Waste management is concerned with three categories of waste: solid, liquid and gaseous.
Human activities, whether domestic, commercial or industrial, convert usable materials or products to a state which is no longer useful for the original purpose. These materials can be either re-used, their composite substances separated and recycled through industrial processing, or they can be disposed of. Disposal may involve energy recovery: directly if incinerated (wood, plastic), or indirectly if converted to fuel (biomass, oils). Solid and liquid wastes can be placed in a long-term deposit, such as a landfill.
The aims of waste management are to prevent the entry of harmful substances into the environment, to protect human health, to maintain the quality of landscape and urban aesthetic values, and to improve economic and industrial efficiency. The reduction of wastes of all types serves all of these aims simultaneously.
The organisations involved in waste management are government agencies, local municipal councils, public utilities, environment services, NGOs, and the general public. The scale of the refuse accumulation problem is a liability for governments and social stability.
In September, 2015, the Lebanese government was placed under siege in Beirut by an angry populace protesting against the lack of rubbish collection. It became a symbol of dysfunctional government and corruption in public institutions. Naples, Italy, has experienced frequent interruptions to rubbish collection, due to industrial action, government inefficiency, and corruption. These cases remind us that vermin, disease and malodour are serious public health concerns and causes of social unrest.
Municipal wastes are considerable in volume, and cause onerous costs to city councils for their collection and disposal. In line with sustainable development policies, recycling is a first step in solid municipal and industrial waste management. A major aim of recycling is the reduction of the quantities of waste which are landfilled.
Waste is separated, initially by the consumer, into the range of materials which are then entered by municipal councils into separate management streams, for reuse or recycling of substances, or exploitation of energy content. This aims to ensure that only wastes which have no value as material or energy sources are taken to be deposited in a landfill.
The substances which are most easily recycled are: glass, metals (ferrous and non-ferrous), paper, PET.
Substances which are reclaimed for their energy value: wood, organic waste (kitchen and garden), and oils. These are either incinerated for electricity production converted to biofuels, or composted for use as agricultural fertiliser. Much other waste, such as plastic, can be incinerated, but there are problems related to the flue gases generated, such as dioxins. The resultant inert furnace slag is then landfilled.
Some solid wastes must by law be handled separately because they qualify for a special waste category. Hazardous wastes are those which present a danger to the environment or human health unless treated specifically prior to disposal. Some common examples are: batteries, medical waste (bio-hazards), heavy metals, electronic scrap, and any substance which is toxic, caustic, or explosive. There are also regulations for restricting the mixing of wastes which may produce dangerous secondary products.
Liquid wastes usually need to be treated to some degree, such as to filter or otherwise remove harmful substances, or to chemically neutralize acids and alkalis. Chemical treatment is very expensive, so eliminating contaminants at source is the most cost-effective way to manage wastes.
Sewage and much industrial effluent is termed black water, and water with lesser degrees of contamination, such as sink water and road run-off, is grey water. Sewage passes through primary and secondary treatment phases before being used as fertiliser, incinerated, landfilled, or in some cases dumped at sea.
Many liquids used commercially contain hazardous substances, which must be treated separately. These include: solvents, acids, alkalis, paint sludge, pesticides, some categories of hospital waste, laboratory chemicals, and liquids containing heavy metal impurities or persistent organic pollutants.
Industrial and vehicle exhausts, and other gas emissions, need to be filtered and/or electrostatically 'scrubbed' to remove substances which may not be safely released into the ambient air.
Although not toxic in low concentrations, gases like methane and CO2 are subject to restrictions since they are greenhouse gases. CFCs (Chlorofluorocarbons) may not be released to the atmosphere, since they cause depletion of the ozone layer.
Vehicle exhausts and furnace flues emit NOx and SOx, which cause acid rain and photochemical pollutants. Other airborne pollutants common to the urban environment are ozone, CO, VOCs and particulate matter.
