Waste-to-energy - AbsoluteAstronomy.com

Waste-to-energy or energy-from-waste (EfW) is the process of creating energy in the form of electricity

Electricity

Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

or heat

Heat

In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

from the incineration of waste source

Waste types

Waste comes in many different forms:*Solid Wastes*Gaseous Wastes*Animal by-products*Biodegradable waste*Biomedical waste*Bulky waste*Business waste*Chemical waste*Clinical waste*Coffee wastewater*Commercial waste...

. WtE is a form of energy recovery

Energy recovery

Energy recovery includes any technique or method of minimizing the input of energy to an overall system by the exchange of energy from one sub-system of the overall system with another...

. Most WtE processes produce electricity directly through combustion, or produce a combustible fuel commodity, such as methane

Methane

Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, methanol

Methanol

Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

, ethanol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

or synthetic fuels.

Incineration

Incineration, the combustion of organic material such as waste with energy recovery is the most common WtE implementation. Incineration may also be implemented without energy and materials recovery; however, this is increasingly being banned in OECD (Organisation for Economic Co-operation and Development) countries. Furthermore, all new WtE plants in OECD countries must meet strict emission standards. Hence, modern incineration plants are vastly different from the old types, some of which neither recovered energy nor materials. Modern incinerators reduce the volume of the original waste by 95-96 %, depending upon composition and degree of recovery of materials such as metals from the ash for recycling.

Concerns regarding the operation of incinerators include fine particulate, heavy metals, trace dioxin and acid gas emissions, even though these emissions are relatively low from modern incinerators. Other concerns include toxic fly ash

Fly ash

Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal...

and incinerator bottom ash

Incinerator bottom ash

Incinerator bottom ash is a form of ash produced in incineration facilities. This material is discharged from the moving grate of municipal solid waste incinerators. Following combustion the ash typically has a small amount of ferrous metals contained within it. This ash can be processed to...

(IBA) management. Discussions regarding waste resource ethics include the opinion that incinerators destroy valuable resources and the fear that they may reduce the incentives for recycling and waste minimization activities. . This is open to question, however, as the Refuse Derived Fuel (RDF) is produced by recycling centres (MRFs), who make their money from selling on recoverable material, and the name Residue Derived Fuel even suggests that it's made from what's left over, not the materials being pulled out. It is not in the interests of the MRF operators to give away for free the very materials they could otherwise sell. Incinerators have electric efficiencies on the order of 14-28%. The rest of the energy can be utilized for e.g. district heating

District heating

District heating is a system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating...

, but is otherwise lost as waste heat.

The method of using incineration to convert municipal solid waste

Municipal solid waste

Municipal solid waste , commonly known as trash or garbage , refuse or rubbish is a waste type consisting of everyday items we consume and discard. It predominantly includes food wastes, yard wastes, containers and product packaging, and other miscellaneous inorganic wastes from residential,...

(MSW) to energy is a relatively old method of waste-to-energy production. Incineration generally entails burning an RDF to boil water which powers steam generators that make electric energy to be used in our homes and businesses. One problem associated with incinerating MSW to make electrical energy, is the potential for pollutants to enter the atmosphere when utilising the fuel to power the generators. These pollutants can be acidic and in the 1980s were reported to cause environmental damage by turning rain into acid rain. Since then, the industry has removed this problem by the use of lime scrubbers and electro-static precipitators on smokestacks. The limestone mineral used in these scrubbers has a pH of approximately 8 which means it is a base. By passing the smoke through the lime scrubbers, any acids that may be in the smoke are neutralized which prevents the acid from reaching the atmosphere and hurting our environment. (Field) 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. "

WtE technologies other than incineration

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 the converted fuel, thereby allowing higher combustion temperatures in e.g. boiler

Boiler

A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...

s, gas turbine

Gas turbine

A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

s, internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s, fuel cell

Fuel cell

A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...

s. Some are able to efficiently convert the energy into liquid or gaseous fuels:

Thermal technologies

Thermal treatment

Thermal treatment is a term given to any waste treatment technology that involves high temperatures in the processing of the waste feedstock. This commonly, although not exclusively involves the combustion of waste materials....

Gasification
Gasification
Gasification is a process that converts organic or fossil based carbonaceous materials into carbon monoxide, hydrogen, carbon dioxide and methane. This is achieved by reacting the material at high temperatures , without combustion, with a controlled amount of oxygen and/or steam...

(produces combustible gas, hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

, synthetic fuel
Synthetic fuel
Synthetic fuel or synfuel is a liquid fuel obtained from coal, natural gas, oil shale, or biomass. It may also refer to fuels derived from other solids such as plastics or rubber waste. It may also refer to gaseous fuels produced in a similar way...

s)
Thermal depolymerization
Thermal depolymerization
Thermal depolymerization is a depolymerization process using hydrous pyrolysis for the reduction of complex organic materials into light crude oil. It mimics the natural geological processes thought to be involved in the production of fossil fuels...

