DfR considers the materials from which a product is manufactured and how these materials are assembled. This approach is described by the six DfR criteria presented in the box below. If applied during a product's conception and carried through to its design, assembly, and disposal, these criteria can be an effective EPR tool to minimize wastes and maximize the reuse of materials.

Use recyclable materials. Design products using materials that can be recycled and for which materials collection and recycling technologies currently are available and commonly used. Generally, metals are easier to recycle than nonmetals, and thermoplastic resins are more desirable than thermoset plastics. Alternatively, set up an effective materials collection system (e.g., offer to accept used lead-acid batteries when new batteries are purchased).

Use recycled materials. Select materials that contain a high percentage of recycled content, as this supports the recycling process for which a product is being designed. Steel and aluminum are materials that are often recycled.

Reduce the number of different materials used within an assembly. Reduce the number of materials used to manufacture a component or assembly. Reducing the number of materials also simplifies the separation process and supports recycling.

Mark parts for simple material identification. Mark all materials with standard material identification codes. Although this process is most feasible for plastic parts, it can be expanded to metals, composite materials, and coatings currently used in vehicle manufacturing.

Use compatible materials within an assembly. Select materials that do not need to be separated for recycling. Generally, mixtures of dissimilar plastics cannot be recycled. Similarly, nonferrous metals (e.g., aluminum, chromium, or zinc) can contaminate and thus decrease the recyclability of ferrous metals (i.e., iron and steel), and vice versa. Layers of paint or plated metal over a base material also represent contaminants not compatible with recycling. If a coating on metal cannot be removed, the paint or metal plating will be a contaminant that decreases the metal's recyclability and/or the applications for which the recycled metal can be used.

Make it easy to disassemble. Also called Design for Disassembly, this criterion guides a designer away from complicated products and assembly processes. Using snap fits and nut/bolt assembly techniques whenever possible assists in disassembly, as does avoiding adhesives, particularly when bonding two incompatible materials or if the adhesive will contaminate the materials so they cannot be recycled.

To be effective, these criteria must be used as a set, not individually. For example, if recyclable materials (following Criterion A) are used to manufacture a complex component that cannot be disassembled (not following Criterion D), the goals of DfR will not be achieved.

When vehicles are recycled, their constituent materials are separated by vehicle shredders. These materials can be recycled either into products of the same value (called "primary," or "closed-loop" recycling) or into products of lesser value (called "secondary," or "open-loop" recycling). 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. The most notable loss is in the "ASR waste stream," a mixture of plastics and other potentially recyclable materials that have been ground together so that the individual materials no longer have any commercial value. Metals also are contaminated; for example, coatings such as paints and plated metals, and trace metals from the shredding process contaminate the metals separated from the rest of the vehicle. 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. Therefore, in order to address these issues, vehicle manufacturers must be encouraged to use fewer materials to achieve the same performance standards and substantially reduce life-cycle (particularly end-of-life) impacts.