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106-414: Waste-to-energy (WtE) or energy-from-waste (EfW) refers to a series of processes designed to convert waste materials into usable forms of energy, typically electricity or heat. As a form of energy recovery, WtE plays a crucial role in both waste management and sustainable energy production by reducing the volume of waste in landfills and providing an alternative energy source. The most common method of WtE

212-415: A combination of impermeable liners several metres thick, geologically stable sites and collection systems to contain and capture this leachate. It can then be treated and evaporated. Once a landfill site is full, it is sealed off to prevent precipitation ingress and new leachate formation. However, liners must have a lifespan, be it several hundred years or more. Eventually, any landfill liner could leak, so

318-533: A community group is actively opposing their local waste-to-energy facility, Sintana Vergara, an assistant professor in the Department of Environmental Resources Engineering at Humboldt State University in California, commented that community resistance is based on both the pollution and the fact that many of these facilities have been sited in communities without any community input, and without any benefits to

424-559: A few industrial scale biomass gasification plants. Since 2008 in Svenljunga, Sweden, a biomass gasification plant generates up to 14 MW th , supplying industries and citizens of Svenljunga with process steam and district heating , respectively. The gasifier uses biomass fuels such as CCA or creosote impregnated waste wood and other kinds of recycled wood to produces syngas that is combusted on site. Examples of demonstration projects include: Landfill A landfill

530-426: A flexible option for thermal applications, as they can be retrofitted into existing gas fueled devices such as ovens , furnaces , boilers , etc., where syngas may replace fossil fuels. Heating values of syngas are generally around 4–10 MJ/m . Currently Industrial-scale gasification is primarily used to produce electricity from fossil fuels such as coal, where the syngas is burned in a gas turbine. Gasification

636-442: A fuel slurry is gasified with oxygen (much less frequent: air) in co-current flow. The gasification reactions take place in a dense cloud of very fine particles. Most coals are suitable for this type of gasifier because of the high operating temperatures and because the coal particles are well separated from one another. The high temperatures and pressures also mean that a higher throughput can be achieved, however thermal efficiency

742-640: A handful have been implemented as plants processing real waste, and most of the time in combination with fossil fuels. One plant (in Chiba , Japan, using the Thermoselect process ) has been processing industrial waste with natural gas and purified oxygen since year 2000, but has not yet documented positive net energy production from the process. In 2007 Ze-gen erected a waste gasification demonstration facility in New Bedford, Massachusetts . The facility

848-527: A limited amount of oxygen or air is introduced into the reactor to allow some of the organic material to be "burned" to produce carbon dioxide and energy, which drives a second reaction that converts further organic material to hydrogen and additional carbon dioxide. Further reactions occur when the formed carbon monoxide and residual water from the organic material react to form methane and excess carbon dioxide (4CO + 2H 2 O → CH 4 + 3CO 2 ). This third reaction occurs more abundantly in reactors that increase

954-423: A permeable bed, although recent developments have reduced these restrictions to some extent. The throughput for this type of gasifier is relatively low. Thermal efficiency is high as the temperatures in the gas exit are relatively low. However, this means that tar and methane production is significant at typical operation temperatures, so product gas must be extensively cleaned before use. The tar can be recycled to

1060-422: A significant role in a renewable energy economy, because biomass production removes the same amount of CO 2 from the atmosphere as is emitted from gasification and combustion. While other biofuel technologies such as biogas and biodiesel are carbon neutral , gasification in principle may run on a wider variety of input materials and can be used to produce a wider variety of output fuels. There are at present

1166-501: A substitute for natural gas. The WtE process contributes to circular economy principles by transforming waste products into valuable resources, reducing dependency on fossil fuels, and mitigating greenhouse gas emissions. However, challenges remain, particularly in ensuring that emissions from WtE plants, such as dioxins and furans , are properly managed to minimize environmental impact. Advanced pollution control technologies are essential to address these concerns and ensure WtE remains

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1272-545: A thermal treatment process in Collie, Western Australia. The system will process 1.5 tonnes of organic matter per hour. Annually the facility will divert 4000 tonnes of municipal waste from landfill and source an additional 8000 tonnes of organic waste from agricultural and forestry operations. Renergi’s patented “grinding pyrolysis” process aims to converts organic materials into biochar, bio-gases and bio-oil by applying heat in an environment with limited oxygen. Another project in

1378-702: A total of 93.5 MW installed capacity of waste-to-energy, with a pipeline of projects in different preparation phases together amounting to another 373MW of capacity. Biofuel Energy Corporation of Denver, Colorado, opened two new biofuel plants in Wood River, Nebraska , and Fairmont, Minnesota , in July 2008. These plants use distillation to make ethanol for use in motor vehicles and other engines. Both plants are currently reported to be working at over 90% capacity. Fulcrum BioEnergy, located in Pleasanton, California ,

1484-522: A variety of biomass and waste-derived feedstocks can be gasified, with wood pellets and chips, waste wood, plastics and aluminium, Municipal Solid Waste (MSW), Refuse-derived fuel (RDF), agricultural and industrial wastes, sewage sludge, switch grass, discarded seed corn, corn stover and other crop residues all being used. Chemrec has developed a process for gasification of black liquor . Waste gasification has several advantages over incineration: A major challenge for waste gasification technologies

