held in an anaerobic area, which can range from a storage tank which is not ventilated to a device which is specifically designed to produce gases. The conditions attract anaerobic bacteria, which start to break down the organic material, producing methane and carbon dioxide as a by-product. Another type of biogas which includes hydrogen, nitrogen, and carbon monoxide can be obtained through the gasification of biomass such as wood or rice husks, a technique which is used to manufacture gas industrially. The gases produced through anaerobic fermentation or gasification are combustible in addition to having a strong smell which makes them stand out to the human nose. Methane leaks from landfills are an ongoing problem, as is the production of biogas in poorly maintained compost piles, manure lagoons, and outhouses. Spontaneous fires and explosions caused by build-ups of gas have
The optical density is proportional to from other trees that are rich in resins, includ- the number of particles in a unit volume of ing coniferous, as well as heather, may be the smoke. In constant conditions, when the used. In some areas, other carbohydrate- dimensions of the particles do not change, the rich material (e.g., bagasse [sugarcane], beet optical density is correlated to the mass con- refuse from sugar making, or coconut husks) centration of the dispersed components in the is used. smoke. Thus photo optical measurements can The smoke consists of gaseous products be used for the determination of smoke of thermal degradation and subsequent partial density, which reflects the contents of all oxidation of the wooden material and of the components. dispersed soot and compounds present in fluid or particle form. The temperature of
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