Incinerationis awaste treatment processthat involves thecombustionof substances contained in waste materials.[1]Industrial plants for waste incineration are commonly referred to aswaste-to-energyfacilities. Incineration and other high-temperature waste treatment systems are described as "thermal treatment".Incineration of waste materials converts the waste intoash,flue gasand heat. The ash is mostly formed by theinorganicconstituents of the waste and may take the form of solid lumps orparticulatescarried by the flue gas. The flue gases must be cleaned of gaseous and particulate pollutants before they are dispersed into theatmosphere.In some cases, the heat that is generated by incineration can be used to generateelectric power.
Incineration withenergy recoveryis one of severalwaste-to-energytechnologies such asgasification,pyrolysisandanaerobic digestion.While incineration and gasification technologies are similar in principle, the energy produced from incineration is high-temperature heat whereas combustible gas is often the main energy product from gasification. Incineration and gasification may also be implemented without energy and materials recovery.
In several countries, there are still concerns from experts and local communities about the environmental effect of incinerators (seearguments against incineration).
In some countries[which?],incinerators built just a few decades ago[when?]often did not include amaterials separationto remove hazardous,bulkyorrecyclablematerials before combustion. These facilities tended to risk the health of the plant workers and the local environment due to inadequate levels of gas cleaning and combustion process control. Most of these facilities did not generate electricity.[citation needed]
Incinerators reduce the solid mass of the original waste by 80–85% and the volume (already compressed somewhat ingarbage trucks) by 95–96%, depending on composition and degree of recovery of materials such as metals from the ash for recycling.[2]This means that while incineration does not completely replacelandfilling,it significantly reduces the necessary volume for disposal. Garbage trucks often reduce the volume of waste in a built-in compressor before delivery to the incinerator. Alternatively, at landfills, the volume of the uncompressed garbage can be reduced by approximately 70% by using a stationary steel compressor, albeit with a significant energy cost. In many countries, simplerwaste compactionis a common practice for compaction at landfills.[3]
Incineration has particularly strong benefits for the treatment of certainwaste typesinnicheareas such asclinical wastesand certainhazardous wasteswherepathogensandtoxinscan be destroyed by high temperatures. Examples include chemical multi-product plants with diverse toxic or very toxic wastewater streams, which cannot be routed to a conventional wastewater treatment plant.
Waste combustion is particularly popular in countries such as Japan, Singapore and the Netherlands, where land is a scarce resource. Denmark and Sweden have been leaders by using the energy generated from incineration for more than a century, in localisedcombined heat and powerfacilities supportingdistrict heatingschemes.[4]In 2005, waste incineration produced 4.8% of the electricity consumption and 13.7% of the total domestic heat consumption in Denmark.[5]A number of other European countries rely heavily on incineration for handling municipal waste, in particularLuxembourg,the Netherlands, Germany, and France.[2]
The first UK incinerators for waste disposal were built inNottinghambyManlove, Alliott & Co. Ltd.in 1874 to a design patented by Alfred Fryer. They were originally known asdestructors.[6]
An incinerator is a furnace for burningwaste.Modern incinerators include pollution mitigation equipment such asfluegas cleaning. There are various types of incinerator plant design: moving grate, fixed grate, rotary-kiln, and fluidised bed.[citation needed]
The burn pile or theburn pitis one of the simplest and earliest forms of waste disposal, essentially consisting of a mound of combustible materials piled on the open ground and set on fire, leading to pollution.
Burn piles can and have spread uncontrolled fires, for example, if the 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 viaconvection,and waft through the air into grasses or onto buildings, igniting them.[citation needed]Burn piles often do not result in full combustion of waste and therefore produce particulate pollution.[citation needed]
The burn barrel is a somewhat more controlled form of private waste incineration, containing the burning material inside a metal barrel, with a metal grating over the exhaust. The barrel prevents the spread of burning material in windy conditions, and as the combustibles are reduced they can only settle down into the barrel. The exhaust grating helps to prevent the spread of burning embers. Typically steel 55-US-gallon (210 L) drums are used as burn barrels, with air vent holes cut or drilled around the base for air intake.[9]Over time, the very high heat of incineration causes the metal to oxidize and rust, and eventually the barrel itself is consumed by the heat and must be replaced.
