Questions: Recycled Materials in Engineering

Question 1

Why do engineers choose to use recycled aluminum instead of mining new aluminum?

• A. Recycled aluminum is always stronger
• B. Recycling aluminum uses about 95% less energy than making new aluminum from ore
• C. Recycled aluminum is free
• D. New aluminum is illegal to mine

Answer: (B)

Recycling aluminum saves approximately 95% of the energy needed to make aluminum from raw bauxite ore. The recycled aluminum has virtually the same properties as new aluminum. This massive energy savings — plus reducing mining waste — makes recycled aluminum a smart engineering and environmental choice.

Question 2

Paper can be recycled an unlimited number of times without losing quality.

• T. True
• F. False

Answer: False

Paper fibers get shorter and weaker with each recycling cycle. After about 5-7 cycles, the fibers are too short to hold together. That is why recycled paper is often mixed with new (virgin) fibers to maintain quality. Metals and glass, by contrast, can be recycled almost indefinitely without significant quality loss.

Question 3

What does 'design for disassembly' mean, and why is it important?

Model answer: Design for disassembly means creating products that can be easily taken apart at the end of their life so that different materials can be separated and recycled. It is important because mixed materials that are glued or fused together are very difficult or impossible to recycle.

If a product mixes plastic, metal, and glass that cannot be separated, the whole thing goes to a landfill even though each individual material is recyclable. Engineers who design for disassembly use screws instead of glue, keep material types separate, and make it easy to identify and sort each material. This extends the life of resources and reduces waste.