Brazil is the largest producer of sugarcane in the world. The production in the harvest season of 2000-2001 reached 252 million tons, but it was as large as 315 million tons in the harvest season of 1999-2000. In that period, the amount of bagasse available at the sugar mills reached 780 PJ. Bagasse is inefficiently consumed in the cogeneration systems of sugarcane mills, generating steam that is first used to produce power and, subsequently, to fulfil process thermal demand. In addition, a small amount of the bagasse is traded and used as fuel by other industrial branches, but these market opportunities are constrained by transport costs and the low prices of fuel oil. In addition, this market tends to be further reduced, as natural gas is made available.

Tops and leaves of the sugarcane plant — the so-called sugarcane trash — are currently burned in the field before manual harvesting. Since this practice will be gradually reduced in the next 10-12 years for environmental reasons, it is pre­dicted that the availability of sugarcane residues in Brazil will steadily increase. Sugarcane trash shall be recovered from the fields through mechanic harvesting, a technology that has been introduced in Brazil in the last few years. Potentially the availability of sugarcane trash is as large as bagasse, but topographic constraints will determine how much is economically recoverable (see also Braunbeck et al., Chapter 6).

Based on opportunity costs for sugarcane bagasse and on predicted costs for sugarcane trash recovery, it is foreseen that the cost of this biomass would be lower than 2 USS/GJ and, in some cases, even lower than 1 USS/GJ. Despite the focus given to sugarcane residues in this study, a wide range of biomass could obviously be used for the purpose of cofiring, such as wood chips, bark, thinnings, sawdust, various agriculture residues, etc.

In Brazil, the installed electricity generation capacity is largely based on hydropower. It is estimated that almost 80 per cent of the current capacity (slightly larger than 85 GW) corresponds to hydropower plants. Clearly this enormous dep­endency on just one energy source is risky and a diversification of power sources is advisable. In fact, in 2001, due to lack of investments in power generation and to a drier summer than usual, power shortages have occurred. Power production from biomass provides both an opportunity for diversification and for expanding the use of renewables in the Brazilian matrix.

Natural gas power plants shall be built in Brazil in the next 5 to 10 years, fostered by governmental policies. Brazilian natural gas reserves are small but the supply is enlarged through imports from Bolivia and, possibly, from Argentina in the near future. As the natural gas market is not yet well developed, thermal power plants have been considered necessary to assure the feasibility of pipeline projects. This would allow the consumption of a large amount of natural gas during the early years of a “take-or-pay” contract.

Additionally, it is important to bear the perspective of private developers in mind, the main investors after privatization and deregulation of the electricity sector. Natural gas thermal power plants appear to be the main option of investment due to the short construction time of the plants, relatively low capital costs ($/kW installed), high efficiency, and large availability. On the other hand, investors identify a risky picture due to the necessity of bulk imports of natural gas and the instability of the Brazilian economy. Medium — to long-term fluctuations of natural gas prices are obviously a matter of concern for investors. The combined use of natural gas with biomass can reduce these risks and increase the fuel flexibility of new power gen­eration capacity. This point is especially relevant in a natural gas market that is still under development.

Two additional points should be observed concerning the natural gas supply. First, the brand new Bolivia-Brazil pipeline crosses — or is relatively close to — the region where approximately 60 to 65 per cent of the Brazilian sugarcane production takes place. Second, as the natural gas market is further developed, and better opportunities for natural gas consumption arise — for instance, on premium markets such as the residential and industrial sectors — biomass could replace natural gas on thermoelectric power plants that shall be built during the early years of the pipeline operation. The period required for the development of a new natural gas market is around ten years.

Competitiveness of electricity production from biomass will strongly depend on the development of new conversion technologies and on the scale of power plants. Future power production from biomass could be based on gasification, for example. Gas turbines are power devices that have some important attributes: reasonable thermal efficiency and initial capital costs that are not as affected by scale effects. It is expected that, with the not-yet-commercially-available BIG-CC cycles (Biomass Gasification Integrated to Combined Cycles), the efficiency of electricity production could reach about 35 to 45 per cent (Walter et al., 2000).

Performance penalties associated with gas turbine adaptation to gasified biomass are meaningful. Biomass-derived gas from air-blown gasifiers has only about 8 to 10 per cent of the energy content of natural gas, resulting in larger mass flow through gas turbines. As a consequence, technical problems can occur, such as compressor surge, increased thermal and mechanical loads on compressor airfoils, the need of an adapted combustion/injection system and problems with flame stability (Rodrigues et al., 2003a). Regarding the BIG-CC technology, cofiring with natural gas is here mainly proposed as a short-term approach to cope with penalties on both effi­ciency and power resulting from gas turbine derating. The expansion of power plant capacities due to cofiring is also an important contribution for the competitiveness of electricity production from biomass (Rodrigues et al., 2003b).

However, the BIG-CC is not the only technical option for cofired biomass and natural gas plants. Commercial and proven technologies could be used as well. For instance, biomass could be fired independently from natural gas, producing steam in conventional boilers. In addition, steam production would be complemented from HRSGs — heat recovery steam generators — and both streams could be mixed to feed steam turbines of combined cycles. Furthermore, from strategic and economic points of view, electricity production from cofiring natural gas and biomass could be effectively developed as an alternative for the reduction of GHG emissions.