The private burning of dry cellulosic/paper products is generally clean-burning, producing no visible smoke, but plastics in the household waste can cause private burning to create a public nuisance, generating acrid odors and fumes that make eyes burn and water. A two-layered design enables secondary combustion, reducing smoke.[10]Most urban communities ban burn barrels and certain rural communities may have prohibitions on open burning, especially those home to many residents not familiar with this common rural practice.[citation needed]
As of 2006[update]in the United States, private rural household or farm waste incineration of small quantities was typically permitted so long as it is not a nuisance to others, does not pose a risk of fire such as in dry conditions, and the fire does not produce dense, noxious smoke. A handful of states, such as New York, Minnesota, and Wisconsin, have laws or regulations either banning or strictly regulating open burning due to health and nuisance effects.[11]People intending to burn waste may be required to contact a state agency in advance to check current fire risk and conditions, and to alert officials of the controlled fire that will occur.[12]
Control room of a typical moving grate incinerator overseeing two boiler linesMunicipal solid waste in the furnace of a moving grate incinerator capable of handling 15 metric tons (17 short tons) of waste per hour. The holes in the grate supplying the primary combustion air are visible.
The typical incineration plant formunicipal solid wasteis 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 asmunicipal solid waste incinerators(MSWIs).
The waste is introduced by awaste cranethrough the "throat" at one end of the grate, from where it moves down over the descending grate to the ash pit in the other end. Here the ash is removed through a water lock.
Part of the combustion air (primary combustion air) is supplied through the grate from below. This air flow also has the purpose of cooling the grate itself. Cooling is important for the mechanical strength of the grate, and many moving grates are also water-cooled internally.
Secondary combustion air is supplied into the boiler at high speed through nozzles over the grate. It facilitates complete combustion of the flue gases by introducingturbulencefor better mixing and by ensuring a surplus of oxygen. In multiple/stepped hearth incinerators, the secondary combustion air is introduced in a separate chamber downstream the primary combustion chamber.
According to the EuropeanWaste Incineration Directive,incineration plants must be designed to ensure that theflue gasesreach a temperature of at least 850 °C (1,560 °F) for 2 seconds in order to ensure proper breakdown of toxic organic substances. In order to comply with this at all times, it is required to install backup auxiliary burners (often fueled by oil), which are fired into the boiler in case theheating valueof the waste becomes too low to reach this temperature alone.
Theflue gasesare then cooled in thesuperheaters,where the heat is transferred to steam, heating the steam to typically 400 °C (752 °F) at a pressure of 40bars(580psi) for the electricity generation in theturbine.At this point, the flue gas has a temperature of around 200 °C (392 °F), and is passed to theflue gas cleaning system.
InScandinavia,scheduled maintenance is always performed during summer, where the demand fordistrict heatingis low. Often, incineration plants consist of several separate 'boiler lines' (boilers and flue gas treatment plants), so that waste can continue to be received at one boiler line while the others are undergoing maintenance, repair, or upgrading.
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 calledclinkers.Many small incinerators formerly found in apartment houses have now been replaced bywaste compactors.[13][full citation needed]
Therotary-kilnincinerator[14]is used by municipalities and by large industrial plants. This design of incinerator has two 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 refractory layer needs to be replaced from time to time.[15]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 neededdraft.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".[16]
A strong airflow is forced through a sandbed. 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 afluidized bedis 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.[citation needed]
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.
The heat produced by an incinerator can be used to generate steam which may then be used to drive aturbinein order to produce electricity. The typical amount of net energy that can be produced per tonne municipal waste is about 2/3 MWh of electricity and 2 MWh of district heating.[2]Thus, incinerating about 600 metric tons (660 short tons) per day of waste will produce about 400 MWh of electrical energy per day (17MWof electrical power continuously for 24 hours) and 1200 MWh of district heating energy each day.
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 NOxthan coal-fired power plants, but more than natural gas–fired power plants.[17]According toGermany'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.[18]
The most publicized concerns about the incineration of municipal solid wastes (MSW) involve the fear that it produces significant amounts ofdioxinandfuranemissions.[19]Dioxins and furans are considered by many to be serious health hazards. The EPA announced in 2012 that the safe limit for human oral consumption is 0.7 picograms Toxic Equivalence (TEQ) per kilogram bodyweight per day,[20]which works out to 17 billionths of a gram for a 150 lb person per year.
In 2005, the Ministry of the Environment of Germany, where there were 66 incinerators at that time, estimated that "...whereas in 1990 one third of all dioxin emissions in Germany came from incineration plants, for the year 2000 the figure was less than 1%.Chimneysand tiled stoves in private households alone discharge approximately 20 times more dioxin into the environment than incineration plants. "[18]
According to theUnited States Environmental Protection Agency,[11]the combustion percentages of the total dioxin and furan inventory from all known and estimated sources in the U.S. (not only incineration) for each type of incineration are as follows: 35.1% backyard barrels; 26.6% medical waste; 6.3% municipalwastewater treatment sludge;5.9% municipal waste combustion; 2.9% industrial wood combustion. Thus, the controlled combustion of waste accounted for 41.7% of the total dioxin inventory.
