55
Although there are different carbon intensity of the fuels that are used in ordinary
manufacturing industries, GHG emissions are broadly proportional to energy consumption. However, this does not apply to biofuels. Byproducts and residues of
biomass cultivation processes and production processes are carbon-neutral biomass.
When these byproducts and residues are used as energy sources, this counts as
energy consumption but does not count as GHG emissions. Therefore, life cycle
energy consumption and life cycle GHG emissions must be evaluated differently.
LCA could indicate that biofuel does not save energy but does lead to a reduction in
GHGs.
6.2 Biofuel LCA
6.2.1 LCA Framework
When biofuels are used as a fuel for vehicles, LCA is applied in a way that enables
comparison with a LCA for conventional fuels, such as gasoline or diesel fuels.
When these fossil fuels are used, crude oil is extracted from an oil well, transported,
refined, sold, and loaded into a vehicle fuel tank. These steps are referred to as the
well-to-tank (WTT) stage. The fossil fuel is then burned while the vehicle is running, which is referred to as the tank-to-wheel (TTW) stage. An analysis of the two
together is referred to as a well-to-wheel (WTW) analysis. It is convenient to use
this division for biofuels also for comparison with fossil fuels.
GHG emissions from fossil fuels are small in the WTT stage and large in the
TTW stage. In contrast, with a biofuel that is a carbon-neutral fuel, the environmental loading is small for the TTW stage and large for the WTT stage, complicating the
analysis.
Although biofuels are not obtained by digging oil wells like petroleum, the WTT
stage consists of raw material acquisition, processing, storage, and distribution
(Fig. 6.2).
The raw material acquisition stage includes growing an energy crop. Analysis of
the energy loading of this cultivation step is an analysis of the energy loading for
agricultural activity, which differs from the industrial production for which LCA is
usually used. For industrial production, the raw materials and energy that are input,
and the pollutants generated by the artificial manufacturing are ascertained. These
are originally understood at the design stage for the artificial manufacturing process,
so data and reports are easy to obtain. In contrast, agriculture depends on nature, and
effects on the environment that result from artificial utilization of land must be
evaluated. Unlike an industrial process that is performed under controlled conditions, the environmental loading of agriculture has to be evaluated under conditions
that are greatly influenced by climate and the like. The fate of fertilizers that are
used and changes in the soil that are caused by agricultural activities should also be
included.
6 The Effect of Biofuel Production on Greenhouse Gas Emission Reductions
Although there are different carbon intensity of the fuels that are used in ordinary
manufacturing industries, GHG emissions are broadly proportional to energy consumption. However, this does not apply to biofuels. Byproducts and residues of
biomass cultivation processes and production processes are carbon-neutral biomass.
When these byproducts and residues are used as energy sources, this counts as
energy consumption but does not count as GHG emissions. Therefore, life cycle
energy consumption and life cycle GHG emissions must be evaluated differently.
LCA could indicate that biofuel does not save energy but does lead to a reduction in
GHGs.
6.2 Biofuel LCA
6.2.1 LCA Framework
When biofuels are used as a fuel for vehicles, LCA is applied in a way that enables
comparison with a LCA for conventional fuels, such as gasoline or diesel fuels.
When these fossil fuels are used, crude oil is extracted from an oil well, transported,
refined, sold, and loaded into a vehicle fuel tank. These steps are referred to as the
well-to-tank (WTT) stage. The fossil fuel is then burned while the vehicle is running, which is referred to as the tank-to-wheel (TTW) stage. An analysis of the two
together is referred to as a well-to-wheel (WTW) analysis. It is convenient to use
this division for biofuels also for comparison with fossil fuels.
GHG emissions from fossil fuels are small in the WTT stage and large in the
TTW stage. In contrast, with a biofuel that is a carbon-neutral fuel, the environmental loading is small for the TTW stage and large for the WTT stage, complicating the
analysis.
Although biofuels are not obtained by digging oil wells like petroleum, the WTT
stage consists of raw material acquisition, processing, storage, and distribution
(Fig. 6.2).
The raw material acquisition stage includes growing an energy crop. Analysis of
the energy loading of this cultivation step is an analysis of the energy loading for
agricultural activity, which differs from the industrial production for which LCA is
usually used. For industrial production, the raw materials and energy that are input,
and the pollutants generated by the artificial manufacturing are ascertained. These
are originally understood at the design stage for the artificial manufacturing process,
so data and reports are easy to obtain. In contrast, agriculture depends on nature, and
effects on the environment that result from artificial utilization of land must be
evaluated. Unlike an industrial process that is performed under controlled conditions, the environmental loading of agriculture has to be evaluated under conditions
that are greatly influenced by climate and the like. The fate of fertilizers that are
used and changes in the soil that are caused by agricultural activities should also be
included.
6 The Effect of Biofuel Production on Greenhouse Gas Emission Reductions