Selecting Appropriate Tires for Different Terrains

Towed cargo vehicle

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A trailer is an unpowered vehicle towed by a powered vehicle. It is commonly used for the transport of goods and materials.

Sometimes recreational vehicles, travel trailers, or mobile homes with limited living facilities where people can camp or stay have been referred to as trailers. In earlier days, many such vehicles were towable trailers.

Alexander Winston is widely credited for inventing the trailer in Cleveland, Ohio.^[1]

United States

[edit]

In the United States, the term is sometimes used interchangeably with travel trailer and mobile home, varieties of trailers, and manufactured housing designed for human habitation. Their origins lay in utility trailers built in a similar fashion to horse-drawn wagons. A trailer park is an area where mobile homes are placed for habitation.

In the United States trailers ranging in size from single-axle dollies to 6-axle, 13-foot-6-inch-high (4.1 m), 53-foot-long (16.2 m) semi-trailers are commonplace. The latter, when towed as part of a tractor-trailer or "18-wheeler", carries a large percentage of the freight that travels over land in North America.

Types

[edit]

Some trailers are made for personal (or small business) use with practically any powered vehicle having an appropriate hitch, but some trailers are part of large trucks called semi-trailer trucks for transportation of cargo.

Enclosed toy trailers and motorcycle trailers can be towed by commonly accessible pickup truck or van, which generally require no special permit beyond a regular driver's license. Specialized trailers like open-air motorcycle trailers, bicycle trailers are much smaller, accessible to small automobiles, as are some simple trailers, have a drawbar and ride on a single axle. Other trailers, such as utility trailers and travel trailers or campers come in single and multiple axle varieties, to allow for varying sizes of tow vehicles.

There also exist highly specialized trailers, such as genset trailers, pusher trailers and other types that are also used to power the towing vehicle. Others are custom-built to hold entire kitchens and other specialized equipment used by carnival vendors. There are also trailers for hauling boats.

Trackless train

[edit]

Main article: Trackless train

This section needs expansion. You can help by adding to it. (July 2021)

A utility trailer is a general purpose trailer designed to by towed by a light vehicle and to carry light, compact loads of up to a few metric tonnes. It typically has short metal sides (either rigid or folding) to constrain the load, and may have cage sides, and a rear folding gate or ramps. Utility trailers do not have a roof. Utility trailers have one axle set comprising one, two or three axles. If it does not have sides then it is usually called a flatbed or flat-deck trailer. If it has rails rather than sides, with ramps at the rear, it is usually called an open car transporter, auto-transporter, or a plant trailer, as they are designed to transport vehicles and mobile plant. If it has fully rigid sides and a roof with a rear door, creating a weatherproof compartment, this is usually called a furniture trailer, cargo trailer, box van trailer or box trailer.

This section needs expansion. You can help by adding to it. (April 2021)

A Fixed Plant Trailer is a special purpose trailer built to carry units which usually are immobile such as large generators & pumps

A bicycle trailer is a motor less wheeled frame with a hitch system for transporting cargo by bicycle.^[2]

Toilets are usually provided separately.^[3]

Construction trailers are mobile structures (trailers) used to accommodate temporary offices, dining facilities and storage of building materials during construction projects. The trailers are equipped with radios for communication.

Popular campers use lightweight trailers, aerodynamic trailers that can be towed by a small car, such as the BMW Air Camper. They are built to be lower than the tow vehicle, minimizing drag.

Others range from two-axle campers that can be pulled by most mid-sized pickups to trailers that are as long as the host country's law allows for drivers without special permits. Larger campers tend to be fully integrated recreational vehicles, which often are used to tow single-axle dolly trailers to allow the users to bring small cars on their travels.

A semi-trailer is a trailer without a front axle. A large proportion of its weight is supported either by a road tractor or by a detachable front axle assembly known as a dolly. A semi-trailer is normally equipped with legs, called "landing gear", which can be lowered to support it when it is uncoupled. In the United States, a single trailer cannot exceed a length of 57 ft 0 in (17.37 m) on interstate highways (unless a special permit is granted), although it is possible to link two smaller trailers together to a maximum length of 63 ft 0 in (19.20 m).

