"A dust explosion occurs when fine particles suspended in the air ignite and burn rapidly, causing a violent increase in pressure. In order to cause an explosion, the combustible mixture of air and dust must be contained in some type of vessel. Grains and other agricultural products are a common fuel for dust explosions due to the nature of their handling and storage. Any time that grain is handled or moved, potentially explosive dust is generated.
The size of the dust particles also plays an important role in determining the severity of an explosion. A solid fuel only burns at its surface, where it is exposed to air. A cloud of very fine dust particles has a much greater surface area than a cloud of coarser particles. In addition, fine particles weigh less and tend to stay suspended in air longer. Generally speaking, particles smaller than 840 microns (0.033 inches) can be an explosion hazard."
US 4,608,137 (1986) (Chevron Research Co.)
"The carbonaceous materials suitable for use in accordance with the present invention include a wide variety of material such as bituminous coal, chars made from coal, lignite, peat, active carbons, coke, carbon blacks, graphite; wood or other lignocellulosic materials including forest products, such as wood waste, wood chips, sawdust, wood dust, bark, shavings, wood pellets; including various biomass materials as land or marine vegetation or its waste after other processing, including grasses, various cuttings, crops and crop wastes, coffee grounds, leaves, straw, pits, hulls, shells, stems, husks, cobs and waste materials including animal manure; sewage sludge resulting from municipal treatment plants, and plastics or the scraps or wastes formed in the production of plastic such as polyethylene, cellulose acetate and the like. Thus, it is seen that substantially any fuel or waste material whether a liquid, such as oil, a gas, such as ! ! ! methane or other ! ! hydrocarbon or waste material containing carbon, with the exception of CO.sub.2, provides a suitable source of carbonaceous material for use according to this invention."

