Waste Management Techniques

8/10/2019 Waste Management Techniques

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Waste management

Waste management is the collection, transport, processing or disposal of waste materials, usuallyones produced by human activity, in an effort to reduce their effect on human health or localamenity. A subfocus in recent decades has been to reduce waste materials' effect on the

environment and to recover resources from them.

Waste management can involve solid, liquid or gaseous wastes, with different methods and fields of expertise for each.

Waste management practices differ for developed and developing nations, for urban and rural areas,and for residential industrial, and commercial producers. Waste management for non-hazardousresidential and institutional waste in metropolitan areas is usually the responsibility of overnmentauthorities, while management for non-hazardous commercial and industrial waste is usually theresponsibility of the generator.

Waste Management Concepts

Waste management has a number of different concepts, which vary in their usage between countriesor regions.

The Waste Hierarchy

!he waste hierarchy classifies waste management strategies according to their desirability. !heterm "# $s%, or "$educe-$euse-$ecycle%, has also been used for the same purpose. !he wastehierarchy has ta&en many forms over the past decade, but the basic concept has remained the

cornerstone of most waste minimisation strategies. !he aim of the waste hierarchy is to extract themaximum practical benefits from products and to generate the minimum amount of waste.

ome waste management experts have recently incorporated a 'fourth $'( )$e-thin&), with theimplied meaning that the present system may have fundamental flaws, and that a thoroughlyeffective system of waste management may need an entirely new way of loo&ing at waste. ome)re-thin&) solutions may be counter-intuitive, such as cutting fabric patterns with slightly more)waste material) left -- the now larger scraps are then used for cutting small parts of the pattern,resulting in a decrease in net waste . !his type of solution is by no means limited to the clothingindustry.

*ong story short, treatment and disposal are the last choices preferred in effective wastemanagement.

Source Reduction

Source reduction involves efforts to reduce hazardous and other materials by modifying industrial production. ource reduction methods involve changes in manufacturing technology, raw materialinputs, and product formulation. At times, the term )pollution prevention) may refer to sourcereduction.

ome practices commonly described as )in-process recycling) may qualify as pollution prevention.$ecycling that is conducted in an environmentally sound manner shares many of the advantages of prevention+it can reduce the need for treatment or disposal, and conserve energy and resources.)

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@lder or poorly managed landfills can create number of adverse environmental impacts, includingwind-blown litter, attraction of vermin and soluble contaminants 0leachate1 leaching into and

polluting groundwater. Another product of landfills containing putrescible wastes is landfill gas0mostly composed of methane and carbon dioxide1, which is produced as the waste brea&s down.

8haracteristics of a modern, well-run landfill should include methods to contain leachate, such as

clay or plastic liners. 7isposed waste should be compacted and covered to prevent vermin andwind-blown litter. 6any landfills also have a landfill gas extraction system installed after they areclosed to extract the gas generated by the decomposing waste materials. !his gas is often burnt togenerate power. enerally, even flaring the gas off is a better environmental outcome than allowingit to escape to the atmosphere, as this consumes the methane 0a far more potent greenhouse gas thancarbon dioxide1.

6any local authorities 0especially in urban areas1 have found it difficult to establish new landfills,due to opposition from ad4acent landowners. 9ew people want a landfill in their localneighbourhood. As a result, solid waste disposal in these areas has become more expensive asmaterial must be transported further away for disposal.

ome oppose the use of landfills in any way, anywhere, arguing that the logical end result of landfill operations is that it will eventually leave a drastically polluted planet with no canyons, andno wild space. ome futurists have stated that landfills will be the )mines of the future)( as someresources become more scarce, they will become valuable enough that it would be necessary to'mine' them from landfills where these materials were previously discarded as valueless.

!his fact, as well as growing concern about the impacts of excessive materials consumption, hasgiven rise to efforts to minimise the amount of waste sent to landfill in many areas. !hese effortsinclude taxing or levying waste sent to landfill, recycling the materials, converting material toenergy, designing products that require less material, etc. A related sub4ect is that of industrialecology, where the material flows between industries is studied. !he by-products of one industrymay be a useful commodity to another, leading to reduced waste materials.

"ncineration

3ncineration is the process of destroying waste material by burning it. 3ncineration is carried out both on a small scale by individuals, and on a large scale by industry. 3t is recognised as a practicalmethod of disposing of hazardous waste materials 0such as biological medical waste1.

!hough still widely used in many areas 0especially developing countries1, incineration as a wastemanagement tool is becoming controversial for several reasons.

