Hammerschlag Roel
Institute for Lifecycle Environmental Assessment, P.O. Box 22437, Seattle, Washington 98122, USA.
Environ Sci Technol. 2006 Mar 15;40(6):1744-50. doi: 10.1021/es052024h.
Various authors have reported conflicting values for the energy return on investment (rE) of ethanol manufacture. Energy policy analysts predisposed to or against ethanol frequently cite selections from these studies to supporttheir positions. This literature review takes an objective look at the disagreement by normalizing and comparing the data sets from ten such studies. Six of the reviewed studies treat starch ethanol from corn, and four treat cellulosic ethanol. Each normalized data set is also submitted to a uniform calculation of rEdefined as the total product energy divided by nonrenewable energy input to its manufacture. Defined this way rE > 1 indicates that the ethanol product has nominally captured at least some renewable energy, and rE > 0.76 indicates that it consumes less nonrenewable energy in its manufacture than gasoline. The reviewed corn ethanol studies imply 0.84 < or = rE < or = 1.65; three of the cellulosic ethanol studies imply 4.40 < or = rE < or = 6.61. The fourth cellulosic ethanol study reports rE= 0.69 and may reasonably be considered an outlier.
不同作者报告的乙醇生产能源投资回报率（rE）数值相互矛盾。倾向或反对乙醇的能源政策分析师经常引用这些研究中的部分内容来支持他们的观点。这篇文献综述通过对十项此类研究的数据集进行归一化处理和比较，客观地审视了这一争议。其中六项被审查的研究涉及玉米淀粉乙醇，四项涉及纤维素乙醇。每个归一化后的数据集还会进行统一的rE计算，rE定义为产品总能量除以其生产过程中的不可再生能源投入。按照这种定义，rE>1表明乙醇产品名义上至少捕获了一些可再生能源，rE>0.76表明其生产过程中消耗的不可再生能源比汽油少。被审查的玉米乙醇研究表明0.84≤rE≤1.65；三项纤维素乙醇研究表明4.40≤rE≤6.61。第四项纤维素乙醇研究报告的rE=0.69，可合理地视为一个异常值。
