Wood pellets

Wood pellets are a type of wood fuel, sometimes made from compacted sawdust or other wastes from sawmilling and other wood products manufacture, but also commonly from controversial sources such as whole-tree removal or tree tops and branches leftover after logging and which otherwise help replenish soil nutrients. Pellets are manufactured in several types and grades as fuels for electric power plants, homes, and other applications in between.[1] 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.

Further, their regular geometry and small size allow automatic feeding with very fine calibration. They can be fed to a burner by auger feeding or by pneumatic conveying. Their high density also permits compact storage and rational 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 stoves, central heating furnaces, and other heating appliances have been developed and marketed since 1999. With the surge in the price of fossil fuels in 2005, the demand for pellet heating has increased in Europe and North America, and a sizable industry is emerging.

Wood pellets - Author: Tom Bruton

Wood pellets


Pellets are produced by compressing the wood material which has first passed through a hammer mill 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 plastifies slightly forming a natural "glue" that holds the pellet together as it cools.[2]

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 (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.

Pellets conforming to the European standards norms cannot contain any recycled wood or outside contaminants. Recycled materials such particle board, treated or painted wood, melamine resin-coated panels and the like are particularly unsuitable for use in pellets, since they may produce noxious emissions and uncontrolled variations in the burning characteristics of the pellets.

Standards used in the United States are different, developed by the Pellet Fuels Institute, are not mandatory, and are generally less strict than those of Europe; for example, it is accepted that pellets exposed to large volumes of water in the US may significantly degrade (turning into "mush"). 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 price inflation of 2007–2008, but subsequently have decreased significantly in late 2008 and early 2009, and are generally lower on a per-BTU basis than most fossil fuels, excluding coal, which is not an option highly favored for heating by many residential and commercial consumers, due to frequent maintenance and tending requirements for end users, high carbon emissions, air pollution (often leading to nuisance complaints from neighbors and investigation by boards of health and environmental agencies), the mess generated by coal dust and improper storage, as well as potentially dangerous fly ash.

Energy output and efficiency

The energy content of wood pellets is approximately 4.7 – 4.9 MWh/tonne[3] (~7450 BTU/lb).

High-efficiency wood pellet stoves and boilers have been developed in recent years, offering combustion efficiencies of over 90%. Wood pellet boilers, having 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 heating systems due to the hydronic system's greater ability to store heat. Pellet burners capable of being retrofitted to oil-burning boilers are predicted to be available on the market within the next several years.

Air pollution emissions

Emissions such as NOx, SOx and volatile organic compounds from pellet burning equipment are in general very low in comparison to other forms of combustion heating. An additional consideration, though, is such air pollutant emissions caused in producing the energy used to manufacture pellets. A recognized problem is the emission of fine (particulate matter) to the air, especially in urban areas that have a high concentration of pellet heating 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 (or renewable biogas), though on large installations electrostatic precipitators or baghouse particle filters may reduce the problem if installed and properly maintained and operated. Research is particularly needed concerning the health effects of ultrafine particles produced by the high burn temperatures of wood pellets.[4] These nano-scale particles are substantially smaller than PM2.5, and can penetrate into the smallest passages of the lungs and in some cases directly into the bloodstream.[4] They have unique physical and chemical properties because of their extremely high surface area per unit of mass, an inherent consequence of their nano-scale size. Even a very small mass of such particles constitutes a very large number of them.[4]

Pellet stove operation

A fully automated stove requires filling up with the pellets and turning on, the stove does the rest: it automatically lights, automatically feeds the pellets into the flame with an auger, automatically adjusts the rate to keep the room at a pre-set temperature with an electric thermostat.

Cost issues

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 effected by the building cycle leading to fluctuations in the supply of sawdust and offcuts.

Usage by region

Pellets are most widely used in Sweden, 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.

New Zealand
The total sales of wood pellets in New Zealand was 3–5,000 tonnes in 2003. Recent construction of new wood pellet plants has given a huge increase in production capacity.[26]

United States
Some companies import European-made boilers.

Pellet Use (ton)[24]
Sweden1 400 000
Italy550 000
Germany450 000
Austria400 000
Denmark*n. 400 000
Finland*n. 50 000
*Households 2005.[25]

Retail cost

United States
In 2008, the cost for heating with pellets was $19.59 per million BTU.[27] This corresponds to a price of $5.14 per 40 pound bag, or $257 per ton.

In 2009, the cost of woodpellets was 4 eurocent per kWh or 16 $ per million BTU.[28] Retail prices depend on the size and specifications of the order (bulk, big bag, 15 kg sacks,...).

