![Pellets hand](https://upload.wikimedia.org/wikipedia/commons/0/0c/Pellets_hand.jpg)
Pellet fuels (or pellets) are
biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
s made from compressed organic matter or biomass. Pellets can be made from any one of five general categories of biomass: industrial waste and co-products,
food waste
Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...
,
agricultural residues
Crop residues are materials left in an agricultural field after the crop has been harvested. These residues include stalks and stubble (stems), leaves and seed pods. Good management of field residues can increase efficiency of irrigation and c ...
,
energy crop
Energy crops are low-cost and low-maintenance crops grown solely for energy production by combustion (not for food). The crops are processed into solid, liquid or gaseous fuels, such as pellets, bioethanol or biogas. The fuels are burned to g ...
s, and
untreated lumber. Wood pellets are the most common type of pellet fuel and are generally made from compacted
sawdust
Sawdust (or wood dust) is a by-product or waste product of woodworking operations such as sawing, sanding, milling, planing, and routing. It is composed of small chippings of wood. These operations can be performed by woodworking machinery, ...
and related industrial wastes from the
mill
Mill may refer to:
Science and technology
*
* Mill (grinding)
* Milling (machining)
* Millwork
* Textile mill
* Steel mill, a factory for the manufacture of steel
* List of types of mill
* Mill, the arithmetic unit of the Analytical Engine early ...
ing of lumber, manufacture of
wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
products and
furniture
Furniture refers to movable objects intended to support various human activities such as seating (e.g., stools, chairs, and sofas), eating (tables), storing items, eating and/or working with an item, and sleeping (e.g., beds and hammocks). Fu ...
, and
construction
Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and com ...
. Other industrial waste sources include empty fruit bunches,
palm kernel
The palm kernel is the edible seed of the oil palm fruit. The fruit yields two distinct oils: palm oil derived from the outer parts of the fruit, and palm kernel oil derived from the kernel.
The pulp left after oil is rendered from the kernel is ...
shells,
coconut
The coconut tree (''Cocos nucifera'') is a member of the palm tree family ( Arecaceae) and the only living species of the genus ''Cocos''. The term "coconut" (or the archaic "cocoanut") can refer to the whole coconut palm, the seed, or the ...
shells, and tree tops and branches discarded during
logging
Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars.
Logging is the beginning of a supply chain ...
operations. So-called "black pellets" are made of
biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
, refined to resemble hard
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
and were developed to be used in existing coal-fired
power plants
A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.
Many pow ...
. Pellets are categorized by their
heating value
The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it.
The ''calorific value'' is the total energy relea ...
,
moisture
Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...
and
ash
Ash or ashes are the solid remnants of fires. Specifically, ''ash'' refers to all non-aqueous, non- gaseous residues that remain after something burns. In analytical chemistry, to analyse the mineral and metal content of chemical samples, ash ...
content, and dimensions. They can be used as fuels for power generation, commercial or residential heating, and
cooking
Cooking, cookery, or culinary arts is the art, science and craft of using heat to Outline of food preparation, prepare food for consumption. Cooking techniques and ingredients vary widely, from grilling food over an open fire to using electric ...
.
Pellets are extremely dense and can be produced with a low moisture content (below 10%) that allows them to be burned with a very high combustion
efficiency
Efficiency is the often measurable ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without ...
.
Further, their regular geometry and small size allow automatic feeding with very fine calibration. They can be fed to a burner by
auger
Auger may refer to:
Engineering
* Wood auger, a drill for making holes in wood (or in the ground)
** Auger bit, a drill bit
* Auger conveyor, a device for moving material by means of a rotating helical flighting
* Auger (platform), the world's f ...
feeding or by
pneumatic
Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air.
Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...
conveying. Their high density also permits compact storage and transport over long distance. They can be conveniently blown from a tanker to a storage bunker or silo on a customer's premises.
