Energetics of ethanol production from sugarcane and its implications

Two data sets obtained from two provinces (Batangas and Negros Occidental) in the Philippines were used in the estimates of non-renewable energy costs, net ethanol/yield per ha and energy balance (energy efficiency and intensity) of ethanol production from sugarcane. The implications of the estimates and of the large scale ethanol program were discussed. On the average, it was estimated that ethanol production utilized a total of 12.607 li of diesel oil equivalent/tonne cane (LDOE/TC). Growing and hauling canes to the mill used 10.89 LDOE/TC (74%). For processing sugarcane juice into ethanol, the energy value of 1.717 LDOE/TC (12%) was adopted from Brazil to complete the calculations of non-renewable energy since there is no operational distillery plant processing sugarcane juice into ethanol in the Philippines as of this date. An additional 2.12 LDOE/TC (14%) is incurred in applying the distillery slop as fertilizer material in the field (Batangas experience) which led to a total of 14.73 LDOE/TC. Processing canes into ethanol uses low amount of non-renewable oil since much of the power is supplied by burning bagasse. Producing one liter ethanol as renewable energy consumed about 0.31 li of non-renewable energy or an energy intensity of Ei=0.31. Ethanol production from sugarcane in the country revealed a low energy efficiency (Ee=3.26) compared with the reported 8-12 energy efficiency in Brazil. The use of high amount of non-renewable energy in cane production (fertilizer, hauling and preparing lands to establish new crop) which accounted for 87% of the total non-renewable energy consumed explained this low Ee. Chemical fertilizer, particularly nitrogen consumed the highest non-renewable energy expense at 55.7%. What this low Ee means is low net ethanol yield per ha (3,868 li EtOH/ha) which means that large area (140,000 ha) should be planted to sugarcane to replace 10% of gasoline. If the yield level will be increased to 100 TC/ha, only 60% of the areas will be needed. Ethanol production is also accompanied by the production of huge liquid waste effluent called distillery slop or vinasse ranging from 12-18 li per li of ethanol. The ethanol production target of 541 M li by year 2011-2012 will produce about 6.492 to 9.738 billion liters of vinasse. Disposing distillery slop waste presents an enormous energy expense. Practical and ecological ways using and disposing vinasse must be adopted.