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FUEL FROM THE FIELDS: CHARCOAL FROM AGRICULTURAL WASTE Introduction Worldwide, 2.4 billion people use wood, charcoal, other plant material (biomass), and coal as their primary source of cooking fuel. In developing countries, the burning of biomass accounts for up to 80% of all household fuel use. Widespread burning of unprocessed biomass has well- characterized impacts on health and the environment. Indoor air pollution, which is largely due to exposure to smoke and particulate matter emitted by
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  FUEL FROM THE FIELDS: CHARCOAL FROM AGRICULTURAL WASTE Introduction Worldwide, 2.4 billion people use wood, charcoal, other plant material (biomass), and coal as their primary source of cooking fuel. In developing countries, the burning of biomass accounts for up to 80% of all household fuel use. Widespread burning of unprocessed biomass has well-characterized impacts on health and the environment. Indoor air pollution, which is largely due to exposure to smoke and particulate matter emitted by the combustion of unprocessed biomass, is estimated to kill over 1.6 million people each year (fig. 1); women and young children are worst affected. Deforestation also causes soil erosion, increasing vulnerability to flooding and causing lower crop yields from farms. The Fuel from the Fields (FftF) team developed a method of producing charcoal from previously unused agricultural waste products. Charcoal provides significant advantages over raw biomass fuels because the process of carbonisation reduces the particulate emissions, and reduces the risk of developing respiratory infections. Unlike Liquefied Petroleum Gas (LPG) or kerosene, charcoal does not require people to purchase new stoves or change the way they cook. The Background Charcoal making is a traditional industry across the world – charcoal is an energy dense fuel that can easily be transported from rural to urban environments. In Haiti, the charcoal industry employs an estimated 150 000 people. Making charcoal requires three conditions: ã    A carbon-rich material (traditionally wood) ã   Heat ã    Anaerobic conditions (i.e. it must burn without air present) Traditionally, charcoal is made by cutting down a tree, setting fire to the trunk, and covering it with soil. The tree carbonises (turns into charcoal) over 1-3 weeks. The environmental impact is worsened because hardwood trees (those that grow most slowly) make the highest quality charcoal. The Fuel from the Fields technology involves filling a metal kiln with agricultural waste (the source of carbon.) This waste is ignited, and later sealed, to create anaerobic conditions. After two hours, charcoal is formed. Raw Material Charcoal can be produced from any appropriate agricultural waste. The FftF team encourage the use of biomass that has no other value – that is unsuitable for animal or human consumption, or for composting. In Haiti, bagasse (dried sugar cane) is a readily available by-product of sugar production. In other countries, we have tested corn cobs, palm fronds and Practical Action, The Schumacher Centre for Technology and Development, Bourton on Dunsmore, Rugby, Warwickshire, CV23 9QZ, UK T  +44 (0)1926 634400 | F +44 (0)1926 634401 | E infoserv@practicalaction.org.uk | W www.practicalaction.org Figure 1: Indoor air pollution from cooking with biomass is associated with pneumonia. Photo credit: Fuel from the Fields Practical Action is a registered charity and company limited by guarantee. Company Reg. No. 871954, England | Reg. Charity No.247257 | VAT No. 880 9924 76 | Patron HRH The Prince of Wales, KG, KT, GCB  Fuel from the Fields: Charcoal from Agricultural Waste Practical Action coconut shells, but other crop wastes may also be used. One full oil drum needs about 16kg of crop waste, and will produce about 4kg of charcoal. The Equipment The FftF technology has been deliberately designed in collaboration with Haitian farmers and technicians to be an appropriate technology. All materials are readily available in the developing world; the technology can be manufactured using simple tools and welding equipment; the total equipment cost is $20-40 (All prices are quoted in US dollars) A 55-gallon steel oil drum ( fig. 2). This forms the kiln, in which the waste is burned, to produce charcoal. Oil drums are used to transport crude oil and other materials throughout the developing world; they are readily available and cheap, costing around $1020. A lid for the oil drum is also needed , which can be made out of scrap metal. A briquette press.  (fig 3) This is a small, cheap impact press, which costs around $2-3 in the developing world, and is used to make briquettes from carbonised powder. Figure 2: A steel oil drum with lid forms the kiln. Photo credit: Fuel from the Fields Figure 3: A briquette press, made from angle iron and sheet metal. Photo credit: Fuel from the Fields Other required materials: ã   A long, straight object like a stick  – to create a central chimney in the oil drum; it should be taller than the oil drum, and as wide as a fist in diameter. ã   Three bricks or flat stones about the same size ã   Rice bags or other large bags - to crush the charcoal powder in ã   Grated cassava, or some other starch - to make strong briquettes, a small quantity of starch binder must be added to the charcoal powder. Grated cassava porridge is ideal, although any other starch (e.g. cornflour or cassava flour) can be used. ã   A basin – to mix the charcoal powder with the starch porridge ã   Matches – to set fire to the agricultural waste. ã   Sand, Mud or Dirt  – to help create an airtight seal around the drum Preparing the Equipment The oil drum The first time you make charcoal, the 55-gallon oil drum must be turned into a kiln. To do so, cut one large hole in the top (this is a loading hole), and a number of small holes in the bottom (these are air holes). The holes in the oil drum may be cut with either