Management of waste

The management of waste (Rudologie) is the collection, the Transport, the Traitement (treatment of reject), the re-use or the elimination of the Déchets, usually those produced by the human activity, in order to reduce their effects on the human health, the environment, esthetics or local approval. The stress was laid, these last decades, on the reduction of the effect of waste on nature and the environment and their valorization.

The management of waste relates to all the types of waste, which they are solid, liquid or gas, each one having its specific die. The manners of managing waste differ according to whether one is in a developed country or in the process of development, in a city or an rural area, that one deals with private individual, industrialist or tradesman. The management of nontoxic waste for the private individuals or the institutions in the agglomerations is usually under the responsibility of the local authorities, whereas the management of waste of the tradesmen and industrialists is under their own responsibility.

History of the management of waste

See also: History of the reprocessing of waste

Principles of management of waste

See also: Principle of management of waste

There are several principles of management of waste of which the use varies according to the countries or the areas.

The hierarchy of the strategies (rule of the Three R):

  • R éduire;
  • R éutiliser;
  • R ecycler.

classify the policies of management of waste according to the preference which one must grant to them. The hierarchy of the strategies has several times changed of aspect these ten last years, but the subjacent concept is remained the angular stone of the majority of the strategies of management of waste: the objective is to use to the maximum materials and to generate the minimum of rejects.

Certain experts in management of waste recently added a “fourth R”: “To reconsider”, which implies that the current system has weaknesses and that a perfectly effective system would require that a completely different glance be related to waste. Certain solutions " reconsidered are sometimes not very intuitive. One can take for example a case in textile industry. In order to reduce the quantity of paper used for the owners, it was advised to cut out them in larger sheets, in order to be able to use the falls to cut out the small parts of the owner. Thus, there is a reduction of the total residue. This type of solution is of course not limited to textile industry

The reduction with the source requires efforts to reduce toxic waste and other residues by modifying the industrial production. The methods of reduction to the source imply changes in the manufacturing processes, the raw material contributions and the composition of the products. Sometimes the principle of “prevention of pollution” indicates in fact the implementation of one policy of reduction to the source.

Another method of reduction of waste to the source is to increase the incentives with recycling. Several cities with the the United States set up taxes whose amount is function of the quantities of refuse deposited (Pay when you throw: Pay Ace You Throw - PAYT) which proved effective to reduce the volume of urban waste.

The effectiveness of the policies of reduction to the source is measured with the importance of the reduction of the production of waste. Another approach, more discussed, is to consider the reduction of the use of toxic substances. One is interested here to reduce the use of toxic substances, while at the same time the tendency is rather with the rise. This approach, in which it is the Precaution principle which is proposed, meets a sharp opposition of chemical industries. They show this step to stigmatize the chemicals. Certain American states, like the Massachusetts, the New Jersey and the Oregon set up policies of reduction of toxic waste.

Waste, a resource to be developed

A relatively recent idea consists in regarding waste as a resource to be exploited and not as rejects of which it is necessary to get rid. The methods to produce new resources starting from waste are various and numerous: for example one can extract the raw materials from waste then to recycle them, or to burn them to produce electricity. These methods are under development full, grace in particular to the contributions of new technologies.

This process of valorization of waste is called valorization matter, or recycling, if reusable materials are recovered, and energy valorization if one obtains in the place energy. To treat waste as raw materials becomes increasingly current, in particular in the agglomerations where space to open new discharges rarefies. The public opinion evolves seriously to the position estimating that, on the long run, one cannot be satisfied to get rid of waste whereas the raw materials available only in quantity are not limited.

In certain countries in the process of development the valorization of waste takes place already: men sort with the hand the mountains of waste to recover the materials which can be resold on the market of recovery. These not recognized workers called collecting of waste are the hidden part of this branch of industry but play a big role to reduce the workload of the municipal services of management of waste. More and more their contribution to the safeguarding of the environment is recognized and one tries to integrate them into the official system of management of waste, which is on the one hand useful but also that makes it possible to reduce urban poverty. Nevertheless the very high cost in human life of these activities: diseases, accidents and life expectancy reduced in contact with toxic substances or contaminated would not be tolerated in a developed country.

Recycling

See also: Recycling

The recycling is a process by which the Matériau X which compose a product at the end of the lifetime (generally of the Déchet S industrialists or domestic) are re-used in all or partly. For the majority of people in the developed countries, recycling gathers the recovery and the re-use of various household waste. Those are collected and sorted in various categories so that the raw materials which compose them are re-used (recycled).

In the developed countries, the articles of consumption most usually recycled are the aluminum quills, iron, the cans and the bombs aerosol, the plastic bottles PEHD and FART, the bottles and pots out of glass, the paperboard, the newspapers, and the magazines. Other types of plastics: PVC, PEBD, PP and PS (cf identifying codes of the plastics) also which can be recycled but is not usually collected. These objects are often composed of only one type of material, which facilitates their recycling.