1590-440: A viable and abundant source of materials and energy . In the developing world, waste pickers often scavenge for still-usable materials. In commercial contexts, companies have also discovered landfill sites, and many have begun harvesting materials and energy. Well-known examples include gas-recovery facilities. Other commercial facilities include waste incinerators which have built-in material recovery. This material recovery

1696-529: A viable, environmentally sound solution. WtE technologies present a significant opportunity to manage waste sustainably while contributing to global energy demands. They represent an essential component of integrated waste management strategies and a shift toward renewable energy systems. As technology advances, WtE may play an increasingly critical role in both reducing landfill use and enhancing energy security. Gasification and pyrolysis processes have been known and used for centuries and for coal as early as

1802-526: Is direct combustion of waste to produce heat, which can then be used to generate electricity via steam turbines. This method is widely employed in many countries and offers a dual benefit: it disposes of waste while generating energy, making it an efficient process for both waste reduction and energy production. In addition to combustion, other WtE technologies focus on converting waste into fuel sources . For example, gasification and pyrolysis are processes that thermochemically decompose organic materials in

1908-551: Is CO 2 . The gas also contains about 5% molecular nitrogen (N 2 ), less than 1% hydrogen sulfide (H 2 S), and a low concentration of non-methane organic compounds (NMOC) , about 2700 ppmv . Landfill gases can seep out of the landfill and into the surrounding air and soil. Methane is a greenhouse gas , and is flammable and potentially explosive at certain concentrations, which makes it perfect for burning to generate electricity cleanly. Since decomposing plant matter and food waste only release carbon that has been captured from

2014-466: Is a plant with seven different processes: biomass processing, fuel delivery, gasification, gas cleaning, waste disposal, electricity generation and heat recovery. Diesel engines can be operated on dual fuel mode using producer gas. Diesel substitution of over 80% at high loads and 70–80% under normal load variations can easily be achieved. Spark ignition engines and solid oxide fuel cells can operate on 100% gasification gas. Mechanical energy from

2120-439: Is a relatively old method of WtE generation. Incineration generally entails burning waste (residual MSW, commercial, industrial and RDF) to boil water which powers steam generators that generate electric energy and heat to be used in homes, businesses, institutions and industries. One problem associated is the potential for pollutants to enter the atmosphere with the flue gases from the boiler. These pollutants can be acidic and in

2226-680: Is a site for the disposal of waste materials. It is the oldest and most common form of waste disposal , although the systematic burial of waste with daily, intermediate and final covers only began in the 1940s. In the past, waste was simply left in piles or thrown into pits (known in archeology as middens ). Landfills take up a lot of land and pose environmental risks. Some landfill sites are used for waste management purposes, such as temporary storage, consolidation and transfer, or for various stages of processing waste material, such as sorting, treatment, or recycling. Unless they are stabilized, landfills may undergo severe shaking or soil liquefaction of

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2332-421: Is also used industrially in the production of electricity, ammonia and liquid fuels (oil) using Integrated Gasification Combined Cycles ( IGCC ), with the possibility of producing methane and hydrogen for fuel cells. IGCC is also a more efficient method of CO 2 capture as compared to conventional technologies. IGCC demonstration plants have been operating since the early 1970s and some of the plants constructed in

2438-476: Is an open one, as European countries which recycle the most (up to 70%) also incinerate to avoid landfilling . Incinerators have electric efficiencies of 14-28%. In order to avoid losing the rest of the energy, it can be used for e.g. district heating ( cogeneration ). The total efficiencies of cogeneration incinerators are typically higher than 80% (based on the lower heating value of the waste). The method of incineration to convert municipal solid waste (MSW)

2544-427: Is building a WtE plant near Reno, NV . The plant is scheduled to open in 2019 under the name of Sierra BioFuels plant. BioEnergy incorporated predicts that the plant will produce approximately 10.5 million gallons per year of ethanol from nearly 200,000 tons per year of MSW. Waste-to-energy technology includes fermentation , which can take biomass and create ethanol , using waste cellulosic or organic material. In

2650-594: Is currently widely used on industrial scales to generate electricity. Gasification can generate lower amounts of some pollutants as SO x and NO x than combustion. Energy has been produced at industrial scale via gasification since the early 19th century. Initially coal and peat were gasified to produce town gas for lighting and cooking, with the first public street lighting installed in Pall Mall, London on January 28, 1807, spreading shortly to supply commercial gas lighting to most industrialized cities until

2756-537: Is from biogenic material. Consequently, this energy is often recognised as renewable energy according to the waste input. Several methods have been developed by the European CEN 343 working group to determine the biomass fraction of waste fuels, such as Refuse Derived Fuel /Solid Recovered Fuel. The initial two methods developed (CEN/TS 15440) were the manual sorting method and the selective dissolution method . A detailed systematic comparison of these two methods

