Global Ecological Problems and Issues

Finnish researchers also recommend that the fire should be lit from the top and not from the bottom, which can only be done if the wood is very dry. This is a very effective way to reduce the dangerous particulate emissions and to get more heat energy out from the same amount of fuelwood. A large percentage of the energy content of the wood is in the form of volatile chemicals. When a smaller or larger pile of wood is lit from the bottom, the wood above the fire is heated so much that these volatile chemicals evaporate and escape from the wood. However, most of them escape without burning, which both wastes a large percentage of the wood's energy content and produces a lot of dangerous emissions. If the fire is lit from the top, or simultaneously from the top and from the bottom, also these volatile chemicals are burned in the process. The fire burns with a hotter and much cleaner flame, and produces only very small amounts of suspended particulate matter and other harmful substances.

Charcoal produces much less harmful emissions than fuelwood. Most of the harmful particulates and other toxic compounds are released during the charcoal-making process. Because of this charcoal burns quite cleanly, even though it can produce high carbon monoxide emissions if the burning is not complete enough.

However, charcoal is more expensive than fuelwood. Another problem is that it is often produced by simple earth kilns that waste up to 90 per cent of the energy value of the wood. Part of the loss is compensated by the fact that charcoal is more efficient to use than wood. Because it burns well it can be used in smaller quantities and in a more economic way than wood. This reduced the amount of wastage by a factor or two or three. Improved charcoal kilns can preserve up to 70 per cent of the wood's energy content, but they are in most cases too expensive for the poor charcoal makers. The development of improved earth kilns as an intermediary stage in the charcoal production technology could be a partial answer to the dilemma.

Charcoal retorts also make it possible to recover the various liquid chemicals that are extracted from the wood in the charcoal-making process. (In the traditional charcoal-producing methods these chemicals often seep into the soil and pollute the groundwater.) Such biochemicals can be used to protect houses and other wooden structures from termites, which could also save a lot of wood. Alternatively, they could be collected and sold as a raw material for chemical industries. If industrial end uses for these chemicals would be developed and the collection of them is organized in a proper way, their market value could actually become higher than the market value of the charcoal.

Still in the beginning of 1940's, plant-based materials dominated the chemical industries. Since then chemicals manufactured from oil and coal have largely replaced chemicals derived from wood and other plant materials. The output of petrochemicals in the USA was only 10 000 tons in 1921, but increased to 1.5 million tons in 1939 and 109 million tons in the mid-1990's, which is sixteen times more than the production of biochemicals. In 1945 petroleum-based synthetic fibres had only 0.5 per cent of the American clothing market, while the plant-based synthetic fibres had a 10 per cent market share. By 1980 the petroleum-based clothing materials already had a 64 per cent share of the market. First plastics were made from plant material, but since then it has been almost completely replaced by petrochemicals in the manufacturing of plastics.

This shift from plant-based raw materials to chemicals derived from coal and oil has not been environmentally benign: breaking down organic minerals like oil or coal requires high pressures, high temperatures and - in many cases - strong inorganic acids or alkalis. The manufacturing of petrochemicals consumes a lot of energy and produces very large emissions of greenhouse gases and other pollutants.

The main reason for this dramatic shift has been the development of the oil refining and automobile industries. The production of petrol for motor vehicles produces a lot of waste chemicals, and the oil companies wanted to find end uses for them. Because these chemicals were manufactured in very large quantities by the oil refineries as a waste-product, they became much cheaper than the plant-based chemicals and gradually replaced them.

However, the large-scale use of charcoal kilns that are capable of recovering the liquid chemicals of the wood, might again change the whole picture. Not unlike the oil refineries, the numerous charcoal kilns could together produce an impressive amount of liquid chemicals as a by-product. A charcoal retort can recover, on average, 50 litres of liquid biochemicals for each cubic metre of wood.

The state-owned chemical industries should start to develop different uses for the wood-based chemicals. If there is no demand for them, it will not necessarily be profitable for the charcoal-makers to invest in expensive charcoal retorts.

In other words, improved charcoal kilns could, at least partly, replace oil and coal with charcoal and also lead to a partial replacement of petrochemicals by plant-based raw materials in the chemical industries. Above all, the increased charcoal production would reduce the people's exposure to particulate pollution and to many other dangerous pollutants.

From the view-point of public health the use of biogas, fuel alcohol or solar cookers are still better alternatives than charcoal. For example, nipa palm stands could annually produce about 11 000 litres of fuel alcohol per hectare, but it would probably still be too expensive for the poorest families. In South Asia, the average cost of a biogas generator sufficient for the needs of one family has been about USD 200, which is also a bit too much for the low-income households. Some of the new models developed in Vietnam cost only USD 20, which is already much more affordable. Besides the cow dung and human waste the Vietnamese biogas generators - which are in practise large plastic bags - can also use food waste, crop residues and other plant matter.

Solar cookers are even cheaper. Many models cost USD 20-40, but it is also possible to construct a solar cooker from materials that only cost a few rupees. Such a solar-cooker can be made for instance by taking some mud, clay or cow dung and by moulding it to a parabolic shape (into the shape of a satellite antenna). Besides this only some thin aluminium foil and some glue is needed. When the aluminium foil is glued on the parabolic-shaped base, it will act as an efficient reflector that concentrates the sun's rays on a pot that is hanged over the cooker.

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