A secondary raw material is a type of waste that can be recycled and is not classified as primary produce from manufacturing and industrial facilities. Secondary raw materials reduce the need for virgin raw materials and provide sustainable sources of materials that can be used over prolonged periods of time.
Examples of secondary raw materials are the following.
- Residuals of coal combustion from steam electric utilities.
- Spent foundry sand from metal casting.
- Materials from the construction and demolition of roads, buildings, and other infrastructure.
When Did Recycling of Secondary Raw Materials Begin?
Secondary raw materials have been used since 2,000 BC when bronze was heavily reused to produce weapons, armor, and tools. Secondary raw material collectors, known as cartmen, obtained rags, bones, and coal dust for making paper, glue, and bricks. World Wars I and II also made use of secondary raw materials due to the scarcity of supplies during those periods. Reuse of secondary raw materials remains to be practiced today to help in sustainability and conservation efforts.
What are the Benefits of Reusing Secondary Raw Materials?
Secondary raw materials can be used in place of virgin raw materials since they share similar chemical and physical characteristics to produce quality, functional, and environmentally safe products.
Additional benefits of reusing secondary raw materials include cost reduction, conservation of natural resources, decreased pollution in the water and air as well as greenhouse gas emissions, and minimized use of landfills.
What Can Be Produced Out of Secondary Raw Materials?
Examples of practical uses and applications for secondary raw materials are as follows.
- Replacing portland cement in concrete with coal fly ash.
- Substituting mined gypsum in wallboard with flue gas desulfurization gypsum.
- Using spent foundry sand for manufactured soil and road sub-base.
Secondary raw materials can be used in making the structural and flowable filling, bridges, road embankments, and pavement aggregates.