A broad range of
pellet stove
A pellet stove is a stove that burns compressed wood or biomass pellets to create a source of heat for residential and sometimes industrial spaces. By steadily feeding fuel from a storage container (hopper) into a burn pot area, it produces a con ...
s, central heating furnaces, and other heating appliances have been developed and marketed since the mid-1980s. In 1997 fully automatic wood
pellet boiler
A pellet boiler is a heating system that burns wood pellets. Pellet boilers are used in central heating systems for heat requirements (heating load) from 3.9 kW (kilowatt) to 1 MW (megawatt) or more. Pellet central heating systems are used i ...
s with similar comfort level as oil and gas boilers became available in
Austria
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
. With the surge in the price of
fossil fuel
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
s since 2005, the demand for pellet heating has increased in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
and
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, and a sizable industry is emerging. According to the
International Energy Agency
The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organisation, established in 1974, that provides policy recommendations, analysis and data on the entire global energy sector, with a recent focus on curbing carb ...
Task 40, wood pellet production has more than doubled between 2006 and 2010 to over 14 million tons.
In a 2012 report, the Biomass Energy Resource Center says that it expects wood pellet production in North America to double again in the next five years.
Production
![8](https://upload.wikimedia.org/wikipedia/commons/d/df/8._Station_-_Holzpelletproduktion_der_WestPellets_GmbH_and_Co._KG_%286219816410%29.jpg)
Pellets are produced by compressing the wood material which has first passed through a
hammer mill
A hammer mill, hammer forge or hammer works was a workshop in the pre- industrial era that was typically used to manufacture semi-finished, wrought iron products or, sometimes, finished agricultural or mining tools, or military weapons. The feat ...
to provide a uniform dough-like mass. This mass is fed to a press, where it is squeezed through a die having holes of the size required (normally 6 mm diameter, sometimes 8 mm or larger). The high pressure of the press causes the temperature of the wood to increase greatly, and the
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
plasticizes slightly, forming a natural "glue" that holds the pellet together as it cools.
Pellets can be made from
grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...
and other non-woody forms of biomass that do not contain lignin. A 2005 news story from
Cornell University
Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to teach an ...
News suggested that grass pellet production was more advanced in Europe than North America. It suggested the benefits of grass as a feedstock included its short growing time (70 days), and ease of cultivation and processing. The story quoted Jerry Cherney, an agriculture professor at the school, stating that grasses produce 96% of the heat of wood and that "any mixture of grasses can be used, cut in mid- to late summer, left in the field to leach out minerals, then baled and pelleted. Drying of the hay is not required for pelleting, making the cost of processing less than with wood pelleting." In 2012, the Department of Agriculture of
Nova Scotia
Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland".
Most of the population are native Eng ...
announced as a demonstration project conversion of an oil-fired
boiler
A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central h ...
to grass pellets at a research facility.
Rice-husk fuel-pellets are made by compacting rice-husk obtained as by-product of
rice
Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima
''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...
-growing from the fields. It also has similar characteristics to the wood-pellets and more
environment-friendly
Environment friendly processes, or environmental-friendly processes (also referred to as eco-friendly, nature-friendly, and green), are sustainability and marketing terms referring to goods and services, laws, guidelines and policies that clai ...
, as the raw material is a
waste-product. The
energy content
In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or .
Often only the ''useful'' or extrac ...
is about 4-4.2 kcal/kg and moisture content is typically less than 10%. The size of pellets is generally kept to be about 6 mm diameter and 25 mm length in the form of a cylinder; though larger cylinder or briquette forms are not uncommon. It is much cheaper than similar energy-pellets and can be compacted/manufactured from the husk at the farm itself, using cheap machinery. They generally are more environment-friendly as compared to wood-pellets. In the regions of the world where
wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
is the predominant food-crop, wheat husk can also be compacted to produce energy-pellets, with characteristics similar to rice-husk pellets.
A report by
CORRIM
The Consortium for Research on Renewable Industrial Materials (CORRIM) is a non-profit organization dedicated to developing life-cycle assessment (LCA) data related to wood-based materials and energy, and their alternatives.
Research results
In ...
