Scrap is a term used to describe recyclable materials left over from every manner of product consumption, such as parts of vehicles, building supplies, and surplus materials. Often confused with waste, scrap in fact has significant monetary value. Overall, the scrap industry processes more than 145,000,000 short tons (129,464,286 long tons; 131,541,787 t) of recyclable material each year into raw material feedstock for industrial manufacturing around the world. In 2007 the United States' exported over 10 billion dollars worth of scrap steel.

Scrap is often taken to a wrecking yard (also known as a scrap yard, junkyard, or breaker's yard), where it is processed for later melting into new products. A wrecking yard, depending on its location, may allow customers to browse their lot and purchase items before they are sent to the smelters although many scrap yards that deal in large quantities of scrap usually do not, often selling entire units such as engines or machinery by weight with no regard to their functional status. Customers are typically required to supply all of their own tools and labor to extract parts, and some scrap yards may first require waiving liability for personal injury before entering. Many scrap yards also sell bulk metals (stainless steel, etc) by weight, often at prices substantially below the retail purchasing costs of similar pieces.

In contrast to wreckers, scrap yards typically sell everything by weight, rather than by item. To the scrap yard, the primary value of the scrap is what the smelter will give them for it, rather than the value of whatever shape the metal may be in. An auto wrecker, on the other hand, would price the exact same scrap based on what the item does, regardless of what it weighs. Typically, if a wrecker cannot sell something above the value of the metal in it, they would then take it to the scrap yard and sell it by weight. Equipment containing parts of various metals can often be purchased at a price below that of either of the metals, due to saving the scrap yard the labor of separating the metals before shipping them to be recycled. As an example, a scrap yard in Arcata, California sells automobile engines for $0.25 per pound, while aluminum, of which the engine is mostly made, sells for $1.25 per pound. Scrap prices are reported in a handful of U.S. publications, including American Metal Market, based on confirmed sales.

Risks
Great potential exists in the scrap metal industry for accidents in which a hazardous material which is present in scrap causes death, injury or environmental damage. A classic example is radioactivity in scrap; see the Goiania accident and the Mayapuri radiological accident as examples of accidents involving radioactive materials which entered the scrap metal industry and some details of the behavior of contaminating chemical elements in metal smelters. The general nature of many of the tools used in scrap yards such as Alligator shear, which cut metal using hydraulics give themselves the need for safety.

Recycling involves processing used 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 virgin production. Recycling is a key component of modern waste reduction and is the third component of the "Reduce, Reuse, Recycle" waste hierarchy.

Recyclable materials include many kinds of glass, paper, metal, plastic, textiles, and electronics. Although similar in effect, the composting or other reuse of biodegradable waste – such as food or garden waste – is not typically considered recycling. 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.

In a strict sense, recycling of a material would produce a fresh supply of the same material, for example used office paper to more office paper, or used foamed polystyrene to more 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. Another form of recycling is the salvage of certain materials from complex products, either due to their intrinsic value (e.g., lead from car batteries, or gold from computer components), or due to their hazardous nature (e.g., removal and reuse of mercury from various items).

Critics dispute the net economic and environmental benefits of recycling over its costs, and suggest that proponents of recycling often make matters worse and suffer from confirmation bias. Specifically, critics argue that the costs and energy used in collection and transportation detract from (and outweigh) the costs and energy saved in the production process; also that the jobs produced by the recycling industry can be a poor trade for the jobs lost in logging, mining, and other industries associated with virgin production; and that materials such as paper pulp can only be recycled a few times before material degradation prevents further recycling. Proponents of recycling dispute each of these claims, and the validity of arguments from both sides has led to enduring controversy.

Ship breaking or ship demolition is a type of ship disposal involving the breaking up of ships for scrap recycling, with the hulls being discarded in ship graveyards. Most ships have a lifespan of a few decades before there is so much wear that refitting and repair becomes uneconomical. Ship breaking allows materials from the ship, especially steel, to be reused. Equipment on board the vessel can also be reused.

Efficiency of facilities:-Ship breaking can occur in a wide variety of facilities. They range from advanced sites like Van Heyghen Recycling and other "Green Ship Recycling" approved facilities in industrialized ports, to low-tech facilities such as at Along, India. At present the only truly environmentally correct option is the use of "Green Ship Recycling" at approved facilities. These facilities can recover up to 99% of the ship's materials and correctly process hazardous waste such as asbestos.

Supply
For a recycling program to work, having a large, stable supply of recyclable material is crucial. Three legislative options have been used to create such a supply: mandatory recycling collection, container deposit legislation, and refuse bans. Mandatory collection laws set recycling targets for cities to aim for, usually in the form that a certain percentage of a material must be diverted from the city's waste stream by a target date. The city is then responsible for working to meet this target.

Container deposit legislation involves offering a refund for the return of certain containers, typically glass, plastic, and metal. When a product in such a container is purchased, a small surcharge is added to the price. This surcharge can be reclaimed by the consumer if the container is returned to a collection point. These programs have been very successful, often resulting in an 80% recycling rate. Despite such good results, the shift in collection costs from local government to industry and consumers has created strong opposition to the creation of such programs in some areas.

A third method of increase supply of recyclates is to ban the disposal of certain materials as waste, often including used oil, old batteries, tires and garden waste. One aim of this method is to create a viable economy for proper disposal of banned products. Care must be taken that enough of these recycling services exist, or such bans simply lead to increased illegal dumping.