The nice thing about Brazil's ethanol program is the closed-loop cycle that they use. The sugar cane is harvested and brought to the mill where it pressed into a sugary syrup and dry mass. The dry mass is burned in efficient double-stage heat-capture boilers (at least in the better plants) to provide all the energy required to run the mill. The syrup is fermented uising high-yield yeast strains to 15-20% ethanol 'cane beer'. This is then distilled to 96% pure ethanol (the azeotrope limit) using energy from burning the dry cane (bargasse). There are a number of methods for taking 96% ethanol to 100% ethanol; 100% ethanol blends well with gasoline or diesel fuel.
The waste - ash from burning the cane (phosphate-rich) and yeasty sediment residue (nitrogen-rich) is then trucked right back out to the fields, replenishing the soil and vastly reducing any need for fossil-fuel fertilizers. Crop
rotation might also be a good idea. Basically, this is an energy-efficient and environmentally friendly large-scale method of fuel production; it deserves careful study by anyone embarking on such a project. Compare this to the coal-fired ethanol distilleries currently being built for 'economic efficiency' in the Midwestern states - sure it helps stimulate the demand for coal, the dirtiest, lowest-energy, and most climate-damaging of all the fossil fuels.
Peter I. Solem
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