(Consortium On Research on Renewable Industrial Material) for the Life-Cycle Inventory of Wood Pellet Manufacturing and Utilization estimates the energy required to dry, pelletize and transport pellets is less than 11% of the energy content of the pellets if using pre-dried industrial wood waste. If the pellets are made directly from forest material, it takes up to 18% of the energy to dry the wood and additional 8% for transportation and manufacturing energy. An
environmental impact assessment
Environmental Impact assessment (EIA) is the assessment of the environmental consequences of a plan, policy, program, or actual projects prior to the decision to move forward with the proposed action. In this context, the term "environmental imp ...
of exported wood pellets by the Department of Chemical and Mineral Engineering,
University of Bologna
The University of Bologna ( it, Alma Mater Studiorum – Università di Bologna, UNIBO) is a public research university in Bologna, Italy. Founded in 1088 by an organised guild of students (''studiorum''), it is the oldest university in continuo ...
,
Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...
and the Clean Energy Research Centre, at the
University of British Columbia
The University of British Columbia (UBC) is a public university, public research university with campuses near Vancouver and in Kelowna, British Columbia. Established in 1908, it is British Columbia's oldest university. The university ranks a ...
, published in 2009, concluded that the energy consumed to ship Canadian wood pellets from
Vancouver
Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the ...
to
Stockholm
Stockholm () is the Capital city, capital and List of urban areas in Sweden by population, largest city of Sweden as well as the List of urban areas in the Nordic countries, largest urban area in Scandinavia. Approximately 980,000 people liv ...
(15,500 km via the
Panama Canal
The Panama Canal ( es, Canal de Panamá, link=no) is an artificial waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean and divides North and South America. The canal cuts across the Isthmus of Panama and is a conduit ...
), is about 14% of the total energy content of the wood pellets.
Pellet standards
Pellets conforming to the norms commonly used in Europe (DIN 51731 or
Ö-Norm M-7135) have less than 10% water content, are uniform in
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
(higher than 1 ton per cubic meter, thus it sinks in water)(bulk density about 0.6-0.7 ton per cubic meter), have good structural strength, and low dust and ash content.
Because the wood fibres are broken down by the hammer mill, there is virtually no difference in the finished pellets between different wood types. Pellets can be made from nearly any wood variety, provided the pellet press is equipped with good instrumentation, the differences in feed material can be compensated for in the press regulation. In Europe, the main production areas are located in south
Scandinavia
Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...
,
Finland
Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...
,
Central Europe
Central Europe is an area of Europe between Western Europe and Eastern Europe, based on a common historical, social and cultural identity. The Thirty Years' War (1618–1648) between Catholicism and Protestantism significantly shaped the area' ...
,
Austria
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
, and the
Baltic
Baltic may refer to:
Peoples and languages
* Baltic languages, a subfamily of Indo-European languages, including Lithuanian, Latvian and extinct Old Prussian
*Balts (or Baltic peoples), ethnic groups speaking the Baltic languages and/or originati ...
countries.
Pellets conforming to the European standards norms which contain recycled wood or outside contaminants are considered Class B pellets.
Recycled materials
Recycling is the process of converting waste materials into new materials and objects. The Energy recycling, recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability t ...
such as particle board, treated or painted wood,
melamine resin
Melamine resin or melamine formaldehyde (also shortened to melamine) is a resin with melamine rings terminated with multiple hydroxyl groups derived from formaldehyde. This thermosetting plastic material is made from melamine and formaldehyde. ...
-coated panels and the like are particularly unsuitable for use in pellets, since they may produce noxious
emissions
Emission may refer to:
Chemical products
* Emission of air pollutants, notably:
**Flue gas, gas exiting to the atmosphere via a flue
** Exhaust gas, flue gas generated by fuel combustion
** Emission of greenhouse gases, which absorb and emit rad ...
and uncontrolled variations in the burning characteristics of the pellets.
Standards used in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
are different, developed by the
Pellet Fuels Institute Pellet Fuels Institute (PFI) is a North American trade organization that represents manufacturers, retailers and distributors of wood pellet fuel supplies and appliances. The PFI was formed in 1985 as the Fiber Fuels Institute.
