Sugarcane production in Brazil increased from 224 million tons in 1989 to 300 million tons in 1998 and 340 million tons of cane in 2003/04. The fraction of sugarcane used for ethanol production was close to 50 per cent in 1998 as opposed to approximately 65 per cent in 1989. Thus the ratio of ethanol to sugar has decreased, but still half of the cane is being used for ethanol production.

As shown in Table 6.1, the average energy balance (output renewable energy/fossil input ratio) in the Brazilian ethanol production is 9.2, an exceptional figure also when compared with other biomass systems (i. e. ethanol from corn in the US). It should be kept in mind that the figures provided in Table 6.1 are based on the current average situation of sugarcane mills in Brazil. The majority of them use bagasse to meet their needs for electric power and thermal energy, but utilize low efficiency steam-based cogeneration systems for this purpose (Goldemberg et al., 1993). As will be gathered from the discussions here, there are opportunities to further improve this balance.

In 1998, the sugarcane industry contributed nearly 200000 barrels of oil equivalent of ethanol per day to the Brazilian energy system. This contrasts with the Brazilian domestic production of nearly 1.4 million barrels of oil per day. In addition, the bagasse was being used in the cogeneration of electric, mechanical and thermal power. Bagasse is used at a rate of 0.14 ton dry matter per ton of cane, leading to an annual production of 40 million tons (dry matter). Nearly all the power from bagasse is used in-house at the mills. Estimates indicate a use of 3600 GWh for electric power plus 4500 GWh for mechanical drives, in addition to all the thermal energy requirements for processing sugarcane to ethanol and sugar.

A recent legislation is the restriction of sugarcane burning in the largest produc­tion areas of Brazil. It is expected that at least 50 per cent of the cane in the major producing areas will be harvested without burning and with mechanized techno­logies in the next 10 years. This shall result in a substantial increase in biomass availability. Together with more efficient technologies, this shift can significantly improve the overall energy balance of the system as a whole.

Table 6.2 shows an evaluation of the biomass that can be made available for energy generation as the new practice is established. The figures are based on an average trash availability of 10 tons dry matter/ha when approximately 55 per cent of the total planted area is harvested without burning the cane (55 per cent is an approximate value for the sugarcane area which can be harvested mechanically with today’s technology). Table 6.2 provides calculations for 50 and 100 per cent trash recovery since this may vary depending on agronomic considerations. The following variables have been accounted for:

• Average amount of trash in sugarcane (tops and leaves);

• Main agronomic routes to harvest green cane with trash recovery;

• Soil properties with trash left on field;

• Advantages of trash left in field for herbicide elimination;

• Trash properties as fuel;

• Recovery costs;

• Utilization of biomass as boiler fuel or for gasification;

• Environmental impacts of trash recovery/utilization.

For an annual yield of 300 million tons of cane, with a trash recovery of only 50 per cent in 55 per cent of the planted area, the annual amount of new biomass available will be around 11 million tons (DM). This biomass can be effectively used for the purpose of energy generation. Conventional technologies can be employed, such as traditional biomass fired steam boilers and furnaces. Other technologies are also being seriously considered, particularly gasification and power generation with gas turbines, and hydrolysis followed by fermentation to produce ethanol. Pilot plant developments in both areas are underway.

However, it is important to point out that the potential utilization is attractive even with conventional technologies. The development of the cogeneration energy market in Brazil is overdue. The privatization of the electricity markets, the energy crisis of 2001 and the Kyoto Protocol to the Climate Convention have raised the interest for these new opportunities which can be gradually realized as the Brazilian economy recovers. Yet, the future development is not to be taken for granted. Gas markets based on imported gas from Bolivia shall become a strong competitor in many applications (see also Walter et al., Chapter 9). Thus, there is a risk that the better environmental choice based on domestic biomass resources is left behind.