As illustrated in section II, and in Figs. 4 and 5, the pulp and paper industry enjoys substantial flexibility in its choice of energy inputs. This historical fuel flexibility of the industry results from its direct access to wood fuels and its heavy use of steam for process heat. Because steam systems can use a wide variety of fuels, the industry has been able to shift with relative ease from residual fuel oil to gas and to substitute bark and forest residues for fossil fuels. In addition, the industry contributes to energy supply indirectly by supplying some of the materials that contribute to methane generation in landfills that can be used for electric power generation and the like.
1.5.1 Wood Fuels: Categories and Importance
Wood fuels are a renewable and climate-friendly energy source because they are considered carbon neutral if used and produced in a sustainable and efficient manner. Wood fuels consist of four main commodities: fuelwood (also called firewood), charcoal, black liquor, and wood waste.
Fuelwood is used extensively in most developing countries and is collected from the forest, often as fallen branches or twigs. In domestic applications, it is converted into heat in simple ovens, often for cooking, baking, or drying, and/or is used for space and water heating. The fuel gases are also used for the smoking of food products. Contrary to popular belief, the gathering of fuelwood is not responsible for large-scale deforestation; however, it can contribute to localized forest and soil degradation. Larger issues associated with the traditional use of fuelwood are the health effects of using inefficient stoves in poorly ventilated areas. This leads to emissions of pollutants such as carbon monoxide, methane, and nitrogen oxides that carry serious health risks. For instance, those pollutants are known to cause respiratory infections, adverse pregnancy outcomes, and tuberculosis. In addition, the collection of fuelwood is hard physical labor. Because women are mostly responsible for collecting fuel – wood and cooking, women and small children are most adversely affected. Commercial fuelwood is also used as an industrial source of energy in many developing countries. Typical industrial uses include curing and drying, food processing, and lime and brick burning. Although the total amount of wood consumed by the industrial sector is much smaller than that consumed by households, it is nonetheless significant. For example, in Kenya and Sri Lanka, 26 and 18% of fuelwood is used by industry, accounting for more than 70 and 65% of all industrial energy use, respectively.
Charcoal is produced from wood through carbonization or pyrolysis. The wood is heated in a closed container that is devoid of oxygen. The absence of oxygen prevents the wood from burning to ashes; thus, the wood decomposes to charcoal, among other residues. Charcoal plays an important but a much smaller role than does fuelwood in both industrial and household sectors of most developing countries. In households, it is used for tasks similar to those of fuelwood, but a switch from fuelwood to charcoal provides numerous benefits. Those include the fact that charcoal generally does not decompose in storage, it burns without smoke for the most part, it does not create dangerous flames while cooking, and it requires a simple stove whose heat output is relatively easy to control. As a result, a switch to charcoal often represents an increase in the quality of life. The disadvantages of charcoal use are related primarily to the inefficiencies inherent in its produc
tion and use. Production efficiency in most developing countries ranges between 8 and 28% and is a function of moisture content and type of equipment. Charcoal is also inefficient in use. Although charcoal stoves are more efficient than fuelwood stoves (2035% vs 10-25%), charcoal stoves are much less efficient than modern fuel stoves such as kerosene (35-50%) and electric stoves (75-85%). The combined production and use inefficiencies have important consequences for the abundance of local wood resources given that cooking with charcoal often uses three to four times more wood than does cooking with fuelwood. Charcoal is also used in industrial settings in both developing and developed countries, for instance, in the production of iron and steel, in metallurgy, and in the chemicals industry.
The other two categories of wood fuels are derived from secondary sources and consist of black liquors from pulp production and wood waste from forest products industries and other products from society such as wastepaper.
Wood fuels account for approximately 7% of the world’s total energy supply and are an extremely important source of energy in many developing countries. According to the Food and Agricultural Organization (FAO), developing countries consume approximately 77% of the world’s supply of wood fuels, and this in turn accounts for 15% of total energy consumption in the developing world. Consumption in developed countries accounts for the remaining 23%, but this share amounts to 2% of total energy consumption in the developed world. Of course, substantial regional and national differences exist. Developing countries rely mostly on fuelwood and charcoal, but in most developed countries the pulp and paper industry is instrumental in supplying and using such energy. For instance, in 1997 in New Zealand, black liquor accounted for nearly 100% of all energy derived from forest products, and in Japan, Portugal, Sweden, Norway, and Finland, it accounted for 95, 87, 81, 79, and 80%, respectively (Table III). Forest products provided approximately 17% of total national energy supply in Finland and Sweden.
In the United States, black liquor alone contributes 63% of all energy derived from forest products, accounting for slightly over 2% of total energy supply.