Headquartered in ...
and, as in Europe, are not mandatory. Still, many manufacturers comply, as warranties of US-manufactured or imported combustion equipment may not cover damage by pellets non-conformant with regulations. Prices for US pellets surged during the
fossil fuel
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
price
inflation
In economics, inflation is an increase in the general price level of goods and services in an economy. When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation corresponds to a reductio ...
of 2007–2008, but later dropped markedly and are generally lower on a price per energy amount basis than most fossil fuels, excluding
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
.
Regulatory agencies in Europe and North America are in the process of tightening the emissions standards for all forms of wood heat, including wood pellets and pellet stoves. These standards will become mandatory, with independently certified testing to ensure compliance.
In the United States, the new rules initiated in 2009 have completed the
EPA
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
regulatory review process,
with final new rules issued for comment on June 24, 2014.
The
will be the independent certification agency for the new pellet standards.
Hazards
Wood pellets can emit large quantities of poisonous
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
during storage. Fatal accidents have taken place in private storerooms and onboard marine vessels.
When handled, wood pellets give off fine dust which can cause serious
dust explosions
A dust explosion is the rapid combustion of fine particles suspended in the air within an enclosed location. Dust explosions can occur where any dispersed powdered combustible material is present in high-enough concentrations in the atmosphere or ...
.
Wood pellets are typically stored in bulk in large silos. Pellets may self-heat, ignite and give rise to a deep-seated smoldering fire that is very difficult to extinguish. The smoldering fire produces toxic carbon monoxide and flammable
pyrolysis
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...
gases that can lead to silo explosions.
Pellet stove operation
There are three general types of pellet heating appliances: free standing pellet stoves, pellet stove inserts and
pellet boiler
A pellet boiler is a heating system that burns wood pellets. Pellet boilers are used in central heating systems for heat requirements (heating load) from 3.9 kW (kilowatt) to 1 MW (megawatt) or more. Pellet central heating systems are used i ...
s.
Pellet stoves work like modern
furnace
A furnace is a structure in which heat is produced with the help of combustion.
Furnace may also refer to:
Appliances Buildings
* Furnace (central heating): a furnace , or a heater or boiler , used to generate heat for buildings
* Boiler, used t ...
s, where fuel, wood, or other biomass pellets, is stored in a storage bin called a hopper. The hopper can be located on the top of the appliance, the side of it or remotely. A mechanical auger automatically feeds pellets into a burn pot. From there, they burn at high temperatures with minimal emissions. Heat-exchange tubes send air heated by fire into room. Convection fans circulate air through heat-exchange tubes and into room. Pellet stoves have circuit boards inside that act like a thermostat and to regulate temperature.
A pellet stove insert is a stove that is inserted into an existing masonry or prefabricated wood
fireplace
A fireplace or hearth is a structure made of brick, stone or metal designed to contain a fire. Fireplaces are used for the relaxing ambiance they create and for heating a room. Modern fireplaces vary in heat efficiency, depending on the design.
...
, similar to a
fireplace insert
Invented in 1896 by Joab R. Donaldson of Oliphant Furnace, Pennsylvania, US,Joab R. Donaldson (1896) "Fireplace" the fireplace insert is a device inserted into an existing masonry or prefabricated wood fireplace. Joab was a 59-year-old coal mine ...
.
Pellet boilers are standalone central heating and hot water systems designed to replace traditional fossil fuel systems in residential, commercial and institutional applications. Automatic or auto-pellet boilers include silos for bulk storage of pellets, a fuel delivery system that moves the fuel from the silo to the hopper, a logic controller to regulate temperature across multiple heating zones and an automated ash removal system for long-term automated operations.
Pellet baskets
A pellet basket is a small metal basket that sits inside a woodstove or fireplace and holds wood pellets. Pellet baskets allow a person to heat their home using existing stoves or fireplaces; thus eliminating the need for electric and natural gas. ...
allow a person to heat their home using pellets in existing stoves or fireplaces.
Energy output and efficiency
![Wood-pellet heater](https://upload.wikimedia.org/wikipedia/commons/f/f8/Wood-pellet_heater.jpg)
The
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
content of wood pellets is approximately 4.7 – 5.2
MWh/
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
(~7450 BTU/lb), 14.4-20.3 MJ/kg.
