Clay Culture: Zero Waste April Gocha, PhD

Appears in the June/July/August 2017 issue of Ceramics Monthly.

One way to increase efficiency is to reduce waste. And when it comes to manufacturing ceramic tile, there’s some room for improvement.

An estimated 1.5 million tons of waste are produced yearly from ceramic tile manufacturing in the European Union alone.

Although approximately 65% of that raw material waste is often captured and recycled back into the manufacturing process, 35% of tile manufacturing waste is pure waste—it’s sent to landfills or used as a filler in other materials as a means of disposal.

Most of the wasted waste is in the form of fired scrap or waste containing soluble salts, such as polishing sludge and kiln filter waste. That’s because those materials aren’t as easy to reuse as raw material ingredients, which can be recycled directly back into the process.

But that doesn’t mean it can’t be done—and that’s exactly what a European project called Lifeceram is working toward.

Analyzing the Problem

The project—coordinated by the Instituto de Tecnología Cerámica (ITC) of the Universitat Jaime I of Castellón in Spain and including Spanish Association of Ceramic Tile and Paving Manufacturers and several commercial partners—began in 2013 with the goal of achieving absolutely zero waste in ceramic tile manufacturing.

To do so, the project has two goals: to develop an outdoor ceramic tile—urban flooring—containing more than 80% waste content; and to develop a sustainable manufacturing process, using dry milling and granulation, to produce such recycled tiles.

Practical Solutions

According to a recent press release, completed testing shows that producing such a recycled-content tile is indeed possible. The Lifeceram team tested various milling conditions using the entirety of collected waste materials from ceramic tile manufacturing.

Taking into account the properties of like urban flooring materials, including concrete, terrazzo, natural stone, and even porcelain tiles, the team developed a suitable recycled-content formulation that can be used exclusively to manufacture outdoor ceramic tiles.

“The composition of the new material closely matches the relative proportions in which the different ceramic waste products [scraps, sludges, and dusts] are generated,” Javier García Ten, research leader at ITC, says in the release. “We have achieved the porosity, mechanical resistance, and environmental properties we set out to, and the end product can be processed at existing industrial installations, meaning no changes to processes or equipment at ceramics plants are necessary.”

 

Although not yet tested, the team expects the recycled tiles will hold up well when exposed to the elements. “A benchmarking study defined the target properties, including bending strength, breaking load, impact, slip, stain, and frost resistance. Since we could fulfill these properties, we expect that the performance of the product should be suitable for outdoor applications,” García Ten adds in an email.

A Wide Variety of Benefits

No processing changes at manufacturing plants means no added costs. And because the process uses entirely waste materials, it saves material costs, too. According to García Ten, “The cost of the product is 20% lower than similar porcelain tiles due to the use of waste (only considering transport costs) and the low thermal energy required for granulation in comparison to spray-drying.”

In addition, the scientists say commercial scale-up is completely feasible. “We conducted some industrial tests during the project, and the product behaves quite well during all manufacturing stages (pressing, glazing and decoration, and firing). The point is that the homogenization of some wastes is required, especially for glaze and polishing sludge,” García Ten says.

Plus, there are the green benefits to increasing efficiency and reducing wastes. According to its website, Lifeceram altogether expects to achieve 20% reduction of waste disposal, 65% water savings, 30% reduction in carbon dioxide emissions, and 30% savings in energy input.

Next Steps

But, the project’s success so far represents just one step along the way—key challenges still remain. “To recycle all types of ceramic waste (unfired and fired scraps, glaze and polishing sludge, etc.), the body preparation process is based on dry milling technologies and granulation,” García Ten explains via email. “Dry milling allows us to skip the rheological problems that arise when wastes with soluble salts are recycled. In addition, it is possible to use the very hard fired scraps as chamotte [grog]. However, currently there is not an industrial facility able to dry mill and granulate the residues, because the Spanish ceramic sector is based on wet milling and spray drying.”

So, García Ten explains, the Lifeceram project is developing contacts at smaller companies equipped with dry mills in an effort to next develop an industrial installation to prepare the pressing powder.

the author April Gocha, Ph.D. is managing editor for our sister publication, the Ceramic Bulletin, and also writes for the Ceramic Tech Today blog, where this story first appeared, www.ceramics.org/ctt.