The recycling of the obsolete computers and the electronics components is important but more expensive because of the problems of separation and extraction of the components. Many electronic waste are sent in Asia, where the recovery of the Or and the Cuivre can generate environmental problems because the screens contain Plomb and Heavy metals, the such Sélénium and the Cadmium, as one frequently finds some in the electronics components.

The recycled or worn materials are in competition with new materials. The cost of collection and sorting of materials explains why they are often also expensive, to see more, the new materials. It is what one notes most of the time in the developed countries, where industries producing the raw materials, places from there for a long time, are well optimized. Some practical, like the abstract Recovery of waste, can make recycling even less profitable, by taking materials having the most value (like the aluminum pirns). In certain countries, the programs of recycling are subsidized by the instructions on packing (see the Législation on the instructions of packing).

The market of the recycling of the wrecks of cars is also depend on the course of rough metal except if the legislation imposes it (as in Germany).

However the majority of the economic systems do not take into account the environmental impact of the recycling of materials when that one compares it with the extraction virgin materials. In general much less energy, of water and other resources are necessary to recycle materials that to produce the new ones. For example, when one 1 ton of aluminum quills is recycled, one is saved the extraction of approximately 5 tons of ore of Bauxite (source ALCOA Australia). One also avoids the rejection in the atmosphere of 15,17 tons gas with greenhouse effect. To recycle steel uses only 5% of energy necessary to refine rough ore (source: American office of the mines).

In certain countries, the materials to be recycled are separately collected household refuse, with containers and rounds of dedicated collectings. The other management systems of waste recover these materials in the mass of other waste. This in general makes it possible to recover more than when a recycling is carried out by the consumers but the implementation is more complex and expensive.

Management sciences of waste

Traditionally, the management of urban waste , industrial and commercial consisted in recovering them then to store them. Once collected, various treatments can be applied to waste. The goal of these treatments can be to reduce the dangerosity of waste, to revalorize materials by recycling, to produce energy starting from waste, or to reduce their volume, to be able to have which it more easily.

The methods of recovery vary much between the various countries and areas, and it would be impossible to describe them all. For example in Australia the majority of the urban hearths have a dustbin of 240 liters which is emptied each week by the local authorities. Many areas, especially in the least developed countries, do not have structured systems of recovery of waste.

In the Canadian agglomerations recycling is the most widespread method of recovery of waste and/or which can be recycled and organic waste according to a definite planning. In the rural regions the inhabitants bring their refuse in places of collection. Waste thus collected is then transported towards a regional Décharge.

The methods of storage vary also much. In Australia, the most current method of storage of solid waste is the discharge, because the country is vast and the population density is low. On the other hand with the Japan it is more frequent to incinerate waste because the country is small and the place is rare.

Discharge

See also: Discharge (waste)

To store waste in a discharge is the most traditional method of storage of waste, and remains the most current practice in the majority of the countries. Historically, the discharges were often established in careers, mines or holes of unused Excavation. To use a discharge which minimizes the impacts on the Environnement can be a healthy solution and with lower costs to store waste; nevertheless a more effective method will be without any doubt necessary when suitable free spaces decrease.

The old careers or those badly managed can have strong environmental impacts, like the scattering of waste by the wind, the attraction of vermins and the Polluant S as the Lixiviats which can infiltrate and pollute the Ground water and the Rivières. Another product of the discharges containing of harmful waste and the Biogas, composed most of the time of Methane and Carbon dioxide, which is produced at the time of the Fermentation waste.

The characteristics of a modern discharge are methods of retention of the lixiviats, such as plastic layers of clay or covers. Stored waste must be compacted and covered to avoid attracting the Souris and the Rat S and avoiding the scattering. Many discharges are also equipped with systems with extraction with gases installed after covering to extract gas produced by the decomposition from waste. This biogas is often burned in a boiler to produce electricity. It is even preferable for the environment to burn this gas to let it escape in the atmosphere, which makes it possible to consume methane, a gas with greenhouse effect even more harmful than carbon dioxide. Part of this biogas can also be used like Carburant.

Many local authorities, particularly in the urban areas, have difficulties in open new discharges because the residents are opposed to it. Few people want of a discharge in their vicinity. This is why the storage cost of solid waste in these areas is more expensive, the refuses having to be transported further to be stored.

Some are opposed to the discharges some are the conditions or the place, by explaining why with final storage in discharge a planet truly will leave polluted with more any crack or spaces wild. Some futurologists declared that the discharges will be the “mines of the future”: as certain resources are impoverished, one will be able to justify that it is necessary to extract them from the discharges where they had been hidden regarded then as not suitable for beneficiation.