High-efficiency wood pellet stoves and boilers have been developed in recent years, typically offering combustion efficiencies of over 85%. The newest generation of wood pellet boilers can work in condensing mode and therefore achieve 12% higher efficiency values. Wood pellet boilers have limited control over the rate and presence of combustion compared to liquid or gaseous-fired systems; however, for this reason they are better suited for
hydronic
Hydronics () is the use of liquid water or gaseous water (steam) or a water solution (usually glycol with water) as Heat transfer, heat-transfer medium in heating system, heating and cooling systems. The name differentiates such systems from Oil ...
heating systems due to the hydronic system's greater ability to store heat. Pellet burners capable of being retrofitted to oil-burning boilers are also available.
Air pollution emissions
Emissions such as
NOx,
SOx and
volatile organic compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s from pellet burning equipment are in general very low in comparison to other forms of combustion heating.
A recognized problem is the emission of fine
particulate matter
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
to the air, especially in urban areas that have a high concentration of
pellet heating
Pellets are small particles typically created by compressing an original material.
Pellet or pellets may refer to:
People
* Alain Pellet (born 1947), French lawyer
* Gustave Pellet (1859–1919), French publisher of art
* Laurent Pellet (born 197 ...
systems or coal or oil heating systems in close proximity. This
PM2.5 emissions of older pellet stoves and boilers can be problematic in close quarters, especially in comparison to
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
(or renewable
biogas
Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
), though on large installations
electrostatic precipitator
An electrostatic precipitator (ESP) is a filterless device that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit.
In cont ...
s,
cyclonic separators, or
baghouse particle filters can control particulates when properly maintained and operated.
Global warming
There is uncertainty to what degree
making heat or electricity by burning wood pellets contributes to global
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
, as well as how the impact on climate compares to the impact of using competing sources of heat.
Factors in the uncertainty include the wood source,
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
emissions from production and transport as well as from final combustion, and what time scale is appropriate for the consideration.
A report
by the
Manomet Center for Conservation Sciences, "Biomass Sustainability and
Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
Policy Study" issued in June 2010 for the Massachusetts Department of Energy Resources, concludes that burning biomass such as wood pellets or wood chips releases a large amount of into the air, creating a "carbon debt" that is not retired for 20–25 years and after which there is a net benefit.
In June 2011 the department was preparing to file its final regulation, expecting to significantly tighten controls on the use of biomass for energy, including wood pellets. Biomass energy proponents have disputed the Manomet report's conclusions, and scientists have pointed out oversights in the report, suggesting that climate impacts are worse than reported.
Until ca. 2008 it was commonly assumed, even in scientific papers, that biomass energy (including from wood pellets) is carbon neutral, largely because regrowth of vegetation was believed to recapture and store the carbon that is emitted to the air. Then, scientific papers studying the climate implications of biomass began to appear which refuted the simplistic assumption of its
carbon neutrality
Carbon neutrality is a state of net-zero carbon dioxide emissions. This can be achieved by balancing emissions of carbon dioxide with its removal (often through carbon offsetting) or by eliminating emissions from society (the transition to the "p ...
.
According to the Biomass Energy Resource Center, the assumption of carbon neutrality "has shifted to a recognition that the carbon implications of biomass depend on how the fuel is harvested, from what forest types, what kinds of
forest management Forest management is a branch of forestry concerned with overall administrative, legal, economic, and social aspects, as well as scientific and technical aspects, such as silviculture, protection, and forest regulation. This includes management for ...
are applied, and how biomass is used over time and across the landscape."
In 2011 twelve prominent U.S. environmental organization, including as Greenpeace USA and the
Southern Environmental Law Center
Southern Environmental Law Center (SELC) is the largest 501(c)(3) organization, 501(c)(3) environmental nonprofit organization in the Southern region, with more than 80 attorneys and 75 staff members working at the local, state, and federal level ...
, adopted policy setting a high bar for government incentives of biomass energy, including wood pellets. It states in part that, "
omass sources and facilities qualifying for (government) incentives must result in lower life-cycle, cumulative and net
GHG and ocean acidifying emissions, within 20 years and also over the longer term, than the energy sources they replace or compete with."
