Brick and tile industry sets standards in resource efficiency and climate protection

Recycling options for brick waste

The study sheds light on resource efficiency along the entire production chain: from raw material extraction and processing to drying, firing and recycling. The use of external secondary raw materials and the high-quality recycling of brick waste from production are particularly promising.

In 2019, 84% of the around 5 million tonnes of separately collected brick waste was processed in recycling plants, 12% was used as backfill material and only 1% was sent to landfill. The study identifies four key recycling options:

• Concrete production: bricks can be used for R-concrete or as a clinker substitute in cement. Quotas of 10-30 per cent are technically possible, but are not yet fully utilised.

• Cultivation substrate: Purely recycled bricks are suitable for vegetation and green roof substrates, with great potential in the sponge city strategy.

• Recycled bricks: “Cold bricks” are produced from recycled brick remnants and mineral binders without a firing process.

• Road construction: Reprocessed recycled brick building materials can be used in road construction and on tennis courts at rates of up to 30 %.

Adjusting screws for resource efficiency

The integration of external secondary raw materials and the recycling of in-house materials in particular offer great potential:

• Filter cake: The by-product filter cake made from clay minerals can be used as a clay substitute.

• Excavated soil: Excavated soil from large-scale projects is a valuable but previously underutilised alternative source of raw materials. Intensified co-operation with earthworks companies and recipe adjustments are required.

• Grinding dust: Dust produced during surface grinding is already fully recycled by the brick industry.

• Broken bricks: Sorted fired material or offcuts can either be reintroduced into production or utilised in the open-loop system.

• Raw mix: Unused raw mix is used to produce new green bricks.

Quality requirements and technical limits

The production of backing bricks enables an average substitution rate of 8 per cent, with a potential of up to 10 per cent. It is not necessary to change the recipe to this extent. Research into biogenic porosity agents opens up further possibilities. However, roof tiles and clinker bricks are subject to stricter requirements in terms of grain size and mineral composition; raw materials from secondary sources generally exhibit higher fluctuation ranges and compositional inaccuracies. The deviation tolerance of the required grain size and mineral suitability is low, which technically limits the use of secondary materials.

Scenarios for saving resources

Three scenarios show: Dematerialisation - e.g. increasing the proportion of perforations - and extending the life cycle can significantly reduce emissions and resource consumption. The BVZi is therefore calling for the observation period to be increased from 50 to 80 years. The reuse of bricks in their original function for new construction projects also contributes to the conservation of resources. The same applies to the reuse of insulating materials in backing bricks. Overall, the assessment shows that the increased use of excavated soil and filter cake as well as recycled material has a positive impact on the resource and climate balance of the brick and tile industry.

Outlook and next steps

“The results of the study impressively illustrate how great the potential of the brick industry is for conserving resources and protecting the climate. With innovative recycling solutions and optimised production processes, we are making a decisive contribution to sustainable construction,” says Attila Gerhäuser, Managing Director of BVZi. Clay blocks in particular offer potential for CO₂ reduction, while the substitution of primary material is limited for roof tiles and clinker bricks. The “Brick Recycling Technical Data Sheet” is intended to further facilitate the utilisation of recycled material.

In future, research and innovation should be strengthened and bureaucratic hurdles for product development reduced. Building owners and planners should increasingly focus on the choice of building materials and recyclability. The brick industry remains committed to its resource efficiency and the climate targets up to 2045.

The short report and the complete study are available in the BVZi download area.