This irrefutable fact and the increasing taking into account of the impacts of the excessive consumption of the resources allowed, in several areas, to increase the efforts to minimize the quantity of waste put in discharge. These efforts are the installation of taxation or taking away of the waste put in discharge, the recycling of materials, their conversion energy, the design of products requiring less resources, and a legislation imposing to the manufacturers the assumption of responsibility of the costs of packing and storage of waste (this is why, in Germany, the manufacturers set up the Grüne Punkt to respect this legislation). A related subject is the concept of industrial ecology, where matter flows between industries are studied. Under products of an industry can be useful for another, that allows to reduce flows of waste.

Incineration

See also: Incineration, Energy with waste

The incineration is the process of destruction of a material by burning it. The incineration is often called “Energy starting from waste” or “of waste towards energy”; these names are misleading since there are other ways of recovering energy starting from waste without directly burning them (see Fermentation, Pyrolyse and Gazéification).

It is known to be a practical method to get rid of contaminated waste, like the medical waste biological. Many organizations use today the exposure of waste at high temperature to treat them thermically (that includes also the gasification and pyrolysis). This technique includes the recovery of the metal and the energy of municipal solid waste like the adapted storage of the solid residues (blast-furnace slags) and the reduction of the volume of waste.

The incineration is a tested and spread technique, in Europe as in the countries in the process of development, even if it is subjected to controversy for several reasons. The controversies generally relate to the environmental and medical problems related to the incinerators which functioned in the past, before the application of the current standards.

Initially, it is about a mode of elimination of waste which has a limited rate of valorization. The incineration destroys the Natural resources contained in waste and does not allow to recover 100% of the calorific value of waste. Recovered energy, in the form of heat or electricity, comes from the cooling of smoke of Combustion in a boiler, which makes it possible to recover heat, which can be used directly or in its turn to involve a Turbine to produce electricity. The incineration in spite of is very identified in France in 2002 like the second renewable energy source for the electrical production (after hydraulics) and for the production of heat (after the biomass).

Secondly, the incineration of solid waste of the cities produces a certain quantity of atmospheric pollutants (Dioxine S and Furanne S, heavy metals, acid gases, Poussière S), whose limiting values of emissions are fixed by the regulation. During years 1990, projections in the field of the control of the rejections and new governmental payments allowed a massive reduction of the quantity of the various atmospheric pollutants, including dioxanes and of furans. The European Union and the American Agence of environmental protection (EPA) made the decision to create very strict standards concerning the incineration of waste.

The incineration produces also a great number of solid residues (blast-furnace slags) which must be eliminated in discharge or which are the subject of a treatment if a valorization in road engineering is considered. In the years 1980, storage in sure place of the blast-furnace slags, which at that time were also mixed with ashes, was an important environmental problem. In the middle of the Nineties, experiments in France were carried out to treat and work out blast-furnace slags (extraction of ferrous metals and aluminum, sifting, crushing, crushing, maturation with the free air to support reactions of carbonation and oxidation). The positive tests of the follow-ups of experimental platforms using of the blast-furnace slags under the roads allowed the development of this die.

Compost and fermentation

See also: Compost, Anaerobic digestion

Organic waste, like the plants, food remainders, or paper, are recycled more and more. This waste is deposited in a Composteur or to control the biological process of Décomposition of the organic matters and to kill the disease-causing agents. The stable organic material which results from it is recycled like Paillis or compost for agriculture or the gardening.

There is very a large range of methods of composting and fermentation which vary in complexity of the simple heap of compost of plants to an automated tank of fermentation of various domestic waste. These methods of biological decomposition are distinguished in aerobe, like the compost, or anaerobe, like the digesters, although exist also methods combining aerobic and anaerobic.

Example of policy of compost and anaerobic digestion

The policy " Green Bin " (green dustbin), recycling of the organic matters, used with Toronto, Ontario (Canada) and in the neighbouring cities like Markham, allows the reduction of the quantities of waste sent in the Lake Michigan the United States of America. It is about a new side of the management system of waste in three axes which was set up in Toronto and is an additional projection to achieve the goal to reduce by 70% the quantity of waste which is currently put in discharge. The policy " Green Bin " allows that organic waste which would have been sent in discharge is put in compost and transformed thus into rich and nutritive compost. The waste concerned with the program " Green Bin " are the food remainders, dirty papers and the medical towels. Currently Markham, like the other municipalities of the agglomeration of Toronto, send all their waste to the Michigan at a cost of 22$ EDGE the ton.

The policy " Green Bin " is currently studied by other cities in the province of Ontario like a means of avoiding the sending of waste in discharge. In particular Toronto and Ottawa are almost ready to adopt a similar policy.

