Landfill mining

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Landfill mining and reclamation (LFMR) is a process which excavates and processes solid wastes which have previously been landfilled. [1] The process aims to reduce the amount of landfill mass encapsulated within the closed landfill and/or temporarily remove hazardous material to allow protective measures to be taken before the landfill mass is replaced. In the process, mining recovers valuable recyclable materials, a combustible fraction, soil, and landfill space. The aeration of the landfill soil is a secondary benefit with regard to the landfill's future use.[ citation needed ] The combustible fraction is useful for the generation of power. The overall appearance of the landfill mining procedure is a sequence of processing machines laid out in a functional conveyor system. The operating principle is to excavate, sieve and sort the landfill material.

Waste Unwanted or unusable materials

Waste are unwanted or unusable materials. Waste is any substance which is discarded after primary use, or is worthless, defective and of no use. A by-product by contrast is a joint product of relatively minor economic value. A waste product may become a by-product, joint product or resource through an invention that raises a waste product's value above zero.

Landfill site for the disposal of waste materials by burial

A landfill site is a site for the disposal of waste materials by burial. Landfill is the oldest form of waste treatment, although the burial of the waste is modern; historically, refuse was simply left in piles or thrown into pits. Historically, landfills have been the most common method of organized waste disposal and remain so in many places around the world.

Contents

The Hiriya landfill operated by the Dan Region Authority next to the city of Tel Aviv, Israel, introduced the concept of mining as early as 1953. [2]

Tel Aviv City in Israel

Tel Aviv-Yafo, often referred to as just Tel Aviv, is the most populous city in the largest metropolitan area of Israel. Located on the country's Mediterranean coastline and with a population of 451,523, it is the economic and technological center of the country. If East Jerusalem is considered part of Israel, Tel Aviv is the country's second most populous city after Jerusalem; if not, Tel Aviv is the most populous city before West Jerusalem.

Israel country in the Middle East

Israel, also known as the State of Israel, is a country in Western Asia, located on the southeastern shore of the Mediterranean Sea and the northern shore of the Red Sea. It has land borders with Lebanon to the north, Syria to the northeast, Jordan on the east, the Palestinian territories of the West Bank and Gaza Strip to the east and west, respectively, and Egypt to the southwest. The country contains geographically diverse features within its relatively small area. Israel's economic and technological center is Tel Aviv, while its seat of government and proclaimed capital is Jerusalem, although the state's sovereignty over Jerusalem has only partial recognition.

Waste contains many resources with high value, the most notable of which are non-ferrous metals such as aluminium cans and scrap metal. The concentration of aluminium in many landfills is higher than the concentration of aluminum in bauxite from which the metal is derived. [3]

Bauxite aluminium ore

Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite (FeO(OH)) and haematite (Fe2O3), the aluminium clay mineral kaolinite (Al2Si2O5(OH)) and small amounts of anatase (TiO2) and ilmenite (FeTiO3 or FeO.TiO2).

Practical applications

Landfill mining is also possible in countries where land is not available for new landfill sites. In this instance landfill space can be reclaimed by the extraction of biodegradable waste and other substances then refilled with wastes requiring disposal.

Biodegradable waste includes any organic matter in waste which can be broken down into carbon dioxide, water, methane or simple organic molecules by micro-organisms and other living things by composting, aerobic digestion, anaerobic digestion or similar processes. In waste management, it also includes some inorganic materials which can be decomposed by bacteria. Such materials include gypsum and its products such as plasterboard and other simple organic sulfates which can decompose to yield hydrogen sulphide in anaerobic land-fill conditions.

Mining construction landfill sites is the simplest form of landfill mining. Construction landfills in the United States contain three basic components, wood, scrap metal and gypsum, or drywall, along with a minimal amount of other construction materials. The wood collected can be used as fuel in coal burning power plants and the scrap metal reprocessed. European landfills tend to have more masonry from demolished bricks, tiles and concrete. [4]

Mining of municipal landfills is more complicated and has to be based on the expected content of the landfill. Older landfills, in the United States before 1994, were often capped and closed, essentially entombing the waste. This can be beneficial for waste recovery. It can also create a higher risk for toxic waste and leachate exposure as the landfill has not fully processed the stewing wastes. Mining of bioreactor landfills and properly stabilized modern sanitary landfills provides its own benefits. The biodegradable wastes are more easily sieved out, leaving the non-biodegradable materials readily accessible. The quality of these materials for recycling and reprocessing purposes is not as high as initially recycled materials, however materials such as aluminum and steel are usually excluded from this.