On 11 February 2021 five hundred scientists and economists wrote a letter regarding the use of forests for bioenergy to world leaders. It warns that "The burning of wood will increase warming for decades to centuries. That is true even when the wood replaces coal, oil or natural gas". The letter calls for an end to subsidies for the burning of wood and an end to the treatment of the burning of biomass as carbon neutral in renewable energy standards and emissions trading systems.
Sustainability
The
wood products industry is concerned that if large-scale use of wood energy is instituted, the supply of raw materials for construction and manufacturing (
lumber
Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...
) will be significantly curtailed.
Cost
Due to the rapid increase in popularity since 2005, pellet availability and cost may be an issue. This is an important consideration when buying a pellet stove, furnace, pellet baskets or other devices known in the industry as Bradley Burners. However, current pellet production is increasing and there are plans to bring several new pellet mills online in the US in 2008–2009.
The cost of the pellets can be affected by the building cycle leading to fluctuations in the supply of sawdust and offcuts.
Per the
New Hampshire
New Hampshire is a U.S. state, state in the New England region of the northeastern United States. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec t ...
Office of Energy and Planning release on Fuel Prices updated on 5 Oct 2015, the cost of #2
fuel oil
Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), bun ...
delivered can be compared to the cost of Bulk Delivered Wood Fuel Pellets using their BTU equivalent: 1
ton
Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses.
Mainly it describes units of weight. Confusion can arise because ''ton'' can mean
* the long ton, which is 2,240 pounds
...
pellets = 118.97
gallon
The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use:
*the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Austral ...
of #2 Fuel Oil. This assumes that one ton of pellets produces 16,500,000 BTU and one gallon of #2 Fuel Oil produces 138,690 BTU. Thus if #2 Fuel Oil delivered costs $1.90/Gal, the breakeven price for pellets is $238.00/Ton delivered.
Usage by region
Europe
Usage across Europe varies due to government regulations. In the
Netherlands
)
, anthem = ( en, "William of Nassau")
, image_map =
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Kingdom of the Netherlands
, established_title = Before independence
, established_date = Spanish Netherl ...
,
Belgium
Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...
, and the
UK, pellets are used mainly in large-scale power plants. The UK's largest power plant, the
Drax power station, converted some of its units to pellet burners starting in 2012; by 2015 Drax had made the UK the largest recipient of exports of wood pellets from the US. In
Denmark
)
, song = ( en, "King Christian stood by the lofty mast")
, song_type = National and royal anthem
, image_map = EU-Denmark.svg
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Danish Realm, Kingdom of Denmark
...
and
Sweden
Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
, pellets are used in large-scale power plants, medium-scale district heating systems, and small-scale residential heat. In
Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
,
Austria
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
,
Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...
, and
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
, pellets are used mostly for small-scale residential and industrial heat.
The UK has initiated a grant scheme called the
Renewable Heat Incentive The Renewable Heat Incentive (the RHI) is a payment system in England, Scotland and Wales, for the generation of heat from renewable energy sources. Introduced on 28 November 2011, the RHI replaces the Low Carbon Building Programme, which closed in ...
(RHI) allowing non-domestic and domestic wood pellet boiler installations to receive payments over a period of between 7 and 20 years. It is the first such scheme in the world and aims to increase the amount of renewable energy generated in the UK, in line with
EU commitments.
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
and
Northern Ireland
Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...
have separate but similar schemes. From Spring 2015, any biomass owners—whether domestic or commercial—must buy their fuels from BSL (Biomass Suppliers List) approved suppliers in order to receive RHI payments. The
Renewable Heat Incentive scandal
The Renewable Heat Incentive scandal (RHI scandal), also referred to as RHIgate and the Cash for Ash scandal, is a political scandal in Northern Ireland that centres on a failed renewable energy (wood pellet burning) incentive scheme that has be ...
also referred to as the "cash for ash scandal", was a political scandal in Northern Ireland that centred on a failed renewable energy (wood pellet burning) incentive scheme.
Pellets are widely used in Sweden, the main pellet producer in Europe,
mainly as an alternative to oil-fired central heating. In Austria, the leading market for pellet central heating furnaces (relative to its population), it is estimated that 2/3 of all new domestic heating furnaces are pellet burners. In Italy, a large market for automatically fed pellet stoves has developed. Italy's main usage for pellets is small-scale private residential and industrial boilers for heating.
