The interdisciplinary issues resulting from energy and climate change policies recognize high demand for a systematic evaluation. Energy analysis showing only total energy consumption does not enable policy maker to discern facts as to nature of energy consumption and production with the subsequent emissions of a given system. A change in the demand activity changes the relative fraction of other input factors in energy production. From the LCA perspective, the technological structural change in the composition of the energy production can also have a different effect on the energy and CO2 structure of a demand activity. Thus, energy analysis about influences of one sector to the other sector should be identified because these influences always exist. The objective of this research is to develop a supply and demand energy model based on input-output analysis for life cycle environmental performance assessment.
The basic premise for the model development is that the environmental load depends on not only the amount of energy consumption in the system but also the type of energy use. The effect of energy consumption on the environment can be reduced by minimizing the amount of energy consumed and the selection of energy use. The backbone of the proposed system is that it distinguishes the function of energy used between supply energy and demand energy into two matrixes and allows their influences to be noted through a generic model and then connects this with the life cycle activity of transport using a specific model. The key components of this model include the following: the construction of an energy input-output table for supply energy; the formation of a normalized supply energy table; the construction of an energy input-output table for demand energy, an estimation of normalized demand energy; the development of a generic model of an energy supply-demand model, the development of a specific model for transportation responsibility and the formation of a sub-specific model for emissions. The difference in the results between the existing model and the proposed model was analyzed and compared through the rail transportation system.
The comparison between the existing model and proposed model will give a different picture as to the distribution of the environmental load of energy consumption among different life cycle activities. This will lead to an understanding as to which significant issues can be identified. Using the proposed system will make it possible to predict the effects of energy and CO2 structures in demand energy resulting from a fractional change in the input of the supply energy e.g. a grid mix change in electricity generation as well as an energy choice made by the demand energy side. The energy structure for the demand and supply of twelve types of energy enable us to correctly determine CO2 emissions and other gas emissions, including the incorporated costs for each type of energy. The proposed model is complementary to the existing model. This is not only because the total energy or primary energy consumption is noted but also the influence and selection of primary, secondary and tertiary of energy is considered in the energy analysis to reflect the impact the environmental load of a system on the environment.
The proposed model was applied to the passenger transportation system in Korea where a comprehensive study of the life cycle of energy and CO2 has not yet been published. The total energy consumption associated with the life cycle activity of rail passenger transport is 1.08 MJ/pkm. The energy input described is heavily dominated by supply energy, 6.27E-01 MJ/pkm, resulting in demand energy of 2.99E-01 MJ/pkm by the operation stage. Road transport is also dominated by operation and accounts for 1.81 MJ/ pkm from the total energy input of 2.06 MJ/pkm. Road operation is estimated to be using 1.41, 3.77E-01 and 2.53E-02 MJ per pkm of fuel oil, other petroleum products (LPG) and gas, respectively. According to these requirements, this model reports that 1.76E-02, 1.20E-01, 3.26E-02, 1.98E-02, 3.30E-02 and 2.83E-02 MJ of coal, crude petroleum, natural gas, nuclear, non-fuel oil and other energy sources, respectively, are consumed for the operation of energy production. Total rail and road passenger emissions, on a traffic volume basis, is 38.39 and 118 g CO2-eq./pkm, respectively. The results show that on a pkm basis, passenger roads have life cycle emissions about three times those of rail, while that ratio is over ten times greater when the scope of evaluation is the tailpipe. For the sensitivity analysis, a structural change in the electricity grid mix reduces CO2 emissions by 20% in total for rail passenger transport but by only 1% for road passenger transport because the main energy used for rail passenger transportation is electricity.
For policy makers the energy structures serves as guidelines and show the results about energy types, their CO2 contributions as well as the energy costs of different energy types. Also, the analysis performed here may help policy makers in their dealing with the problem of CO2 emissions as well as the costs as they will be better informed about the root causes of the problems. When the proposed model viewpoint is incorporated in the identification of significant issues, more opportunities in identifying the roots of significant issues and minimizing the impact of these can be possible.