Recycling returns useful materials to production and can reduce demand for newly extracted resources. The benefit depends on collection, sorting, cleaning, recovery losses and processing energy. Aluminium recycling typically avoids the energy-intensive reduction of fresh ore, but a numerical comparison must use the same product amount and the supplied data. Recovery percentage is recovered useful mass divided by available useful mass times 100.
Thermoplastics can often be remelted, while cross-linked thermosets are harder to reshape by heating. Mixing incompatible polymers can reduce recyclate quality. Composites combine materials to obtain properties such as low mass and high strength, but separating tightly bonded components can be difficult. Renewable feedstocks, efficient reactions, durable design and easier separation are distinct ways to reduce resource demand; none alone guarantees zero environmental impact.
Example 1
Recycling produces 72kg usable metal from 90kg metal collected. Find recovery.
Recovery =9072×100=80%. The 18kg difference represents processing loss or unrecovered material under the stated mass boundary.
Example 2
Primary production needs 150 MJ kg−1 and recycling 15 MJ kg−1. Find percentage energy saving for equal product mass.
Saving =150150−15×100=90%. The comparison is on the same per-kilogram basis.
Watch out: Collection, sorting and processing determine actual recovery; useful recycling still requires energy and can produce waste.