LAND POLLUTION
ME 6180: ENERGY AND
ENVIRONMENT TERM PAPER
TOPIC: Causes and effects of land pollution and Solid Waste
Management
K.J.D.AKASH (ME10B027)
K.DEEPAK (ME10B028)
MANISH JACKSON (ME09B033)
List Of Contents:
1) Causes and effects of land pollution
2) Solid Waste Management (SWM)
3) Global overview of Waste-toenergy (WTE)
4) Conclusion and scenario in India
LAND POLLUTION: CAUSES AND AFFECTS
When we talk about air or water pollution, the reactions garnered are stronger. This is because we can see the effects caused by the pollutants and their extent very clearly. It is normal human psychology to believe in what you see firsthand. Our land on the other hand is living a nightmare too. We may not be able to see the effects with clarity, but land is being polluted and abused constantly and we are unable to calculate the damages incurred. Land Pollution has come to become one of the serious concerns that we collectively battle.
Land pollution, in other words, means degradation or destruction of earth’s surface and soil, directly or indirectly as a result of human activities. Anthropogenic activities are conducted citing development, and the same affects the land drastically, we witness land pollution; by drastic we are referring to any activity that lessens the quality and/or productivity of the land as an ideal place for agriculture, forestation, construction etc.
The degradation of land that could be used constructively in other words is land pollution. Land Pollution has led to a series of issues that we have come to realize in recent times, after decades of neglect. The increasing numbers of barren land plots and the decreasing numbers of forest cover is at an alarming ratio. Moreover the extension of cities and towns due to increasing population is leading to further exploitation of the land. Landfills and reclamations are being planned and executed to meet the increased demand of lands. This leads to further deterioration of land, and pollution caused by the land fill contents. Also due to the lack of green cover, the land gets affected in several ways like soil erosion occurs washing away the fertile portions of the land. Or even a landslide can be seen as an example.
CAUSES OF LAND POLLUTION
1. Deforestation and soil erosion: Deforestation carried out to create dry lands is one of the major concerns. Land that is once converted into a dry or barren land can never be made fertile again, whatever the magnitude of measures taken to redeem it is. Land conversion, meaning the alteration or modification of the original properties of the land to make it use-worthy for a specific purpose is another major cause. This hampers the land immensely. Also there is a constant waste of land. Unused available land over the years turns barren; this land then cannot be used. So in search of more land, potent land is hunted and its indigenous state is compromised with.
2. Agricultural activities: With growing human population, demand for food has increased considerably. Farmers often use highly toxic fertilizers and pesticides to get rid off insects, fungi and bacteria from their crops. However with the overuse of these chemicals, they result in contamination and poisoning of soil.
3. Mining activities: During extraction and mining activities, several land spaces are created beneath the surface. We constant hear about land caving in; this is nothing but nature’s way of filling the spaces left out after mining or extraction activity.
4. Overcrowded landfills: Each household produces tonnes of garbage each year.
Garbage like aluminum, plastic, paper, cloth, wood is collected and sent to the local recycling unit. Items that cannot be recycled become a part of the landfills that hampers the beauty of the city and cause land pollution.
5. Industrialization: Due to increase in demand for food, shelter and house, more goods are produced. This resulted in creation of more waste that needs to be disposed of. To meet the demand of the growing population, more industries were developed which led to deforestation. Research and development paved the way for modern fertilizers and chemicals that were highly toxic and led to soil contamination.
6. Construction activities: Due to urbanization, large amount of construction activities are taking place which has resulted in large waste articles like wood, metal, bricks, plastic that can be seen by naked eyes outside any building or office which is under construction. 7. Nuclear waste: Nuclear Plants can produce huge amount of energy through nuclear fission and fusion. The left over radioactive material contains harmful and toxic chemicals that can affect human health. They are dumped beneath the earth to avoid any casualty.
8. Sewage treatment: Large amount of solid waste is leftover once the sewage has been treated. The leftover material is sent to landfill site which end up in polluting the environment. Effects of Land Pollution
1. Soil pollution: Soil pollution is another form of land pollution, where the upper layer of the soil is damaged. This is caused by the overuse of chemical fertilizers, soil erosion caused by running water and other pest control measures; this leads to loss of fertile land for agriculture, forest cover, fodder patches for grazing etc.
2. Change in climate patterns: The effects of land pollution are very hazardous and can lead to the loss of ecosystems. When land is polluted, it directly or indirectly affects the climate patterns.
3. Environmental Impact: When deforestation is committed, the tree cover is compromised on. This leads to a steep imbalance in the rain cycle. A disturbed rain cycle affects a lot of factors. To begin with, the green cover is reduced. Trees and plants help balance the atmosphere, without them we are subjected to various concerns like
Global Warming, the greenhouse effect, irregular rainfall and flash floods among other imbalances. 4. Effect on human health: The land when contaminated with toxic chemicals and pesticides lead to problem of skin cancer and human respiratory system. The toxic chemicals can reach our body through foods and vegetables that we eat as they are grown in polluted soil.
5. Effect on wildlife: The animal kingdom has suffered mostly in the past decades. They face a serious threat with regards to loss of habitat and natural environment. The constant human activity on land is leaving it polluted; forcing these species to move further away and adapt to new regions or die trying to adjust. Several species are pushed to the verge of extinction, due to no homeland.
Other issues that we face include increased temperature, unseasonal weather activity, acid rains etc. The discharge of chemicals on land makes it dangerous for the ecosystem too. These chemicals are consumed by the animals and plants and thereby make their way in the ecosystem. This process is called bio magnification and is a serious threat to the ecology.
Solutions for Land Pollution
1. Make people aware about the concept of Reduce, Recycle and Reuse.
2. Reduce the use of pesticides and fertilizers in agricultural activities.
3. Avoid buying packages items as they will lead to garbage and end up in landfill site.
4. Ensure that you do not litter on the ground and do proper disposal of garbage.
5. Buy biodegradable products.
6. Do Organic Gardening and eat organic food that will be grown without the use of pesticides. 7. Create dumping ground away from residential areas.
SOLID WASTE MANAGEMENT
Waste management is the collection, transport, processing or disposal, managing and monitoring of waste materials. The term usually relates to materials produced by human activity, and the process is generally undertaken to reduce their effect on health, the environment or aesthetics. Waste management is a distinct practice from resource recovery which focuses on delaying the rate of consumption of natural resources. All waste materials, whether they are solid, liquid, gaseous or radioactive fall within the remit of waste management.
Waste management practices can differ for developed and developing nations, for urban and rural areas, and for residential and industrial producers. Management of nonhazardous waste residential and institutional waste in metropolitan areas is usually the responsibility of local government authorities, while management for non-hazardous commercial and industrial waste is usually the responsibility of the generator subject to local, national or international authorities.
Throughout most of history, the amount of waste generated by humans was insignificant due to low population density and low societal levels of the exploitation of natural resources. Common waste produced during pre-modern times was mainly ashes and human biodegradable waste, and these were released back into the ground locally, with minimum environmental impact. Tools made out of wood or metal were generally reused or passed down through the generations.
However, some civilizations do seem to have been more profligate in their waste output than others. In particular, the Maya of Central America had a fixed monthly ritual, in which the people of the village would gather together and burn their rubbish in large dumps. METHODS OF DISPOSAL
Landfill:
A landfill site (also known as a tip, dump, rubbish dump or dumping ground and historically as a midden) is a site for the disposal of waste materials by burial and is the oldest form of waste treatment. Historically, landfills have been the most common methods of organized waste disposal and remain so in many places around the world.
Some landfills are also used for waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling).
A landfill also may refer to ground that has been filled in with rocks instead of waste materials, so that it can be used for a specific purpose, such as for building houses.
Unless they are stabilized, these areas may experience severe shaking or liquefaction of the ground in a large earthquake.
Operations
A section of a landfill located in Barclay, Ontario.
Typically, in nonhazardous waste landfills, in order to meet predefined specifications, techniques are applied by which the wastes are:
1. Confined to as small an area as possible.
2. Compacted to reduce their volume.
3. Covered (usually daily) with layers of soil.
During landfill operations the waste collection vehicles are weighed at a weighbridge on arrival and their load is inspected for wastes that do not accord with the landfill’s waste acceptance criteria. 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 are used to spread and compact the waste on the working face. Before leaving the landfill boundaries, the waste collection vehicles pass through a wheel cleaning facility. If necessary, they
return to the weighbridge in order to be weighed without their load. Through the weighing process, the daily incoming waste tonnage can be calculated and listed in databases for record keeping. In addition to trucks, some landfills may be equipped 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 are chipped wood or other "green waste", several sprayed-on foam products, chemically 'fixed' bio-solids and temporary blankets. Blankets can be lifted into place at night 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.
Impacts
Landfill operation in Hawaii.
Many adverse impacts may occur from landfill operations. Damage can include infrastructure disruption (e.g. damage to access roads by heavy vehicles); pollution of the local environment (such as contamination of groundwater and/or aquifers by leakage or sinkholes and residual soil contamination during landfill usage, as well as after landfill closure); off gassing of methane generated by decaying organic wastes
(methane is a greenhouse gas many times more potent than carbon dioxide, and can
itself be a danger to inhabitants of an area); harboring of disease vectors such as rats and flies, particularly from improperly operated landfills, which are common in developing countries; injuries to wildlife; and simple nuisance problems (e.g., dust, odor, vermin, or noise pollution).
