There are many ways to eliminate waste, and the method used depends on several criteria:
- The type of waste. Not all waste can be treated in the same way. For example, glass cannot be composted.
- Treatment cost. Costs can vary tenfold depending on the process used (e.g., landfilling or vitrification).
- Equipment availability. Because of this focus on scale economies, not every small town has its own sorting center.
- Environmental impact*. Incinerators produce atmospheric emissions but also make it possible to recover energy from waste. Similarly, a poorly managed landfill can pollute groundwater and release methane (a powerful greenhouse gas* ).
The environmental impact needs to be evaluated on a comprehensive basis, taking into account transport distances and real emissions. Resources such as lifecycle analyses* should be used to get a full view of environmental impact.

Storage
Storage is the simplest and most widely used solution worldwide.
However, there are serious problems associated with old-fashioned landfills, including pollution of groundwater* by landfill leachate*, the release of biogas* (mainly methane) from fermentation into the atmosphere, unpleasant odors, undesirable animals and insects (rats, flies, cockroaches, etc.) and the risk of explosion.
Modern landfills, however, have nothing in common with the dumps of the past. New facilities are designed to keep emissions to a minimum. Built preferably on impermeable ground, modern landfills are separated from the water table by a series of passive barriers (a thick layer of compacted clay and liners known as geomembranes) and active barriers (a series of drains and pipes to collect leachate for treatment). The landfill is divided into sections that are filled one after another and then covered with a layer of clay and another geomembrane to prevent infiltrating rainwater from reaching the waste. The site is then covered with a layer of vegetated topsoil. Another series of pipes and drains collect the biogas, which is either converted into energy or purified for use off-site. Closed landfills are monitored for several decades.

In France, there are three types of landfills:
- Class 1: these particularly well protected sites are reserved for hazardous industrial waste*. Most of this waste must be stabilized* beforehand.
- Class 2: these sites are used for household waste* and non-hazardous industrial waste*.
- Class 3: these sites are reserved for inert waste from buildings, construction projects, etc.
Other storage methods include using certain types of construction waste in embankments or roadbuilding, disposing of hazardous waste in old mines and storing short or long-lived nuclear waste in special centers.

Thermal treatment
Incineration has also changed over the years. Modern incinerators are large facilities that use sophisticated technologies to measure and control emissions. Many incinerators handle household waste and can also treat purification-plant sludge and hospital waste. Others burn only hazardous waste, at much higher temperatures. Some of this waste is also treated in cement kilns.

Municipal waste is fed into a furnace, most often onto grates but sometimes onto a fluid bed. Air is injected to promote combustion. The high-temperature waste gas gives off part of its heat in a heat recovery boiler. This energy is transformed into electricity or steam, or both in a process known as cogeneration*. The waste gas then passes through a series of filters and scrubbers before exiting the plant via the exhaus stack. Combustion by-products include clinker, from which metals can be extracted for recycling, and scrubber residue. An incinerator produces around 300 kg of clinker for each metric ton of incinerated waste. This clinker is used in roadbuilding or stored in class 2 landfills. Scrubber residue is buried in hazardous waste landfills.

Another waste-processing solution known as thermolysis is less widely used. In a thermolyzer, waste is heated to between 450 °C and 600 °C, depending on the process, in an oxygen-free environment. The system produces gas and solid or liquid carbonaceous residue, which can be burned in another furnace.

Recycling
Recycling* is an age-old practice that used to be the ragman's trade. Recycling is profitable for many products, especially when the waste is homogenous and there are clearly identified outlets. Examples include unsold newspapers, abattoir waste used to make animal feed, recovered pallets and regeneration of sulfuric acid or used solvents. One company's waste can often be another's raw material. Waste exchanges can help match up supply and demand.
Over the past few years, the focus has turned to new products for which recycling is not profitable, notably household waste items such as packaging and newspapers. Financial incentives have been set up to promote recycling, including per-unit fees paid by packaging manufacturers. Public officials can also make recycling more competitive by taxing other solutions.

To be recycled, waste needs to be of an acceptable quality. This secondary raw material* is a product like any other, covered by specifications and quality control. Sorting must begin as far upstream as possible to be cost effective, for example in the manufacturer's workshop or the consumer's kitchen. However, since selective collection isn't always enough, waste must often be sent to a sorting center. Some types of waste, like packaging, even go through two sorting phases. The first separates the waste stream by material (paper, cardboard, glass, aluminum, ferrous metals and plastic), while the second eliminates sorting errors and impurities that could compromise the recycling process.
However recycling has its limits. Sorting and recycling products have an environmental impact as they consume water and energy, produce solid and liquid waste and release gaseous emissions. The environmental and cost advantages of recycling should be evaluated case-by-case, taking into account such parameters as collection methods, transportation distances and recycling processes...

Recycling paper at Smokey Mountain (Manila, The Philippines)

Biological treatment
A number of processes use micro-organisms to digest organic waste. Composting* for example, decomposes plant matter (sometimes mixed with sludge) to obtain a sort of soil. In this process, aeration and humidity are carefully controlled to promote microbe activity. In addition, carbonaceous waste, such as branches, is balanced with nitrogenous waste, such as grass, to obtain an effective mix. As with recycling, there needs to be an outlet for the end product. To be used in gardens or fields, compost must comply with stringent standards concerning such things as metal contaminant levels, the absence of pathogenic microbes and the advantages for different crops. The waste to be composted must therefore be carefully sorted.
Purification plant sludge and liquid manure are often spread in fields, either directly or after partial dewatering.

Methanization is a waste-to-energy biological process that is much better known in the Netherlands than in France. Waste is placed in an oxygen-poor environment where it is digested by microbes who produce a methane-rich gas that can be used as an energy source.

Specific treatment for hazardous waste
Special treatment is required for hazardous industrial waste*. Some of this waste is incinerated in dedicated furnaces or cement kilns, but a substantial percentage is landfilled in class 1 facilities. Some types of waste are stabilized beforehand. This entails solidifying waste that could leach heavy metals, salts and other contaminants into the groundwater* if rainwater were to infiltrate the landfill. Stabilization* methods use inorganic binders such as cement, organic binders like asphalt, or vitrification, in which the waste is transformed into a glassy substance through heat and fusion.
Other processes for treating hazardous waste include evaporation-incineration, chrome removal, resin regeneration and cyanide removal.