Semi-trailers vary considerably in design, ranging from open-topped grain haulers through Tautliners to normal-looking but refrigerated 13 ft 6 in (4.11 m) x 53 ft 0 in (16.15 m) enclosures ("reefers"). Many semi-trailers are part of semi-trailer trucks. Other types of semi-trailers include dry vans, flatbeds and chassis.

Many commercial organizations choose to rent or lease semi-trailer equipment rather than own their own semi-trailers, to free up capital and to keep trailer debt from appearing on their balance sheet.

• 
  Semi tank trailer in Japan
• 
  SinoTruk HOWO with flatbed trailer
• 
  LKW Kipper dump trailer
• 
  Sainsburys lorry refrigerated trailer
• 
  A car carrier trailer
• 
  A truck pulling a semi-trailer using a trailer Dolly
• 
  Indian auto-rickshaw adapted with trailer

A full trailer is a term used in the United States and New Zealand^[4] for a freight trailer supported by front and rear axles and pulled by a drawbar. In Europe this is known as an A-frame drawbar trailer, and in Australia it is known as a dog trailer. Commercial freight trailers are produced to length and width specifications defined by the country of operation. In America this is 96 or 102 in (2.4 or 2.6 m) wide and 35 or 40 ft (11 or 12 m) long. In New Zealand, the maximum width is 2.55 m (100 in) while the maximum length is 11.5 m (38 ft), giving a 22-pallet capacity.

As per AIS 053, full trailer is a towed vehicle having at least two axles, and equipped with a towing device which can move vertically in relation to the trailer and controls the direction of the front axle(s), but which transmits no significant static load to the towing vehicle. Common types of full trailers are flat deck, hardside/box, curtainside or bathtub tipper style with axle configurations up to two at the drawbar end and three at the rear of the trailer.

This style of trailer is also popular for use with farm tractors.

A close-coupled trailer is fitted with a rigid towbar which projects from its front and hooks onto a hook on the tractor. It does not pivot as a drawbar does.

This section needs expansion. You can help by adding to it. (April 2011)

A motorcycle trailer may be a trailer designed to haul motorcycles behind an automobile or truck. Such trailers may be open or enclosed, ranging in size from trailers capable of carrying several motorcycles or only one. They may be designed specifically to carry motorcycles, with ramps and tie-downs, or may be a utility trailer adapted permanently or occasionally to haul one or more motorcycles.

Another type of motorcycle trailer is a wheeled frame with a hitch system designed for transporting cargo by motorcycle. Motorcycle trailers are often narrow and styled to match the appearance of the motorcycle they are intended to be towed behind. There are two-wheeled versions and single-wheeled versions. Single-wheeled trailers, such as the Unigo or Pav 40/41, are designed to allow the bike to have all the normal flexibility of a motorcycle, usually using a universal joint to enable the trailer to lean and turn with the motorcycle. No motorcycle manufacturer recommends that its motorcycles be used to tow a trailer because it results in additional safety hazards for motorcyclists.

There are a number of different styles of trailers used to haul livestock such as cattle, horses, sheep and pigs. The most common is the stock trailer, a trailer that is enclosed on the bottom, but has openings at approximately the eye level of the animals to allow ventilation. The horse trailer is a more elaborate form of stock trailer. Because horses are usually hauled for the purpose of competition or work, where they must be in peak physical condition, horse trailers are designed for the comfort and safety of the animals. They usually have adjustable vents and windows as well as suspension designed to provide a smooth ride and less stress on the animals. In addition, horse trailers have internal partitions that assist the animal in staying upright during travel and protect horses from injuring each other in transit. Larger horse trailers may incorporate additional storage areas for horse tack and may even include elaborate living quarters with sleeping areas, bathroom and cooking facilities, and other comforts.

Both stock trailers and horse trailers range in size from small units capable of holding one to three animals, able to be pulled by a pickup truck, SUV or even a quad bike; to large semi-trailers that can haul a significant number of animals.