Toxic waste

Toxic waste is any unwanted material in all forms that can cause harm. Many of today's household products such as televisions, computers and phones contain toxic chemicals that can pollute the air and contaminate soil and water. Disposing of such waste is a major public health issue.

Leachate Any liquid that, in the course of passing through matter, extracts soluble or suspended solids

A leachate is any liquid that, in the course of passing through matter, extracts soluble or suspended solids, or any other component of the material through which it has passed.

Landfills are the primary method of waste disposal in many parts of the world, including United States and Canada. Bioreactor landfills are expected to reduce the amount of and costs associated with management of leachate, to increase the rate of production of methane for commercial purposes and reduce the amount of land required for land-fills. Bioreactor landfills are monitored and manipulate oxygen and moisture levels to increase the rate of decomposition by microbial activity.

Landfill mining is most useful as a method to remediate hazardous landfills. Landfills that were established before landfill liner technology was well established often leak their unprocessed leachate into underlying aquifers. This is both an environmental hazard and also a legal liability. In the US, the Environmental Protection Agency requires closed landfills to be monitored for at least 30 years after waste placement ceases. Mining the landfill simply to lay a safe liner is a last, but sometimes necessary resort.

Methods

The parts of the mining process are the different mining machines. Depending on the complexity of the process more or fewer machines can be used. Machinery is easily transported on trucks from site to site, mounted on trailers.

An excavator or front end loader uncovers the landfilled materials and places them on a moving floor conveyor belt to be taken to the sorting machinery. A trommel is used to separate materials by size. First, a large trommel separates materials like appliances and fabrics. A smaller trommel then allows the biodegraded soil fraction to pass through leaving non-biodegradable, recyclable materials on the screen to be collected.

An electromagnet is used to remove the ferrous material from the waste mass as it passes along the conveyor belt.

A front end loader is used to move sorted materials to trucks for further processing.

Odor control sprayers are wheeled tractors with a cab and movable spray arm mounted on a rotating platform. A large reservoir tank mounted behind the cab holds neutralizing agents, usually in liquid form, to reduce the smell of exposed wastes.

Depending on the level of resource recovery, material can be put through an air classifier which separates light organic material from heavy organic material. The separate streams are then loaded, by front end loaders, onto trucks either for further processing or for sale. Further manual processing can be done on site if processing facilities are too far away to justify the transportation costs.

See also

Related Research Articles

Recycling Process using materials into new products to prevent waste of potentially useful materials

Recycling is the process of converting waste materials into new materials and objects. It is an alternative to "conventional" waste disposal that can save material and help lower greenhouse gas emissions. Recycling can prevent the waste of potentially useful materials and reduce the consumption of fresh raw materials, thereby reducing: energy usage, air pollution, and water pollution.

Scrap recyclable materials left over from product manufacturing and consumption

Scrap consists of recyclable materials left over from product manufacturing and consumption, such as parts of vehicles, building supplies, and surplus materials. Unlike waste, scrap has monetary value, especially recovered metals, and non-metallic materials are also recovered for recycling.

Materials recovery facility plant to process recyclates

A materials recovery facility, materials reclamation facility, materials recycling facility or Multi re-use facility is a specialized plant that receives, separates and prepares recyclable materials for marketing to end-user manufacturers. Generally, there are two different types: clean and dirty materials recovery facilities.

In metallurgy, a non-ferrous metal is a metal, including alloys, that does not contain iron (ferrite) in appreciable amounts.

Concrete recycling

When structures made of concrete are demolished or renovated, concrete recycling is an increasingly common method of utilizing the rubble. Concrete was once routinely trucked to landfills for disposal, but recycling has a number of benefits that have made it a more attractive option in this age of greater environmental awareness, more environmental laws, and the desire to keep construction costs down.

