3. Sectorial process efficiencies and potential improvements
3.1.Reduction of energy consumption
With the possibility of selling surplus electricity to the grid, sugarcane mills have been improving the performance of their units to promote a reduction in the energy consumption in the process, as well as the production of higher amounts of electricity.
The use of electric drives for sugarcane preparation and extraction has been preferred lately over steam turbines, which are less efficient and require more steam. The use of diffusers instead of mills also allows decrease of steam consumption, since the amount of mechanical energy required to operate diffusers is significantly smaller than the energy required for mills (about 10 kWh/t of cane for diffusers comparedto15kWh/t of cane for mills, according to Pellegrini and Oliveira Júnior (2011)). However, one or two additional mills are required to dry final bagasse. Alternative fermentation processes such as low temperature or extractive fermentation allow production of wine with higher ethanol content leading to lower energy consumption in distillation (Dias etal.,2012b). Product recovery through the use of membranes can also be used to produce high ethanol concentration wines, but technological issues, such as membrane fouling remain to be solved (Abels etal.,2013). Pinch Analysis has also been considered for the reduction of process steam consumption in sugarcane facilities. This analysis, based on thermal integration between hot and cold streams of the process, can significantly improve energy savings of conventional and future biorefinery configurations (Dias etal.,2011a; Palacios-Bereche et al.,2014b).