The town of Edmonton in Alberta in Canada adopted the compost with large scales to manage its urban waste. Its factory of compost is largest of this type in the world, and accounts for 35% of the full capacity of compost of Canada. The Co-dater in itself with a size of 38.690 square meters, which is equivalent to 8 football fields. It was conceived to treat 200.000 tons of waste domestic solid per annum and 22.500 tons dry of Biosolide S, transforming the whole into 80.000 tons of compost each year.

Biological and mechanical treatment

The biological and mechanical treatment (TBM) is a technique which combines a tri mechanics and a biological treatment of the organic part of municipal waste. The TBM is also sometimes called TMB (mechanical and biological treatment) that depends on the order in which the operations are carried out.

The “mechanical” part is often a stage of Tri of bulk. That makes it possible to withdraw the elements which can be recycled of the flow of waste (such metals, plastics and glass). The systems which are designed to produce RDF include also Herhofand Ecodeco. It is an error to think that all processes TBM produce RDF . It is not the case. Certain systems as ArrowBio develops simply waste which can be recycled in a form which can be then sent to be recycled.

The “biological” part refers as for it with an anaerobic fermentation or composting. Anaerobic fermentation destroys the biodegradable elements of waste to produce Biogaz and compost. Biogas can be used to create renewable energy. More advanced processes such as ArrowBio allow a strong production rate of gas and green energy without producing RDF . This is facilitated by treating waste in water. The “biological” part can also refer to a stage of composting. In this case the organic components are treated by micro-organisms with the free air. They destroy waste by transforming them into carbon dioxide and compost. There is no energy produced by composting.

TBM is recognized more and more as an effective method in the countries where management the sciences of waste evolve/move like the the United Kingdom or Australia, country where company WSN Environmental solutions took a major position in the development of the factories of the type TBM.

Pyrolysis and gasification

See also: Pyrolysis, Gasification

The Pyrolysis and the gasification are two dependant methods of heat treatments where the materials are heated at very high temperature and with few Oxygène. This process is typically carried out in a tight tank under high Pression. Transforming materials into energy this method is more effective than the direct Incinération, more energy being able to be recovered and used.

The pyrolysis of solid waste transforms materials into solid, liquid or gas products. Pyrolytic oil and the gases can be flarings to produce energy or to be refined in other products. The solid residues (coal) can be transformed later into products the such activated carbon.

The gasification is used to directly transform organic matters into a gas of synthesis called syngaz composed of Carbon monoxide and Hydrogène. This gas is then burned to produce electricity and vapor. The gasification is used in the power stations producing of energy starting from the biomass to produce renewable energy and heat.

The guns plasma allow the gasification of the matter in a medium oxygen rarefied to break up waste of basic molecular structures. The gasification plasma does not burn waste as the incinerators do it. That transforms organic waste into a carburizing gas which contains all the chemical compounds and the calorific energy of waste. That transforms nonorganic waste into amorphous vitrified solids.

Plasma is regarded as the fourth state of the matter, the three others being the gas, liquid and solid states. Electricity supplies a torch creating an electric arc between its two electrodes. Inert gas is insufflated through the electric arc which heats it at temperatures being able to reach 13.000°C. The temperature with one meter of the torch can rise with approximately 4.000°C. Because of these very high temperatures waste is broken up into their elementary components. It does not result any tar or furfuranne. At these temperatures all metals found and run at the bottom of the furnace. The nonorganic compounds like silica, the concrete, the gravel, glass, etc are vitrified and fall at the bottom from the furnace. There are no ashes resulting from this process which should be stored in discharge.

The plasma furnaces do not make distinction between the various types of waste. All types of waste can be introduced. The only variable is the quantity of energy necessary to destroy various waste. This is why no sorting of waste is necessary. Only the nuclear waste is proscribe.

The furnaces are large and function in weak depression what means that the feeding system is simplified because the gases are not tempted to escape. The gases are withdrawn from the furnace by the aspiration of a compressor. Each furnace can destroy 20 tons per hour (t/h) compared to 3 t/h of a furnace water aerator. Because of size and depression, the feeding system makes it possible to introduce loads up to 1 cubic meter. Barrels or bags dustbin can thus be introduced directly into the furnace, which allows the production great volume.

The gases produced by a furnace plasma are charged in contaminants than any other incinerator or water aerator. As there is less of emissions which escape from the furnace with this process it is possible to have a significant reduction of the rejections in entirety. The water aerators are not worried moisture of waste. Moisture consumes more energy to vaporize and can have an economic impact, nevertheless that does not affect the process.

The gases of the plasma furnaces can be flarings to produce energy or to be synthesized out of ethanol and to be used like fuel for the cars.

See too

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