(produces synthetic crude oil, which can be further refined)
Pyrolysis
Pyrolysis
Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...

(produces combustible tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...

/biooil and char
Char
Char is the solid material that remains after light gases and tar coal tar have been driven out or released from a carbonaceous material during the initial stage of combustion, which is known as carbonization, charring, devolatilization or pyrolysis.Further stages of efficient combustion are...

s)
Plasma arc gasification PGP or plasma gasification process (produces rich syngas
Syngas
Syngas is the name given to a gas mixture that contains varying amounts of carbon monoxide and hydrogen. Examples of production methods include steam reforming of natural gas or liquid hydrocarbons to produce hydrogen, the gasification of coal, biomass, and in some types of waste-to-energy...

including hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

and carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

usable for fuel cells or generating electricity to drive the plasma arch, usable vitrified silicate and metal ingots, salt and sulphur)

Non-thermal technologies:

Anaerobic digestion
Anaerobic digestion
Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is used for industrial or domestic purposes to manage waste and/or to release energy....

(Biogas
Biogas
Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal dung, and kitchen waste can be converted into a gaseous fuel called biogas...

rich in methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

)
Fermentation
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...

production (examples are ethanol, lactic acid, hydrogen)
Mechanical biological treatment
Mechanical biological treatment
A mechanical biological treatment system is a type of waste processing facility that combines a sorting facility with a form of biological treatment such as composting or anaerobic digestion...

(MBT)
- MBT + Anaerobic digestion
  Anaerobic digestion
  Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is used for industrial or domestic purposes to manage waste and/or to release energy....
- MBT to Refuse derived fuel

Global WTE developments

During the 2001-2007 period, the WTE capacity increased by about four million metric tons per annum.
Japan and China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

built several plants that were based on direct smelting or on fluid bed combustion of solid waste. In China

China

there are about 50 WTE plants. Japan is the largest user in thermal treatment of MSW in the world with 40 million tons.
Some of the newest plants use stoker technology and others use the advanced oxygen enrichment technology. There are also over one hundred thermal treatment plants using relatively novel processes such as direct smelting, the Ebara fluidization process and the Thermo- select -JFE gasification and melting technology process. In Patras, Greece, a Greek company just finished testing a system that shows potential. It generates 25kwatts of electricity and 25kwatts of heat from waste water. In India its first energy bio-science center was developed to reduce the country’s green house gases and its dependency on fossil fuel.

Global Group Consulting Services, LLC, with headquarters in Miami, FL (USA) and branches throughout Latin America

Latin America

Latin America is a region of the Americas where Romance languages – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

and the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

has focused a significant part of their practice in promoting Green Solutions in Latin America. Their goal is to implement proven Waste to Energy (WTE) technologies that will complement or solve Municipal Solid Waste needs in small to midsize cities. With representation of various technologies, coupled with funding sources they seek to provide solutions that will empower local communities with education, jobs as well as a healthier environments.

Biofuel Energy Corporation of Denver, CO, opened two new biofuel plants in Wood River, NE, and Fairmont, MN, 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 incorporated located in Pleasanton, CA, is currently building a WTE plant near Reno, NV. The plant is scheduled to open in early 2010 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 90,000 tons per year of MSW.(Biofuels News)

Waste to energy technology includes fermentation, which can take biomass and create ethanol, using waste cellulosic or organic material. In the fermentation process, the sugar in the waste is changed 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 the other relevant factors such as transportation distance, amount of oil present in the feedstock, and others.
Gasification and pyrolysis by now can reach thermal conversion efficiencies from of 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 the combined process self sustaining.

Carbon dioxide emissions

In thermal WtE technologies, nearly all of the carbon content in the waste is emitted as carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

to the atmosphere (when including final combustion of the products from pyrolysis and gasification; except when producing bio-char for fertilizer). Municipal solid waste (MSW

Municipal solid waste

) contain approximately the same mass fraction of carbon as itself (27%), so treatment of 1 metric ton of MSW produce approximately 1 metric ton of .

In the event that the waste was landfill

Landfill

A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...

ed, 1 metric ton of MSW would produce approximately 62 cubic metres (2,189.5 cu ft) methane

Methane

via the anaerobic decomposition of the biodegradable

Biodegradable waste

Biodegradable waste is a type of waste, typically originating from plant or animal sources, which may be degraded by other living organisms. Waste that cannot be broken down by other living organisms are called non-biodegradable....

part of the waste. This amount of methane has more than twice the global warming potential

Global warming potential

Global-warming potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time...

than the 1 metric ton of , which would have been produced by combustion. In some countries, large amounts of landfill gas

Landfill gas

Landfill gas is a complex mix of different gases created by the action of microorganisms within a landfill.-Production:Landfill gas production results from chemical reactions and microbes acting upon the waste as the putrescible materials begins to break down in the landfill...

are collected, but still the global warming potential of the landfill gas emitted to atmosphere in e.g. the US in 1999 was approximately 32 % higher than the amount of that would have been emitted by combustion.