Though offsite impacts of landfills are of primary concern to regulators, the status of the resident microbial community in a landfill may determine the efficiency with which natural attenuation of contaminants proceeds on site. It was shown that bacterial diversity, including diversity of pollutant degraders was variable within a major landfill site and was related to the level of contamination within a particular zone.
Some local authorities have found it difficult to locate new landfills. Communities may charge a fee or levy to discourage waste and/or recover the costs of site operations.
Many landfills are publicly funded, but some are commercial businesses, operated for profit. Trash and garbage is a common sight in urban and rural areas of India. It is a major source of pollution. Indian cities alone generate more than 100 million tons of solid waste a year. Street corners are piled with trash. Public places and sidewalks are despoiled with filth and litter, rivers and canals act as garbage dumps. In part, India's garbage crisis is from rising consumption. India's waste problem also points to a stunning failure of governance.
In 2000, India's Supreme Court directed all Indian cities to implement a comprehensive waste-management program that would include household collection of segregated waste, recycling and composting. The Organization for Economic Cooperation and
Development estimates that up to 40 percent of municipal waste in India remains simply uncollected. In 2011, several Indian cities embarked on waste-to-energy projects of the type in use in
Germany, Switzerland and Japan. For example, New Delhi is implementing two incinerator projects aimed at turning the city’s trash problem into electricity resource.
These plants are being welcomed for addressing the city’s chronic problems of excess untreated waste and a shortage of electric power. They are also being welcomed by those who seek to prevent water pollution, hygiene problems, and eliminate rotting trash that produces potent greenhouse gas methane. The projects are being opposed by waste collection workers and local unions who fear changing technology may deprive them of their livelihood and way of life.
Incineration
Incineration is a disposal method in which solid organic wastes are subjected to combustion so as to convert them into residue and gaseous products. This method is useful for disposal of residue of both solid waste management and solid residue from waste water management. This process reduces the volumes of solid waste to 20 to 30 percent of the original volume. Incineration and other high temperature waste treatment systems are sometimes described as "thermal treatment". Incinerators convert waste materials into heat, gas, steam and ash.
Incineration is carried out both on a small scale by individuals and on a large scale by industry. It is used to dispose of solid, liquid and gaseous waste. It is recognized as a practical method of disposing of certain hazardous waste materials (such as biological medical waste). Incineration is a controversial method of waste disposal, due to issues such as emission of gaseous pollutants.
Incineration is common in countries such as Japan where land is more scarce, as these facilities generally do not require as much area as landfills. Waste-to-energy (WtE) or energy-from-waste (EfW) are broad terms for facilities that burn waste in a furnace or boiler to generate heat, steam or electricity. Combustion in an incinerator is not always perfect and there have been concerns about pollutants in gaseous emissions from incinerator stacks. Particular concern has focused on some very persistent organics
such as dioxins, furans, PAHs which may be created which may have serious environmental consequences.
Technology
An incinerator is a furnace for burning waste. Modern incinerators include pollution mitigation equipment such as flue gas cleaning. There are various types of incinerator plant design: moving grate, fixed grate, rotary-kiln, and fluidised bed.
Burn pile
The burn pile or burn pit is one of the simplest and earliest forms of waste disposal, essentially consisting of a mound of combustible materials piled on bare ground and set on fire. Indiscriminate piles of household waste are strongly discouraged and may be illegal in urban areas, but are permitted in certain rural situations such as clearing forested land for farming, where the stumps are uprooted and burned. Rural burn piles of yard waste are allowed in many rural communities, along with small quantities of
domestic or agricultural waste generated on site, though not large quantities asphalt shingles, plastics, or other petroleum products that can produce dense black smoke.
Burn piles can and have spread uncontrolled fires, for example if wind blows burning material off the pile into surrounding combustible grasses or onto buildings. As interior structures of the pile are consumed, the pile can shift and collapse, spreading the burn area. Even in a situation of no wind, small lightweight ignited embers can lift off the pile via convection, and waft through the air into grasses or onto buildings, igniting them.
Moving grate
Control room of a typical moving grate incinerator overseeing two boiler lines
The typical incineration plant for municipal solid waste is a moving grate incinerator. The moving grate enables the movement of waste through the combustion chamber to be optimized to allow a more efficient and complete combustion. A single moving grate boiler can handle up to 35 metric tons (39 short tons) of waste per hour, and can operate 8,000 hours per year with only one scheduled stop for inspection and maintenance of about one month's duration. Moving grate incinerators are sometimes referred to as Municipal Solid Waste Incinerators (MSWIs).
Fixed grate
The older and simpler kind of incinerator was a brick-lined cell with a fixed metal grate over a lower ash pit, with one opening in the top or side for loading and another opening in the side for removing incombustible solids called clinkers. Many small incinerators formerly found in apartment houses have now been replaced by waste compactors.
Rotary-kiln
The rotary-kiln incinerator is used by municipalities and by large industrial plants. This design of incinerator has 2 chambers: a primary chamber and secondary chamber. The primary chamber in a rotary kiln incinerator consists of an inclined refractory lined cylindrical tube. The inner refractory lining serves as sacrificial layer to protect the kiln structure. This layer needs to be replaced from time to time. Movement of the cylinder on its axis facilitates movement of waste. In the primary chamber, there is conversion of solid fraction to gases, through volatilization, destructive distillation and partial combustion reactions. The secondary chamber is necessary to complete gas phase combustion reactions.
The clinkers spill out at the end of the cylinder. A tall flue-gas stack, fan, or steam jet supplies the needed draft. Ash drops through the grate, but many particles are carried along with the hot gases. The particles and any combustible gases may be combusted in an "afterburner".
Fluidized bed
A strong airflow is forced through a sand bed. The air seeps through the sand until a point is reached where the sand particles separate to let the air through and mixing and churning occurs, thus a fluidized bed is created and fuel and waste can now be introduced. The sand with the pre-treated waste and/or fuel is kept suspended on pumped air currents and takes on a fluid-like character. The bed is thereby violently mixed and
agitated keeping small inert particles and air in a fluid-like state. This allows all of the mass of waste, fuel and sand to be fully circulated through the furnace.
Specialized incineration
Furniture factory sawdust incinerators need much attention as these have to handle resin powder and many flammable substances. Controlled combustion, burn back prevention systems are essential as dust when suspended resembles the fire catch phenomenon of any liquid petroleum gas.
Pollution
Incineration has a number of outputs such as the ash and the emission to the atmosphere of flue gas. Before the flue gas cleaning system, if installed, the flue gases may contain significant amounts of particulate matter, heavy metals, dioxins, furans, sulfur dioxide, methane, and hydrochloric acid. If plants have inadequate controls, these outputs may add a significant pollution component to stack emissions.
In a study from 1997, Delaware Solid Waste Authority found that, for same amount of produced energy, incineration plants emitted fewer particles, hydrocarbons and less
SO2, HCl, CO and NOx than coal-fired power plants, but more than natural gas–fired power plants. According to Germany's Ministry of the Environment, waste incinerators reduce the amount of some atmospheric pollutants by substituting power produced by coal-fired plants with power from waste-fired plants.
Recycling
Steel crushed and baled for recycling
Recycling is a resource recovery practice that refers to the collection and reuse of waste materials such as empty beverage containers. The materials from which the items are made can be reprocessed into new products. Material for recycling may be collected separately from general waste using dedicated bins and collection vehicles are sorted directly from mixed waste streams and are known as kerb-side recycling, it requires the owner of the waste to separate it into various different bins (typically wheelie bins) prior to its collection.
The most common consumer products recycled include aluminium such as beverage cans, copper such as wire, steel from food and aerosol cans, old steel furnishings or equipment, polyethylene and PET bottles, glass bottles and jars, paperboard cartons, newspapers, magazines and light paper, and corrugated fiberboard boxes.
PVC, LDPE, PP, and PS (see resin identification code) are also recyclable. These items are usually composed of a single type of material, making them relatively easy to recycle into new products. The recycling of complex products (such as computers and electronic equipment) is more difficult, due to the additional dismantling and separation required. The type of material accepted for recycling varies by city and country. Each city and country has different recycling programs in place that can handle the various types of recyclable materials. However, certain variation in acceptance is reflected in the resale value of the material once it is reprocessed.
Sustainability
The management of waste is a key component in a business' ability to maintaining
ISO14001 accreditation. Companies are encouraged to improve their environmental efficiencies each year by eliminating waste through resource recovery practices, which
are sustainability-related activities. One way to do this is by shifting away from waste management to resource recovery practices like recycling materials such as glass, food scraps, paper and cardboard, plastic bottles and metal.
Energy recovery
Anaerobic digestion component of Lübeck mechanical biological treatment plant in Germany
The energy content of waste products can be harnessed directly by using them as a direct combustion fuel, or indirectly by processing them into another type of fuel.
