The problem
Sand casting is the backbone of India’s metal industry, which Rhino’s managing director describes as the world’s second-largest foundry sector after China. Manish Kothari told The Better India that the industry produces around 10 to 12 million tonnes of castings a year and uses about 800 kg of sand for every tonne of castings (The Better India).
Rhino Machines builds reclamation plants that clean this sand so it can be used again. But Kothari says only about 70% can be reclaimed; the other 30% ends up as foundry dust, a fine mix of silica, clay and carbon that is too small to reuse. It is hard to dispose of because the light particles stay in the air. Foundry clients kept asking Rhino how to reach zero discharge.
At the same time, Indian cities and villages are full of plastic waste such as multilayer wrappers and mixed films that recyclers do not want, which is often burned or dumped.
The product
The Silica Plastic Block (SPB) combines the two problems. Rhino’s current product page describes a blend of 30 to 50% foundry waste with 50 to 70% low-grade plastic, used to make pavers, blocks and pots (Rhino Machines). In 2020, Rhino described a mix of 75% foundry dust and 25% plastic for its first bricks.
SPB products include:
- bricks for walls, which Rhino said in 2020 needed no curing with water;
- paver blocks for paths, yards and parking areas;
- interlocking blocks for mortar-free “dry construction”;
- pots and planters.
Rhino describes SPB as research started in-house in 2017 and validated with industry. The technology has spread beyond foundries to urban and rural plastic waste recycling (Rhino waste-to-value). Production is partly handled by Meemansa, a former garment business hosted at Rhino’s premises, which calls itself a registered recycler under pollution control law (Meemansa).
How it works
- Collect sand: foundries supply used sand and fine dust that their reclamation systems cannot reuse.
- Collect plastic: low-grade plastic is gathered from institutions, housing societies and schools; it must be separated from wet waste.
- Shred: the plastic is cut into small pieces.
- Mix and bind: the shredded plastic is combined with the sand and acts as the binder in place of cement (Rhino does not publish process temperatures or settings).
- Mould: the mix is pressed into moulds for bricks, pavers or interlocking blocks.
- Cool: in 2020, Rhino said the bricks were ready after about 30 minutes of resting, with no water used (The Better India).
Timeline
| Date | Milestone |
|---|---|
| 1983 | R.C. Kothari starts foundry consulting and engineering (Rhino’s site; another profile says 1984) |
| 2017 | SPB research begins, according to Rhino |
| Late 2018 | First version of the bricks |
| Sep 2019 | Sri Krishna Hospital, Ahmedabad, starts giving plastic waste to Rhino |
| Feb 2020 | Bricks and paver blocks launched; first orders of over 1,000 bricks and 650 pavers |
| Feb 2025 | Rhino installs a 100 kg/hour SPB machine; first orders total about 21 tonnes |
Impact and numbers
- Waste ratio: up to 3 kg of used sand recycled per 1 kg of plastic (Rhino Machines).
- Strength (2020 test claim): about 14 to 15 kg per cm², against 3.5 to 7 kg per cm² for conventional clay bricks, and said to be 25% lighter.
- Price (2020): about Rs 10 per brick.
- Early plant: about 600 kg of waste processed a day, for an investment of nearly Rs 30 lakh.
- Plastic diverted: Sri Krishna Hospital in Ahmedabad had handed over more than 3,600 kg by mid-2020.
- Foundry pilot: AIA Engineering sent 300 kg of foundry dust to make about 900 bricks, and planned its own plant.
- Recent output: about 21 tonnes of SPB products from the first orders after the February 2025 machine (Meemansa).
- Reach: Meemansa reports SPB projects as far as Makhrelui village in Senapati district, Manipur.
Honest caveats. Almost every figure comes from Rhino, Meemansa or a 2020 feature based on company interviews; no independent test report or certificate was found. The recipe has shifted from 25% plastic in 2020 to 50 to 70% plastic now, so the 2020 strength figures may not apply to today’s products, and a block that is mostly plastic is less a sand product than a plastic product with mineral filler. There is no Bureau of Indian Standards specification for plastic-bound sand blocks, which limits use in public works. Plastic-based pavers can soften in high heat, burn and release fumes in a fire, and weather in the sun; the risk of microplastic release from wear, and of leaching from foundry dust that can contain metals and binders, has not been studied in public sources. The products cannot easily be recycled again into the same thing once mixed. Volumes so far are small: tonnes, not the millions of tonnes of foundry sand produced.
What’s next
Rhino’s plan is to set up SPB units at foundries, so waste is handled where it is produced, and to license the technology to small producers like Meemansa that create local jobs. Interlocking dry-construction blocks are the next product push, removing cement mortar from walls. To grow beyond pilot volumes, SPB will need third-party testing, a published durability and leaching record and acceptance by public works departments.
Why it matters for Europe / green buyers
European foundries face the same problem of spent sand and dust, and Europe has far more developed rules on when waste becomes a product: under the Waste Framework Directive, end-of-waste status depends on a market, technical standards and no adverse environmental or health effects (EUR-Lex). A product like SPB would have to prove those points before being sold in the EU. For buyers anywhere, the key questions are what proportion of the block is plastic, what tests exist for strength, fire, UV and leaching, and where the blocks will be used.
In India, the timing is useful. The Environment (Construction and Demolition) Waste Management Rules, 2025, in force from 1 April 2026, push builders to use recycled material for a rising share of construction (MPCB copy of the Gazette notification). India also has thousands of foundry clusters in places like Rajkot, Coimbatore, Kolhapur and Belagavi. Blocks for footpaths, factory yards and garden paving are a sensible first market, where loads are light and the risk of fire is low, while full load-bearing walls should wait for independent testing.
Sources & image credits
- Rhino Machines, “Silica Plastic Block - SPB”: https://www.rhinomachines.net/product-page/silica-plastic-block-spb
- Rhino Machines, “Silica Plastic Block (SPB) Technology”: https://www.rhinomachines.net/category/waste-to-value-products
- Rhino Machines, home page: https://www.rhinomachines.net/
- The Better India, “Made Using 100% Waste, These Bricks Cost Just Rs 10” (20 Jul 2020): https://thebetterindia.com/233190/plastic-waste-bricks-cheap-low-cost-purchase-features-recycle-engineer-architect-anand-gujarat-ang136/
- Meemansa, “Could Purpose Builds Resilience: How SPB is Rebuilding an Enterprise” (5 Oct 2025): https://www.meemansaspb.com/post/could-purpose-builds-resilience-how-spb-is-rebuilding-an-enterprise
- Meemansa, “SPB: Media, Videos, Publications and Presentations”: https://www.meemansaspb.com/spb-media
- Ministry of Environment, Forest and Climate Change, Environment (Construction and Demolition) Waste Management Rules, 2025 (MPCB copy): https://www.mpcb.gov.in/sites/default/files/construction-demolition-waste/Construction_and_Demolition_waste_Rules_2025.pdf
- EUR-Lex, Directive 2008/98/EC on waste: https://eur-lex.europa.eu/eli/dir/2008/98/oj/eng
Images:
- “Foundry sand” by srub, licensed under CC BY 3.0 (https://creativecommons.org/licenses/by/3.0), via Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Foundry_sand_-_panoramio.jpg
