The production of ceramic materials such as bricks, tiles, and sanitary ceramics traditionally generates large amounts of CO₂ because it requires firing clay-based materials at very high temperatures. To support the transition to climate‑neutral manufacturing, researchers at the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) have developed in cooperation with Riedhammer a new high‑temperature sintering kiln that can operate using either natural gas or hydrogen. Using hydrogen enables CO₂‑free firing processes without compromising product quality.
 
Existing hydrogen‑fired kilns cannot usually switch back to natural gas, making Fraunhofer’s dual‑fuel capability unique worldwide according to Dr. Olga Ravkina, group manager for high-temperature membranes and storage at IKTS. The high-temperature furnace from #Riedhammerindustrialkilns at the Fraunhofer IKTS site in Arnstadt can be operated with natural gas or hydrogen. The furnace is suitable for various ceramic applications, including construction, household, and industrial ceramics. Switching from natural gas to hydrogen is technically complex: hydrogen combustion changes kiln conditions and introduces more steam, which can alter product properties, such as color. The new IKTS furnace enables side‑by‑side testing of natural gas and hydrogen firing so manufacturers can evaluate how different fuels affect their specific products. This flexible approach allows companies to transition selectively to hydrogen where the results are satisfactory, while still using natural gas for other products.
 
The prototype furnace, funded with €10.3 million by the state of Thuringia and realized by Riedhammer, has a 500‑liter capacity, reaches up to a maximum temperature of 1,700 °C, and can fire about 150 kg of material per test. Only the five burner heads need to be swapped to change fuels. Conventional kilns can also be retrofitted relatively cheaply with new burners for hydrogen use, emitting only water vapor which allows companies with extensive firing processes to comply with the legal prescriptions for reduced CO2 emissions.
 
The furnace includes extensive sensor and digital monitoring systems that track temperature distribution, heating rates, and atmospheric conditions, enabling detailed analysis of the entire firing process. Many manufacturers cannot conduct such tests in their own facilities without interrupting the ongoing production. In the new IKTS furnace, several thermocouples measure temperatures at various points inside the kiln as well as in the postcombustion zone. Parameters such as heating speed, heating rate, soaking time, and the furnace atmosphere are monitored. The fuel-air ratio can be adjusted for both oxidizing and reducing conditions. This makes even it possible to comparatively test debinding processes.
 
However, widespread industrial adoption is currently limited by the shortage and high cost of green hydrogen in Germany, as well as missing pipeline infrastructure. Some companies, such as Hagemeister Klinkerwerk, have already demonstrated that hydrogen-fired bricks can achieve excellent quality, but they cannot switch permanently due to economic and supply constraints. In some regions, hydrogen pipelines may not be available until around 2030.