4.2 Energy balance of cassava-based ethanol: a comparison with other studies
The estimation of GHG and energy balances can potentially produce variable results depending on 1)
the types of biofuel feedstock; 2) the specific application of energy inputs in farming operations; 3)
feedstock yields; and 4) the energy intensity level of the ethanol industry [26]. Our analysis focuses
on cassava-based ethanol, keeping the first factor constant. The three remaining factors are
examined in the 2011 survey. The changeability of these factors possibly causes result variations in
comparison with other studies. Besides, the different application of the opportunity cost approach in
this study induces a specific result for Vietnam compared to other country based studies.
For comparison purpose, our attention is paid to the studies on energy and GHG balance analysis
in the same line of cassava-based ethanol. A comparison of energy balances among different studies
is presented in Table 5. The energy balance is the difference between the reference value and input
energy. The reference value is explained by the energy base of either gasoline or ethanol itself with
the base of 1. Our study uses the energy base of gasoline with the fuel consumption-based
substitution ratio of 1.06 which better suits the opportunity cost approach and is tested recently in
2009.