In 1987, before the governmental regulations required the use of emission controls, there was a total of 8,905.1 grams (314.12 oz) Toxic Equivalence (TEQ) of dioxin emissions from US municipal waste combustors. Today, the total emissions from the plants are 83.8 grams (2.96 oz) TEQ annually, a reduction of 99%.
Backyard barrel burningof household andgarden wastes,still allowed in some rural areas, generates 580 grams (20 oz) of dioxins annually.
Studies conducted by the US-EPA[21]demonstrated that one family using a burn barrel produced more emissions than an incineration plant disposing of 200 metric tons (220 short tons) of waste per day by 1997 and five times that by 2007 due to increased chemicals in household trash and decreased emission by municipal incinerators using better technology.[22]
Most of the improvement in U.S. dioxin emissions has been for large-scale municipal waste incinerators. As of 2000, although small-scale incinerators (those with a daily capacity of less than 250 tons) processed only 9% of the total waste combusted, these produced 83% of the dioxins and furans emitted by municipal waste combustion.[11]
The breakdown of dioxin requires exposure of the molecular ring to a sufficiently high temperature so as to trigger thermal breakdown of the strong molecular bonds holding it together. Small pieces of fly ash may be somewhat thick, and too brief an exposure to high temperature may only degrade dioxin on the surface of the ash. For a large volume air chamber, too brief an exposure may also result in only some of the exhaust gases reaching the full breakdown temperature. For this reason there is also a time element to the temperature exposure to ensure heating completely through the thickness of the fly ash and the volume of waste gases.
There are trade-offs between increasing either the temperature or exposure time. Generally where the molecular breakdown temperature is higher, the exposure time for heating can be shorter, but excessively high temperatures can also cause wear and damage to other parts of the incineration equipment. Likewise the breakdown temperature can be lowered to some degree but then the exhaust gases would require a greater lingering period of perhaps several minutes, which would require large/long treatment chambers that take up a great deal of treatment plant space.
A side effect of breaking the strong molecular bonds of dioxin is the potential for breaking the bonds of nitrogen gas (N2) and oxygen gas (O2) in the supply air. As the exhaust flow cools, these highly reactive detached atoms spontaneously reform bonds into reactive oxides such asNOxin the flue gas, which can result in smog formation andacid rainif they were released directly into the local environment. These reactive oxides must be further neutralized withselective catalytic reduction(SCR) orselective non-catalytic reduction(see below).
The temperatures needed to break down dioxin are typically not reached when burning plastics outdoors in a burn barrel or garbage pit, causing high dioxin emissions as mentioned above. While plastic does usually burn in an open-air fire, the dioxins remain after combustion and either float off into the atmosphere, or may remain in the ash where it can be leached down into groundwater when rain falls on the ash pile. Fortunately, dioxin and furan compounds bond very strongly to solid surfaces and are not dissolved by water, so leaching processes are limited to the first few millimeters below the ash pile. The gas-phase dioxins can be substantially destroyed using catalysts, some of which can be present as part of the fabric filter bag structure.
Modern municipal incinerator designs include a high-temperature zone, where the flue gas is sustained at a temperature above 850 °C (1,560 °F) for at least 2 seconds before it is cooled down. They are equipped with auxiliary heaters to ensure this at all times. These are often fueled by oil or natural gas, and are normally only active for a very small fraction of the time. Further, most modern incinerators utilize fabric filters (often with Teflon membranes to enhance collection of sub-micron particles) which can capture dioxins present in or on solid particles.
For very small municipal incinerators, the required temperature for thermal breakdown of dioxin may be reached using a high-temperature electrical heating element, plus aselective catalytic reductionstage.
Although dioxins and furans may be destroyed by combustion, their reformation by a process known as 'de novo synthesis' as the emission gases cool is a probable source of the dioxins measured in emission stack tests from plants that have high combustion temperatures held at long residence times.[11]
As for other complete combustion processes, nearly all of the carbon content in the waste is emitted as CO2to the atmosphere.MSWcontains approximately the same mass fraction of carbon as CO2itself (27%), so incineration of 1 ton of MSW produces approximately 1 ton of CO2.