Baggage trailers are used for the transportation of loose baggage, oversized bags, mail bags, loose cargo carton boxes, etc. between the aircraft and the terminal or sorting facility. Dollies for loose baggage are fitted with a brake system which blocks the wheels from moving when the connecting rod is not attached to a tug. Most dollies for loose baggage are completely enclosed except for the sides which use plastic curtains to protect items from weather. In the US, these dollies are called baggage carts, but in Europe baggage cart means passenger baggage trolleys.

A hydraulic modular trailer (HMT) is a special platform trailer unit which feature swing axles, hydraulic suspension, independently steerable axles, two or more axle rows, compatible to join two or more units longitudinally and laterally and uses power pack unit (PPU) to steer and adjust height. These trailer units are used to transport oversized load, which are difficult to disassemble and are overweight. These trailers are manufactured using high tensile steel, which makes it  possible to bear the weight of the load with the help of one or more ballast tractors which push and pull these units via drawbar or gooseneck together making a heavy hauler unit.

Typical loads include oil rig modules, bridge sections, buildings, ship sections, and industrial machinery such as generators and turbines. There is a limited number of manufacturers who produce these heavy-duty trailers because the market share of oversized loads is very thin when we talk about transportation industry. There are self powered units of hydraulic modular trailer which are called SPMT which are used when the ballast tractors can not be applied.

A bus trailer is for transporting passengers hauled by a tractor unit similar like that of a truck. These trailers have become obsolete due to the issue of the communication between the driver and the conductor and traffic jams.^{[citation needed]}

• 
  Camel bus in Havana
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  Karosa NO 80 trailer bus
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  Bus trailer in Lauterbrunnen

A trailer hitch, fifth-wheel coupling or other type of tow hitch is needed to draw a trailer with a car, truck or other traction engine.

A trailer coupler is used to secure the trailer to the towing vehicle. The trailer coupler attaches to the trailer ball. This forms a ball and socket connection to allow for relative movement between the towing vehicle and trailer while towing over uneven road surfaces. The trailer ball is mounted to the rear bumper or to a draw bar, which may be removable. The draw bar is secured to the trailer hitch by inserting it into the hitch receiver and pinning it. The three most common types of couplers are straight couplers, A-frame couplers, and adjustable couplers. Bumper-pull hitches and draw bars can exert tremendous leverage on the tow vehicle making it harder to recover from a swerving situation.

These are available for loads between 10,000 and 30,000 pounds (4.5–13.6 t; 5.0–15.0 short tons; 4.5–13.4 long tons).^[5][6] Both the hitches are better than a receiver hitch and allow a more efficient and central attachment of a large trailer to the tow vehicle. They can haul large loads without disrupting the stability of the vehicle. Traditional hitches are connected to the rear of the vehicle at the frame or bumper, while fifth wheel and gooseneck trailers are attached to the truck bed above the rear axle. This coupling location allows the truck to make sharper turns and haul heavier trailers. They can be mounted in the bed of a pickup truck or any type of flatbed. A fifth-wheel coupling is also referred to as a kingpin hitch and is a smaller version of the semi-trailer "fifth wheel". Though a fifth wheel and a gooseneck trailer look much the same, their method for coupling is different. A fifth wheel uses a large horseshoe-shaped coupling device mounted 1 foot (0.30 m) or more above the bed of the tow vehicle. A gooseneck couples to a standard 2+5⁄16-inch (59 mm) ball mounted on the bed of the tow vehicle. The operational difference between the two is the range of movement in the hitch. The gooseneck is very maneuverable and can tilt in all directions, while the fifth wheel is intended for level roads and limited tilt side to side. Gooseneck mounts are often used for agricultural and industrial trailers. Fifth-wheel mounts are often used for recreational trailers. Standard bumper-hitch trailers typically allow a 10% or 15% hitch load while a fifth wheel and gooseneck can handle 20% or 25% weight transfer.