2862-463: Is ground and melted and then pyrolyzed. Catalytic converters help in the process. The vapours are condensed with oil or fuel and accumulated in settling tanks and filtered. Fuel is obtained after homogenation and can be used for automobiles and machinery. It is commonly termed as thermofuel or energy from plastic. A new process uses a two-part catalyst, cobalt and zeolite, to convert plastics into propane . It works on polyethylene and polypropylene and

2968-403: Is mixed with the fuel prior to gasification. Addition of a little limestone will usually suffice for the lowering the fusion temperatures. The fuel particles must be much smaller than for other types of gasifiers. This means the fuel must be pulverized, which requires somewhat more energy than for the other types of gasifiers. By far the most energy consumption related to entrained flow gasification

3074-641: Is not the milling of the fuel but the production of oxygen used for the gasification. In a plasma gasifier a high-voltage current is fed to a torch, creating a high-temperature arc. The inorganic residue is retrieved as a glass like substance. There are a large number of different feedstock types for use in a gasifier, each with different characteristics, including size, shape, bulk density, moisture content, energy content, chemical composition, ash fusion characteristics, and homogeneity of all these properties. Coal and petroleum coke are used as primary feedstocks for many large gasification plants worldwide. Additionally,

3180-548: Is possible through the use of filters ( electro filter , active-carbon and potassium filter, quench, HCl-washer, SO 2 -washer, bottom ash -grating, etc.). In addition to waste reduction and recycling strategies, there are various alternatives to landfills, including waste-to-energy incineration, anaerobic digestion , composting , mechanical biological treatment , pyrolysis and plasma arc gasification . Depending on local economics and incentives, these can be made more financially attractive than landfills. The goal of

3286-671: Is rapidly displaced by CO 2 in the effluent gas. Hydrolysis of the biodegradable fraction of the solid waste begins in the acid formation phase, which leads to rapid accumulation of volatile fatty acids (VFAs) in the leachate. The increased organic acid content decreases the leachate pH from approximately 7.5 to 5.6. During this phase, the decomposition intermediate compounds like the VFAs contribute much chemical oxygen demand (COD). Long-chain volatile organic acids (VOAs) are converted to acetic acid (C 2 H 4 O 2 ), CO 2 , and hydrogen gas (H 2 ). High concentrations of VFAs increase both

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3392-430: Is somewhat lower as the gas must be cooled before it can be cleaned with existing technology. The high temperatures also mean that tar and methane are not present in the product gas; however the oxygen requirement is higher than for the other types of gasifiers. All entrained flow gasifiers remove the major part of the ash as a slag as the operating temperature is well above the ash fusion temperature. A smaller fraction of

3498-465: Is still the global warming potential of the landfill gas being emitted to atmosphere. For example, in the US in 1999 landfill gas emission was approximately 32% higher than the amount of CO 2 that would have been emitted by combustion. In addition, nearly all biodegradable waste is biomass . That is, it has biological origin. This material has been formed by plants using atmospheric CO 2 typically within

3604-518: Is the first stage by which wastes are broken down in a landfill. These are followed by four stages of anaerobic degradation. Usually, solid organic material in solid phase decays rapidly as larger organic molecules degrade into smaller molecules. These smaller organic molecules begin to dissolve and move to the liquid phase, followed by hydrolysis of these organic molecules, and the hydrolyzed compounds then undergo transformation and volatilization as carbon dioxide (CO 2 ) and methane (CH 4 ), with rest of

3710-561: Is the largest user in thermal treatment of municipal solid waste in the world, with 40 million tons. Some of the newest plants use stoker technology and others use the advanced oxygen enrichment technology. Several treatment plants exist worldwide using relatively novel processes such as direct smelting, the Ebara fluidization process and the Thermoselect JFE gasification and melting technology process. As of June 2014, Indonesia had

3816-403: Is the longest decomposition phase. The rate of microbiological activity slows during the last phase of waste decomposition as the supply of nutrients limits the chemical reactions, e.g. as bioavailable phosphorus becomes increasingly scarce. CH 4 production almost completely disappears, with O 2 and oxidized species gradually reappearing in the gas wells as O 2 permeates downwardly from

3922-430: Is to reach an acceptable (positive) gross electric efficiency. The high efficiency of converting syngas to electric power is counteracted by significant power consumption in the waste preprocessing, the consumption of large amounts of pure oxygen (which is often used as gasification agent), and gas cleaning. Another challenge becoming apparent when implementing the processes in real life is to obtain long service intervals in

4028-509: The Fischer–Tropsch process into synthetic fuel . For some materials gasification can be an alternative to landfilling and incineration , resulting in lowered emissions of atmospheric pollutants such as methane and particulates . Some gasification processes aim at refining out corrosive ash elements such as chloride and potassium , allowing clean gas production from otherwise problematic feedstock material. Gasification of fossil fuels

4134-712: The Landfill Allowance Trading Scheme has been established for local authorities to trade landfill quotas in England. A different system operates in Wales where authorities cannot 'trade' amongst themselves, but have allowances known as the Landfill Allowance Scheme. U.S. landfills are regulated by each state's environmental agency, which establishes minimum guidelines; however, none of these standards may fall below those set by