Volkswagen has recently been indicted for fixing the results of diesel exhaust level tests. Humans exposed to particulate matter, especially those particles less than 10 microns in diameter (PM10), produced by diesel engines, run the risk of developing lung disease. The company has been forced to withdraw millions of cars from the roads in Europe and the USA, and faces crippling fines. There are calls for those responsible to face criminal charges. Such is the seriousness of air pollution.
In December 1952, London experienced a serious smog condition, caused by the burning of coal for domestic heating. The death toll was around 4,000 people in just 5 days. This forced the introduction of strict air pollution regulations, including the banning of coal as a domestic fuel. London also pioneered traffic restriction schemes in the 1990s, to limit vehicle access to the city centre.
A perennial cloud of smog hangs over much of Asia. This cloud is produced by many sources, the primary ones being legal and illegal forest burning (for clearing), vehicle emissions, industrial emissions and smoke from fossil fuel burning for electricity generation. The impact on human health and quality of life, and the economic costs, defy estimate.
The best way to manage waste is to minimise its creation. Green design and green manufacturing aim to ensure that waste products, energy consumption, and emissions during manufacture, are kept to the minimum.
Waste management methods, infrastructure, legislation, as well as cultural and sociological factors, vary greatly from country to country.
Radioactive and other hazardous wastes, such as electronic scrap containing heavy metals, and asbestos-containing ships to be scrapped, are regulated by international treaties. The Basel Convention on the Transboundary Movement of Hazardous Wastes effectively prevents the more developed countries (MDC) from externalising the environmental impacts and costs onto LDCs. The USA is the only MDC which openly continues this trade, despite intense opposition and pressure to comply to international standards. It currently exports 80% of its electronic scrap.
Until the advent of the industrial revolution, human populations and consumption levels were small, and technology was based on natural products, such as plant extracts and non-toxic metals and minerals. Waste would largely be neutralized or would decompose, without the need for much management.
With the increase in industrialisation, and consequent consumption levels, volumes and types of waste in large urban conglomerates began to increase to a scale which started to present serious difficulties for human health and clearance management.
Victorian London saw epidemics, such as cholera outbreaks, due primarily to poor hygiene conditions, congested living quarters and contaminated water, and lack of adequate utilities, in particular water supply and sewage.
The twentieth century saw chemistry begin to produce and employ new types of materials, such as plastics and heavy metals, which did not decompose. Natural processes could not be relied on to dispose of the unwanted material, and too often unnatural substances were caused to circulate through natural cycles. The need for scientific waste management became apparent.
Solutions came in the form of new legislation, technologies, and public administration. Although industry attempted to adapt and invent to meet new requirements, ever greater quantities of wastes of every form resulted in unprecedented pressures on the aquatic, land, and atmospheric environments. A political divide was created by the conflict of interests between those who sought profits and those who sought to protect the common environment. Waste management had become a factor in micro- and macro-economic planning.
Today, across the board, there are laws, standards, voluntary and imposed, international treaties, and nationally-sponsored incentives, to change and adapt away from damaging practices. Yet, the problems continue, with some industry sectors employing evasive strategies to perpetuate their externalisation of the costs onto society and the environment. The recent Volkswagen diesel emission test scandal is a case in point: a company making the deliberate decision to prioritise their financial interests over law and public health.
Legislation and environmental standards, such as ISO 14000 and EMAS, attempt to bring about changes in the design of products and manufacturing processes. Once the product is no longer wanted, it should be easily separated into its component materials, which can cost-effectively enter into the various waste streams.
Yoghurt tubs are thin plastic cups, with a cardboard label support around it, and an aluminium lid. These three materials can all be recycled, and the yoghurt tub can be easily separated into the three components by the user for disposal.
A famous Life Cycle Assessment case was comparing plastic beakers to paper cups, for office coffee vessels. The results were surprisingly in favour of plastic beakers, and revealed the complex equation behind the term 'best for the environment'. When weight (transport costs), reuse (energy reclamation), and raw material sources were examined, paper turned out to be more 'expensive' in all categories. Of course, using reusable items, such as ceramic cups in this case, will almost always be the better solution than single-use, throw-aways, like the convenience coffee cups in the photo.