Thermal treatment ranges from using waste as a fuel source for cooking or heating and the use of the gas fuel (see above), to fuel for boilers to generate steam and electricity in a turbine. Pyrolysis and gasification are two related forms of thermal treatment where waste materials are heated to high temperatures with limited oxygen availability. The process usually occurs in a sealed vessel under high pressure. Pyrolysis of solid waste converts the material into solid, liquid and gas products. The liquid and gas can be burnt to produce energy or refined into other chemical products (chemical refinery). The solid residue (char) can be further refined into products such as activated carbon.
Gasification and advanced Plasma arc gasification are used to convert organic materials directly into a synthetic gas (syngas) composed of carbon monoxide and hydrogen. The gas is then burnt to produce electricity and steam. An alternative to pyrolysis is high temperature and pressure supercritical water decomposition
(hydrothermal monophasic oxidation).
GLOBAL WASTE-TO-ENERGY OVERVIEW
Worldwide, about 130 million tonnes of municipal solid waste (MSW) are combusted annually in over 600 waste-to-energy (WTE) facilities that produce electricity and steam for district heating and recovered metals for recycling. Since 1995, the global WTE industry increased by more than 16 million tonnes of MSW. Currently, there are WTE facilities in 35 nations, including large countries such as China and small ones such as
Bermuda. Some of the newest plants are located in Asia.
According to a directive from the European Union, landfilling of combustible materials must be phased out within the decade. However, it is not clear that the capital investments required will be made by all of the member countries. Some of them have little WTE capacity and some - for example, Greece - none at all. One of the newcomers to WTE is China, with seven plants in operation and an estimated annual capacity of 1.6 million metric tonnes per year.
Current state of the global WTE industry
A 2002 review of the European WTE industry by the International Solid Waste
Association showed that the total installed capacity was more than 40 million tonnes per year and the generation of electrical and thermal energy was 41 million GJ and 110 GJ, respectively (Table 1). It should be noted that, in contrast to Europe, the US makes very little use of the exhaust steam from the power-generating turbines for either district or industrial heating. A good example of cogeneration of thermal and electric energies is the Brescia WTE facility in Italy that provides an estimated 650 kWh of electricity per tonne of MSW combusted. In the cold season, it supplies at least as much energy as for district heating.
TABLE 1. Reported WTE capacity in Europe
Tonnes/year (in
Country
1999) Kilograms/capita
Thermal energy
Electric energy
(gigajoules)
(gigajoules)
Austria
450,000
56
3,053,000
131,000
2,562,000
477
10,543,000
3,472,000
France
10,984,000
180
32,303,000
2,164,000
Germany
12,853,000
157
27,190,000
12,042,000
352,000
6
2,000
399,000
Italy
2,169,000
137
3,354,000
2,338,000
Netherlands
4,818,000
482
Norway
220,000
49
1,409,000
27,000
Portugal
322,000
32
1,000
558,000
Spain
1,039,000
26
Sweden
2,005,000
225
22,996,000
4,360,000
Switzerland
1,636,000
164
8,698,000
2,311,000
UK
1,074,000
18
1,000
1,895,000
40,484,000
154.5
109,550,000
40,761,000
Denmark
Hungary
Total reported 9,130,000
1,934,000
(average)
Current state of WTE technology
The dominant WTE technology is mass burning, because of its simplicity and relatively low capital cost. The most common grate technology, developed by Martin GmbH (Munich,
Germany), has an annual installed capacity of about 59 million metric tonnes. The Martin grate at the Brescia (Italy) plant is one of the newest WTE facilities in Europe. Figure 1 shows a
schematic diagram of its mass-burn combustion chamber. The Von Roll (Zurich, Switzerland) mass-burning process follows with 32 million tonnes worldwide. All other mass-burning and refuse-derived- fuel (RDF) processes together have a total estimated capacity of more than 40 million tonnes.
FIGURE 1. Schematic diagram of the Brescia mass-burn combustion chamber
The SEMASS facility in Rochester, Massachusetts, USA, developed by Energy
Answers Corp. and now operated by American Ref-Fuel, has a capacity of 0.9 million tonnes/year and is one of the most successful RDF-type processes. The MSW is first pre-shredded, ferrous metals are separated magnetically, and combustion is carried out partly by suspension firing and partly on the horizontal moving grate (Figure 2).
FIGURE 2. Schematic diagram of the SEMASS process at Rochester,
Massachusetts, USA
WTE emissions
In the late 1980s, WTE plants were listed by the US Environmental Protection Agency
(EPA) as major sources of mercury and dioxin/furan emissions. However, in response to the Maximum Available Technology (MACT) regulations promulgated in 1995 by the
US EPA, the US WTE industry spent more than one billion dollars in retrofitting pollution control systems and becoming one of the lowest emitters of high temperature processes. The US EPA recently affirmed that WTE plants in the US 'produce 2800 MW of electricity with less environmental impact that almost any other source of electricity'.
Dioxins
The emissions of the large US WTE plants (about 89% of total US capacity) decreased from 4260 grams TEQ (toxic equivalent) in 1990 to 12 grams TEQ in 2000. Figure 3
shows the post-MACT cumulative dioxin emissions of the US WTE facilities, plant by plant. The diagonal straight line shows the allowable limit of toxic dioxins (in grams
TEQ) using the present EU limit of 0.1 ng/m3 and the cumulative processing rate of
MSW (x-axis). It can be seen that the total emissions in the US are well below the EU limit. The fact that WTEs stopped being the major emitters of dioxins in the US is illustrated in Figure 4 that depicts the distribution of dioxin sources in recent years; it should be noted that in the same period, the total dioxin emissions in the US decreased tenfold, from 14,000 to 1100 grams TEQ.
FIGURE 3. Post-MACT cumulative dioxin emissions from US WTE plants in 2000; each point represents the emissions of a single plant, in grams TEQ
The current WTE industry in the US, and also those in other developed nations, is an insignificant source of dioxins. Modern WTE facilities in Europe have dioxin emissions that are much lower than the EU limit. For example, the level of dioxin emissions of the state-of-the-art Brescia (Italy) plant is only 0.01 ng TEQ/m3.
Mercury
The use of mercury in the US decreased from 3000 tonnes per year in the 1970s to less than 400 tonnes by the end of the century. Due to the lower input and also the use of activated carbon injection and fabric bag filters, the US WTE emissions decreased by a
factor of 60 between 1987 and 2000. Figure 5 shows that, by 2000, WTE mercury emissions were a small fraction of those from coal-fired power plants.
FIGURE 5. Mercury emissions from WTE (1989-1999) and coal-fired power plants
Environmental benefits of WTE
Despite the great reduction in emissions attained by WTE facilities in the last 15 years, some environmental groups in the US continue to oppose new WTE facilities on principle, unaware that the only alternative for MSW disposal - landfills - have much larger environmental impacts. For every tonne of waste landfilled, greenhouse gas emissions in the form of carbon dioxide increase by at least 1.3 tonnes. During the life of a modern landfill and for a mandated period after closure, aqueous effluents are collected and treated chemically; however, chemical reactions and volume decrease of the landfilled MSW can continue for decades and centuries. Thus, there is potential for future contamination of adjacent waters. It is for this reason that communities built on sandy soil, such as those in Long Island in New York State and the state of Florida have opted for WTE disposal of their MSW.
Landfill gaseous emissions
Modern landfills try to collect the biogas produced by anaerobic digestion. However, the number of gas wells provided is limited (about one well per 4,000 m2 of landfill), so that only part of the biogas is actually collected. Landfill biogas generally contains about
54% methane and 46% carbon dioxide. On the assumption that 25% of the landfilled
MSW is biodegradable (food, plant, wastes, paper, leather, wood), the maximum amount of natural gas generated by biodegradation has been estimated at 130
Nm3/metric tonne. The maximum capacity of landfilled MSW to produce methane is reported by Franklin to be 62 standard m3 of CH4 per tonne. Also, the compilation of US landfill gas data showed the annual capture of landfill gas to be 8 billion Nm3 (778 million scfd).
Mercury emissions from landfills
Mercury concentration in US MSW has been estimated at about one part per million. On this basis, the amount of mercury disposed annually in US landfills is about 120 tonnes per year (i.e. about 25% of the present mercury consumption in the US). Most of the mercury in MSW is in metallic form (fluorescent lamps, thermometers, etc.), and the vapour pressure of mercury at landfill temperatures (40°C) is 0.007 mm Hg, as compared with the vapour pressure of water of 5.67 mm Hg at 40°C.Therefore, if an exposed water droplet evaporates in one hour, then a mercury droplet of the same size will evaporate in four weeks.10 Also, the conditions in an MSW landfill (such as temperature, moisture, and reducing capacity) are favourable for aqueous mobilization of mercury (e.g. in the form of methyl mercury). However, since both gaseous emissions and aqueous mobilization are dispersed sources, they are not easy to measure.
