Jamaica Biofuels Report - Ministry of Energy

5. Processing and Distribution5.1 Technology-neutral processing regime required to activate the desiredbiofuel developmentsSugarcane ProcessingThe total amount of energy in 1 t of cane (aerials part) is about 7400 MJ, more than a barrel ofoil (6000 MJ), but it is divided about 2400 MJ in sugars, 2500 MJ in the bagasse and 2500 MJ inthe straw (mainly leaves and sometimes called cane trash). The efficiency of recovery of thesugar, in various final non-energy forms, and the balance as energy differs between each typedue to the process differences. While sugar recovery reaches efficiencies of over 90% withcurrent technology, the recovery of the energy in terms of process steam and electricity byusing the bagasse as a boiler fuel is lower. Whereas modern high-pressure bagasse boilers canachieve thermal efficiencies of 85%, older lower pressure units have efficiencies often below75%. In addition, the overall steam to electricity conversion efficiencies that for modern unitscan exceed 30% is often lower than 10% at older plants. In order to reduce the cost of ethanolproduced from the cane sugar whether in the case of a combined granular sugar and ethanolplant or is a purpose built cane to ethanol with no granular sugar plant, the main approachadopted in the last 20 years has been to introduce higher energy efficiency in the processessuch that surplus electricity can be maximized and sold to create additional revenue that can beused to reduce the price of the ethanol when this is needed for overall financial viability. Longerterm research, development and initial pre-commercialization of advanced biofuel productionprocesses that begin after the hydrolysis of the fiber (celluloses and hemicelluloses), offer theprospect of an approach that provided better overall returns and will make sugar cane almostunbeatable in terms of energy production. This new technology will place greater emphasis ondeveloping varieties of cane that may be higher in fiber and or mature earlier or later. It willcertainly increase the needs for well-managed operations in the field as well as in the processto maximize outputs and minimize unit costs.Ethanol production can be built as an extension of current sugar mill operations with theaddition primarily of fermentation and distillation capabilities, as the dashed section of Figure7 shows. Sugarcane processing for ethanol production is a well-established commercialprocess that can be readily purchased and installed off the shelf as a turn-key operation by asmall number of international suppliers. As seen in Fig. 7, sugarcane delivered to the plant iscrushed to extract the sugar juice. The sucrose-rich juice is then concentrated and processedto sugar and molasses (for rum production) or fermented by yeast to ethanol in continuousstirred fermentation units. The dilute fermentation broth is directed to a distillation column,where ethanol is recovered as a 95.6% (by weight) aqueous solution. In Jamaica the molassesare turned into rum by the country’s spirits industry.The ethanol solution is further refined to anhydrous ethanol using molecular sieves to removethe remaining water. The sieves consist of zeolites, which facilitate the separation of ethanol39