From the energy point of view, the most important characteristics of a fuel are given by its composition, heating value and other properties related to the energy con­version technology where it will be used. Table 6.4 shows the results of an analysis conducted at the Alternative Fuels Laboratory at UNICAMP for eucalyptus, bagasse and trash from sugarcane. It turns out that the energy value of cane trash

was only 15 per cent lower than that of the bagasse at similar moisture content. Unfortunately, important characteristics such as the ash melting point, critical when a fuel is used in boilers, are not properly documented. Experiments on trash com­bustion are not reported either.

Wood from native forests has been historically used to provide useful energy through direct combustion. Also in Brazilian sugar mills, wood was and is still used to a limited extent to complement bagasse as energy source. Bagasse provides enough heat through direct combustion in steam boilers to meet the needs to crush the cane in the mills, to provide process heat in the factory operations and also to generate enough electricity by turbo-generators to drive all electric motors and meet other electricity requirements at the mill. Bagasse-based energy is not only enough to meet these needs but is also produced in excess in sugar mills and ethanol distilleries in Brazil. Many factories have to adjust their boilers to simply burn all excess bagasse because, otherwise, the material will deteriorate and pose risks.

Meanwhile, in the State of Sao Paulo, where most of Brazilian sugarcane is produced, fuel wood is used in the manufacture of bricks, in food industries, bakeries and restaurants. The wood is usually transported from distant locations using diesel trucks. It has become scarcer and more costly and is being gradually substituted for natural gas and even conventional burning oil.

There is a significant potential for bagasse to immediately substitute firing wood. The limiting factors are apparently associated with lack of entrepreneurship to disseminate a “bagasse culture” that helps promote a more diversified use of substitutes. One example of successful substitution is given by the Destilaria Rosa located in Boituva, Sao Paulo, where a small brick industry was installed just a few meters from the ethanol distillery. The excess bagasse, nearly 30 per cent of the total, is used to produce low cost bricks. Tests were conducted in their furnace to evaluate both efficiency and quality of the bricks (Aradas et al., 1998). In spite of good results, this example has not been emulated by other mills.

Bagasse is used in isolated cases in other industries, for example, in the vegetable oil industry. A more intensive use outside the sugar and ethanol sector has been observed in the orange juice industry, where bagasse boilers similar to those employed in the sugar mills are installed. The Brazilian orange juice industry is amongst the largest in the world and a large production is located in Sao Paulo, near the sugarcane production area. Unfortunately, the consumption of bagasse in the orange juice production does not create sufficient demand so as to provide a real incentive to the supply side. In fact, the demand for bagasse in the orange juice industry is presently threatened due to the availability of the Bolivian natural gas, which is leading to a review of bagasse contracts.

The market price for bagasse varies depending on the local availability and dis­tance. Usually, bagasse is sold at prices ranging from US$ 5 to 12 per ton of bagasse (representing a range of US$0.60 to 1.35/MMBTU) in the core sugarcane regions in Sao Paulo. Small enterprises are producing equipment for direct combustion of vege­table residues, including cane bagasse. Such equipment is simple in conception and is being sold at prices around US$ 1600 for a feeding capacity of 500 kg of biomass/h.