TABLE 4. Gaseous emissions of US landfills
Molecular
Mean concentration in
Landfill emissions,
weight
landfill gas, ppbv
kg/million tonnes of MSW
Acetone
58.08
6,838
826
Benzene
78.01
2,057
339
Chlorobenzene
112.56
82
17
Chloroform
119.39
245
61
1,1-Dichloroethane
98.97
2,801
574
Dichloromethane
84.80
25,694
4,539
Diethylene chloride
58.00
2,835
339
106.16
7,334
1,626
72.10
3,092
461
1,1,1-Trichloroethane
133.42
615
174
Trichloroethylene
131.40
2,079
565
92.13
34,907
6,704
165.85
5,244
1,809
62.50
3,508
461
104.15
1,517
330
Volatile compound
Ethyl benzene
Methyl ethyl ketone
Toluene
Tetrachloroethylene
Vinyl chloride
Styrenes
Vinyl acetate
Xylenes
62.50
5,663
1,017
106.16
2,651
583
Total VOC emissions
20,435
Ammonia
17.03
550,000
-
Sulphides/mercaptans
60.00
500,000
-
Volatile organic compounds
The annual gaseous emissions of landfills in the US can be estimated by multiplying the above estimate of non-captured landfill gas flow (about 46 Nm3 of methane plus CO2 escaping per tonne of MSW) by the reported concentrations of volatile organic compounds (VOC) in landfill gas. Table 4 shows the estimated emissions from US landfills, expressed on the basis of kilograms per million tonnes of MSW landfilled.
The next generation of WTE processes
The existing WTE combustion chambers have been developed largely empirically. Their size, percentage of excess air used, and the volume of process gas are much larger than for coal-fired power plants of the same combustion capacity. Therefore, the capital and maintenance costs of a WTE facility are nearly three times as high as that for a coal-fired power plant generating the same amount of electricity. One of the objectives of the Waste-to-Energy Research and Technology Council is to apply engineering science in understanding the phenomena occurring in the best of the existing WTE processes and then to implement this knowledge during the design of the next generation of WTE facilities. Two obvious means for increasing the turbulence and transport rates in the WTE chamber are oxygen enrichment, as practised in the metallurgical industry, and flue gas recirculation. The latter has already been
implemented very successfully in the Brescia WTE facility. Also, Martin GmbH has already piloted oxygen enrichment on a large scale and is in the process of building two
'next generation' plants, in Arnoldstein, Austria, and in Sendai, Japan, in collaboration with Mitsubishi Heavy Industries. Figure 6 is a schematic diagram of the Martin
Syncom-Plus® process that will be used in these plants. In addition to oxygen enrichment of the air injected through the grate, Syncom-Plus makes use of an infrared camera for monitoring the temperature of the bed on the grate and a sophisticated control system to ensure complete combustion and produce a bottom ash that is nearly fused and ready to be used beneficially.
FIGURE 6. The Syncom-Plus process of Martin GmbH
Conclusion
Worldwide, about 130 million tonnes of municipal solid wastes are combusted annually in WTE facilities that produce electricity and steam for district heating and also recover metals for recycling. Since 2001, there have been 47 new WTE facilities that either have
started or are under construction, adding 6 million tonnes to the total capacity. WTE expansion in the US has been stymied by environmental opposition that does not consider the enormous reduction in gas emissions made by the US WTE industry following implementation of the US EPA regulations for Maximum Available Control
Technology and by the fact that existing legislation does not recognize the significant environmental benefits of WTE, in terms of energy generation, environmental quality, and reduction of greenhouse gases.
In the last few years, there have been significant advances in WTE technology that include the use of implementation of flue gas recirculation and the design of new plants that will use oxygen enrichment of the primary air. The importance of WTE in the universal effort for sustainable development and its need for R&D resources has led to the formation of the Waste-to-Energy Research and Technology Council. This organization brings together several universities concerned with waste management.
The Council started operations by making an inventory of the global WTE industry and the research resources available. The overall goal of the Council is to improve the economic and environmental performance of technologies that can be used to recover materials and energy from solid wastes.
Waste management concepts
There are a number of concepts about waste management which vary in their usage between countries or regions. Some of the most general, widely used concepts include:
Waste hierarchy - The waste hierarchy refers to the "3 Rs" reduce, reuse and recycle, which classify waste management strategies according to their desirability in terms of waste minimization. The waste hierarchy remains the cornerstone of most waste minimization strategies. The aim of the waste hierarchy is to extract the maximum practical benefits from products and to generate the minimum amount of waste see: resource recovery.
Polluter pays principle - the Polluter Pays Principle is a principle where the polluting party pays for the impact caused to the environment. With respect to waste management, this generally refers to the requirement for a waste generator to pay for appropriate disposal of the unrecoverable material.
CONCLUSION
Solid waste policy in India specifies the duties and responsibilities for hygienic waste management for cities and citizens of India. This policy was framed in September 2000, based on the March 1999 Report of the Committee for Solid Waste Management in
Class 1 Cities of India to the Supreme Court, which urged statutory bodies to comply with the report’s suggestions and recommendations. These also serve as a guide on how to comply with the MSW rules. Both the report and the rules, summarized below, are based on the principle that the best way to keep streets clean is not to dirty them in the first place. So a city without street bins will ultimately become clean and stay clean.
They advocate daily doorstep collection of “wet” (food) wastes for composting, which is the best option for India. This is not only because composting is a cost-effective process practiced since Vedic times, but also because India’s soils need organic manures to prevent loss of fertility through unbalanced use of chemical fertilizers.
Municipality Solid Waste Rules
To stop the present unplanned open dumping of waste outside city limits, the MSW rules have laid down a strict timetable for compliance. Setting up of waste-processing and disposal facilities and provision of a buffer zone around such sites. Biodegradable wastes should be processed by composting, vermicomposting etc. and landfilling shall be restricted to non-biodegradable inert waste and compost rejects.
The rules also require municipalities to ensure community participation in waste segregation (by not mixing “wet” food wastes with “dry” recyclables like paper, plastics, glass, metal etc.) and to promote recycling or reuse of segregated materials. Garbage and dry leaves are not allowed to be burnt. Biomedical wastes and industrial wastes are not allowed to be mixed with municipal wastes. Routine use of pesticides on garbage has been banned by the Supreme Court on 28.7.1997.
Littering and throwing of garbage on roads is prohibited. Citizens should keep their wet
(food) wastes and dry (recyclable) wastes within their premises until collected, and must ensure delivery of wastes as per the collection and segregation system of their city, preferably by house-to-house collection at fixed times in multi-container handcarts or tricycles (to avoid manual handling of waste) or directly into trucks stopping at street corners at regular pre-informed timings. Dry wastes should be left for collection by the informal sector (sold directly to waste-buyers or given free or otherwise to wastepickers, who will earn their livelihood by taking the wastes they need from homes rather than from garbage on the streets. High - rises, private colonies, institutions should provide their own big bins within their own areas, separately for dry and wet wastes.
Report of a Committee for Solid Waste Management in Class 1 Cities of India to the
Supreme Court
The report recommends that cities should provide free waste collection for all slums and public areas, but charge the full cost of collection on “Polluter-Pays” Principle, from hotels, eateries, marriage halls, hospitals & clinics, wholesale markets, shops in
commercial streets, office complexes, cattle - sheds, slaughter - houses, fairs & exhibitions, inner-city cottage industry & petty trade. Debris and construction waste must be stored within premises, not on the road or footpath, and disposed of at pre designated sites or landfills by builder, on payment of full transport cost if removed by the Municipality.
For improved work accountability, “pin-point” work assignments and 365-day cleaning are recommended, with fixed beats for individual sweepers, including the cleaning of adjoining drains less than 2 ft deep. Drain silt should not be left on the road for drying, but loaded directly into hand-carts and taken to a transfer point . Silt and debris should not be dumped at compost - plant.
The quantities of garbage collected and transported need to be monitored against targets, preferably by citizen monitoring, through effective management information systems and a recording weigh - bridge: computerised for 1 million+ cities. At least 80% of waste-clearance vehicles should be on-road, and two-shift use implemented where there is a shortage of vehicles. Decentralised ward-wise composting of well-segregated wet waste in local parks is recommended, for recycling of organics and also for huge savings in garbage transport costs to scarce disposal sites.
The report also recommends that waste-management infrastructure should be a strictlyenforced pre-condition in new development areas. It advocates temporary toilets at all construction sites (located on the eventual sewage-disposal line) and restriction of cattle movement on streets. Livestock should be stall-fed or relocated outside large cities.
Cities must fulfil their obligatory functions (like waste management) before funding any discretionary functions, while being granted fiscal autonomy to raise adequate funds.
Solid-waste-management and other charges should be linked to the cost-of-living index, along with levy of “administrative charges” for chronic littering. Funds should be earmarked for minimum expenditure on solid waste management: Rs 100 per capita per year in 5-lakh-plus cities, or a minimum of Rs 50 per capita in smaller towns. Many
cities are already providing conditional funding to residential areas or colonies willing to take responsibility for improved waste-management of their respective areas.
The Supreme Court intends to monitor compliance with the MSW rules through the High
Courts in each State. This gives all citizens both the opportunity and the obligation to ensure that hygienic waste-management becomes a reality, soon.
The Work was evenly divided among the 3 group partners. Akash (ME10B027) and Deepak
(ME09b028) handled the making of the report completely, whereas Manish Jackson
(ME09B033) handled completely the making of the Power point presentation.