If the waste waslandfilledwithout prior stabilization (typically viaanaerobic digestion), 1 ton of MSW would produce approximately 62 cubic metres (2,200 cu ft)methanevia theanaerobicdecomposition of thebiodegradablepart of the waste. Since theglobal warming potentialof methane is 34 and the weight of 62 cubic meters of methane at 25 degrees Celsius is 40.7 kg, this is equivalent to 1.38 ton of CO2,which is more than the 1 ton of CO2which would have been produced by incineration. In some countries, large amounts oflandfill gasare collected. Still the global warming potential of the landfill gas emitted to atmosphere is significant. In the US it was estimated that the global warming potential of the emitted landfill gas in 1999 was approximately 32% higher than the amount of CO2that would have been emitted by incineration.[23]Since this study, the global warming potential estimate for methane has been increased from 21 to 35, which alone would increase this estimate to almost the triple GWP effect compared to incineration of the same waste.
In addition, nearly all biodegradable waste has biological origin. This material has been formed by plants using atmospheric CO2typically within the last growing season. If these plants are regrown the CO2emitted from their combustion will be taken out from the atmosphere once more.[citation needed]
Such considerations are the main reason why several countries administrate incineration of biodegradable waste asrenewable energy.[24]The rest – mainly plastics and other oil and gas derived products – is generally treated asnon-renewables.
Different results for the CO2footprint of incineration can be reached with different assumptions. Local conditions (such as limited local district heating demand, no fossil fuel generated electricity to replace or high levels of aluminium in the waste stream) can decrease the CO2benefits of incineration.
The methodology and other assumptions may also influence the results significantly. For example, themethane emissionsfrom landfills occurring at a later date may be neglected or given less weight, or biodegradable waste may not be considered CO2neutral. A study by Eunomia Research and Consulting in 2008 on potential waste treatment technologies in London demonstrated that by applying several of these (according to the authors) unusual assumptions the average existing incineration plants performed poorly for CO2balance compared to the theoretical potential of other emerging waste treatment technologies.[25]
Other gaseous emissions in the flue gas from incinerator furnaces includenitrogen oxides,sulfur dioxide,hydrochloric acid,heavy metals,andfine particles.Of the heavy metals,mercuryis a major concern due to its toxicity and high volatility, as essentially all mercury in the municipal waste stream may exit in emissions if not removed by emission controls.[26]
Thesteamcontent in the flue may produce visible fume from the stack, which can be perceived as avisual pollution.It may be avoided by decreasing the steam content byflue-gas condensationand reheating, or by increasing the flue gas exit temperature well above its dew point. Flue-gas condensation allows the latent heat of vaporization of the water to be recovered, subsequently increasing thethermal efficiencyof the plant.[citation needed]
The quantity of pollutants in the flue gas from incineration plants may or may not be reduced by several processes, depending on the plant.
Particulate is collected byparticle filtration,most oftenelectrostatic precipitators(ESP) and/orbaghouse filters.The latter are generally very efficient for collectingfine particles.In an investigation by theMinistry of the Environment of Denmarkin 2006, the average particulate emissions per energy content of incinerated waste from 16 Danish incinerators were below 2.02 g/GJ (grams per energy content of the incinerated waste). Detailed measurements of fine particles with sizes below 2.5micrometres(PM2.5) were performed on three of the incinerators: One incinerator equipped with an ESP for particle filtration emitted 5.3 g/GJ fine particles, while two incinerators equipped with baghouse filters emitted 0.002 and 0.013 g/GJ PM2.5.For ultra fine particles (PM1.0), the numbers were 4.889 g/GJ PM1.0from the ESP plant, while emissions of 0.000 and 0.008 g/GJ PM1.0were measured from the plants equipped with baghouse filters.[27][28]
Acid gasscrubbersare used to removehydrochloric acid,nitric acid,hydrofluoric acid,mercury,lead and otherheavy metals.The efficiency of removal will depend on the specific equipment, the chemical composition of the waste, the design of the plant, the chemistry of reagents, and the ability of engineers to optimize these conditions, which may conflict for different pollutants. For example, mercury removal by wet scrubbers is considered coincidental and may be less than 50%.[26]Basic scrubbers removesulfur dioxide,forminggypsumby reaction withlime.[29]
Waste water from scrubbers must subsequently pass through a waste water treatment plant.[citation needed]
NOxis either reduced by catalytic reduction with ammonia in acatalytic converter(selective catalytic reduction,SCR) or by a high-temperature reaction with ammonia in the furnace (selective non-catalytic reduction,SNCR). Urea may be substituted for ammonia as the reducing reagent but must be supplied earlier in the process so that it can hydrolyze into ammonia. Substitution of urea can reduce costs and potential hazards associated with storage of anhydrous ammonia.[citation needed]