4240-593: The United States Environmental Protection Agency (EPA). Permitting a landfill generally takes between five and seven years, costs millions of dollars and requires rigorous siting, engineering and environmental studies and demonstrations to ensure local environmental and safety concerns are satisfied. The status of a landfill's microbial community may determine its digestive efficiency. Bacteria that digest plastic have been found in landfills. One can treat landfills as

4346-615: The Xe than (literally, "coal car" in Vietnamese ) was a minibus that has been converted to run on coal instead of gasoline . This modification regained popularity in Vietnam during the subsidy period , when gasoline was in short supply. Xe than became much less common during the Đổi Mới period, when gasoline became widely accessible again. In a gasifier, the carbonaceous material undergoes several different processes: In essence,

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4452-574: The biochemical oxygen demand (BOD) and VOA concentrations, which initiates H 2 production by fermentative bacteria, which stimulates the growth of H 2 -oxidizing bacteria. The H 2 generation phase is relatively short because it is complete by the end of the acid formation phase. The increase in the biomass of acidogenic bacteria increases the amount of degradation of the waste material and consuming nutrients. Metals, which are generally more water-soluble at lower pH, may become more mobile during this phase, leading to increasing metal concentrations in

4558-803: The landfill gas utilization and generation of electricity . Landfill gas monitoring alerts workers to the presence of a build-up of gases to a harmful level. In some countries, landfill gas recovery is extensive; in the United States, for example, more than 850 landfills have active landfill gas recovery systems. A Solar landfill is a repurposed used landfill that is converted to a solar array solar farm . Landfills in Canada are regulated by provincial environmental agencies and environmental protection legislation. Older facilities tend to fall under current standards and are monitored for leaching . Some former locations have been converted to parkland. In

4664-518: The residence time of the reactive gases and organic materials, as well as heat and pressure. Catalysts are used in more sophisticated reactors to improve reaction rates, thus moving the system closer to the reaction equilibrium for a fixed residence time. Several types of gasifiers are currently available for commercial use: counter-current fixed bed, co-current fixed bed, fluidized bed , entrained flow, plasma, and free radical. A fixed bed of carbonaceous fuel (e.g. coal or biomass) through which

4770-415: The "gasification agent" (steam, oxygen and/or air) flows in counter-current configuration. The ash is either removed in the dry condition or as a slag . The slagging gasifiers have a lower ratio of steam to carbon, achieving temperatures higher than the ash fusion temperature. The nature of the gasifier means that the fuel must have high mechanical strength and must ideally be non-caking so that it will form

4876-789: The 18th century.... Development technologies for processing [residual solid mixed waste] has only become a focus of attention in recent years stimulated by the search for more efficient energy recovery. (2004) Incineration, the combustion of organic material such as waste with energy recovery, is the most common WtE implementation. All new WtE plants in OECD countries incinerating waste (residual MSW , commercial, industrial or RDF ) must meet strict emission standards, including those on nitrogen oxides (NO x ), sulphur dioxide (SO 2 ), heavy metals and dioxins . Hence, modern incineration plants are vastly different from old types, some of which neither recovered energy nor materials. Modern incinerators reduce

4982-410: The 1980s were reported to cause environmental degradation by turning rain into acid rain . Modern incinerators incorporate carefully engineered primary and secondary burn chambers, and controlled burners designed to burn completely with the lowest possible emissions, eliminating, in some cases, the need for lime scrubbers and electro-static precipitators on smokestacks. By passing the smoke through

5088-467: The 1990s are now entering commercial service. In small business and building applications, where the wood source is sustainable, 250–1000 kWe and new zero carbon biomass gasification plants have been installed in Europe that produce tar free syngas from wood and burn it in reciprocating engines connected to a generator with heat recovery. This type of plant is often referred to as a wood biomass CHP unit but

5194-566: The 20th century, but gained wide use in the 1960s and 1970s, in an effort to eliminate open dumps and other "unsanitary" waste disposal practices. The sanitary landfill is an engineered facility that separates and confines waste. Sanitary landfills are intended as biological reactors ( bioreactors ) in which microbes will break down complex organic waste into simpler, less toxic compounds over time. These reactors must be designed and operated according to regulatory standards and guidelines (See environmental engineering ). Usually, aerobic decomposition

5300-718: The European Union, individual states are obliged to enact legislation to comply with the requirements and obligations of the European Landfill Directive . The majority of EU member states have laws banning or severely restricting the disposal of household trash via landfills. Landfilling is currently the major method of municipal waste disposal in India. India also has Asia's largest dumping ground in Deonar, Mumbai. However, issues frequently arise due to

5406-492: The German Environmental Ministry, "because of stringent regulations, waste incineration plants are no longer significant in terms of emissions of dioxins, dust, and heavy metals". Compared with other waste to energy technologies, incineration seems to be the most attractive due to its higher power production efficiency, lower investment costs, and lower emission rates. Additionally, incineration yields

