flow, and harms aquatic ecosystems.
Air Pollution: Dried slurry becomes airborne, contributing to suspended particulate matter (SPM), which affects human health and vegetation.
Resource Depletion: Stone processing consumes significant freshwater, exacerbating water scarcity.
These challenges demand urgent solutions to mitigate environmental damage and promote resource conservation.
Storage and Handling: Mandates lined storage areas and GPS-enabled vehicles to prevent illegal dumping.
Utilization Options: Encourages using slurry in cement, tiles, road construction, lime production, and as a filler material.
Regulatory Compliance: Requires MoUs between slurry generators and users, and integration of utilization plans in Consent to Operate (CTO) conditions.
Sustainable Applications: Stone slurry’s mineral-rich composition makes it a valuable resource for various industries, promoting a circular economy.
Cement Manufacturing: Slurry replaces 5% of clinker and 4% of gypsum, totaling 9% of input (CPCB, 2025). For example, Mangalam Cement in Rajasthan saves Rs 27 million annually by using Kota stone slurry instead of mineral gypsum.
Tile Manufacturing (Morbi Model): In Morbi, Gujarat (90% of India’s tile production), 40–50% of 750+ units use slurry, replacing 10–13% of feldspar in tiles.
Other Applications
Brick Manufacturing: Slurry replaces clay, maintaining brick strength and saving agricultural land.
Concrete and Mortar: Up to 100% replacement of sand with quarry dust increases compressive strength by 10–12% and improves durability.
Road Construction: Slurry stabilizes soil for highway shoulders, reducing plasticity.
Additional Uses: Includes wall putty, calcium nitrate fertilizer, desulphurization in thermal plants, and filler in mineral grinding units.
These applications reduce waste, conserve resources, and lower production costs, aligning with sustainable development goals.
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Central Pollution Control Board (CPCB) It is a statutory organization established under the Water (Prevention and Control of Pollution) Act of 1974. It was later also entrusted with functions and responsibilities under the Air (Prevention and Control of Pollution) Act of 1981. Key functions of the CPCB
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Limited Adoption: Only 40–50% of Morbi’s tile units and few cement plants use slurry, due to awareness gaps and logistical challenges.
Regulatory Gaps: CPCB guidelines lack timelines for compliance and fail to address noise pollution from stone processing units.
Infrastructure Constraints: Absence of regional waste management facilities limits slurry collection and transport to industries.
Enforcement Issues: Many stone crushing units operate without proper pollution control devices or environmental clearances, weakening compliance.
Scale Up Utilization: Promote slurry use in cement, tiles, and alternative applications like bricks and fertilizers through incentives and awareness campaigns.
Build Infrastructure: Establish regional waste management facilities for efficient slurry collection and distribution.
Strengthen Regulations: Set clear timelines for compliance with CPCB guidelines and enforce noise control measures for stone units.
Enhance Monitoring: Mandate SPCBs to conduct regular inspections and ensure pollution control devices are installed.
Encourage Partnerships: Collaboration between stone industries, cement/tile manufacturers, and research institutions to innovate slurry applications.
Stone slurry, once an environmental burden, holds immense potential as a resource for cement, tiles, and other industries. The CPCB’s 2025 guidelines mark a progressive step, but their success depends on robust enforcement, infrastructure development, and industry adoption.
Source: DOWNTOEARTH
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PRACTICE QUESTION Q. Industrial waste can be a resource, not a burden. Critically analyze. 150 words |
Stone slurry is a waste product generated during the processing of marble, granite, and other natural stones.
Improper dumping of stone slurry leads to air pollution from dried particulate matter and contamination of soil and water bodies.
It is an economic system aimed at eliminating waste and promoting the continuous use of resources.
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