Incineration producesfly ashandbottom ashjust as is the case when coal is combusted. The total amount of ash produced by municipal solid waste incineration ranges from 4 to 10% by volume and 15–20% by weight of the original quantity of waste,[2][30]and the fly ash amounts to about 10–20% of the total ash.[2][30]The fly ash, by far, constitutes more of a potential health hazard than does the bottom ash because the fly ash often contain high concentrations of heavy metals such as lead,cadmium,copper andzincas well as small amounts of dioxins and furans.[31]The bottom ash seldom contain significant levels of heavy metals. At present although some historic samples tested by the incinerator operators' group would meet the being ecotoxic criteria at present the EA say "we have agreed" to regard incinerator bottom ash as "non-hazardous" until the testing programme is complete.[citation needed]
Odorpollution can be a problem with old-style incinerators, but odors and dust are extremely well controlled in newer incineration plants. They receive and store the waste in an enclosed area with a negative pressure with the airflow being routed through the boiler which preventsunpleasant odorsfrom escaping into the atmosphere. A study found that the strongest odor at an incineration facility in Eastern China occurred at its waste tipping port.[32]
An issue that affects community relationships is the increased road traffic ofwaste collection vehiclesto transport municipal waste to the incinerator. Due to this reason, most incinerators are located in industrial areas. This problem can be avoided to an extent through the transport of waste by rail from transfer stations.[citation needed]
Scientific researchers have investigated the human health effects of pollutants produced by waste incineration. Many studies have examined health impacts from exposure to pollutants utilizing U.S. EPA modeling guidelines.[33][34][35]Exposure through inhalation, ingestion, soil, and dermal contact are incorporated in these models. Research studies have also assessed exposure to pollutants through blood or urine samples of residents and workers who live near waste incinerators.[34][36]Findings from asystematic reviewof previous research identified a number of symptoms and diseases related to incinerator pollution exposure. These include neoplasia,[34]respiratory issues,[37]congenital anomalies,[34][37][38]and infant deaths or miscarriages.[34][38]Populations near old, inadequately maintained incinerators experience a higher degree of health issues.[34][37][38]Some studies also identified possible cancer risk.[38]However, difficulties in separating incinerator pollution exposure from combined industry, motor vehicle, and agriculture pollution limits these conclusions on health risks.[34][36][37][38]
Many communities have advocated for the improvement or removal of waste incinerator technology. Specific pollutant exposures, such as high levels of nitrogen dioxide, have been cited in community-led complaints relating to increased emergency room visits for respiratory issues.[39][40]Potential health effects of waste incineration technology have been publicized, notably when located in communities already facing disproportionate health burdens.[41]For example, theWheelabrator Incineratorin Baltimore, Maryland, has been investigated due to increased rates of asthma in its neighboring community, which is predominantly occupied by low-income, people of color.[41]Community-led efforts have suggested a need for future research to address a lack of real-time pollution data.[40][41]These sources have also cited a need for academic, government, and non-profit partnerships to better determine the health impacts of incineration.[40][41]
Use of incinerators forwaste managementis controversial. The debate over incinerators typically involves business interests (representing both waste generators and incinerator firms), government regulators, environmental activists and local citizens who must weigh the economic appeal of local industrial activity with their concerns over health and environmental risk.
People and organizations professionally involved in this issue include theU.S. Environmental Protection Agencyand a great many local and national air quality regulatory agencies worldwide.
The concerns over the health effects ofdioxinandfuranemissions have been significantly lessened by advances in emission control designs and very stringent new governmental regulations that have resulted in large reductions in the amount of dioxins and furans emissions.[18]
The U.K.Health Protection Agencyconcluded in 2009 that "Modern, well managed incinerators make only a small contribution to local concentrations of air pollutants. It is possible that such small additions could have an impact on health but such effects, if they exist, are likely to be very small and not detectable."[42]
Incineration plants can generate electricity and heat that can substitute power plants powered by other fuels at the regional electric anddistrict heatinggrid, and steam supply for industrial customers. Incinerators and other waste-to-energy plants generate at least partially biomass-based renewable energy that offsets greenhouse gas pollution from coal-, oil- andgas-fired power plants.[43]The E.U. considers energy generated from biogenic waste (waste with biological origin) by incinerators as non-fossil renewable energy under its emissions caps. These greenhouse gas reductions are in addition to those generated by the avoidance of landfill methane.
