Material cycles in urban systems are strongly influenced by human-driven activities. Similar to ecosystems, which form via production processes that use material and energy as inputs, urban areas require materials for industrial production. By coupling processes of constructive production and regenerative breakdown, materials can be cycled sustainably in cities. Waste materials are generated when no more utility can be derived from that material. In urban areas, recycling materials plays an important role in maximizing the amount of utility that can be derived from materials flowing into the city, which is evidenced by the increasing trend of recycling certain materials in solid municipal waste management and electronic components.