Recycling involves processing used materials (waste) into new products to prevent disposal of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air and water pollution by reducing the need for "conventional" waste disposal (landfill), and lower greenhouse gas emissions as compared to virgin production. Recycling is a key component of modern waste reduction and is the third component of the "Reduce, Reuse, Recycle" waste hierarchy, according to the 2008/98 European Directive. Recyclable materials include many kinds of glass, paper, metal, plastic, textiles, and electronics. Materials to be recycled are either brought to a collection center or picked up from the curbside, then sorted, cleaned, and reprocessed into new materials bound for manufacturing. The most important element in order recycling to be effective is that citizens should separate the different waste streams at the source.