a hammer and chisel, or an angle grinder. o   Do not use an angle grinder or any other tool that will create sparks unless it is certain that there are no flammable or explosive residues inside the oil drum. o   The drum should not contain any toxic or explosive residues. o   If it has safe residue (oil or food) a small fire should be made inside the drum to clean it out. Allow the drum to cool before starting to cut holes. o   Both flat ends of the drum must be intact. The drum cannot be used if one entire flat side has been cut off. o   There must be no holes in the curved sides of the drum. 2  Figure 4: The square loading hole in the top of the drum. Photo credit: Fuel from the Fields Fuel from the Fields: Charcoal from Agricultural Waste Practical Action The loading hole (fig 4) in the top of the drum may be round or square. The edges of the loading hole should be at least 8cm from the edge of the drum, providing enough space for the lid to rest on. The empty drum will be easier to move if the edges of the loading hole are not rough and jagged so people can lift the drum more easily. Cut about 9 small air holes (fig 5) in the bottom of the drum to allow for air to flow through it, making a hotter initial fire. The air holes should be evenly distributed and roughly 8cm apart. One air hole should be near the centre. They can be any shape, but no more than about 8cm in diameter, to stop material falling through the holes. The cover You need a lid, to cover the large loading hole in the top of the oil drum. The lid should be large enough to cover the loading hole in the oil drum, (fig 2) but small enough not to extend over the edges of the oil drum. An ideal lid is made from a piece of sheet metal. It is easier to place the lid on top of the hot kiln if a handle is welded onto the lid. If you can’t make a curved handle, a handle shaped like a short, flat ‘T’ has worked well. You can also use metal without a handle. The briquette press This is a small impact press used to make briquettes from the charcoal powder. The press can be round or square and can be easily manufactured by any car mechanic or local blacksmith, if they can weld metal. A round press can be manufactured using metal pipes; a square press, using angle iron and sheet metal. The outside diameter of the cup does not have to be exact; the larger the cup, the larger the briquettes produced. The preferred size of briquettes varies in different countries. Presses made by Fuel from the Fields range from around 5 to 10 cm in cup diameter. The press is made up of four parts: the cup, the ejector, the plunger, and the hammering station (a block is shown here) (fig 6). Figure 5: 9 small air holes in the bottom of the drum. Photo credit: Fuel from the Fields Figure 6: Parts of the briquette press. Photo credit: Fuel from the Fields ã   The cup is made from a large, hollow pipe, with sheet metal welded to the bottom. The bottom should have a hole drilled in the centre, wider in diameter than the ejector pin. ã   Cut two sheet metal discs, slightly smaller in diameter than the inside of the cup. These form the ejector and plunger plates. 3  Fuel from the Fields: Charcoal from Agricultural WastePractical Action ã   To make the ejector, weld the ejector plate to a short length of pipe. The ejector should be as tall as the cup. When using the briquette press, the bottom of the pin is pushed on the surface of the hammering station, to eject the briquette. If the ejector is as tall as the cup, the briquette is ejected completely, and the ejector pin stays in the hole at the bottom of the cup. ã   To make the plunger, weld the plunger plate to a longer length of pipe. ã   The hammering station is made by drilling a hole into a table or block of wood. The hole must be larger in diameter and length than the ejector pin, but smaller than the diameter of the cup. This allows the base of the cup to rest flat on the surface of the table, with the ejector pin dropping through the hole, while the press is in use. Making charcoal The process of charcoal production is as much an art as a science. It requires experience to produce high quality charcoal, and to get high yields of charcoal from an oil drum. The method must also be adapted slightly for different materials. Whilst this guide provides approximate details, the time required at each stage is variable; there is no substitute for experience. When conducting a charcoal burn, it is important that the weather is dry. It is possible to make charcoal when it is raining, but it is much harder to light a fire. The oil drum also cools down more quickly, so the yield is lower. Filling the drum When filling the drum, it is necessary to allow air to flow through the drum so that the fire can burn hotly and evenly and produce high quality charcoal. ã   Place a large stick (fig 7) in the centre of the drum and pack the bagasse, stalks or other material around it until the drum is full. ã   If you are using corn cobs, or other material that is more difficult to light, create 4-5 layers of corn cobs, separated by husks or dried grasses. This allows the whole drum to get hot, and produce high quality charcoal. ã   Carefully remove the stick, leaving a hole that goes to the bottom of the drum. ã   Take a small amount of material and poke it into each of the holes in the bottom of the drum, leaving about 20 cm sticking out. (fig 8) This creates a wick, allowing you to easily ignite the material at the bottom of the drum. Lighting the fire ã   Before lighting the fire, place the drum on top of three stones or bricks, so that air can flow in through the holes in the bottom. (fig 9). Place the drum on the stones carefully, so that it will be easy to remove the stones while the raw material is burning, to seal the Figure 8: Make ‘wicks’ in the bottom drum. of the oil drum Photo credit: Fuel from the Fields Figure 7: Fill the drum with a central chimney Photo credit: Fuel from the Fields 4
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