到本世纪未原油的需要量大约短缺25%(见图1)。因而火花点火发动机将需要代用燃料(此处代用燃料的含义是指不依靠从油井中的原油来提炼的)。这些燃料使用很大程度上取决于输入国和输出国的政策,取决于他们在支付、雇佣以及本国自然资源可以利用的程度等方面的平衡。在盛产甘庶的巴西,用乙醇作为汽油 Approximately 25% of the demand for crude oil by the end of this century (see Figure 1). Thus a spark-ignition engine will require a substitute fuel (here substitute fuel means it does not depend on crude oil from the well to be refined). The use of these fuels depends very much on the policies of importing and exporting countries, depending on their balance of payments, employment and the extent to which their natural resources are available. Brazil is rich in sweet potato, with ethanol as gasoline