A good waste management system will minimise the generation of waste, maximise recycling and other reuse of materials, and separate residual waste for safe disposal, according to type. The options for the final disposal of unusable waste include:
Burying waste has been practised for millenia. The modern method involves a lined (plastic or clay) pit, where solid waste is compacted and eventually covered by earth.
When organic material decomposes, it can create two problems: leachate and methane gas. Leachate is a liquid which accumulates at the bottom of the landfill. It has no economic value, and must be siphoned out for special treatment and separate disposal.
Landfill gas is mostly methane, and rises through the waste mound, or may enter escape paths in the ground system around the landfill site. In badly managed landfill sites this has led to explosions and groundwater contamination. Landfill gas can be allowed to escape into the air at non-dangerous concentrations, or, ideally, captured and used as a fuel.
Pilot plants in, for example Düsseldorf, Germany, have demonstrated that practically all waste can be incinerated, so that the mass is reduced, energy is recovered, and volatile substances made inert. Gaseous emissions, however, must be controlled. These can be many types, among which persistent organic compounds, such as dioxins, furans and PAHs.
Other air pollutants which may arise are NOx, SOx, which cause acid rain, CO, ozone, and the greenhouse gas, COx, as well as some VOCs (although it is reasonable to assume that most organics will be removed by the oxidation process), and particulate matter.
The resulting solid furnace slag, if inert, might find some applications, such as aggregate, or simply landfilled.
Incineration plants which generate electricity from the heat of the process are termed waste-to-energy (WtE).
Recycling became popular in the 1980s and 1990s, also because it was a practical and local way to foster public engagement. However, the value of recycling depends greatly on a calculation of the energy needed, and available applications for the recyclable material.
If the alternative raw material is imported great distances, then reclaiming the used material may be advantageous economically. If the material cannot be reused for the original purpose (such as PET), then collecting the material may be a net cost, and the value of the recycling scheme may be more political than economic.
An example of where economic thinking prevails over environmental criteria is New York City, which recently decided to reduce non-economic recycling. The city generates 36,000 tonnes of waste every day, with very low separation rates. New York City now spends c. 1.5 billion dollars a year on collecting and transporting its waste outside its region, with very little investment in local solutions. With federal pressure rising to comply to the minimisation, separation and disposal-at-source principles, this is a policy which has major economic and political liabilities.
The easiest materials to recycle are aluminium, copper, steel, glass, paper. Now, plastics can be more efficiently recycled: PET, polyethylene are two common ones.
Many councils encourage reuse of construction materials, provided they do not contain toxic or banned substances, such as asbestos.
Market prices, such as for copper and aluminium, as well as energy prices, have a significant impact on the level of interest in recycling.
German waste management is regulated by, amongst others, the German Life Cycle and Waste Management Law, Kreislaufwirtschaftsgesetz, 1994/2012 (KrWG PDF 208k). This law, last updated 2012, defines waste as follows:
1) Waste within the meaning of this Act are all substances or objects which the holder discards, or intends or is required to discard. Recyclable waste is waste that will be recycled; wastes which are not recycled, are destined for disposal.
2) A discard within the meaning of paragraph 1 shall be presumed if the owner of substances or products, carries out a recovery within the meaning of Appendix 2, or a disposal within the meaning of Appendix 1, or surrenders physical control over them, dispensing any other purpose.
(3) The intent to discard within the meaning of paragraph 1 in respect of such substances or objects, applies where:
1. energy conversion, manufacture, treatment or use of substances or products, or which result from services, without infringing the intent of the act, or
2. the original purpose is no longer possible, or is abandoned, without a new use being immediately adopted.
TVA Technische Verordnung über Abfall Schweiz, 2011.
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