ENVIRONMENT TERM PAPER
TOPIC: Causes and effects of land pollution and Solid Waste
Management
K.J.D.AKASH (ME10B027)
K.DEEPAK (ME10B028)
MANISH JACKSON (ME09B033)
List Of Contents:
1) Causes and effects of land pollution
2) Solid Waste Management (SWM)
3) Global overview of Waste-toenergy (WTE)
4) Conclusion and scenario in India
LAND POLLUTION: CAUSES AND AFFECTS
When we talk about air or water pollution, the reactions garnered are stronger. This is because we can see the effects caused by the pollutants and their extent very clearly. It is normal human psychology to believe in what you see firsthand. Our land on the other hand is living a nightmare too. We may not be able to see the effects with clarity, but land is being polluted and abused constantly and we are unable to calculate the damages incurred. Land Pollution has come to become one of the serious concerns that we collectively battle.
Land pollution, in other words, means degradation or destruction of earth’s surface and soil, directly or indirectly as a result of human activities. Anthropogenic activities are conducted citing development, and the same affects the land drastically, we witness land pollution; by drastic we are referring to any activity that lessens the quality and/or productivity of the land as an ideal place for agriculture, forestation, construction etc.
The degradation of land that could be used constructively in other words is land pollution. Land Pollution has led to a series of issues that we have come to realize in recent times, after decades of neglect. The increasing numbers of barren land plots and the decreasing numbers of forest cover is at an alarming ratio. Moreover the extension of cities and towns due to increasing population is leading to further exploitation of the land. Landfills and reclamations are being planned and executed to meet the increased demand of lands. This leads to further deterioration of land, and pollution caused by the land fill contents. Also due to the lack of green cover, the land gets affected in several ways like soil erosion occurs washing away the fertile portions of the land. Or even a landslide can be seen as an example.
CAUSES OF LAND POLLUTION
1. Deforestation and soil erosion: Deforestation carried out to create dry lands is one of the major concerns. Land that is once converted into a dry or barren land can never be made fertile again, whatever the magnitude of measures taken to redeem it is. Land conversion, meaning the alteration or modification of the original properties of the land to make it use-worthy for a specific purpose is another major cause. This hampers the land immensely. Also there is a constant waste of land. Unused available land over the years turns barren; this land then cannot be used. So in search of more land, potent land is hunted and its indigenous state is compromised with.
2. Agricultural activities: With growing human population, demand for food has increased considerably. Farmers often use highly toxic fertilizers and pesticides to get rid off insects, fungi and bacteria from their crops. However with the overuse of these chemicals, they result in contamination and poisoning of soil.
3. Mining activities: During extraction and mining activities, several land spaces are created beneath the surface. We constant hear about land caving in; this is nothing but nature’s way of filling the spaces left out after mining or extraction activity.
4. Overcrowded landfills: Each household produces tonnes of garbage each year.
Garbage like aluminum, plastic, paper, cloth, wood is collected and sent to the local recycling unit. Items that cannot be recycled become a part of the landfills that hampers the beauty of the city and cause land pollution.
5. Industrialization: Due to increase in demand for food, shelter and house, more goods are produced. This resulted in creation of more waste that needs to be disposed of. To meet the demand of the growing population, more industries were developed which led to deforestation. Research and development paved the way for modern fertilizers and chemicals that were highly toxic and led to soil contamination.
6. Construction activities: Due to urbanization, large amount of construction activities are taking place which has resulted in large waste articles like wood, metal, bricks, plastic that can be seen by naked eyes outside any building or office which is under construction. 7. Nuclear waste: Nuclear Plants can produce huge amount of energy through nuclear fission and fusion. The left over radioactive material contains harmful and toxic chemicals that can affect human health. They are dumped beneath the earth to avoid any casualty.
8. Sewage treatment: Large amount of solid waste is leftover once the sewage has been treated. The leftover material is sent to landfill site which end up in polluting the environment. Effects of Land Pollution
1. Soil pollution: Soil pollution is another form of land pollution, where the upper layer of the soil is damaged. This is caused by the overuse of chemical fertilizers, soil erosion caused by running water and other pest control measures; this leads to loss of fertile land for agriculture, forest cover, fodder patches for grazing etc.
2. Change in climate patterns: The effects of land pollution are very hazardous and can lead to the loss of ecosystems. When land is polluted, it directly or indirectly affects the climate patterns.
3. Environmental Impact: When deforestation is committed, the tree cover is compromised on. This leads to a steep imbalance in the rain cycle. A disturbed rain cycle affects a lot of factors. To begin with, the green cover is reduced. Trees and plants help balance the atmosphere, without them we are subjected to various concerns like
Global Warming, the greenhouse effect, irregular rainfall and flash floods among other imbalances. 4. Effect on human health: The land when contaminated with toxic chemicals and pesticides lead to problem of skin cancer and human respiratory system. The toxic chemicals can reach our body through foods and vegetables that we eat as they are grown in polluted soil.
5. Effect on wildlife: The animal kingdom has suffered mostly in the past decades. They face a serious threat with regards to loss of habitat and natural environment. The constant human activity on land is leaving it polluted; forcing these species to move further away and adapt to new regions or die trying to adjust. Several species are pushed to the verge of extinction, due to no homeland.
Other issues that we face include increased temperature, unseasonal weather activity, acid rains etc. The discharge of chemicals on land makes it dangerous for the ecosystem too. These chemicals are consumed by the animals and plants and thereby make their way in the ecosystem. This process is called bio magnification and is a serious threat to the ecology.
Solutions for Land Pollution
1. Make people aware about the concept of Reduce, Recycle and Reuse.
2. Reduce the use of pesticides and fertilizers in agricultural activities.
3. Avoid buying packages items as they will lead to garbage and end up in landfill site.
4. Ensure that you do not litter on the ground and do proper disposal of garbage.
5. Buy biodegradable products.
6. Do Organic Gardening and eat organic food that will be grown without the use of pesticides. 7. Create dumping ground away from residential areas.
SOLID WASTE MANAGEMENT
Waste management is the collection, transport, processing or disposal, managing and monitoring of waste materials. The term usually relates to materials produced by human activity, and the process is generally undertaken to reduce their effect on health, the environment or aesthetics. Waste management is a distinct practice from resource recovery which focuses on delaying the rate of consumption of natural resources. All waste materials, whether they are solid, liquid, gaseous or radioactive fall within the remit of waste management.
Waste management practices can differ for developed and developing nations, for urban and rural areas, and for residential and industrial producers. Management of nonhazardous waste residential and institutional waste in metropolitan areas is usually the responsibility of local government authorities, while management for non-hazardous commercial and industrial waste is usually the responsibility of the generator subject to local, national or international authorities.
Throughout most of history, the amount of waste generated by humans was insignificant due to low population density and low societal levels of the exploitation of natural resources. Common waste produced during pre-modern times was mainly ashes and human biodegradable waste, and these were released back into the ground locally, with minimum environmental impact. Tools made out of wood or metal were generally reused or passed down through the generations.
However, some civilizations do seem to have been more profligate in their waste output than others. In particular, the Maya of Central America had a fixed monthly ritual, in which the people of the village would gather together and burn their rubbish in large dumps. METHODS OF DISPOSAL
Landfill:
A landfill site (also known as a tip, dump, rubbish dump or dumping ground and historically as a midden) is a site for the disposal of waste materials by burial and is the oldest form of waste treatment. Historically, landfills have been the most common methods of organized waste disposal and remain so in many places around the world.
Some landfills are also used for waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling).
A landfill also may refer to ground that has been filled in with rocks instead of waste materials, so that it can be used for a specific purpose, such as for building houses.
Unless they are stabilized, these areas may experience severe shaking or liquefaction of the ground in a large earthquake.
Operations
A section of a landfill located in Barclay, Ontario.
Typically, in nonhazardous waste landfills, in order to meet predefined specifications, techniques are applied by which the wastes are:
1. Confined to as small an area as possible.
2. Compacted to reduce their volume.
3. Covered (usually daily) with layers of soil.
During landfill operations the waste collection vehicles are weighed at a weighbridge on arrival and their load is inspected for wastes that do not accord with the landfill’s waste acceptance criteria. 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 are used to spread and compact the waste on the working face. Before leaving the landfill boundaries, the waste collection vehicles pass through a wheel cleaning facility. If necessary, they
return to the weighbridge in order to be weighed without their load. Through the weighing process, the daily incoming waste tonnage can be calculated and listed in databases for record keeping. In addition to trucks, some landfills may be equipped 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 are chipped wood or other "green waste", several sprayed-on foam products, chemically 'fixed' bio-solids and temporary blankets. Blankets can be lifted into place at night 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.
Impacts
Landfill operation in Hawaii.
Many adverse impacts may occur from landfill operations. Damage can include infrastructure disruption (e.g. damage to access roads by heavy vehicles); pollution of the local environment (such as contamination of groundwater and/or aquifers by leakage or sinkholes and residual soil contamination during landfill usage, as well as after landfill closure); off gassing of methane generated by decaying organic wastes
(methane is a greenhouse gas many times more potent than carbon dioxide, and can
itself be a danger to inhabitants of an area); harboring of disease vectors such as rats and flies, particularly from improperly operated landfills, which are common in developing countries; injuries to wildlife; and simple nuisance problems (e.g., dust, odor, vermin, or noise pollution).
