Innovative cullet recovery from residual waste – Stoelzle supports Brantner green solutions in developing the “Glasy” recycling technology

Innovative cullet recovery from residual waste – Stoelzle supports Brantner green solutions in developing the “Glasy” recycling technology

The circular economy specialist Brantner green solutions is presenting a globally unique innovation, developed with support from Stoelzle: the “Glasy” recycling technology makes it possible to recover glass from residues of residual waste incineration with a purity of 99.9999%. The first recovery system is already successfully in operation and supplies high-quality cullet for glass production.

Krems/Köflach, 3 December 2025. With its innovative “Glasy” sorting system, Brantner green solutions is making a major contribution to closing the loop in glass production. Residual waste incineration in Austria alone generates around 600,000 tons of incineration residues every year that still contain numerous recoverable materials. The share of glass is up to 30%. To date, however, sorting technologies have not been sufficient to process the separated glass in such a way that it can be used by the glass industry as a high-quality secondary raw material. Thanks to the upstream thermal treatment step, the recovered material is already free from organic impurities – a type of contamination that can otherwise significantly limit the use of cullet.

Stoelzle involved in development

The packaging glass manufacturer Stoelzle, together with its research and development team, was involved in the development of “Glasy”. In the in-house glass laboratory at Stoelzle Oberglas in Austria, the cullet obtained from the recycling process was thoroughly analysed and tested in lab-scale melts.

Series of trials were carried out to determine whether the cullet quality achieved meets the requirements for use in the industrial production process of high-quality premium flint glass. Even the slightest contamination, for example by metals or ceramics, can negatively affect the batch and reduce the later quality of the packaging glass.

From a technological perspective, the Brantner process includes an integrated advance sampling taken directly from the product stream of the sorting system. Combined with AI-based evaluation of the achieved quality – for example with regard to colour distribution and residual contaminants – the properties of the recovered product are determined almost in real time. For Stoelzle as a glass manufacturer, this means seamless traceability of cullet quality. The system is so far unique and Brantner green solutions has also filed a patent application for it.

The melting tests at Stoelzle showed that the purity level of 99.9999% achieved with “Glasy” meets Stoelzle’s stringent requirements and that the cullet can be safely used in the production of high-end glass packaging. In addition, the laboratory analyses of the material composition confirmed the excellent quality of the cullet.

“As a manufacturer of premium glass packaging, we depend on a consistently available supply of extremely pure cullet. Using recycled glass in the batch saves raw materials, energy and therefore also CO₂ emissions. With ‘Glasy’ we can, for the first time, use glass from waste incineration residues as a secondary raw material on an industrial scale. This is another step towards a truly circular economy,” says Dr August Grupp, CEO of Stoelzle.

Left to right: Manfred Vogl General Manager Brantner green solutions, Fabian Stölzel R&D Stoelzle, DI Dirk Wypchol General Manager Stoelzle Oberglas, Josef Scheidl General Manager Brantner green solutions, Reinhard Grießler General Manager Brantner green solutions

Returning thousands of tons of glass to the loop

Thanks to the innovative recycling plant, around 20,000 tons of glass can be recovered from waste incineration residues in Austria every year and made available to the glass industry as a secondary raw material.

For every ton of cullet used at Stoelzle, around 1,200 kilograms of primary raw materials can be saved.

Using cullet avoids the release of around 200 kg of CO₂ that is bound in this quantity in primary raw materials. Furthermore, each 10% of cullet share in the overall batch reduces the energy required for melting by around 2–3%. With the glass furnaces currently fired with natural gas, this means that for every 10% cullet content, around 6 kilograms of CO₂ per ton of glass produced can be avoided in the actual melting process.

The cooperation between Brantner green solutions and Stoelzle is to be further strengthened in future. The aim is for Stoelzle to use a significant proportion of the cullet recovered with “Glasy” in the production of packaging glass for the pharma and consumer segments at its Köflach plant. This turns incineration residues into a high-quality secondary raw material and further strengthens the circular economy in the Austrian glass industry.