The basic function of a trailer jack is to lift the trailer to a height that allows the trailer to be hitched or unhitched to and from the towing vehicle. Trailer jacks are also used for leveling the trailer during storage. The most common types of trailer jacks are A-frame jacks, swivel jacks, and drop-leg jacks. Some trailers, such as horse trailers, have a built-in jack at the tongue for this purpose.

Many older cars took the feeds for the trailer's lights directly from the towing vehicle's rear light circuits. As bulb-check systems were introduced in the 1990s "by-pass relays" were introduced. These took a small signal from the rear lights to switch a relay which in turn powered the trailer's lights with its own power feed. Many towing electrical installations, including vehicle-specific kits incorporate some form of bypass relays.

In the US, trailer lights usually have a shared light for brake and turn indicators. If such a trailer is to be connected to a car with separate lamps for turn indicator and brake a trailer light converter is needed, which allows for attaching the trailer's lights to the wiring of the vehicle.

Nowadays some vehicles are being fitted with CANbus networks, and some of these use the CANbus to connect the tow bar electrics to various safety systems and controls. For vehicles that use the CANbus to activate towing-related safety systems, a wiring kit that can interact appropriately must be used. Without such a towbar wiring kit the vehicle cannot detect the presence of a trailer and can therefore not activate safety features such as trailer stability program which can electronically control a snaking trailer or caravan.

By-pass systems are cheap, but may not be appropriate on cars with interactive safety features.

Larger trailers are usually fitted with brakes. These can be either electrically operated, air operated, or overrun brakes.

Trailer stability can be defined as the tendency of a trailer to dissipate side-to-side motion. The initial motion may be caused by aerodynamic forces, such as from a cross wind or a passing vehicle. One common criterion for stability is the center of mass location with respect to the wheels, which can usually be detected by tongue weight. If the center of mass of the trailer is behind its wheels, therefore having a negative tongue weight, the trailer will likely be unstable. Another parameter which is less commonly a factor is the trailer moment of inertia. Even if the center of mass is forward of the wheels, a trailer with a long load, and thus large moment of inertia, may be unstable.^[7]

Some vehicles are equipped with a Trailer Stability Program that may be able to compensate for improper loading.

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Look up trailer in Wiktionary, the free dictionary.

Site for the disposal of waste materials

For the practice of filling a body of water to create new land, see Land reclamation. For other uses, see Landfill (disambiguation).

 

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A landfill^[a] is a site for the disposal of waste materials. It is the oldest and most common form of waste disposal, although the systematic burial of waste with daily, intermediate and final covers only began in the 1940s. In the past, waste was simply left in piles or thrown into pits (known in archeology as middens).

Landfills take up a lot of land and pose environmental risks. Some landfill sites are used for waste management purposes, such as temporary storage, consolidation and transfer, or for various stages of processing waste material, such as sorting, treatment, or recycling. Unless they are stabilized, landfills may undergo severe shaking or soil liquefaction of the ground during an earthquake. Once full, the area over a landfill site may be reclaimed for other uses.

Operators of well-run landfills for non-hazardous waste meet predefined specifications by applying techniques to:^[1]

1. confine waste to as small an area as possible
2. compact waste to reduce volume^[2]

They can also cover waste (usually daily) with layers of soil or other types of material such as woodchips and fine particles.

During landfill operations, a scale or weighbridge may weigh waste collection vehicles on arrival and personnel may inspect loads for wastes that do not accord with the landfill's waste-acceptance criteria.^[2] Afterward, the waste collection vehicles use the existing road network on their way to the tipping face or working front, where they unload their contents. After loads are deposited, compactors or bulldozers can spread and compact the waste on the working face. Before leaving the landfill boundaries, the waste collection vehicles may pass through a wheel-cleaning facility. If necessary, they return to the weighbridge for re-weighing without their load. The weighing process can assemble statistics on the daily incoming waste tonnage, which databases can retain for record keeping. In addition to trucks, some landfills may have equipment to handle railroad containers. The use of "rail-haul" permits landfills to be located at more remote sites, without the problems associated with many truck trips.