In 2014 in Germany, the overall wood pellet consumption per year comprised 2,2 million tonnes. These pellets are consumed predominantly by residential small-scale heating sector. The co-firing plants which use pellet sector for energy production are not widespread in the country. The largest amount of wood pellets is certified with DINplus, and these are the pellets of the highest quality. As a rule, the pellets of lower quality are exported.
India
In 2019, India started co-firing biomass pellets in coal fired power stations around its capital city
Delhi
Delhi, officially the National Capital Territory (NCT) of Delhi, is a city and a union territory of India containing New Delhi, the capital of India. Straddling the Yamuna river, primarily its western or right bank, Delhi shares borders w ...
to reduce the air pollution caused by the stubble/biomass burning in open fields to clear the fields for sowing next crop. Plans are made to use biomass pellets for power generation throughout the country to utilize nearly 145 million tonnes of agricultural residue to replace equal quantity of imported coal in power generation.
New Zealand
The total sales of wood pellets in
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
was 3–500,000 tonnes in 2013. Recent construction of new wood pellet plants has given a huge increase in production capacity. Nature's Flame wood pellet processing plant, in Taupo, is due in late 2019 to double its annual production capacity to 85,000 tonnes. Azwood Energy operates a wood pellet processing plant in Nelson, utilising more than 1.2 million cubic metres of forestry residue each year to provide carbon neutral fuel for domestic use, hospitals, schools and industrial processes, including milk-processing.
United States
Some companies import European-made boilers. , about 800,000 Americans were using wood pellets for heat.
It was estimated that 2.33 million tons of wood pellets would be used for heat in the US in 2013.
The US wood pellet export to Europe grew from 1.24 million ton in 2006 to 7 million ton in 2012, but forests grew even more.
Other uses
Horse bedding
When small amounts of water are added to wood pellets, they expand and revert to sawdust. This makes them suitable to use as a
horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million y ...
bedding. The ease of storage and transportation are additional benefits over traditional bedding. However, some species of wood, including walnut, can be toxic to horses and should never be used for bedding.
In
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is bo ...
, rice husk pellets are being produced for animal bedding. They have a high absorption rate which makes them ideal for the purpose.
Cattle fodder
The biomass pellets made from edible matter can also be used as cattle fodder by importing from far away fodder surplus places to overcome the fodder shortage.
Absorbents
Wood pellets are also used to absorb
contaminated water
Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water ...
when drilling oil or gas wells.
Cooking
Wood
pellet grill
Pellet grills, sometimes referred to as pellet smokers, are outdoor cookers that combine elements of charcoal smokers, gas grills, and kitchen ovens. Fueled by wood pellets, they can smoke as well as grill, braise, sear and bake using an PID e ...
s have gained popularity as a versatile way to grill, bake, and smoke. The size of the pellets makes it useful for creating a wood fired grill that still controls its temperature precisely.
See also
*
Solid fuel
Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fuels ...
*
Renewable heat Renewable heat is an application of renewable energy referring to the generation of heat from renewable sources; for example, feeding radiators with water warmed by focused solar radiation rather than by a fossil fuel boiler. Renewable heat technol ...
*
Pellet mill
A pellet mill, also known as a pellet press, is a type of mill or machine press used to create pellets from powdered material. Pellet mills are unlike grinding mills, in that they combine small materials into a larger, homogeneous mass, rather t ...
*
Woodchips
Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste.
Woodchips may be used as a biomass solid fuel and are raw material ...
*
Firelog
A firelog is a manufactured log constructed to be used as wood fuel. Firelogs are designed to be inexpensive, while being easier to ignite, and burn longer, and more efficiently than firewood. Firelogs are traditionally manufactured using two met ...
*
Biochar
Biochar is the lightweight black residue, made of carbon and Ash (analytical chemistry),
ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the th ...
References
External links
European Biomass AssociationPellet Fuels InstituteBiomass Energy
{{Authority control
Wood fuel
Bioenergy