Background
Cosentino is a Spanish family-owned business group with an international presence, dedicated to the production and distribution of innovative and sustainable high value-added surfaces for the architecture and design sectors. Its mission is to offer solutions that inspire and improve people's lives, always acting with responsibility, transparency, and commitment to ESG principles.
Among its main products are Silestone®, Dekton®, and Sensa by Cosentino®, pioneering surfaces and leaders in their respective segments. These materials are developed through technologically advanced and environmentally friendly processes, enabling the creation of unique spaces in both residential and public environments.
Cosentino promotes the circularity of its industrial processes. They consider waste as a source of new opportunities to develop innovative solutions or even manufacture new products with a potential for the commercialization or application in other sectors. Cantera Tecnológica (CT Quarry) is an innovation project funded by the European Union that demonstrates Cosentino’s commitment towards sustainability and will enable the generation of new raw materials from the waste generated in the factory.
The Challenge
Despite a high efficiency in production, the manufacturing of Silestone® generates a volume of waste exceeding 100,000 tons annually.
The Manufacturing Process
Silestone is manufactured from a mass composed of 90% mineral base, which varies in composition depending on the color type, including various minerals such as feldspars, quartzite, glass, and pigments for coloring like titanium dioxide or iron oxide, and 10% polymer (polyester resin).
To manufacture Silestone slabs, this mixture is kneaded and poured into vacuum presses, protected by Kraft-type paper to prevent the mass from sticking to the steel. Next, the polymer is cured at 90ºC.
Afterward, these slabs are calibrated to the proper thickness through a sanding process using rotary abrasive wheels and water (which also removes the paper). Finally, the slabs are polished to achieve the final finish (glossy or matte), again using water to lubricate the tools and avoid dust.
Waste is generated as a result of the calibration and polishing operations and results from the treatment of wastewater, presenting as an amalgam of minerals, polymer, paper traces, and water, remaining as sludge (see granulometry and composition in Annex 1).
The waste is then pressed to obtain blocks of 40x40 cm with an average humidity of 30%. These are collected in a container and transported to storage near the factory.
The treatment of this waste allows for the recovery of most of the water, so no water is discharged, and the remainder stays as moisture in the solid waste.
More info about Silestone production process can be found here:
https://www.youtube.com/watch?v=CM13K4gSZYQ
See diagram and photographs of the process in Annex 2.
Relevant Aspects for Sludge Reuse:
- It is mainly a silicate material (feldspar, glass, quartz).
- High fluxing (feldspar, glass).
- It is relatively chemically stable, not reacting quickly in contact with other substances.
- It has good stability in composition over time.
- Very low or absent concentration of potentially toxic heavy metals. Low concentration of chromophores (iron, chromium, etc.).
- Possibility of white/cream sludge with relatively stable tonality, easily colorable.
- Small particle size, micrometric size.
- High surface area for alkaline or pozzolanic reactions.
- High relative hardness of the particles (Mohs 5-7).
Limitations
Currently, waste of different colors from various production lines and particle sizes from the calibration and polishing processes are mixed. Therefore, the sludge presents some heterogeneity, especially in mineralogical composition and minor components such as pigments used for coloring. However, there is an underway project to separate the waste from some manufacturing lines.
Initial potential uses of the waste have shown some limitations:
- Paper content (<1%)
- Resin (average 10%)
- 30% of moisture content that would need to be reduced for the possible uses described below.
- Flocculant is present due to the water recovery treatment in the filter press.
- Crystalline silica is also present, so safety measures are required for handling the sludge.
Possible uses already studied
Various studies conducted with universities and companies have identified possible uses of the waste for construction materials and civil engineering (see Annex 3 – Possible studied uses). However, these uses are of low added value, which limits their profitability to a radius of 100-200 km due to transportation costs.
These uses have reached different degrees of maturity, and in the case of asphalt mixtures, a TRL9 has been achieved. However, profitability is still far-off.
What Cosentino is looking for
The objective of this challenge is to find additional reuse opportunities to valorize significant quantities of this waste by finding more profitable options or alternatives to those already studied.
COSENTINO Research and Development is seeking an industrial application, marketable product, or another solution to reuse the waste. We also look for companies that can incorporate the raw materials from the waste into their production processes, in any possible field, including architecture and design.
It may be a solution already existing in another field or something completely new and innovative, or that adds value to a product by improving its properties.
Proposals might also further evolve the applications already studied by COSENTINO R&D (described in Annex 3), specifying commercial options that makes it profitable. However, we consider that those applications related to improvement of agricultural soils and construction materials (concrete, asphalt mixtures, and others) have already been sufficiently studied.
Evaluation Criteria
Proposed solutions will be evaluated according to the following criteria:
- Evidence of technical feasibility and technological maturity.
- Higher volume of reused waste (partial volumes will also be evaluated). The objective is to recycle 10,000-40,000 tons/year of sludge. Proposals with lower potential consumption will be given less consideration.
- Best business case (lowest investment and operating cost, and highest value).
- Evidence of commercial and economic feasibility. Existing industry carrying out the proposed application.
This is a one-round challenge with the following deliverables:
1. A document in PDF format including:
- Concise technical description of the proposed application.
- Description of the process/technology for converting the waste material for the proposed application or product.
- Technical feasibility and maturity evidence.
- Business case (including investments, costs, and revenues, if applicable).
- Commercial feasibility evidence (and possible interested companies, if available).
2. Proposal for conducting a pilot/prototype test, through a partner proposed by the solver or provided by Cosentino, if necessary. The proposal must include:
- Pilot approach: Objective and scope, minimum required equipment, workplan, and proposed level of support.
- Estimated budget for the execution of the test (economic proposal in the case of solver companies).
Additionally, you may add other supporting documents to support your submission (they can be uploaded compressed in ZIP format).
To submit the proposal, the solver must register on the ennomotive platform (https://app.ennomotive.com/user/register) and enroll in the challenge, accepting the terms (www.ennomotive.com/terms-and-conditions/) and the privacy policy (www.ennomotive.com/privacy-policy).
Structure and Schedule of the Tournament
This is a one-round challenge with the following deadlines:
- 5 weeks for proposals submission (the deadline is July 29, 2025) + 4 weeks for evaluation.
Prizes
Individual solvers: A maximum of 3 finalist proposals will be selected to be tested by COSENTINO R&D. Each finalist will receive €3,000, and the winner will receive an additional €7,000 (best solution validated with a pilot project).
Companies: Commercial agreement and co-investment for the pilot.
COSENTINO R&D reserves the right to not award the challenge if no proposal meets the described evaluation criteria.
Challenge particular terms & conditions
Confidentiality
According to general terms and conditions. The parties’ obligations under these terms will expire 7 years after the due date for submissions.
Intellectual Property
According to general terms & conditions. In the case of commercial solutions, industrial property rights will remain with their legitimate owner.
Annexed Documents
- Annex 1 – Table of granulometry and waste composition and pictures.
- Annex 2 – Photographs of the process and sludge flow diagram.
- Annex 3 – List of possible uses already studied.
Note: You must register for the challenge to download these attachments.