Typically, in the working face, the compacted waste is covered with soil or alternative materials daily. Alternative waste-cover materials include chipped wood or other "green waste",^[3] several sprayed-on foam products, chemically "fixed" bio-solids, and temporary blankets. Blankets can be lifted into place at night and then removed the following day prior to waste placement. The space that is occupied daily by the compacted waste and the cover material is called a daily cell. Waste compaction is critical to extending the life of the landfill. Factors such as waste compressibility, waste-layer thickness and the number of passes of the compactor over the waste affect the waste densities.

The term landfill is usually shorthand for a municipal landfill or sanitary landfill. These facilities were first introduced early in the 20th century, but gained wide use in the 1960s and 1970s, in an effort to eliminate open dumps and other "unsanitary" waste disposal practices. The sanitary landfill is an engineered facility that separates and confines waste. Sanitary landfills are intended as biological reactors (bioreactors) in which microbes will break down complex organic waste into simpler, less toxic compounds over time. These reactors must be designed and operated according to regulatory standards and guidelines (See environmental engineering).

Usually, aerobic decomposition is the first stage by which wastes are broken down in a landfill. These are followed by four stages of anaerobic degradation. Usually, solid organic material in solid phase decays rapidly as larger organic molecules degrade into smaller molecules. These smaller organic molecules begin to dissolve and move to the liquid phase, followed by hydrolysis of these organic molecules, and the hydrolyzed compounds then undergo transformation and volatilization as carbon dioxide (CO₂) and methane (CH₄), with rest of the waste remaining in solid and liquid phases.

During the early phases, little material volume reaches the leachate, as the biodegradable organic matter of the waste undergoes a rapid decrease in volume. Meanwhile, the leachate's chemical oxygen demand increases with increasing concentrations of the more recalcitrant compounds compared to the more reactive compounds in the leachate. Successful conversion and stabilization of the waste depend on how well microbial populations function in syntrophy, i.e. an interaction of different populations to provide each other's nutritional needs.:^[4]

The life cycle of a municipal landfill undergoes five distinct phases:^[5][4]

As the waste is placed in the landfill, the void spaces contain high volumes of molecular oxygen (O₂). With added and compacted wastes, the O₂ content of the landfill bioreactor strata gradually decreases. Microbial populations grow, density increases. Aerobic biodegradation dominates, i.e. the primary electron acceptor is O₂.

The O₂ is rapidly degraded by the existing microbial populations. The decreasing O₂ leads to less aerobic and more anaerobic conditions in the layers. The primary electron acceptors during transition are nitrates and sulphates since O₂ is rapidly displaced by CO₂ in the effluent gas.

Hydrolysis of the biodegradable fraction of the solid waste begins in the acid formation phase, which leads to rapid accumulation of volatile fatty acids (VFAs) in the leachate. The increased organic acid content decreases the leachate pH from approximately 7.5 to 5.6. During this phase, the decomposition intermediate compounds like the VFAs contribute much chemical oxygen demand (COD). Long-chain volatile organic acids (VOAs) are converted to acetic acid (C₂H₄O₂), CO₂, and hydrogen gas (H₂). High concentrations of VFAs increase both the biochemical oxygen demand (BOD) and VOA concentrations, which initiates H₂ production by fermentative bacteria, which stimulates the growth of H₂-oxidizing bacteria. The H₂ generation phase is relatively short because it is complete by the end of the acid formation phase. The increase in the biomass of acidogenic bacteria increases the amount of degradation of the waste material and consuming nutrients. Metals, which are generally more water-soluble at lower pH, may become more mobile during this phase, leading to increasing metal concentrations in the leachate.

The acid formation phase intermediary products (e.g., acetic, propionic, and butyric acids) are converted to CH₄ and CO₂ by methanogenic microorganisms. As VFAs are metabolized by the methanogens, the landfill water pH returns to neutrality. The leachate's organic strength, expressed as oxygen demand, decreases at a rapid rate with increases in CH₄ and CO₂ gas production. This is the longest decomposition phase.