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5512-1015: The Hurlburt Field Florida Special Operations Command Air Force base. The plant, which cost $ 7.4 million to construct, was closed and sold at a government liquidation auction in May 2013. The opening bid was $ 25. The winning bid was sealed. In December 2022, the Sierra BioFuels Plant opened in Reno, Nevada, converting landfill waste to synthetic crude oil. Syngas can be used for heat production and for generation of mechanical and electrical power. Like other gaseous fuels, producer gas gives greater control over power levels when compared to solid fuels, leading to more efficient and cleaner operation. Syngas can also be used for further processing to liquid fuels or chemicals. Gasifiers offer

5618-661: The Rockingham Industrial Zone, roughly 45 kilometres south of Perth will see a 29 MW plant built with capacity to power 40,000 homes from an annual feedstock of 300,000 tonnes of municipal, industrial and commercial rubbish. As well as supplying electricity to the South West Interconnected System, 25 MW of the plant’s output has already been committed under a power purchase agreement. The Reppie waste to energy plant in Ethiopia

5724-654: The United States, there is already an equivalent carbon 14 method under the standard method ASTM D6866. The second method (so-called balance method ) employs existing data on materials composition and operating conditions of the WtE plant and calculates the most probable result based on a mathematical-statistical model. Currently the balance method is installed at three Austrian and eight Danish incinerators. A comparison between both methods carried out at three full-scale incinerators in Switzerland showed that both methods came to

5830-591: The absence of oxygen to produce syngas, a synthetic gas primarily composed of hydrogen, carbon monoxide, and small amounts of carbon dioxide. This syngas can be converted into methane , methanol , ethanol , or even synthetic fuels , which can be used in various industrial processes or as alternative fuels in transportation. Furthermore, anaerobic digestion , a biological process, converts organic waste into biogas (mainly methane and carbon dioxide) through microbial action. This biogas can be harnessed for energy production or processed into biomethane , which can serve as

5936-415: The age of landfill, type of waste, moisture content and other factors. For example, the maximum amount of landfill gas produced can be illustrated a simplified net reaction of diethyl oxalate that accounts for these simultaneous reactions: 4 C 6 H 10 O 4 + 6 H 2 O → 13 CH 4 + 11 CO 2 On average, about half of the volumetric concentration of landfill gas is CH 4 and slightly less than half

6042-514: The alarming growth rate of landfills and poor management by authorities. On and under surface fires have been commonly seen in the Indian landfills over the last few years. Landfilling practices in the UK have had to change in recent years to meet the challenges of the European Landfill Directive . The UK now imposes landfill tax upon biodegradable waste which is put into landfills. In addition to this

6148-572: The ash is produced either as a very fine dry fly ash or as a black colored fly ash slurry. Some fuels, in particular certain types of biomasses, can form slag that is corrosive for ceramic inner walls that serve to protect the gasifier outer wall. However some entrained flow type of gasifiers do not possess a ceramic inner wall but have an inner water or steam cooled wall covered with partially solidified slag. These types of gasifiers do not suffer from corrosive slags. Some fuels have ashes with very high ash fusion temperatures. In this case mostly limestone

6254-419: The ash. In some gasification processes (slagging gasification) this ash has the form of a glassy solid with low leaching properties, but the net power production in slagging gasification is low (sometimes negative) and costs are higher. Regardless of the final fuel form, gasification itself and subsequent processing neither directly emits nor traps greenhouse gases such as carbon dioxide. Power consumption in

6360-510: The atmosphere through photosynthesis, no new carbon enters the carbon cycle and the atmospheric concentration of CO 2 is not affected. Carbon dioxide traps heat in the atmosphere, contributing to climate change . In properly managed landfills, gas is collected and flared or recovered for landfill gas utilization . Poorly run landfills may become nuisances because of vectors such as rats and flies which can spread infectious diseases . The occurrence of such vectors can be mitigated through

6466-539: The basic lime scrubbers, any acids that might be in the smoke are neutralized which prevents the acid from reaching the atmosphere and hurting the environment. Many other devices, such as fabric filters, reactors, and catalysts destroy or capture other regulated pollutants. According to the New York Times, modern incineration plants are so clean that "many times more dioxin is now released from home fireplaces and backyard barbecues than from incineration". According to

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6572-571: The claims of project proponents did not withstand public and governmental scrutiny of key claims," according to the Global Alliance for Incinerator Alternatives. One facility which operated from 2009–2011 in Ottawa had 29 "emissions incidents" and 13 "spills" over those three years. It was also only able to operate roughly 25% of the time. Several waste gasification processes have been proposed, but few have yet been built and tested, and only

6678-536: The combined process self-sustaining. In thermal WtE technologies, nearly all of the carbon content in the waste is emitted as carbon dioxide (CO 2 ) to the atmosphere (when including final combustion of the products from pyrolysis and gasification; except when producing biochar for fertilizer). Municipal solid waste (MSW) contain approximately the same mass fraction of carbon as CO 2 itself (27%), so treatment of 1 metric ton (1.1 short tons) of MSW produce approximately 1 metric ton (1.1 short tons) of CO 2 . In