9irst, it may be a poor use of many waste materials because it destroys not only the raw material, but also all of the energy, water, and other natural resources used to produce it. ome energy can bereclaimed as electricity by using the combustion to create steam to drive an electrical generator, buteven the best incinerator can only recover a fraction of the caloric value of fuel materials.

econd, incineration creates toxic gas and ash, which can harm local populations and pollutegroundwater. 6odern, well-run incinerators ta&e elaborate measures to reduce the amount of toxic

products released in exhaust gas. =ut concern has increased in recent years about the levels of dioxins that are released when burning mixed waste.

ntil recently, safe disposal of incinerator waste was a ma4or problem. 3n the mid- BB


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inert glassy pebbles, valuable in concrete production. 3ncinerator ash has also been chemicallyseparated into lye and other useful chemicals.

Resource Reco#ery Techniques

A relatively recent idea in waste management has been to treat the waste material as a resource to be exploited, instead of simply a challenge to be managed and disposed of. !here are a number of different methods by which resources may be extracted from waste( the materials may be extractedand recycled, or the calorific content of the waste may be converted to electricity.

!he process of extracting resources or value from waste is variously referred to as secondaryresource recovery, recycling, and other terms. !he practice of treating waste materials as a resourceis becoming more common, especially in metropolitan areas where space for new landfills is

becoming scarcer. !here is also a growing ac&nowledgement that simply disposing of wastematerials is unsustainable in the long term, as there is a finite supply of most raw materials.

!here are a number of methods of recovering resources from waste materials, with newtechnologies and methods being developed continuously.

Recycling

$ecycling means to reuse a material that would otherwise be considered waste. !he popular meaning of "recycling% in most developed countries has come to refer to the widespread collectionand reuse of single-use beverage containers. !hese containers are collected and sorted into commongroups, so that the raw materials of the items can be used again 0recycled1.

3n developed countries, the most common consumer items recycled include aluminimum beveragecans, steel food and aerosol cans, ?7 / and /! plastic bottles, glass bottles and 4ars, paperboardcartons, newspapers, magazines, and cardboard. @ther types of plastic 0e.g C81 are alsorecyclable, although not as commonly collected. !hese items are usually composed of a single typeof material, ma&ing them relatively easy to recycle into new products. !he recycling of obsoletecomputers and electronic equipment is important although more costly due to the separation andextraction problems. !he recycling of 4un&ed automobiles also depends on the scrap 6etal mar&et.

$ecycled or used materials have to compete in the mar&etplace with new 0virgin1 materials. !hecost of collecting and sorting the materials usually means that they are equally or more expensivethan virgin materials. !his is most often the case in developed countries where industries producingthe raw materials are well-established. ractices such as trash pic&ing can reduce this value further,as choice items are removed 0such as aluminium cans1. 3n some countries, recycling programs aresubsidised by deposits paid on beverage

Dot accounted for by most economic systems are the benefits to the environment of recycling thesematerials, compared with extracting virgin materials. 3t usually requires significantly less energy,water and other resources to recycle materials than to produce new materials. 9or example,recycling


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Composting and $igestion

Waste materials that are organic in nature, such as food scraps and paper products, are increasingly being recycled. !hese materials are put through a composting or artificial digestion process todecompose the organic matter and &ill pathogens. !he organic material is then recycled as compostfor agricultural or landscaping purposes.

!here are a large variety of composting methods and technologies, varying in complexity fromsimple window composting of shredded plant material, to automated enclosed-vessel digestion of mixed domestic waste. 8omposting methods can be broadly categorised into aerobic or anaerobicmethods, although hybrids of the two methods also exist.

Aerobic 0meaning "requiring air%1 methods of composting see& to aerate the organic materialcontinuously or frequently, in order to promote rapid and odourless decomposition. Anaerobic 0"notrequiring air%1 methods of composting see& to maximise the generation of gases such as methaneduring the process, in order to produce power from the waste materials.

"ncineration% Pyrolysis and &asi!ication

se of incinerators for waste management is controversial, and most Americans passionatelyoppose it. !his controversy roots from the understandable conflict between short-term concerns andlong-term ones, in this case between burning the wastes now, or postponing this problem by

passing the waste burden to future generations. Whether any form of incineration or thermaltreatment should be defined as )resource recovery) is a matter of dispute in policy-ma&ing circles.

yrolysis and asification are two related forms of thermal treatment where materials areincinerated with limited oxygen. !he process typically occurs in a sealed vessel, under hightemperature and pressure. 8onverting material to energy this way is more efficient than directincineration, with more energy able to be recovered and used.

yrolysis of solid waste converts the material into solid, liquid and gas products. !he liquid oil andgas can be burnt to produce energy or refined into other products. !he solid residue 0char1 can befurther refined into products such as activated 8arbon.

asification used to convert organic materials directly into a synthetic gas composed of 8arbon6onoxide and ?ydrogen. !he gas is then burnt to produce electricity and steam. asification isused in biomass power stations to produce renewable energy and heat.

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Waste Management Techniques