Wood and Charcoal

a renewable source, is not an important industrial fuel today. However, its use continues in some mral areas where it is often supplemented with liquid propane. In some underdeveloped countries, wood is still the principal source of energy. Dry wood contains from 1% to 12% moisture whereas green wood contains from 26% to 50% water. The resinous woods, like pine or cedar, yield about 18.5 MJ/kg of air-dried wood or, allowing for the moisture content, about 21 MJ/kg on a dry weight basis. Hardwoods have a heating value of about 19.4 MJ/kg. The energy available in present forest stocks is estimated to be equivalent to about 270 x 10 t of coal or about 2/3 of the equivalent oil reserves. 

Wood-burning fireplaces have become a popular form of heating in the past few years. The normal open hearth fireplace is not an efficient producer of heat since its draft sends most of the hot air up the chimney, creating a partial vacuum pulling cold air into the home. The recent introduction of glass doors to close in the fire and the introduction of outside air to the fire for the combustion process has improved the efficiency of the fireplace, especially with forced air circulation around the fire chamber. 

Open fires, however, are a source of pollution since the smoke produced contains large quantities of polynuclear aromatic hydrocarbons such as benzo(a)pyrene, a carcinogen also found in cigarette smoke. In some communities, it has been necessary to restrict the burning of wood because of the resulting air pollution. 

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In early 1900s, biomass gasification processes were also widely used to manufacture synthetic gases for production of fuels, chemicals, and hydrogen. During World War II, over 1 million air-blown gasifiers were built to produce synthetic gas from wood and charcoal to power vehicles and to generate steam and electricity.3... 

In combustion of solids such as coal, wood, and charcoal the reaction of O2 occurs with solid carbon, sometimes leaving a solid ash residue. Fuel oil drops react with O2 in a similar process in boilers and in diesel engines. Since the exothermicity of these processes creates very large temperature differences, we will describe them in the next chapter. 

Ramdahl, T., I. Alfheim, S. Rustad, and T. Olsen, Chemical and Biological Characterization of Emissions from Small Residential Stoves Burning Wood and Charcoal, Chemosphere, 11, 601-611 (1982a). 

Brazil is a very large country with a warm and rather humid climate, which permits large, economical production of biomass. Nowadays, wood and charcoal are responsible for 25.7% of the total energy supply in the country. So, the intensive utilization of energy from biomass does not represent something really new. 

At first wood and charcoal were used in smelting copper ores, but in 1632 Edward Jorden patented the use of coal, peat and turf, whilst four years later Sir Phillibert Vernatt patented the use of coal alone as fuel. These inventions stimulated the production of copper, especially in South Wales where coal was abundant. By the close of the eighteenth century Britain was the largest producer of copper in the world. This could not last for long. In 1830 the enormous Chilean deposits began to be developed the resources of Australia and North America rapidly followed suit the tables were now turned in earnest, the procedure of Henry vm reversed, and expert smelters from Britain now travelled to all parts of the world to show others how best to carry on. 

Lee, C.L., 1975. Biological and Geochemical Implications of Amino Acids in Sea Water, Wood and Charcoal. Thesis, University of California, San Diego, Calif., 178 pp. 

Perlack, R.D., Stevenson, G.G., and Shelton, R.B. 1986. Prospects for coal briqnettes as a snbstitute fnel for wood and charcoal in US Agency for international development assisted conntries. Report No. ORNL/ TM9770. Oak Ridge National Laboratory, Oak Ridge, TN. 

FIGURE 4.11 Pore size distribution of charcoals prepared from balsa, grant ipil-ipil, and bamboo, (a) Pore size distribution of raw wood and charcoal carbonized at 700°C for 1 h at a heating rate of 50°C/min and (b) dependence of pore volume on heat treatment temperature and rate. 

Estimates are that more than half of the people who depend on fuelwood have inadequate supplies. In some countries, such as Brazil, where forest areas are at present fairly abundant, the rural poor burn mostly wood and charcoal. However, in many developing countries crop residues account for most of the biomass fuel, e.g., 55% in China, 77% in Egypt, and 90% in Bangladesh. Estimates are that the poor in these countries spend 15-25% of their income for biomass fuel. 

The preparation protocol for individual samples is important because of different preservation stage, sample size and possible samples loss during treatment (Nawrocka et al., 2007, 2009 Rebollo et al., 2008 Szczepaniak et al, 2008). The first stage of wood and charcoal purification was removal of macroscopically visible plant roots. Then the samples have been subjected to the "acid-base-acid" (ABA) preparation step by treatment with IM HCl solution. The aim of this step was to dissolve carbonates and other soluble minerals. The second stage was submerging the samples in the base solution (0,025 M NaOH and 0,5 M NaOH) to remove humic compounds. The last ABA step was the repeated acid treatment (0,25 M HCl). Each time, the samples were bathed in deionised water to restore the neutral pH. 

But experiments which are well made, can never fail in agreeing in their results, whatever be the difference of the methods employed it is nevertheless necessary to remark, that the coincidence in question could not be so perfect as it appears, for every thing depends upon the equality of the humidity which may exist in the wood and charcoal employed, a circumstance which it is impossible to establish. 

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