6784-442: The community. According to a 2019 United Nations Environment Programme report, there are 589 WtE plants in Europe and 82 in the United States. The following are some examples of WtE plants. A single plant is currently under construction: The US Air Force once tested a Transportable Plasma Waste to Energy System (TPWES) facility (PyroGenesis technology) at Hurlburt Field, Florida. The plant, which cost $ 7.4 million to construct,

6890-418: 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. The term landfill is usually shorthand for a municipal landfill or sanitary landfill. These facilities were first introduced early in

6996-461: The contribution of carbon capture and storage . Power generation using plastic waste will significantly increase by 2050. Carbon must be separated during energy recovery processes. Otherwise, the fight against global warming would fail due to plastic waste. MSW to a large extent is of biological origin (biogenic), e.g. paper, cardboard, wood, cloth, food scraps. Typically half of the energy content in MSW

7102-415: The converted fuel, thereby allowing higher combustion temperatures in e.g. boilers , gas turbines , internal combustion engines , fuel cells . Some advanced technologies are able to efficiently convert the energy in the feedstocks into liquid or gaseous fuels, using heat but in the absence of oxygen, without actual combustion, by using a combination of thermal technologies. Typically, they are cleaner, as

7208-424: The counter-current type, but the gasification agent gas flows in co-current configuration with the fuel (downwards, hence the name "down draft gasifier"). Heat needs to be added to the upper part of the bed, either by combusting small amounts of the fuel or from external heat sources. The produced gas leaves the gasifier at a high temperature, and most of this heat is often transferred to the gasification agent added in

7314-478: The end of the 19th century when it was replaced with electrical lighting. Gasification and syngas continued to be used in blast furnaces and more significantly in the production of synthetic chemicals where it has been in use since the 1920s. The thousands of sites left toxic residue. Some sites have been remediated, while others are still polluted. During both world wars , especially the World War II ,

7420-593: The engines may be used for e.g. driving water pumps for irrigation or for coupling with an alternator for electrical power generation. While small scale gasifiers have existed for well over 100 years, there have been few sources to obtain a ready-to-use machine. Small scale devices are typically DIY projects. However, currently in the United States, several companies offer gasifiers to operate small engines. In principle, gasification can proceed from just about any organic material, including biomass and plastic waste . The resulting syngas can be combusted. Alternatively, if

7526-485: The event that the waste was landfilled , 1 metric ton (1.1 short tons) of MSW would produce approximately 62 cubic metres (2,200 cu ft) methane via the anaerobic decomposition of the biodegradable part of the waste. This amount of methane has more than twice the global warming potential than the 1 metric ton (1.1 short tons) of CO 2 , which would have been produced by combustion. In some countries, large amounts of landfill gas are collected. However, there

7632-458: The feedstock is separated prior to treatment to remove the unwanted components: Thermal treatment technologies include: Non-thermal technologies: During the 2001–2007 period, the waste-to-energy capacity increased by about four million metric tons per year. Japan and China each built several plants based on direct smelting or on fluidized bed combustion of solid waste. In China there were about 434 waste-to-energy plants in early 2016. Japan

7738-406: The fermentation process, the sugar in the waste is converted to carbon dioxide and alcohol, in the same general process that is used to make wine. Normally fermentation occurs with no air present. Esterification can also be done using waste-to-energy technologies, and the result of this process is biodiesel . The cost-effectiveness of esterification will depend on the feedstock being used, and all

7844-551: The fuel must be highly reactive; low-grade coals are particularly suitable. The agglomerating gasifiers have slightly higher temperatures, and are suitable for higher rank coals. Fuel throughput is higher than for the fixed bed, but not as high as for the entrained flow gasifier. The conversion efficiency can be rather low due to elutriation of carbonaceous material. Recycle or subsequent combustion of solids can be used to increase conversion. Fluidized bed gasifiers are most useful for fuels that form highly corrosive ash that would damage

7950-444: The gasification and syngas conversion processes may be significant though, and may indirectly cause CO 2 emissions; in slagging and plasma gasification, the electricity consumption may even exceed any power production from the syngas. Combustion of syngas or derived fuels emits exactly the same amount of carbon dioxide as would have been emitted from direct combustion of the initial fuel. Biomass gasification and combustion could play

8056-436: The ground around landfills must be tested for leachate to prevent pollutants from contaminating groundwater . Rotting food and other decaying organic waste create decomposition gases , especially CO 2 and CH 4 from aerobic and anaerobic decomposition, respectively. Both processes occur simultaneously in different parts of a landfill. In addition to available O 2 , the fraction of gas constituents will vary, depending on

8162-525: The ground during an earthquake . Once full, the area over a landfill site may be reclaimed for other uses. Operators of well-run landfills for non-hazardous waste meet predefined specifications by applying techniques to: They can also cover waste (usually daily) with layers of soil or other types of material such as woodchips and fine particles. During landfill operations, a scale or weighbridge may weigh waste collection vehicles on arrival and personnel may inspect loads for wastes that do not accord with

8268-420: The highest amount of electricity with the highest capacity to lessen pile of wastes in landfills through direct combustion. One process that is used to convert plastic into fuel is pyrolysis , the thermal decomposition of materials at high temperatures in an inert atmosphere. It involves change of chemical composition and is mainly used for treatment of organic materials. In large scale production, plastic waste

