Reuse, remanufacturing, recycling: the case of glass for buildings

3. Potential and recommendation for remanufacturing flat glass

Due to the requirements indicated in the previous section, remanufacturing may be more adapted than reusing glass. The following remanufacturing processes can be considered depending on the type and state of glass:

• Edge processing

• Cutting to smaller sizes

• Pre-stressing, including enameling

• Bending

• Laminating

• IGU manufacturing

• Sandblasting

• Acid etching

• Painting

These manufacturing processes can only be applied to certain used glass types; Annex A provides an overview of processes which can be applied per type of used glass.

Note that even when one of the above processes can be applied to a used product, the mechanical and chemical properties of the surface of the used product can have changed compared to when it was first installed. Although these changes may not be visible, they can influence the process and the success of the remanufacturing, e.g., due to an increase of surface haze and modification of adhesion properties and on the mechanical resistance.

The following processes are never recommended for remanufacturing:

• Coating: A possible change in surface chemistry will influence the optical properties of the coating and may also compromise the adhesion. Scratches may become more visible after coating.

• Silvering: mirrors are very sensitive to any optical defect

• Chemical strengthening: This process is expensive, and research would be necessary to confirm that it is suitable for used glass.

4. Assessment of flat glass products for reuse/remanufacturing

When assessing if a used product made of flat glass can be reused or remanufactured, the following impacts must be considered:

• Human safety

• Environmental safety and environmental impact

• Product durability

• Excessive costs

• Risks to machinery

• Safety for the building, etc.

Keeping these impacts in mind, a quality protocol should also be prepared for each project and focus on the following actions when relevant:

1. Assessment of relevant product properties/functions (bending strength, safety properties, U-value, light and solar characteristics, etc.), as well as aesthetic expectations

2. Deconstruction processes

3. Disassembly processes

4. Preparation for reuse

5. Preparation for remanufacturing

6. Remanufacturing process

7. Handling (in all stages)

8. Transport (in all stages)

Finally, the quality protocol should be accompanied by proof that reuse/remanufacturing has a significantly lower CO2 impact compared to the use of a new product. This evaluation should be based on the harmonized methodology outlined in EN 15804:2012+A2:2019+AC:2021 and EN 17074. Considerations going beyond product-related emissions are also needed. If installing reused/remanufactured glass products in a building reduces the efficiency of this building and increases the building’s operational emissions, using reused/remanufactured products may cause more CO2 emissions overall.

When reusing and remanufacturing are not possible, other end-of-life treatment options should be considered, such as recycling, which can reduce CO2 emissions during the production of new glass. Annex A provides all end-of-life possibilities for different glass product types.