The bottom ash residue remaining after combustion has been shown to be a non-hazardous solid waste that can be safely put into landfills or recycled as construction aggregate. Samples are tested for ecotoxic metals.[44]
In densely populated areas, finding space for additional landfills is becoming increasingly difficult.
The Maishima waste treatment center in Osaka, designed by Friedensreich Hundertwasser, uses heat for power generation.Fine particlescan be efficiently removed from the flue gases withbaghouse filters.Even though approximately 40% of the incinerated waste in Denmark was incinerated at plants with no baghouse filters, estimates based on measurements by the Danish Environmental Research Institute showed that incinerators were only responsible for approximately 0.3% of the total domestic emissions of particulate smaller than 2.5micrometres(PM2.5) to the atmosphere in 2006.[27][28]
Incineration of municipal solid waste avoids the release ofmethane.Every ton of MSW incinerated, prevents about one ton of carbon dioxide equivalents from being released to the atmosphere.[23]
Most municipalities that operate incineration facilities have higher recycling rates than neighboring cities and countries that do not send their waste to incinerators.[45][failed verification].In a country overview from 2016[46]by the European Environmental Agency the top recycling performing countries are also the ones having the highest penetration of incineration, even though all material recovery from waste sent to incineration (e.g. metals and construction aggregate) is per definitionnotcounted as recycling in European targets. The recovery of glass, stone and ceramic materials reused in construction, as well as ferrous and in some cases non-ferrous metals recovered from combustion residue thus adds further to the actual recycled amounts.[47]Metals recovered from ash would typically be difficult or impossible to recycle through conventional means, as the removal of attached combustible material through incineration provides an alternative to labor- or energy-intensive mechanical separation methods.
Volume of combusted waste is reduced by approximately 90%, increasing the life of landfills. Ash from modern incinerators is vitrified at temperatures of 1,000 °C (1,830 °F) to 1,100 °C (2,010 °F), reducing the leachability and toxicity of residue. As a result, special landfills are generally no longer required for incinerator ash from municipal waste streams, and existing landfills can see their life dramatically increased by combusting waste, reducing the need for municipalities to site and construct new landfills.[48][49]
The Scottish Protection Agency's (SEPA) comprehensive health effects research concluded "inconclusively" on health effects in October 2009. The authors stress, that even though no conclusive evidence of non-occupational health effects from incinerators were found in the existing literature, "small but important effects might be virtually impossible to detect". The report highlights epidemiological deficiencies in previous UK health studies and suggests areas for future studies.[50]The U.K.Health Protection Agencyproduced a lesser summary in September 2009.[42]Many toxicologists criticise and dispute this report as not being comprehensive epidemiologically, thin on peer review and the effects of fine particle effects on health.[citation needed]
Combustion produces ash concentratesecotoxicheavy metals from waste into ash, mostly thefly ashcomponent. This ash must be stored in specialized landfills.[51]The less toxicbottom ash(incinerator bottom ash,IBA) can be encased intoconcreteas a building material, but there is a risk ofhydrogen gasexplosion due to the aluminum content.[52]The UK Highway Authority put the use of IBA infoam concreteon hold as it investigates a series of explosions in 2009.[53]Recovery of useful metals from ash is a new but even less mature approach.[54][55]
The health effects ofdioxinandfuranemissions from old incinerators; especially during start up and shut down, or where filter bypass is required continue to be a problem.[citation needed]
Erection of incinerators compete with the development and introduction of other emerging technologies. A UK government WRAP report, August 2008 found that in the UK median incinerator costs per ton were generally higher than those for MBT treatments by £18 permetric ton;and £27 per metric ton for most modern (post 2000) incinerators.[56][57]
Building and operating waste processing plants such as incinerators requires long contract periods to recover initial investment costs, causing a long-term lock-in. Incinerator lifetimes normally range from 25 to 30 years. This was highlighted by Peter Jones,OBE,the Mayor of London's waste representative in April 2009.[58]
Incinerators produce fine particles in the furnace. Even with modern particle filtering of the flue gases, a small part of these is emitted to the atmosphere. PM2.5is not separately regulated in the EuropeanWaste Incineration Directive,even though they are repeatedly correlated spatially to infant mortality in the UK (M. Ryan's ONS data based maps around the EfW/CHP waste incinerators at Edmonton, Coventry, Chineham, Kirklees and Sheffield).[59][60][61]Under WID there is no requirement to monitor stack top or downwind incinerator PM2.5levels.[62][better source needed]Several European doctors associations (including cross discipline experts such as physicians, environmental chemists and toxicologists) in June 2008 representing over 33,000 doctors wrote a keynote statement directly to the European Parliament citing widespread concerns on incinerator particle emissions and the absence of specific fine and ultrafine particle size monitoring or in depth industry/government epidemiological studies of these minute and invisible incinerator particle size emissions.[63]
Local communities are often opposed to the idea of locating waste processing plants such as incinerators in their vicinity (theNot in My Back Yardphenomenon). Studies inAndover, Massachusettscorrelated 10% property devaluations with close incinerator proximity.[64]
Prevention,waste minimisation,reuseandrecyclingof waste should all be preferred to incineration according to thewaste hierarchy.Supporters ofzero wasteconsider incinerators and other waste treatment technologies as barriers torecyclingand separation beyond particular levels, and that waste resources are sacrificed for energy production.[65][66][67]
A 2008 Eunomia report found that under some circumstances and assumptions, incineration causes less CO2reduction than other emergingEfWandCHPtechnology combinations for treating residual mixed waste.[25]The authors found that CHP incinerator technology without waste recycling ranked 19 out of 24 combinations (where all alternatives to incineration were combined with advanced waste recycling plants); being 228% less efficient than the ranked 1 Advanced MBT maturation technology; or 211% less efficient than plasma gasification/autoclaving combination ranked 2.