Though offsite impacts of landfills are of primary concern to regulators, the status of the resident microbial community in a landfill may determine the efficiency with which natural attenuation of contaminants proceeds on site. It was shown that bacterial diversity, including diversity of pollutant degraders was variable within a major landfill site and was related to the level of contamination within a particular zone.
Some local authorities have found it difficult to locate new landfills. Communities may charge a fee or levy to discourage waste and/or recover the costs of site operations.
Many landfills are publicly funded, but some are commercial businesses, operated for profit. Trash and garbage is a common sight in urban and rural areas of India. It is a major source of pollution. Indian cities alone generate more than 100 million tons of solid waste a year. Street corners are piled with trash. Public places and sidewalks are despoiled with filth and litter, rivers and canals act as garbage dumps. In part, India's garbage crisis is from rising consumption. India's waste problem also points to a stunning failure of governance.
In 2000, India's Supreme Court directed all Indian cities to implement a comprehensive waste-management program that would include household collection of segregated waste, recycling and composting. The Organization for Economic Cooperation and
Development estimates that up to 40 percent of municipal waste in India remains simply uncollected. In 2011, several Indian cities embarked on waste-to-energy projects of the type in use in
Germany, Switzerland and Japan. For example, New Delhi is implementing two incinerator projects aimed at turning the city’s trash problem into electricity resource.
These plants are being welcomed for addressing the city’s chronic problems of excess untreated waste and a shortage of electric power. They are also being welcomed by those who seek to prevent water pollution, hygiene problems, and eliminate rotting trash that produces potent greenhouse gas methane. The projects are being opposed by waste collection workers and local unions who fear changing technology may deprive them of their livelihood and way of life.
Incineration
Incineration is a disposal method in which solid organic wastes are subjected to combustion so as to convert them into residue and gaseous products. This method is useful for disposal of residue of both solid waste management and solid residue from waste water management. This process reduces the volumes of solid waste to 20 to 30 percent of the original volume. Incineration and other high temperature waste treatment systems are sometimes described as "thermal treatment". Incinerators convert waste materials into heat, gas, steam and ash.
Incineration is carried out both on a small scale by individuals and on a large scale by industry. It is used to dispose of solid, liquid and gaseous waste. It is recognized as a practical method of disposing of certain hazardous waste materials (such as biological medical waste). Incineration is a controversial method of waste disposal, due to issues such as emission of gaseous pollutants.
Incineration is common in countries such as Japan where land is more scarce, as these facilities generally do not require as much area as landfills. Waste-to-energy (WtE) or energy-from-waste (EfW) are broad terms for facilities that burn waste in a furnace or boiler to generate heat, steam or electricity. Combustion in an incinerator is not always perfect and there have been concerns about pollutants in gaseous emissions from incinerator stacks. Particular concern has focused on some very persistent organics
such as dioxins, furans, PAHs which may be created which may have serious environmental consequences.
Technology
An incinerator is a furnace for burning waste. Modern incinerators include pollution mitigation equipment such as flue gas cleaning. There are various types of incinerator plant design: moving grate, fixed grate, rotary-kiln, and fluidised bed.
Burn pile
The burn pile or burn pit is one of the simplest and earliest forms of waste disposal, essentially consisting of a mound of combustible materials piled on bare ground and set on fire. Indiscriminate piles of household waste are strongly discouraged and may be illegal in urban areas, but are permitted in certain rural situations such as clearing forested land for farming, where the stumps are uprooted and burned. Rural burn piles of yard waste are allowed in many rural communities, along with small quantities of
domestic or agricultural waste generated on site, though not large quantities asphalt shingles, plastics, or other petroleum products that can produce dense black smoke.
Burn piles can and have spread uncontrolled fires, for example if wind blows burning material off the pile into surrounding combustible grasses or onto buildings. As interior structures of the pile are consumed, the pile can shift and collapse, spreading the burn area. Even in a situation of no wind, small lightweight ignited embers can lift off the pile via convection, and waft through the air into grasses or onto buildings, igniting them.
Moving grate
Control room of a typical moving grate incinerator overseeing two boiler lines
The typical incineration plant for municipal solid waste is a moving grate incinerator. The moving grate enables the movement of waste through the combustion chamber to be optimized to allow a more efficient and complete combustion. A single moving grate boiler can handle up to 35 metric tons (39 short tons) of waste per hour, and can operate 8,000 hours per year with only one scheduled stop for inspection and maintenance of about one month's duration. Moving grate incinerators are sometimes referred to as Municipal Solid Waste Incinerators (MSWIs).
Fixed grate
The older and simpler kind of incinerator was a brick-lined cell with a fixed metal grate over a lower ash pit, with one opening in the top or side for loading and another opening in the side for removing incombustible solids called clinkers. Many small incinerators formerly found in apartment houses have now been replaced by waste compactors.
Rotary-kiln
The rotary-kiln incinerator is used by municipalities and by large industrial plants. This design of incinerator has 2 chambers: a primary chamber and secondary chamber. The primary chamber in a rotary kiln incinerator consists of an inclined refractory lined cylindrical tube. The inner refractory lining serves as sacrificial layer to protect the kiln structure. This layer needs to be replaced from time to time. Movement of the cylinder on its axis facilitates movement of waste. In the primary chamber, there is conversion of solid fraction to gases, through volatilization, destructive distillation and partial combustion reactions. The secondary chamber is necessary to complete gas phase combustion reactions.
The clinkers spill out at the end of the cylinder. A tall flue-gas stack, fan, or steam jet supplies the needed draft. Ash drops through the grate, but many particles are carried along with the hot gases. The particles and any combustible gases may be combusted in an "afterburner".
Fluidized bed
A strong airflow is forced through a sand bed. The air seeps through the sand until a point is reached where the sand particles separate to let the air through and mixing and churning occurs, thus a fluidized bed is created and fuel and waste can now be introduced. The sand with the pre-treated waste and/or fuel is kept suspended on pumped air currents and takes on a fluid-like character. The bed is thereby violently mixed and
agitated keeping small inert particles and air in a fluid-like state. This allows all of the mass of waste, fuel and sand to be fully circulated through the furnace.
Specialized incineration
Furniture factory sawdust incinerators need much attention as these have to handle resin powder and many flammable substances. Controlled combustion, burn back prevention systems are essential as dust when suspended resembles the fire catch phenomenon of any liquid petroleum gas.
Pollution
Incineration has a number of outputs such as the ash and the emission to the atmosphere of flue gas. Before the flue gas cleaning system, if installed, the flue gases may contain significant amounts of particulate matter, heavy metals, dioxins, furans, sulfur dioxide, methane, and hydrochloric acid. If plants have inadequate controls, these outputs may add a significant pollution component to stack emissions.
In a study from 1997, Delaware Solid Waste Authority found that, for same amount of produced energy, incineration plants emitted fewer particles, hydrocarbons and less
SO2, HCl, CO and NOx than coal-fired power plants, but more than natural gas–fired power plants. According to Germany's Ministry of the Environment, waste incinerators reduce the amount of some atmospheric pollutants by substituting power produced by coal-fired plants with power from waste-fired plants.
Recycling
Steel crushed and baled for recycling
Recycling is a resource recovery practice that refers to the collection and reuse of waste materials such as empty beverage containers. The materials from which the items are made can be reprocessed into new products. Material for recycling may be collected separately from general waste using dedicated bins and collection vehicles are sorted directly from mixed waste streams and are known as kerb-side recycling, it requires the owner of the waste to separate it into various different bins (typically wheelie bins) prior to its collection.
The most common consumer products recycled include aluminium such as beverage cans, copper such as wire, steel from food and aerosol cans, old steel furnishings or equipment, polyethylene and PET bottles, glass bottles and jars, paperboard cartons, newspapers, magazines and light paper, and corrugated fiberboard boxes.
PVC, LDPE, PP, and PS (see resin identification code) are also recyclable. These items are usually composed of a single type of material, making them relatively easy to recycle into new products. The recycling of complex products (such as computers and electronic equipment) is more difficult, due to the additional dismantling and separation required. The type of material accepted for recycling varies by city and country. Each city and country has different recycling programs in place that can handle the various types of recyclable materials. However, certain variation in acceptance is reflected in the resale value of the material once it is reprocessed.
Sustainability
The management of waste is a key component in a business' ability to maintaining
ISO14001 accreditation. Companies are encouraged to improve their environmental efficiencies each year by eliminating waste through resource recovery practices, which
are sustainability-related activities. One way to do this is by shifting away from waste management to resource recovery practices like recycling materials such as glass, food scraps, paper and cardboard, plastic bottles and metal.
Energy recovery
Anaerobic digestion component of Lübeck mechanical biological treatment plant in Germany
The energy content of waste products can be harnessed directly by using them as a direct combustion fuel, or indirectly by processing them into another type of fuel.
