Layers of paint or plated metal over a base material also represent contaminants not compatible with recycling. Make it easy to disassemble. Also called Design for Disassembly, this criterion guides a designer away from complicated products and assembly processes. To be effective, these criteria must be used as a set, not individually. When vehicles are recycled, their constituent materials are separated by vehicle shredders.
Secondary recycling is often easier than primary recycling but results in downgrading of materials.
The current practice of constituent-material recycling, coupled with current vehicle designs, cause the main resource consumption and waste management ASR problems. Interestingly enough, although vehicle shredding may efficiently separate metals from nonmetals, and ferrous metals from nonferrous metals, it does not preserve the greatest material value. These contaminants both make the recycling process more difficult and may limit the applications for which the recycled material can be used. Although recycling is one way to reduce the consumption of natural resources and the generation of waste, it is energy intensive and produces its own wastes and pollutants.