Disposed waste that can be recycled is then further separated into the type of material the item is made out of. This resource recovery practice ensures that used, raw materials can reprocessed into new products, thus reducing the amount of waste in the environment. Commonly recycled items include aluminium such as beverage cans, copper such as wire, steel from food and aerosol cans, old steel furnishings or equipment, rubber tyres, polyethylene and PET bottles, glass bottles and jars, paperboard cartons, newspapers, magazines and light paper, and corrugated fiberboard boxes. Additionally, materials like PVC, LDPE, PP, and PS are also recyclable, as they are usually composed of a single type of material.
Unrecyclable waste is disposed off in landfills, where deposited items are generally and gradually compressed, or incarcerated. The former is one of the more popular - and controversial - methods of waste disposal around the world. Aside from common problems like wind-blown debris and liquid generation, poorly designed landfills can also cause an increase in gas production, which is extremely hazardous. If left untreated, these gases can kill surface vegetation, cause increase greenhouse effects, and emanate a nasty odor. On the other hand is incaceration, where solid organic wastes are subjected to combustion so as to convert them into residue and gaseous products. This method is extremely environmentally-friendly, resulting in the volumes of solid waste being reduced by 80 to 95 percent. They dispose of both municipal solid waste and solid residue from waste water treatment, and work by converting waste materials into heat, gas, steam, and ash. This method is carried out both on a small scale by individuals and on a large scale by industry, and is often used as a best practice to dispose of solid, liquid and gaseous waste. However, incarceration also gives rise to issues such as emission of gaseous pollutants, making it a disputed topic.