Recycling is a process to change waste materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from land-filling) by reducing the need for "conventional" waste disposal, and lower greenhouse gas emissions as compared to plastic production. Recyclable materials include many kinds of glass, paper, metal, plastic, textiles, and electronics. Materials to be recycled are either brought to a collection centre or picked up from the curb side, then sorted, cleaned, and reprocessed into new materials bound for manufacturing. In the strictest sense, recycling of a material would produce a fresh supply of the same material—for example, used office paper would be converted into new office paper, or used foamed polystyrene into new polystyrene. However, this is often difficult or too expensive (compared with producing the same product from raw materials or other sources), so "recycling" of many products or materials involves their reuse in producing different materials (e.g., paperboard) instead.