Electronic waste Discarded electronic devices

Electronic waste or e-waste describes discarded electrical or electronic devices. Used electronics which are destined for refurbishment, reuse, resale, salvage recycling through material recovery, or disposal are also considered e-waste. Informal processing of e-waste in developing countries can lead to adverse human health effects and environmental pollution.

Refuse-derived fuel (RDF) is a fuel produced from various types of waste such as municipal solid waste (MSW), industrial waste or commercial waste.

A mechanical biological treatment (MBT) system is a type of waste processing facility that combines a sorting facility with a form of biological treatment such as composting or anaerobic digestion. MBT plants are designed to process mixed household waste as well as commercial and industrial wastes.

Green waste, also known as "biological waste," is any organic waste that can be composted. It is most usually composed of refuse from gardens such as grass clippings or leaves, and domestic or industrial kitchen wastes. Green waste does not include things such dried leaves, pine straw, or hay. Such materials are rich in carbon and considered "brown wastes," while green wastes contain high in concentrations of nitrogen. Green waste can be used to increase the efficiency of many composting operations and can be added to soil to sustain local nutrient cycling.

Tire recycling Tyre recycling, stages and uses of recycled tyres.

Tire recycling, or rubber recycling, is the process of recycling waste tires that are no longer suitable for use on vehicles due to wear or irreparable damage. These tires are a challenging source of waste, due to the large volume produced, the durability of the tires, and the components in the tire that are ecologically problematic.

Sims Metal Management

Sims Metal Management Ltd is the leading metals and electronics recycling company in the world. The company specializes in ferrous and non-ferrous metals recycling, post-consumer electronic goods recycling, and municipal waste recycling. Founded in 1917, its primary operations are located in the United States, Australia, and the UK.

Single-stream recycling

Single-stream recycling refers to a system in which all paper fibers, plastics, metals, and other containers are mixed in a collection truck, instead of being sorted by the depositor into separate commodities and handled separately throughout the collection process. In single-stream, both the collection and processing systems are designed to handle this fully commingled mixture of recyclables, with materials being separated for reuse at a materials recovery facility (MRF). The single-stream option replaces the dual-stream option, which is where people separate certain recyclable materials and place them in separate containers for collection.

Demolition waste

Demolition waste is waste debris from destruction of buildings, roads, bridges, or other structures. Debris varies in composition, but the major components, by weight, in the US include concrete, wood products, asphalt shingles, brick and clay tile, steel, and drywall. There is the potential to recycle many elements of demolition waste.

Source Separated Organics

Source Separated Organics (SSO) is the system by which waste generators segregate compostable materials from other waste streams at the source for separate collection.

Recycling can be carried out on various materials

Resource recovery is using wastes as an input material to create valuable products as new outputs. The aim is to reduce the amount of waste generated, therefore reducing the need for landfill space and also extracting maximum value from waste. Resource recovery delays the need to use raw materials in the manufacturing process. Materials found in municipal solid waste can be used to make new products. Plastic, paper, aluminium, glass and metal are examples of where value can be found in waste.

Trommel screen

A trommel screen, also known as a rotary screen, is a mechanical screening machine used to separate materials, mainly in the mineral and solid-waste processing industries. It consists of a perforated cylindrical drum that is normally elevated at an angle at the feed end. Physical size separation is achieved as the feed material spirals down the rotating drum, where the undersized material smaller than the screen apertures passes through the screen, while the oversized material exits at the other end of the drum.

References

  1. ↑ Landfill Mining Landfill Mining, Preserving Resources through Integrated Sustainable Management of Waste, Technical Brief from the World Resource Foundation
  2. ↑ Landfill Mining Paper Archived 2006-10-10 at the Wayback Machine D.J. van der Zee, et al. (2004) "Assessing the market opportunities of landfill mining". Waste Manag.24(8):795-804.
  3. ↑ "Landfill mining: new opportunities ahead?" (PDF). macfarlanes.com. Macfarlanes. Archived from the original (PDF) on 2015-06-13. Retrieved 2015-06-11.
  4. ↑ The case for pre demolition audits
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