Thermal treatment ranges from using waste as a fuel source for cooking or heating and the use of the gas fuel (see above), to fuel for boilers to generate steam and electricity in a turbine. Pyrolysis and gasification are two related forms of thermal treatment where waste materials are heated to high temperatures with limited oxygen availability. The process usually occurs in a sealed vessel under high pressure. Pyrolysis of solid waste converts the material into solid, liquid and gas products. The liquid and gas can be burnt to produce energy or refined into other chemical products (chemical refinery). The solid residue (char) can be further refined into products such as activated carbon.
Gasification and advanced Plasma arc gasification are used to convert organic materials directly into a synthetic gas (syngas) composed of carbon monoxide and hydrogen. The gas is then burnt to produce electricity and steam. An alternative to pyrolysis is high temperature and pressure supercritical water decomposition
(hydrothermal monophasic oxidation).
GLOBAL WASTE-TO-ENERGY OVERVIEW
Worldwide, about 130 million tonnes of municipal solid waste (MSW) are combusted annually in over 600 waste-to-energy (WTE) facilities that produce electricity and steam for district heating and recovered metals for recycling. Since 1995, the global WTE industry increased by more than 16 million tonnes of MSW. Currently, there are WTE facilities in 35 nations, including large countries such as China and small ones such as
Bermuda. Some of the newest plants are located in Asia.
According to a directive from the European Union, landfilling of combustible materials must be phased out within the decade. However, it is not clear that the capital investments required will be made by all of the member countries. Some of them have little WTE capacity and some - for example, Greece - none at all. One of the newcomers to WTE is China, with seven plants in operation and an estimated annual capacity of 1.6 million metric tonnes per year.
Current state of the global WTE industry
A 2002 review of the European WTE industry by the International Solid Waste
Association showed that the total installed capacity was more than 40 million tonnes per year and the generation of electrical and thermal energy was 41 million GJ and 110 GJ, respectively (Table 1). It should be noted that, in contrast to Europe, the US makes very little use of the exhaust steam from the power-generating turbines for either district or industrial heating. A good example of cogeneration of thermal and electric energies is the Brescia WTE facility in Italy that provides an estimated 650 kWh of electricity per tonne of MSW combusted. In the cold season, it supplies at least as much energy as for district heating.
TABLE 1. Reported WTE capacity in Europe
Tonnes/year (in
Country
1999) Kilograms/capita
Thermal energy
Electric energy
(gigajoules)
(gigajoules)
Austria
450,000
56
3,053,000
131,000
2,562,000
477
10,543,000
3,472,000
France
10,984,000
180
32,303,000
2,164,000
Germany
12,853,000
157
27,190,000
12,042,000
352,000
6
2,000
399,000
Italy
2,169,000
137
3,354,000
2,338,000
Netherlands
4,818,000
482
Norway
220,000
49
1,409,000
27,000
Portugal
322,000
32
1,000
558,000
Spain
1,039,000
26
Sweden
2,005,000
225
22,996,000
4,360,000
Switzerland
1,636,000
164
8,698,000
2,311,000
UK
1,074,000
18
1,000
1,895,000
40,484,000
154.5
109,550,000
40,761,000
Denmark
Hungary
Total reported 9,130,000
1,934,000
(average)
Current state of WTE technology
The dominant WTE technology is mass burning, because of its simplicity and relatively low capital cost. The most common grate technology, developed by Martin GmbH (Munich,
Germany), has an annual installed capacity of about 59 million metric tonnes. The Martin grate at the Brescia (Italy) plant is one of the newest WTE facilities in Europe. Figure 1 shows a
schematic diagram of its mass-burn combustion chamber. The Von Roll (Zurich, Switzerland) mass-burning process follows with 32 million tonnes worldwide. All other mass-burning and refuse-derived- fuel (RDF) processes together have a total estimated capacity of more than 40 million tonnes.
FIGURE 1. Schematic diagram of the Brescia mass-burn combustion chamber
The SEMASS facility in Rochester, Massachusetts, USA, developed by Energy
Answers Corp. and now operated by American Ref-Fuel, has a capacity of 0.9 million tonnes/year and is one of the most successful RDF-type processes. The MSW is first pre-shredded, ferrous metals are separated magnetically, and combustion is carried out partly by suspension firing and partly on the horizontal moving grate (Figure 2).
FIGURE 2. Schematic diagram of the SEMASS process at Rochester,
Massachusetts, USA
WTE emissions
In the late 1980s, WTE plants were listed by the US Environmental Protection Agency
(EPA) as major sources of mercury and dioxin/furan emissions. However, in response to the Maximum Available Technology (MACT) regulations promulgated in 1995 by the
US EPA, the US WTE industry spent more than one billion dollars in retrofitting pollution control systems and becoming one of the lowest emitters of high temperature processes. The US EPA recently affirmed that WTE plants in the US 'produce 2800 MW of electricity with less environmental impact that almost any other source of electricity'.
Dioxins
The emissions of the large US WTE plants (about 89% of total US capacity) decreased from 4260 grams TEQ (toxic equivalent) in 1990 to 12 grams TEQ in 2000. Figure 3
shows the post-MACT cumulative dioxin emissions of the US WTE facilities, plant by plant. The diagonal straight line shows the allowable limit of toxic dioxins (in grams
TEQ) using the present EU limit of 0.1 ng/m3 and the cumulative processing rate of
MSW (x-axis). It can be seen that the total emissions in the US are well below the EU limit. The fact that WTEs stopped being the major emitters of dioxins in the US is illustrated in Figure 4 that depicts the distribution of dioxin sources in recent years; it should be noted that in the same period, the total dioxin emissions in the US decreased tenfold, from 14,000 to 1100 grams TEQ.
FIGURE 3. Post-MACT cumulative dioxin emissions from US WTE plants in 2000; each point represents the emissions of a single plant, in grams TEQ
The current WTE industry in the US, and also those in other developed nations, is an insignificant source of dioxins. Modern WTE facilities in Europe have dioxin emissions that are much lower than the EU limit. For example, the level of dioxin emissions of the state-of-the-art Brescia (Italy) plant is only 0.01 ng TEQ/m3.
Mercury
The use of mercury in the US decreased from 3000 tonnes per year in the 1970s to less than 400 tonnes by the end of the century. Due to the lower input and also the use of activated carbon injection and fabric bag filters, the US WTE emissions decreased by a
factor of 60 between 1987 and 2000. Figure 5 shows that, by 2000, WTE mercury emissions were a small fraction of those from coal-fired power plants.
FIGURE 5. Mercury emissions from WTE (1989-1999) and coal-fired power plants
Environmental benefits of WTE
Despite the great reduction in emissions attained by WTE facilities in the last 15 years, some environmental groups in the US continue to oppose new WTE facilities on principle, unaware that the only alternative for MSW disposal - landfills - have much larger environmental impacts. For every tonne of waste landfilled, greenhouse gas emissions in the form of carbon dioxide increase by at least 1.3 tonnes. During the life of a modern landfill and for a mandated period after closure, aqueous effluents are collected and treated chemically; however, chemical reactions and volume decrease of the landfilled MSW can continue for decades and centuries. Thus, there is potential for future contamination of adjacent waters. It is for this reason that communities built on sandy soil, such as those in Long Island in New York State and the state of Florida have opted for WTE disposal of their MSW.
Landfill gaseous emissions
Modern landfills try to collect the biogas produced by anaerobic digestion. However, the number of gas wells provided is limited (about one well per 4,000 m2 of landfill), so that only part of the biogas is actually collected. Landfill biogas generally contains about
54% methane and 46% carbon dioxide. On the assumption that 25% of the landfilled
MSW is biodegradable (food, plant, wastes, paper, leather, wood), the maximum amount of natural gas generated by biodegradation has been estimated at 130
Nm3/metric tonne. The maximum capacity of landfilled MSW to produce methane is reported by Franklin to be 62 standard m3 of CH4 per tonne. Also, the compilation of US landfill gas data showed the annual capture of landfill gas to be 8 billion Nm3 (778 million scfd).
Mercury emissions from landfills
Mercury concentration in US MSW has been estimated at about one part per million. On this basis, the amount of mercury disposed annually in US landfills is about 120 tonnes per year (i.e. about 25% of the present mercury consumption in the US). Most of the mercury in MSW is in metallic form (fluorescent lamps, thermometers, etc.), and the vapour pressure of mercury at landfill temperatures (40°C) is 0.007 mm Hg, as compared with the vapour pressure of water of 5.67 mm Hg at 40°C.Therefore, if an exposed water droplet evaporates in one hour, then a mercury droplet of the same size will evaporate in four weeks.10 Also, the conditions in an MSW landfill (such as temperature, moisture, and reducing capacity) are favourable for aqueous mobilization of mercury (e.g. in the form of methyl mercury). However, since both gaseous emissions and aqueous mobilization are dispersed sources, they are not easy to measure.