In addition, nearly all biodegradable waste is biomass

Biomass

Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

. That is, it has biological origin. This material has been formed by plants using atmospheric typically within the last growing season. If these plants are regrown the 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

Renewable energy

Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...

. The rest—mainly plastics and other oil and gas derived products—is generally treated as non-renewables

Non-renewable resources

A non-renewable resource is a natural resource which cannot be produced, grown, generated, or used on a scale which can sustain its consumption rate, once depleted there is no more available for future needs. Also considered non-renewable are resources that are consumed much faster than nature...

Determination of the biomass fraction

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 has been recently published. 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

Radiocarbon dating

Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...

. 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) will be published in 2008. In 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 incinerators.

A comparison between both methods carried out at three full-scale incinerators in Switzerland showed that both methods came to 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 the one commissioned by the Renewable Energy Association

Renewable Energy Association

The Renewable Energy Association is the main trade association for the renewables industry in the UK.-History:It was formed in 2001 as the Renewable Power Association, changing to its current name in October 2005. The organisation used to be based on Waterloo Place.-Structure:It is the largest, by...

in the UK, have been published that demonstrate how the carbon 14 result can be used to calculate the biomass calorific value.

Examples of waste-to-energy plants

According to ISWA there are 431 WtE plants in Europe (2005) and 89 in the United States (2004). The following are some examples of WtE plants.

Waste incineration

Incineration

Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration and other high temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas, and...

WtE plants:

Montgomery County Resource Recovery Facility in Dickerson, Maryland
Dickerson, Maryland
Dickerson is an unincorporated area in Montgomery County, Maryland. It is located on Maryland Route 28, between Sugarloaf Mountain and the Potomac River. It is a community situated near the town of Poolesville, Maryland. Dickerson is .-History of Dickerson:...

, USA (1995)
Spittelau (1971), and Flötzersteig (1963), Vienna, Austria (Wien Energie)
SYSAV in Malmö (2003 and 2008), Sweden (Flash presentation)
Algonquin Power
Algonquin Power
Algonquin Power and Utilities Corp , owns power generation assets in Canada and the United States. The company also owns water distribution systems in the United States.-Assets:...

, Brampton, Ontario, Canada
Teesside EfW plant near Middlesbrough
Middlesbrough
Middlesbrough is a large town situated on the south bank of the River Tees in north east England, that sits within the ceremonial county of North Yorkshire...

, North East England
North East England
North East England is one of the nine official regions of England. It covers Northumberland, County Durham, Tyne and Wear, and Teesside . The only cities in the region are Durham, Newcastle upon Tyne and Sunderland...

(1998)
Edmonton Incinerator
Edmonton Incinerator
Edmonton Incinerator is a municipal waste incinerator and waste-to-energy power station which burns London's waste to provide electricity for the National Grid...

in Greater London
Greater London
Greater London is the top-level administrative division of England covering London. It was created in 1965 and spans the City of London, including Middle Temple and Inner Temple, and the 32 London boroughs. This territory is coterminate with the London Government Office Region and the London...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

(1974)

Liquid fuel producing plants (planned or under construction)

Edmonton Waste-to-ethanol Facility, Enerkem-process, fueled by RDF
Refuse-derived fuel
Refuse-derived fuel or solid recovered fuel/ specified recovered fuel is a fuel produced by shredding and dehydrating solid waste with a Waste converter technology. RDF consists largely of combustible components of municipal waste such as plastics and biodegradable waste...

, scheduled for completion 2012, Edmonton, Alberta, Canada.
Mississippi Waste-to-ethanol Plant, Enerkem-process, scheduled for completion 2013, Pontotoc, Mississippi
Pontotoc, Mississippi
Pontotoc is a city in Pontotoc County, Mississippi, United States. Pontotoc is west of the much larger city of Tupelo. The population was 5,625 at the 2010 census...

, USA.

Plasma Gasification Waste-to-Energy plants:

• The US Air Force Transportable Plasma Waste to Energy System (TPWES) facility (PyroGenesis technology) at Hurlburt Field, Florida.

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Incineration

WtE technologies other than incineration

Global WTE developments

Carbon dioxide emissions

Determination of the biomass fraction

Examples of waste-to-energy plants

See also

Further reading

External links