How to Repurpose Industrial Waste Into Eco-Friendly Building Materials

How to Repurpose Industrial Waste Into Eco-Friendly Building Materials


The construction industry produces large quantities of waste and uses lots of resources. These resources often come from unsustainable practices that harm the environment. Finding ways to reuse industrial waste and byproducts can help make building materials more sustainable. I aim to provide an in-depth guide on repurposing industrial waste into eco-friendly building materials.

Types of Industrial Waste That Can Be Repurposed

There are several types of industrial waste that can be repurposed into building materials. The most common include:

Fly Ash

Fly ash is a byproduct of coal combustion in power plants. It is a fine powder that can be used as a partial substitute for cement in concrete. Using fly ash reduces the concrete’s overall carbon footprint.


Slag is a byproduct of steel production. There are several types of slag that can be used in construction, including ground granulated blast furnace slag and steel slag. They can replace a portion of the cement in concrete. Using slag reduces the need for virgin materials.

Glass Cullet

Glass cullet refers to crushed waste glass. It can be incorporated into concrete as an aggregate. The glass helps make the concrete more durable and decorative. Recycling glass reduces waste going to landfills.

Recycled Plastics

Waste plastics like PET bottles can be shredded and repurposed into materials such as plastic lumber. The lumber can be used for outdoor decking, fencing, and similar applications. This gives waste plastics a second life.


Sawdust is a wood industry waste product that can be compressed into boards and used for furniture or flooring. This kind of upcycling turns a waste into a higher value product.

Key Benefits of Using Repurposed Waste

There are several excellent reasons to incorporate repurposed industrial waste into building materials:

  • Reduces use of virgin resources – Repurposing waste decreases the need for additional raw materials extraction. This protects natural resources and habitats.

  • Prevents waste from going to landfills – Diverting industrial waste into useful building materials reduces landfill volumes. Less waste in landfills means lower environmental impact.

  • Lowers carbon footprint – Some waste materials like fly ash and slag can replace high-carbon cement in concrete. This significantly lowers the carbon footprint of concrete.

  • Can be cost-competitive – Repurposed waste materials are often cost-competitive with conventional materials. Their use does not necessarily increase overall project costs.

  • Enhances brand image – Companies that repurpose waste are often seen as innovative and sustainable. This can improve brand reputation.

Techniques for Repurposing Different Types of Waste

The techniques for repurposing industrial waste depend on the type of waste in question. Here are some common methods:

Repurposing Fly Ash and Slag

Fly ash and slag can be used as supplementary cementitious materials (SCMs). They are added to the concrete mix to replace a portion of the Portland cement, typically between 30-40%. This involves:

  • Processing the fly ash or slag to the fineness required for concrete mixes
  • Blending the SCMs in the right proportion with cement during concrete production

No significant changes are needed to concrete production systems. The SCM concrete has comparable strength and durability to regular concrete.

Incorporating Glass Cullet as Aggregate

Waste glass can be crushed into tiny fragments called glass cullet. The cullet can replace a portion of the sand or gravel aggregates in concrete, typically 10-20% by volume. The steps include:

  • Collecting waste glass of appropriate type and color
  • Cleaning and crushing the glass into cullet
  • Screening the cullet to size specifications
  • Mixing the cullet with natural aggregates during concrete production

The angular shape of glass cullet enhances the concrete’s strength. The cullet is also chemically inert within the concrete.

Manufacturing Plastic Lumber

Waste plastics have to undergo the following steps to be converted into plastic lumber:

  • Shredding plastic waste into small flakes
  • Cleaning and drying the plastic flakes
  • Extruding the flakes under heat and pressure to create dimensional lumber

The plastic lumber can be manufactured to different sizes as per end-use requirements. They require minimal maintenance and do not splinter or rot like wood.

Compressing Sawdust Into Boards

Sawdust can be compressed into sturdy boards using resins and wax in the following basic steps:

  • Drying and cleaning the sawdust to remove contaminants
  • Mixing sawdust particles with organic binders like lignin
  • Compressing the mixture under high heat and pressure
  • Trimming and finishing the boards as required

The resulting boards have good stiffness and finishing suitable for indoor applications.

Quality Control and Testing Requirements

To ensure the safety and quality of repurposed waste building materials, they must be tested before and during use. Some key requirements include:

  • Testing repurposed materials – Materials like plastic lumber and sawdust boards should be tested for strength, toxicity, durability, and aesthetics.

  • Evaluation of concrete mixes – Concrete containing waste materials must be tested for slump, strength, time of setting, shrinkage, and other parameters.

  • Quality control during production – Continuous quality control checks should be performed during the production of repurposed waste materials to ensure consistency.

  • Compliance with regulations – The materials must comply with local building codes and environmental regulations regarding recycling.

  • Certifications – Obtaining third-party certifications like UL’s GREENGUARD can validate the eco-friendliness of repurposed waste materials.

Proper testing and quality control is important to convince stakeholders about using unconventional recycled materials.

Examples of Projects Using Repurposed Waste

Many pioneering projects have utilized recycled industrial waste, proving their viability:

  • The Enterprise Center in Los Angeles uses fly ash concrete and recycled content carpets. 84% of the building’s materials contain recycled content.

  • Shanghai Natural History Museum utilized around 7,500 tons of blast furnace slag and 4,500 tons of fly ash, reducing the need for cement.

  • House E in Finland derived over 50% of its insulation material from recycled glass, plastic, and nylon fibers.

  • At Texas A&M University, benches were constructed using plastic lumber made from approximately 18,000 recycled bottles.

  • A school building in Spain named La Esguelva integrates sawdust particle boards to create curved interior walls.

These projects highlight the diverse real-world applications of recycled industrial waste streams.


Repurposing industrial waste into building materials is a circular solution that tackles sustainability challenges faced by the construction sector. With careful sourcing, manufacturing, testing and quality control, a wide range of waste materials can find second life in our built environment. It presents an exciting opportunity to reduce extraction of virgin resources and move towards closed-loop material flows. With greater adoption, eco-friendly repurposed materials can progressively become mainstream and make our cities greener.