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Pellet fuels (or pellets) are fuels made from compressed organic matter, or, biomass.〔(【引用サイトリンク】url=http://www.altenergy.org/renewables/biomass.html/ )〕 Pellets can be made from any one of five general categories of biomass: industrial waste and co-products, food waste, agricultural residues, energy crops and virgin lumber.〔(【引用サイトリンク】url=http://www.biomassenergycentre.org.uk/portal/page?_pageid=75,15174&_dad=portal&_schema=PORTAL )〕 Wood pellets are the most common type of pellet fuel and are generally made from compacted sawdust〔http://www.organicenergy.co.uk/wood-pellets.html〕 and related industrial wastes from the milling of lumber, manufacture of wood products and furniture, and construction. Other industrial waste sources include Empty Fruit Bunches (), palm kernel shells, coconut shells, and tree tops and branches discarded during logging operations.〔(【引用サイトリンク】url=http://www.biofuelresource.com/use-efb-pellet-as-renewable-energy/ )〕〔(【引用サイトリンク】title=Wood Pellets from PKS and Coconut Shell )〕 So-called "black pellets" are made of biomass, refined to resemble hard coal and were developed to be used in existing coal-fired power plants.〔(【引用サイトリンク】url= http://news.vattenfall.com/en/article/pretty-weird-and-awfully-clever/ )〕 Pellets are categorized by their heating value, moisture and ash content, and dimensions. They can be used as fuels for power generation, commercial or residential heating, and cooking. 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.〔(【引用サイトリンク】url=http://www.mywoodpelletsolution.com/overview/ )〕 A broad range of pellet stoves, central heating furnaces, and other heating appliances have been developed and marketed since the mid-1980s.〔(【引用サイトリンク】url=http://www.opalco.com/news_article/dr-jerry-whitfield-of-shaw-island-to-fill-district-4-board-vacancy/ )〕 In 1997 fully automatic wood pellet boilers with similar comfort level as oil and gas boilers became available in Austria. With the surge in the price of fossil fuels since 2005, the demand for pellet heating has increased in Europe and North America, and a sizable industry is emerging. According to the International Energy Agency 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 == 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 plasticizes slightly, forming a natural "glue" that holds the pellet together as it cools.〔 Pellets can be made from grass and other non-woody forms of biomass that do not contain lignin: distiller's dried grains (a brewing industry byproduct) can be added to provide the necessary durability. A 2005 news story from Cornell University 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 announced as a demonstration project conversion of an oil-fired boiler to grass pellets at a research facility. Rice-husk fuel-pellets are made by compacting rice-husk obtained as by-product of rice-growing from the fields. It also has similar characteristics to the wood-pellets and more environment-friendly, as the raw material is a waste-product. The energy content 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 6mm diameter and 25mm 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.〔(http://www.vikaco.com/en/export-rice-husk-pellet/146-rice-husk-pellet-vietnam.html, http://pubs.acs.org/doi/abs/10.1021/ef201271b, http://www.tis-gdv.de/tis_e/ware/futter/pellets/weizenkl/weizenkl.htm, http://factory.dhgate.com/agricultural-wastage/rice-husk-pellets-for-fuel-p40985821.html, http://www.chatdotcongnghiep.com/rice-husk-pallets, http://www.knowledgebank.irri.org/rkb/index.php/rice-milling/byproducts-and-their-utilization/rice-husk, http://fwci.com/publications/tech_papers/files/TP_CFB_08_05.pdf)〕 In the regions of the world where wheat 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 (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 of exported wood pellets, by the Department of Chemical and Mineral Engineering, University of Bologna, Italy and the Clean Energy Research Centre, at the University of British Columbia, published in 2009, concluded that the energy consumed to ship Canadian wood pellets from Vancouver to Stockholm (15,500 km via the Panama Canal), is about 14% of the total energy content of the wood pellets.〔http://www.forgreenheat.org/blog/An%20environmental%20impact%20assessment%20of%20exported%20wood%20pellets%20from%20Canada%20to%20Europe.pdf〕〔http://www.corrim.org/pubs/articles/2012/FPJ_vol62_num04/06_FPJ-vol62-num04-2012.pdf〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「pellet fuel」の詳細全文を読む スポンサード リンク
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