The initial motivation for acid recycling was to minimize material input, but full-acid recycling leads to high energy consumption. Allwood reviewed the different types of recycling processes; under certain circumstances, materials can be reused without the energy-intensive process of recycling; but for certain materials (e.g., alloys and glasses need intensive energy for melting for the purpose of separation), the energy required for recycling is greater than that required to extract it from natural minerals. To decrease the overall demand for materials and energy, a partial reduction in total purchasing or production of a certain material could be implemented.