Some incinerators are visually undesirable. In many countries they require a visually intrusive chimney stack.[citation needed]
If reusable waste fractions are handled in waste processing plants such as incinerators in developing nations, it would cut out viable work for local economies. It is estimated that there are 1 million people making a livelihood off collecting waste.[68]
The reduced levels of emissions from municipal waste incinerators and waste to energy plants from historical peaks are largely the product of the proficient use of emission control technology. Emission controls add to the initial and operational expenses. It should not be assumed that all new plants will employ the best available control technology if not required by law.[citation needed]
Waste that has been deposited on a landfillcan be minedeven decades and centuries later, and recycled with future technologies – which is not the case with incineration.
The history ofmunicipal solid waste(MSW) incineration is linked intimately to the history oflandfillsand otherwaste treatment technology.The merits of incineration are inevitably judged in relation to the alternatives available. Since the 1970s, recycling and other prevention measures have changed the context for such judgements. Since the 1990s alternative waste treatment technologies have been maturing and becoming viable.
Incineration is a key process in the treatment of hazardous wastes and clinical wastes. It is often imperative that medical waste be subjected to the high temperatures of incineration to destroypathogensandtoxiccontamination it contains.
The first incinerator in the U.S. was built in 1885 onGovernors Islandin New York.[69]
In 1949, Robert C. Ross founded one of the first hazardous waste management companies in the U.S. He began Robert Ross Industrial Disposal because he saw an opportunity to meet the hazardous waste management needs of companies in northern Ohio. In 1958, the company built one of the first hazardous waste incinerators in the U.S.[70]
The first full-scale, municipally operated incineration facility in the U.S. was the Arnold O. Chantland Resource Recovery Plant built in 1975 inAmes, Iowa.The plant is still in operation and producesrefuse-derived fuelthat is sent to local power plants for fuel.[71]The first commercially successful incineration plant in the U.S. was built inSaugus, Massachusetts,in October 1975 by Wheelabrator Technologies, and is still in operation today.[30]
There are several environmental or waste management corporations that transport ultimately to an incinerator or cement kiln treatment center. Currently (2009), there are three main businesses that incinerate waste: Clean Harbours, WTI-Heritage, and Ross Incineration Services. Clean Harbours has acquired many of the smaller, independently run facilities, accumulating 5–7 incinerators in the process across the U.S. WTI-Heritage has one incinerator, located in the southeastern corner ofOhioacross the Ohio River from West Virginia.[citation needed]
Several old generation incinerators have been closed; of the 186 MSW incinerators in 1990, only 89 remained by 2007, and of the 6200 medical waste incinerators in 1988, only 115 remained in 2003.[72]
No new incinerators were built between 1996 and 2007.[citation needed]The main reasons for lack of activity have been:
Economics. With the increase in the number of large inexpensive regional landfills and, up until recently, the relatively low price of electricity, incinerators were not able to compete for the 'fuel', i.e., waste in the U.S.[citation needed]
Tax policies. Tax credits for plants producing electricity from waste were rescinded in the U.S. between 1990 and 2004.[citation needed]
There has been renewed interest in incineration and other waste-to-energy technologies in the U.S. and Canada. In the U.S., incineration was granted qualification forrenewable energy production tax creditsin 2004.[73]Projects to add capacity to existing plants are underway, and municipalities are once again evaluating the option of building incineration plants rather than continue landfilling municipal wastes. However, many of these projects have faced continued political opposition in spite of renewed arguments for the greenhouse gas benefits of incineration and improved air pollution control and ash recycling.
