The energy balance is expressed as the ratio of the energy content of the fuel to the primary energy input for the entire production cycle of the fuel. If the energy balance exceeds 1 the energy content of the ethanol is higher than the energy used to produce it.
The energy balance of ethanol from cereals was shown to be on average, 1.6, and varied between 0.7 and 2.8. Corresponding average figures for ethanol from corn, sugar beets and lignocellulosic biomass (e.g. energy forest) were 1.4, 1.8 and 3.2, respectively.
There are several reasons why the energy balances differ between the different studies, even where the feedstock is identical. The sources of differences can be divided between those related to differences in local and geographical conditions, and those related to differences in the methodological approach applied.
Depending on the definition of the system that is studied (systems boundaries), and how the energy input is divided between the ethanol and the by-products generated in the process (allocation methods), the energy balance may differ by a factor of 5.
The energy balance of cereal-based ethanol can be improved by more efficient cultivation methods, but mainly by improved conversion processes. One possibility is by using bio-refineries where not only ethanol but also biogas, heat and electricity are produced from cereals and, for example, energy forest. 
Source: Energy Balance of Bioethanol – A Review, Pål Börjesson, Department of Technology and Society, Environmental and Energy Systems Studies, Lund Institute of Technology, March 2006