TABLE 4. Gaseous emissions of US landfills
Molecular
Mean concentration in
Landfill emissions,
weight
landfill gas, ppbv
kg/million tonnes of MSW
Acetone
58.08
6,838
826
Benzene
78.01
2,057
339
Chlorobenzene
112.56
82
17
Chloroform
119.39
245
61
1,1-Dichloroethane
98.97
2,801
574
Dichloromethane
84.80
25,694
4,539
Diethylene chloride
58.00
2,835
339
106.16
7,334
1,626
72.10
3,092
461
1,1,1-Trichloroethane
133.42
615
174
Trichloroethylene
131.40
2,079
565
92.13
34,907
6,704
165.85
5,244
1,809
62.50
3,508
461
104.15
1,517
330
Volatile compound
Ethyl benzene
Methyl ethyl ketone
Toluene
Tetrachloroethylene
Vinyl chloride
Styrenes
Vinyl acetate
Xylenes
62.50
5,663
1,017
106.16
2,651
583
Total VOC emissions
20,435
Ammonia
17.03
550,000
-
Sulphides/mercaptans
60.00
500,000
-
Volatile organic compounds
The annual gaseous emissions of landfills in the US can be estimated by multiplying the above estimate of non-captured landfill gas flow (about 46 Nm3 of methane plus CO2 escaping per tonne of MSW) by the reported concentrations of volatile organic compounds (VOC) in landfill gas. Table 4 shows the estimated emissions from US landfills, expressed on the basis of kilograms per million tonnes of MSW landfilled.
The next generation of WTE processes
The existing WTE combustion chambers have been developed largely empirically. Their size, percentage of excess air used, and the volume of process gas are much larger than for coal-fired power plants of the same combustion capacity. Therefore, the capital and maintenance costs of a WTE facility are nearly three times as high as that for a coal-fired power plant generating the same amount of electricity. One of the objectives of the Waste-to-Energy Research and Technology Council is to apply engineering science in understanding the phenomena occurring in the best of the existing WTE processes and then to implement this knowledge during the design of the next generation of WTE facilities. Two obvious means for increasing the turbulence and transport rates in the WTE chamber are oxygen enrichment, as practised in the metallurgical industry, and flue gas recirculation. The latter has already been
implemented very successfully in the Brescia WTE facility. Also, Martin GmbH has already piloted oxygen enrichment on a large scale and is in the process of building two
'next generation' plants, in Arnoldstein, Austria, and in Sendai, Japan, in collaboration with Mitsubishi Heavy Industries. Figure 6 is a schematic diagram of the Martin
Syncom-Plus® process that will be used in these plants. In addition to oxygen enrichment of the air injected through the grate, Syncom-Plus makes use of an infrared camera for monitoring the temperature of the bed on the grate and a sophisticated control system to ensure complete combustion and produce a bottom ash that is nearly fused and ready to be used beneficially.
FIGURE 6. The Syncom-Plus process of Martin GmbH
Conclusion
Worldwide, about 130 million tonnes of municipal solid wastes are combusted annually in WTE facilities that produce electricity and steam for district heating and also recover metals for recycling. Since 2001, there have been 47 new WTE facilities that either have
started or are under construction, adding 6 million tonnes to the total capacity. WTE expansion in the US has been stymied by environmental opposition that does not consider the enormous reduction in gas emissions made by the US WTE industry following implementation of the US EPA regulations for Maximum Available Control
Technology and by the fact that existing legislation does not recognize the significant environmental benefits of WTE, in terms of energy generation, environmental quality, and reduction of greenhouse gases.
In the last few years, there have been significant advances in WTE technology that include the use of implementation of flue gas recirculation and the design of new plants that will use oxygen enrichment of the primary air. The importance of WTE in the universal effort for sustainable development and its need for R&D resources has led to the formation of the Waste-to-Energy Research and Technology Council. This organization brings together several universities concerned with waste management.
The Council started operations by making an inventory of the global WTE industry and the research resources available. The overall goal of the Council is to improve the economic and environmental performance of technologies that can be used to recover materials and energy from solid wastes.
Waste management concepts
There are a number of concepts about waste management which vary in their usage between countries or regions. Some of the most general, widely used concepts include:
Waste hierarchy - The waste hierarchy refers to the "3 Rs" reduce, reuse and recycle, which classify waste management strategies according to their desirability in terms of waste minimization. The waste hierarchy remains the cornerstone of most waste minimization strategies. The aim of the waste hierarchy is to extract the maximum practical benefits from products and to generate the minimum amount of waste see: resource recovery.
Polluter pays principle - the Polluter Pays Principle is a principle where the polluting party pays for the impact caused to the environment. With respect to waste management, this generally refers to the requirement for a waste generator to pay for appropriate disposal of the unrecoverable material.
CONCLUSION
Solid waste policy in India specifies the duties and responsibilities for hygienic waste management for cities and citizens of India. This policy was framed in September 2000, based on the March 1999 Report of the Committee for Solid Waste Management in
Class 1 Cities of India to the Supreme Court, which urged statutory bodies to comply with the report’s suggestions and recommendations. These also serve as a guide on how to comply with the MSW rules. Both the report and the rules, summarized below, are based on the principle that the best way to keep streets clean is not to dirty them in the first place. So a city without street bins will ultimately become clean and stay clean.
They advocate daily doorstep collection of “wet” (food) wastes for composting, which is the best option for India. This is not only because composting is a cost-effective process practiced since Vedic times, but also because India’s soils need organic manures to prevent loss of fertility through unbalanced use of chemical fertilizers.
Municipality Solid Waste Rules
To stop the present unplanned open dumping of waste outside city limits, the MSW rules have laid down a strict timetable for compliance. Setting up of waste-processing and disposal facilities and provision of a buffer zone around such sites. Biodegradable wastes should be processed by composting, vermicomposting etc. and landfilling shall be restricted to non-biodegradable inert waste and compost rejects.
The rules also require municipalities to ensure community participation in waste segregation (by not mixing “wet” food wastes with “dry” recyclables like paper, plastics, glass, metal etc.) and to promote recycling or reuse of segregated materials. Garbage and dry leaves are not allowed to be burnt. Biomedical wastes and industrial wastes are not allowed to be mixed with municipal wastes. Routine use of pesticides on garbage has been banned by the Supreme Court on 28.7.1997.
Littering and throwing of garbage on roads is prohibited. Citizens should keep their wet
(food) wastes and dry (recyclable) wastes within their premises until collected, and must ensure delivery of wastes as per the collection and segregation system of their city, preferably by house-to-house collection at fixed times in multi-container handcarts or tricycles (to avoid manual handling of waste) or directly into trucks stopping at street corners at regular pre-informed timings. Dry wastes should be left for collection by the informal sector (sold directly to waste-buyers or given free or otherwise to wastepickers, who will earn their livelihood by taking the wastes they need from homes rather than from garbage on the streets. High - rises, private colonies, institutions should provide their own big bins within their own areas, separately for dry and wet wastes.
Report of a Committee for Solid Waste Management in Class 1 Cities of India to the
Supreme Court
The report recommends that cities should provide free waste collection for all slums and public areas, but charge the full cost of collection on “Polluter-Pays” Principle, from hotels, eateries, marriage halls, hospitals & clinics, wholesale markets, shops in
commercial streets, office complexes, cattle - sheds, slaughter - houses, fairs & exhibitions, inner-city cottage industry & petty trade. Debris and construction waste must be stored within premises, not on the road or footpath, and disposed of at pre designated sites or landfills by builder, on payment of full transport cost if removed by the Municipality.
For improved work accountability, “pin-point” work assignments and 365-day cleaning are recommended, with fixed beats for individual sweepers, including the cleaning of adjoining drains less than 2 ft deep. Drain silt should not be left on the road for drying, but loaded directly into hand-carts and taken to a transfer point . Silt and debris should not be dumped at compost - plant.
The quantities of garbage collected and transported need to be monitored against targets, preferably by citizen monitoring, through effective management information systems and a recording weigh - bridge: computerised for 1 million+ cities. At least 80% of waste-clearance vehicles should be on-road, and two-shift use implemented where there is a shortage of vehicles. Decentralised ward-wise composting of well-segregated wet waste in local parks is recommended, for recycling of organics and also for huge savings in garbage transport costs to scarce disposal sites.
The report also recommends that waste-management infrastructure should be a strictlyenforced pre-condition in new development areas. It advocates temporary toilets at all construction sites (located on the eventual sewage-disposal line) and restriction of cattle movement on streets. Livestock should be stall-fed or relocated outside large cities.
Cities must fulfil their obligatory functions (like waste management) before funding any discretionary functions, while being granted fiscal autonomy to raise adequate funds.
Solid-waste-management and other charges should be linked to the cost-of-living index, along with levy of “administrative charges” for chronic littering. Funds should be earmarked for minimum expenditure on solid waste management: Rs 100 per capita per year in 5-lakh-plus cities, or a minimum of Rs 50 per capita in smaller towns. Many
cities are already providing conditional funding to residential areas or colonies willing to take responsibility for improved waste-management of their respective areas.
The Supreme Court intends to monitor compliance with the MSW rules through the High
Courts in each State. This gives all citizens both the opportunity and the obligation to ensure that hygienic waste-management becomes a reality, soon.
The Work was evenly divided among the 3 group partners. Akash (ME10B027) and Deepak
(ME09b028) handled the making of the report completely, whereas Manish Jackson
(ME09B033) handled completely the making of the Power point presentation.
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