The rate of microbiological activity slows during the last phase of waste decomposition as the supply of nutrients limits the chemical reactions, e.g. as bioavailable phosphorus becomes increasingly scarce. CH₄ production almost completely disappears, with O₂ and oxidized species gradually reappearing in the gas wells as O₂ permeates downwardly from the troposphere. This transforms the oxidation–reduction potential (ORP) in the leachate toward oxidative processes. The residual organic materials may incrementally be converted to the gas phase, and as organic matter is composted; i.e. the organic matter is converted to humic-like compounds.^[6]

Landfills have the potential to cause a number of issues. Infrastructure disruption, such as damage to access roads by heavy vehicles, may occur. Pollution of local roads and watercourses from wheels on vehicles when they leave the landfill can be significant and can be mitigated by wheel washing systems. Pollution of the local environment, such as contamination of groundwater or aquifers or soil contamination may occur, as well.

When precipitation falls on open landfills, water percolates through the garbage and becomes contaminated with suspended and dissolved material, forming leachate. If this is not contained it can contaminate groundwater. All modern landfill sites use a combination of impermeable liners several metres thick, geologically stable sites and collection systems to contain and capture this leachate. It can then be treated and evaporated. Once a landfill site is full, it is sealed off to prevent precipitation ingress and new leachate formation. However, liners must have a lifespan, be it several hundred years or more. Eventually, any landfill liner could leak,^[7] so the ground around landfills must be tested for leachate to prevent pollutants from contaminating groundwater.

Rotting food and other decaying organic waste create decomposition gases, especially CO₂ and CH₄ from aerobic and anaerobic decomposition, respectively. Both processes occur simultaneously in different parts of a landfill. In addition to available O₂, the fraction of gas constituents will vary, depending on the age of landfill, type of waste, moisture content and other factors. For example, the maximum amount of landfill gas produced can be illustrated a simplified net reaction of diethyl oxalate that accounts for these simultaneous reactions:^[8]

4 C₆H₁₀O₄ + 6 H₂O → 13 CH₄ + 11 CO₂

On average, about half of the volumetric concentration of landfill gas is CH₄ and slightly less than half is CO₂. The gas also contains about 5% molecular nitrogen (N₂), less than 1% hydrogen sulfide (H₂S), and a low concentration of non-methane organic compounds (NMOC), about 2700 ppmv.^[8]

Landfill gases can seep out of the landfill and into the surrounding air and soil. Methane is a greenhouse gas, and is flammable and potentially explosive at certain concentrations, which makes it perfect for burning to generate electricity cleanly. Since decomposing plant matter and food waste only release carbon that has been captured from the atmosphere through photosynthesis, no new carbon enters the carbon cycle and the atmospheric concentration of CO₂ is not affected. Carbon dioxide traps heat in the atmosphere, contributing to climate change.^[9] In properly managed landfills, gas is collected and flared or recovered for landfill gas utilization.

Poorly run landfills may become nuisances because of vectors such as rats and flies which can spread infectious diseases. The occurrence of such vectors can be mitigated through the use of daily cover.

Other potential issues include wildlife disruption due to occupation of habitat^[10] and animal health disruption caused by consuming waste from landfills,^[11] dust, odor, noise pollution, and reduced local property values.

Gases are produced in landfills due to the anaerobic digestion by microbes. In a properly managed landfill, this gas is collected and used. Its uses range from simple flaring to the landfill gas utilization and generation of electricity. Landfill gas monitoring alerts workers to the presence of a build-up of gases to a harmful level. In some countries, landfill gas recovery is extensive; in the United States, for example, more than 850 landfills have active landfill gas recovery systems.^[12]

A Solar landfill is a repurposed used landfill that is converted to a solar array solar farm.^[13]

Landfills in Canada are regulated by provincial environmental agencies and environmental protection legislation.^[14] Older facilities tend to fall under current standards and are monitored for leaching.^[15] Some former locations have been converted to parkland.

In the European Union, individual states are obliged to enact legislation to comply with the requirements and obligations of the European Landfill Directive.