See also

  1. ^European Pellet Standards. Powerpoint
  2. ^NOTE: Information that should be added to the text is the energy required to manufacture and transport pellets, relative to their energy content.
  3. ^
  4. ^ abc Howard, V. (2009). "Statement of Evidence: Particulate Emissions and Health (An Bord Plenala, on Proposed Ringaskiddy Waste-to-Energy Facility)." [1] Retrieved 2011-04-26.
  5. ^ abcdefg Manomet Center for Conservation Science. 2010. Biomass sustainability and Carbon Policy Study: Report to the Commonwealth of Massachusetts Department of Energy Resources.[2]

     20. ^ Large-scale biomass ‘risks UK jobs and carbon emissions.’
               Carbon Offsets Daily, 2 July 2010. [12]  
     21. ^ /HeatNE%20Vision%20Master%
     22. ^ Forest Guild. 2010. Forest Biomass Retention and Harvesting
               Guidelines for the Northeast. [13]
     23. ^Massachusetts Forest Watch
     24. ^Bioenergie: Großes Potenzial für Pellets-Märkte in Europa und weltweit
     25. ^Pellets for small-scale domestic heating systems 5/2007, European
               Biomass Association Aebiom (Resmac project)
     26. ^ Nielsen, S; George A. Estcourt and Carolyn J. Hodgson (October 2004).
               "New Bioenergy options for New Zealand – an evaluation of wood pellet
. Forest Research. Retrieved 2008-10-17.
     27. ^ Ryan, Matt (June 20, 2008). Homeowners seek cheaper winter heat.
               Burlington Free Press.
     28. ^

External links

Pellet Fuels Institute
– A non-profit trade association made up of pellet manufacturers and associated industry suppliers

Compound feed

Compound feeds are feedstuffs that are blended from various raw materials and additives. These blends are formulated according to the specific requirements of the target animal. They are manufactured by feed compounders as meal type, pellets or crumbles.

Compound feeds can be complete feeds that provide all the daily required nutrients, concentrates that provide a part of the ration (protein, energy) or supplements that only provide additional micronutrients, such as minerals and vitamins.

According to the American Feed Industry Association, as much as $20 billion worth of feed ingredients are purchased each year. These products range from grain mixes to orange rinds to beet pulps. The feed industry is one of the most competitive businesses in the agricultural sector, and is by far the largest purchaser of U.S. corn, feed grains, and soybean meal. Tens of thousands of farmers with feed mills on their own farms are able to compete with huge conglomerates with national distribution. Feed crops generated $23.2 billion in cash receipts on U.S. farms in 2001. At the same time, farmers spent a total of $24.5 billion on feed that year.

Around 600 million tons of feed are produced annually around the world.

A pelleted ration designed for horses. Author: BLW

A pelleted ration designed for horses


The beginning of industrial scale production of animal feeds can be traced back to the late 19th century; this is around the time that advances in human and animal nutrition were able to identify the benefits of a balanced diet, and the importance of the role that the processing of certain raw materials played. Corn gluten feed was first manufactured in 1882, while leading world feed producer Purina feeds was established in 1894 by William H. Danforth. Cargill, which was mainly dealing in grains from its beginnings in 1865, started to deal in feed at about 1884.

The feed industry expanded rapidly in the first quarter of the 20th century, with "Purina" expanding its operations into Canada, and opened its first feed mill in 1927 (which is still in operation).

In 1928, the feed industry was revolutionized by the introduction of the first pelleted feeds - Purina Checkers.


The main ingredients used in commercially prepared feed are the feed grains, which include corn, soybeans, sorghum, oats, and barley. Corn production was valued at nearly $25 billion in 2003, while soybean production was valued at $17.5 billion. Roughly 66 percent of sorghum production, which was valued at $965 million in 2003, is used as livestock feed. Approximately 60 percent of barley production, which totaled 227 million bushels (4,610,000 metric tons) and was valued at $765 million in 2003, is used as livestock feed. Annual oat production in 2003 was valued at $218 million.

The sale and manufacture of premixes is an industry within an industry. Premixes are composed of microingredients such as vitamins, minerals, chemical preservatives, antibiotics, fermentation products, and other essential ingredients that are purchased from premix companies, usually in sacked form, for blending into commercial rations. Because of the availability of these products, a farmer who uses his own grain can formulate his own rations and be assured his animals are getting the recommended levels of minerals and vitamins.


The job of the feed manufacturer is to buy the commodities and blend them in the feed mill according to the specifications outlined by the nutritionist. There is little room for error because, if the ration is not apportioned correctly, lowered animal production and diminished outward appearance can occur.

Industry leaders

The world's largest feed manufacturer is the CP Group Thailand, producing 18 million tonnes of compound feed at various locations across East Asia.

The merge of the Hamburg-based traditional commodity trade firm, Cremer, and the Düsseldorf based Deuka (Deutsche Kraftfutterwerke), led to one of the largest feed companies in Europe. The new Cremer Group produces around 3.5 million tons.

United States
Leading U.S. companies involved in prepared feeds production in the early first decade of the 21st century included ConAgra Inc., an Omaha, Nebraska-based firm; and Cargill, Incorporated, a diversified company that was the nation's top exporter of grain. In 1998, Ralston Purina Company, based in St. Louis, Missouri, formed Agribrands International, Inc. to control its international animal feed and agricultural products division. Agribrands produced feed and other products for livestock in markets outside of the United States, and had about 75 facilities operating in 16 countries. In 2001, it was acquired by Cargill.

Other significant industry players included Conti Group Companies, Inc., the world's leading cattle feeder; CHS, Inc. (previously known as Cenex Harvest States Cooperative), which was primarily involved in grain trading; and Farmland Industries, Inc., the leading agricultural cooperative in the United States. Farmland was a worldwide exporter of products, such as grain. In May 2002, the firm declared bankruptcy, and in the following year, Smithfield Foods acquired most of Farmland's assets.

See also

External links

Convince yourself of our products for your applications.

We recommend the following products for your process medium:

hose diaphragm valves

hose pinch valves

knife-gate valve

ball valves and plug valves

butterfly valves