8374-670: The information they look for when considering such proposals. A 2019 report commissioned by the Global Alliance for Incinerator Alternatives (GAIA), done by the Tishman Environment and Design Center at The New School , found that 79% of the then 73 operating waste-to-energy facilities in the U.S. are located in low-income communities and/or "communities of color", because "of historic residential, racial segregation and expulsive zoning laws that allowed whiter, wealthier communities to exclude industrial uses and people of color from their boundaries." In Chester, Pennsylvania , where

8480-427: The landfill bioreactor strata gradually decreases. Microbial populations grow, density increases. Aerobic biodegradation dominates, i.e. the primary electron acceptor is O 2 . The O 2 is rapidly degraded by the existing microbial populations. The decreasing O 2 leads to less aerobic and more anaerobic conditions in the layers. The primary electron acceptors during transition are nitrates and sulphates since O 2

8586-469: The landfill can be significant and can be mitigated by wheel washing systems . Pollution of the local environment , such as contamination of groundwater or aquifers or soil contamination may occur, as well. When precipitation falls on open landfills, water percolates through the garbage and becomes contaminated with suspended and dissolved material, forming leachate. If this is not contained it can contaminate groundwater. All modern landfill sites use

8692-451: 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 can spread and compact the waste on the working face. Before leaving the landfill boundaries, the waste collection vehicles may pass through a wheel-cleaning facility. If necessary, they return to

8798-613: The last growing season. If these plants are regrown the CO 2 emitted from their combustion will be taken out from the atmosphere once more. Such considerations are the main reason why several countries administrate WtE of the biomass part of waste as renewable energy . The rest—mainly plastics and other oil and gas derived products—is generally treated as non-renewables . The CO 2 emissions from plastic waste-to-energy systems are higher than those from current fossil fuel-based power systems per unit of power generated, even after considering

8904-459: The leachate. The acid formation phase intermediary products (e.g., acetic, propionic, and butyric acids) are converted to CH 4 and CO 2 by methanogenic microorganisms. As VFAs are metabolized by the methanogens, the landfill water pH returns to neutrality. The leachate's organic strength, expressed as oxygen demand, decreases at a rapid rate with increases in CH 4 and CO 2 gas production. This

9010-455: The need for fuel produced by gasification reemerged due to the shortage of petroleum. Wood gas generators , called Gasogene or Gazogène, were used to power motor vehicles in Europe . By 1945 there were trucks, buses and agricultural machines that were powered by gasification. It is estimated that there were close to 9,000,000 vehicles running on producer gas all over the world. Another example,

9116-646: The one commissioned by the Renewable Energy Association in the UK, have been published that demonstrate how the carbon 14 result can be used to calculate the biomass calorific value. The UK gas and electricity markets authority, Ofgem , released a statement in 2011 accepting the use of Carbon 14 as a way to determine the biomass energy content of waste feedstock under their administration of the Renewables Obligation. Their Fuel Measurement and Sampling (FMS) questionnaire describes

9222-412: The other relevant factors such as transportation distance, amount of oil present in the feedstock, and others. Gasification and pyrolysis by now can reach gross thermal conversion efficiencies (fuel to gas) up to 75%, however, a complete combustion is superior in terms of fuel conversion efficiency. Some pyrolysis processes need an outside heat source which may be supplied by the gasification process, making

9328-422: The plants, so that it is not necessary to close down the plant every few months for cleaning the reactor. Environmental advocates have called gasification "incineration in disguise" and argue that the technology is still dangerous to air quality and public health. "Since 2003 numerous proposals for waste treatment facilities hoping to use... gasification technologies failed to receive final approval to operate when

9434-408: The propane yield is approximately 80%. There are a number of other new and emerging technologies that are able to produce energy from waste and other fuels without direct combustion. Many of these technologies have the potential to produce more electric power from the same amount of fuel than would be possible by direct combustion. This is mainly due to the separation of corrosive components (ash) from

9540-444: The reactor. In the gasification of fine, undensified biomass such as rice hulls , it is necessary to blow air into the reactor by means of a fan. This creates very high gasification temperature, as high as 1000 C. Above the gasification zone, a bed of fine and hot char is formed, and as the gas is blow forced through this bed, most complex hydrocarbons are broken down into simple components of hydrogen and carbon monoxide. Similar to

9646-562: The same results. Carbon 14 dating can determine with precision the biomass fraction of waste, and also determine the biomass calorific value . Determining the calorific value is important for green certificate programs such as the Renewable Obligation Certificate program in the United Kingdom. These programs award certificates based on the energy produced from biomass. Several research papers, including

9752-477: The syngas is clean enough, it may be used for power production in gas engines, gas turbines or even fuel cells, or converted efficiently to dimethyl ether (DME) by methanol dehydration, methane via the Sabatier reaction , or diesel-like synthetic fuel via the Fischer–Tropsch process . In many gasification processes most of the inorganic components of the input material, such as metals and minerals, are retained in