The majority of EU member states have laws banning or severely restricting the disposal of household trash via landfills.^[16]

Landfilling is currently the major method of municipal waste disposal in India. India also has Asia's largest dumping ground in Deonar, Mumbai.^[17] However, issues frequently arise due to the alarming growth rate of landfills and poor management by authorities.^[18] On and under surface fires have been commonly seen in the Indian landfills over the last few years.^[17]

Landfilling practices in the UK have had to change in recent years to meet the challenges of the European Landfill Directive. The UK now imposes landfill tax upon biodegradable waste which is put into landfills. In addition to this the Landfill Allowance Trading Scheme has been established for local authorities to trade landfill quotas in England. A different system operates in Wales where authorities cannot 'trade' amongst themselves, but have allowances known as the Landfill Allowance Scheme.

U.S. landfills are regulated by each state's environmental agency, which establishes minimum guidelines; however, none of these standards may fall below those set by the United States Environmental Protection Agency (EPA).^[19]

Permitting a landfill generally takes between five and seven years, costs millions of dollars and requires rigorous siting, engineering and environmental studies and demonstrations to ensure local environmental and safety concerns are satisfied.^[20]

• Municipal solid waste: takes in household waste and nonhazardous material. Included in this type of landfill is a Bioreactor Landfill that specifically degrades organic material.
• Industrial waste: for commercial and industrial waste. Other related landfills include Construction and Demolition Debris Landfills and Coal Combustion Residual Landfills.
• Hazardous waste^[21] or PCB waste:^[22] Polychlorinated Biphenyl (PCB) landfills that are monitored in the United States by the Toxic Substances Control Act of 1976 (TSCA).

The status of a landfill's microbial community may determine its digestive efficiency.^[23]

Bacteria that digest plastic have been found in landfills.^[24]

One can treat landfills as a viable and abundant source of materials and energy. In the developing world, waste pickers often scavenge for still-usable materials. In commercial contexts, companies have also discovered landfill sites, and many^[quantify] have begun harvesting materials and energy.^[25] Well-known examples include gas-recovery facilities.^[26] Other commercial facilities include waste incinerators which have built-in material recovery. This material recovery is possible through the use of filters (electro filter, active-carbon and potassium filter, quench, HCl-washer, SO₂-washer, bottom ash-grating, etc.).

In addition to waste reduction and recycling strategies, there are various alternatives to landfills, including waste-to-energy incineration, anaerobic digestion, composting, mechanical biological treatment, pyrolysis and plasma arc gasification. Depending on local economics and incentives, these can be made more financially attractive than landfills.

The goal of the zero waste concept is to minimize landfill volume.^[27]

Countries including Germany, Austria, Sweden,^[28] Denmark, Belgium, the Netherlands, and Switzerland, have banned the disposal of untreated waste in landfills.^{[citation needed]} In these countries, only certain hazardous wastes, fly ashes from incineration or the stabilized output of mechanical biological treatment plants may still be deposited.^{[citation needed]}

• "Modern landfills". Archived from the original on February 22, 2015. Retrieved February 21, 2015.
• "Council Directive 1999/31/EC of 26 April 1999, on the landfill of waste" (PDF). Archived from the original (PDF) on July 5, 2010. Retrieved August 29, 2005.
• "The Landfill Operation Management Advisor Web Based Expert System". Archived from the original on October 30, 2005. Retrieved August 29, 2005.
• H. Lanier Hickman Jr. and Richard W. Eldredge. "Part 3: The Sanitary Landfill". A Brief History of Solid Waste Management in the US During the Last 50 Years. Archived from the original on November 23, 2005. Retrieved August 29, 2005.cite web: CS1 maint: unfit URL (link)
• Daniel A. Vallero, Environmental Biotechnology: A Biosystems Approach. 2nd Edition. Academic Press, Amsterdam, Netherlands and Boston MA, Print Book ISBN 9780124077768; eBook ISBN 9780124078970. 2015.

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• US National Waste & Recycling Association
• Solid Waste Association of North America
• A Compact Guide to Landfill Operation: Machinery, Management and Misconceptions