The Tarastejärvi Incineration Plant in Taraste,Tampere,Finland
In Europe, as a result of a ban on landfilling untreated waste,[74]many incinerators have been built in the last decade, with more under construction. Recently, a number of municipal governments have begun the process of contracting for the construction and operation of incinerators. In Europe, some of the electricity generated from waste is deemed to be from a 'Renewable Energy Source' (RES) and is thus eligible for tax credits if privately operated. Also, some incinerators in Europe are equipped with waste recovery, allowing the reuse of ferrous and non-ferrous materials found in the burned waste. A prominent example is the AEB Waste Fired Power Plant, Amsterdam.[75][76]
In Sweden, about 50% of the generated waste is burned in waste-to-energy facilities, producing electricity and supplying local cities' district heating systems.[77]The importance of waste in Sweden's electricity generation scheme is reflected on their 2,700,000 tons of waste imported per year (in 2014) to supply waste-to-energy facilities.[78]
Due to increasing targets for municipal solid waste recycling in the EU, at least 55% by 2025 up to 65% by 2035,[79]several traditional incineration countries are at risk of not meeting them, since at most 35% will remain available for thermal treatment and disposal.[80][81]Denmark has since decided to reduce its incineration capacity by 30% by 2030.[82]
Incineration of non-hazardous waste was not included as a form of green investment in theEU taxonomy for sustainable activities[83]due to concerns about harming the circularity agenda, effectively stopping future EU funding to the municipal solid waste incineration sector.
The technology employed in the UK waste management industry has been greatly lagging behind that of Europe due to the wide availability of landfills. TheLandfill Directiveset down by theEuropean Unionled to the Government of the United Kingdom imposingwaste legislationincluding thelandfill taxandLandfill Allowance Trading Scheme.This legislation is designed to reduce the release of greenhouse gases produced by landfills through the use of alternative methods of waste treatment. It is the UK Government's position that incineration will play an increasingly large role in the treatment of municipal waste and supply of energy in the UK.[citation needed]
In 2008, plans for potential incinerator locations exists for approximately 100 sites. These have been interactively mapped by UK NGO's.[84][85][86][87]
Under a new plan in June 2012, a DEFRA-backed grant scheme (The Farming and Forestry Improvement Scheme) was set up to encourage the use of low-capacity incinerators on agricultural sites to improve their bio security.[88]
A permit has recently been granted[89]for what would be the UK's largest waste incinerator in the centre of theCambridge – Milton Keynes – Oxford corridor,inBedfordshire.Following the construction of a large incinerator at Greatmoor inBuckinghamshire,and plans to construct a further one nearBedford,[90]the Cambridge – Milton Keynes – Oxford corridor will become a major incineration hub in the UK.
This sectionis missing informationabout internal technology; how cleanly do they burn medical plastic.Please expand the section to include this information. Further details may exist on thetalk page.(May 2022)
Emergency incineration systems exist for the urgent and biosecure disposal of animals and their by-products following a mass mortality or disease outbreak. An increase in regulation and enforcement from governments and institutions worldwide has been forced through public pressure and significant economic exposure.
Contagious animal disease has cost governments and industry $200 billion over 20 years to 2012 and is responsible for over 65% of infectious disease outbreaks worldwide in the past sixty years. One-third of global meat exports (approx 6 million tonnes) is affected by trade restrictions at any time and as such the focus of Governments, public bodies and commercial operators is on cleaner, safer and more robust methods of animal carcass disposal to contain and control disease.
Large-scale incineration systems are available from niche suppliers and are often bought by governments as a safety net in case of contagious outbreak. Many are mobile and can be quickly deployed to locations requiring biosecure disposal.
Small-scale incinerators exist for special purposes. For example, mobile small-scale incinerators are aimed forhygienicallysafe destruction of medical waste indeveloping countries.[91]Companies such as Inciner8, a UK based company, are a good example of mobile incinerator manufacturers with their I8-M50 and I8-M70 models. Small incinerators can be quickly deployed to remote areas where an outbreak has occurred to dispose of infected animals quickly and without the risk of cross contamination.[citation needed]
An example of a containerised waste incinerator-Incinco
Containerised incinerators are a unique type of incinerator that are specifically designed to function in remote locations where traditional infrastructure may not be available. These incinerators are typically built within a shipping container for easy transport and installation.
