Cassava is the best energy crop used to produce ethanol. This is because the ethanol yield of cassava per unit land area is the highest among all known energy crops. The comparison of ethanol yield produced from different energy crops shows that cassava has the highest ethanol yield of 6,000 kg/ha/ yr and highest conversion rate of 150 L/tonne of all the energy crops. Though sugar cane and carrot have higher crop yield of 70 and 45 tonnes/ha/ yr respectively compared to 20 tonnes/ha/yr for cassava, the huge quantities of water which they require during their growth periods is a strong limitation when compared to cassava which can actually grow under much drier conditions. Kuiper et al., (2007) noted that a tonne of fresh cassava tubers yields about 150 litres of ethanol.

Adelekan (2010) investigated ethanol productivity of cassava crop in a laboratory experiment by correlating volumes and masses of ethanol produced to the masses of samples used. Cassava tubers (variety TMS 30555) were peeled, cut and washed. 5, 15, 25 and 35 kg samples of the tubers were weighed in three replicates, soaked in water for a period of a day, after which each sample was dried, crushed and the mash mixed with 500, 650, 800, and 950 ml of N-hexane (C6H14) respectively. This crushed mash was then allowed to ferment for a period of 8 days and afterwards pressed on a 0.6 mm aperture size and sieved to yield the alcohol contained in it. The alcohol was heated at 79°C for 10 h at intervals of 2 h followed by an h cooling. Ethanol yield was at average volumes of 0.31, 0.96, 1.61 and 2.21 litres, respectively, for the selected masses of cassava samples. This study found that a total of 6.77 million tonnes or 1338.77 million gallons of ethanol are available from total cassava production from tropical countries. The production and use of ethanol from cassava crop in the cassava-growing tropical countries of the world certain holds much promise for energy security and is therefore recommended.

Some benefits of using ethanol are that it is not poisonous and neither causes pollution nor any environmental hazard. It does not contribute to the greenhouse effect. It has a higher octane value than gasoline and is therefore an octane booster and anti-knock agent. It reduces a country’s dependence on petroleum and it is an excellent raw material for synthetic chemicals. The main crops presently being used for ethanol production are maize, sugarcane and cassava, and among these, cassava has a competitive advantage because of its lower cost of raw material and a simpler ethanol processing technology. Nguyen and Gheewala (2008) conducted a well-to-wheel analysis for cassava-based ethanol in Thailand. The aim of the analysis was to assess the potentials of cassava-based ethanol in the form of gasohol E10 for promoting energy security and reducing environmental impacts in comparison with conventional gasoline. The results showed that cassava-based ethanol in the form of E10, along its whole life cycle, reduced certain environmental loads compared to conventional gasoline. The percentage reductions relative to conventional gasoline are 6.1% for fossil energy use, 6.0% for global warming potential, 6.8% for acidification, and 12.2% for nutrient enrichment. The paper concluded that using biomass in place of fossil fuels for process energy in the manufacture of ethanol leads to improved overall life cycle energy and environmental performance of ethanol blends relative to conventional gasoline.