9858-461: The syngas produced by most gasification systems requires additional processing and reforming to remove the contaminants and other gases such as CO and CO 2 to be suitable for low-temperature fuel cell use, but high-temperature solid oxide fuel cells are capable of directly accepting mixtures of H 2 , CO, CO 2 , steam, and methane. Syngas is most commonly burned directly in gas engines , used to produce methanol and hydrogen, or converted via

9964-406: The top of the bed, resulting in an energy efficiency on level with the counter-current type. Since all tars must pass through a hot bed of char in this configuration, tar levels are much lower than the counter-current type. The fuel is fluidized in oxygen and steam or air. The ash is removed dry or as heavy agglomerates that defluidize. The temperatures are relatively low in dry ash gasifiers, so

10070-531: The troposphere. This transforms the oxidation–reduction potential (ORP) in the leachate toward oxidative processes. The residual organic materials may incrementally be converted to the gas phase, and as organic matter is composted; i.e. the organic matter is converted to humic -like compounds. Landfills have the potential to cause a number of issues. Infrastructure disruption, such as damage to access roads by heavy vehicles, may occur. Pollution of local roads and watercourses from wheels on vehicles when they leave

10176-432: The use of daily cover . Other potential issues include wildlife disruption due to occupation of habitat and animal health disruption caused by consuming waste from landfills, dust, odor, noise pollution , and reduced local property values. Gases are produced in landfills due to the anaerobic digestion by microbes. In a properly managed landfill, this gas is collected and used. Its uses range from simple flaring to

10282-654: The volume of the original waste by 95-96 percent, depending upon composition and degree of recovery of materials such as metals from the ash for recycling. Incinerators may emit fine particulate , heavy metals, trace dioxin and acid gas , even though these emissions are relatively low from modern incinerators. Other concerns include proper management of residues: toxic fly ash , which must be handled in hazardous waste disposal installation as well as incinerator bottom ash (IBA), which must be reused properly. Critics argue that incinerators destroy valuable resources and they may reduce incentives for recycling. The question, however,

10388-597: The walls of slagging gasifiers. Biomass fuels generally contain high levels of corrosive ash. Fluidized bed gasifiers uses inert bed material at a fluidized state which enhance the heat and biomass distribution inside a gasifier. At a fluidized state, the superficial fluid velocity is greater than the minimum fluidization velocity required to lift the bed material against the weight of the bed. Fluidized bed gasifiers are divided into Bubbling Fluidized Bed (BFB), Circulating Fluidized Bed (CFB) and Dual Fluidized Bed (DFB) gasifiers. A dry pulverized solid, an atomized liquid fuel or

10494-404: The waste depend on how well microbial populations function in syntrophy , i.e. an interaction of different populations to provide each other's nutritional needs.: The life cycle of a municipal landfill undergoes five distinct phases: As the waste is placed in the landfill, the void spaces contain high volumes of molecular oxygen (O 2 ). With added and compacted wastes, the O 2 content of

10600-435: The waste remaining in solid and liquid phases. During the early phases, little material volume reaches the leachate , as the biodegradable organic matter of the waste undergoes a rapid decrease in volume. Meanwhile, the leachate's chemical oxygen demand increases with increasing concentrations of the more recalcitrant compounds compared to the more reactive compounds in the leachate. Successful conversion and stabilization of

10706-416: The weighbridge for re-weighing without their load. The weighing process can assemble statistics on the daily incoming waste tonnage, which databases can retain for record keeping. In addition to trucks, some landfills may have equipment 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

10812-399: The working face, the compacted waste is covered with soil or alternative materials daily. Alternative waste-cover materials include 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 and then removed the following day prior to waste placement. The space that is occupied daily by

10918-549: Was closed and sold at a government liquidation auction in May 2013, less than three years after its commissioning. The opening bid was $ 25. The winning bid was sealed. Besides large plants, domestic waste-to-energy incinerators also exist. For example, the Refuge de Sarenne has a domestic waste-to-energy plant. It is made by combining a wood-fired gasification boiler with a Stirling motor . Renergi will scale up their system of converting waste organic materials into liquid fuels using

11024-536: Was designed to demonstrate gasification of specific non-MSW waste streams using liquid metal gasification . This facility came after widespread public opposition shelved plans for a similar plant in Attleboro, Massachusetts . Today Ze-gen appears to be defunct, and the company website was taken down in 2014. Also in the US, in 2011 a plasma system delivered by PyroGenesis Canada Inc. was tested to gasify municipal solid waste, hazardous waste and biomedical waste at

11130-411: Was published in 2010. Since each method suffered from limitations in properly characterizing the biomass fraction, two alternative methods have been developed. The first method uses the principles of radiocarbon dating . A technical review (CEN/TR 15591:2007) outlining the carbon 14 method was published in 2007. A technical standard of the carbon dating method (CEN/TS 15747:2008) is published in 2008. In

11236-492: Was the first such plant in Africa. The plant became operational in 2018. Gasification An advantage of gasification is that syngas can be more efficient than direct combustion of the original feedstock material because it can be combusted at higher temperatures so that the thermodynamic upper limit to the efficiency defined by Carnot's rule is higher. Syngas may also be used as the hydrogen source in fuel cells, however

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