Agronomic features, ethanol yields and resource use of four feedstocks for ethanol production in the Philippines

As an agronomic crop, sugarcane is the easiest to manage as feedstock for ethanol for the following reasons: 1)one planting is done every 4 years; 2)the crop does not succomb to moisture extremes due to its deeper root system and longer field duration(10-14 months); 3) in the advent of strong typhoons, its stems lodge and later recline back when weather becomes favorable; and 4)sugarcane tolerates some delays in harvesting (12-14 months). Sugarcane yields the highest net ethanol (2,507 L/ha to 4,771 L/ha per year) at 7 to 11x more than corn, 4 to 9x than cassava; and 18 to 25x than sweet sorghum. Two crops of corn can be grown in one year due to its shorter maturity, but the total ethanol yield is still lower than one sugarcane crop; the same holds true with sweet sorghum. In terms of resource use(labor, capital and production inputs like fertilizer), sugarcane produced 5 to 7 L ethanol, cassava 0.89 to 1.68 L ethanol, corn 0.72 to 1.36 L ethanol, and sweet sorghum 0.48 to 0.52 L ethanol. Sugarcane produced 20.90 and 32.94 L of ethanol per man-day, cassava 3.66 and 11.27 L, corn 4.5 and 7.72 L, and only 1.3 and 1.65 for sweet sorghum for average and high yields, respectively. As to labor use efficiency, sugarcane produced 16 to 20x more ethanol than sweet sorghum per man-day labor, 3 to 5.7x more ethanol than cassava and 4.6x more ethanol than corn. Sugarcane yielded 12 to 15x more ethanol per peso spent than sweet sorghum as feedstock source, 4.83 to 9.63x more than corn and 3.83 to 6.9x more than cassava. In addition to its being resource-use efficient, bagasse combustion adequately provides the huge energy requirements during sugarcane juice extraction, clarification, and later distillation of fermented juice. On the other hand, corn, cassava and sorghum grains do not have similar by-products that can supply the energy(fuel) needed by the factory to produce the ethanol. This explains sugarcane's highest energy efficiency. Sugarcane juice is readily fermentable while starches from cassava, corn and sorghum grains require saccharification before fermentation. As feedstock for ethanol production, even without inputting the added cost of saccharification for the other feedstocks, sugarcane is the cheapest for average (PhP 16.15) and high (PhP 19.29/L) purchase price of cane per ton. In comparison, at PhP 4 to PhP6/kg of cassava roots and PhP 12 to PhP 15/kg corn grain, cassava and corn are the most expensive feedstocks for ethanol production at PhP 33.3 to PhP 36.5/L, respectively. Sweet sorghum as feedstock costs PhP29 to PhP 34.4 per liter of ethanol(average for grain and stems).