69
tion of electricity via the bagasse gasification results in larger savings of NRE
expenditure and GHG emissions per VKT (Fig. 6.10a), due to displacement of grid
electricity. On the other hand, the enhanced ethanol scenario (scenario B) that shows
the lower generation of surplus electricity results in the lowest savings. However,
through a feedstock-oriented FU (Fig. 6.10b), results reveal different perspectives.
The enhanced ethanol scenario (scenario B) that prioritizes the production of ethanol via biochemical synthesis of bagasse seems to be the most advantageous when
applying a feedstock-based FU, as it shows higher yield of ethanol production per
ton of sugarcane. Despite the lower savings by the use of small amount of waste
biomass, the enhanced ethanol scenario shows larger savings during the operation
stage, as it has higher yields of ethanol production per ton of sugarcane, than scenarios A and C. Therefore, savings per ton of sugarcane are more significant than in
the other evaluated routes.
6.4 Final Remarks
The potential of biofuels to mitigate climate change and reduce dependency on fossil fuels is involved in an intense controversy, as its real benefits are significantly
constrained by local geographic factors, technology of production, background
assumptions, and methodological parameters of LCA. Major sources of uncertainty
are data inventory, selection of allocation procedures, system boundaries, and functional unit. An LCA was conducted to discuss the source of uncertainty in LCA and
to evaluate the GHG emission and NRE consumption category impacts of sugarcane ethanol production and utilization in Brazil within a 2030 horizon.
The results suggest that ethanol carriers effectively yield GHG and NRE savings,
both in the production and operation stages. In the production stage, a key advantage is the recovery of sugarcane byproducts, straw, and bagasse, either to maximize
the production of ethanol or to prioritize the generation of electricity. The former
has lower direct emissions, but the latter results in GHG and energy credits as generated surplus electricity displaces grid electricity in Brazil. In the operation stage, the
use of ethanol either in conventional, ethanol-dedicated, or flexible-fuel vehicles
results in negligible GHG emission and NRE consumption, as ethanol is admitted to
be a carbon-neutral renewable fuel.
The integrated WTW analysis discloses the overall benefits of ethanol carriers.
Applying both a product-based and feedstock-related FU, ethanol shows gains in
terms of GHG emission and NRE consumption, but results have dual interpretation
according to which FU is selected. When applying a VKT as FU and system expansion approach, the enhanced electricity route reveals higher credits. On the contrary,
a ton of sugarcane FU indicates that the enhanced ethanol pathway brings more
advantages. This implies that the better process choice depends on the purpose and
evaluation criteria.
6 The Effect of Biofuel Production on Greenhouse Gas Emission Reductions
tion of electricity via the bagasse gasification results in larger savings of NRE
expenditure and GHG emissions per VKT (Fig. 6.10a), due to displacement of grid
electricity. On the other hand, the enhanced ethanol scenario (scenario B) that shows
the lower generation of surplus electricity results in the lowest savings. However,
through a feedstock-oriented FU (Fig. 6.10b), results reveal different perspectives.
The enhanced ethanol scenario (scenario B) that prioritizes the production of ethanol via biochemical synthesis of bagasse seems to be the most advantageous when
applying a feedstock-based FU, as it shows higher yield of ethanol production per
ton of sugarcane. Despite the lower savings by the use of small amount of waste
biomass, the enhanced ethanol scenario shows larger savings during the operation
stage, as it has higher yields of ethanol production per ton of sugarcane, than scenarios A and C. Therefore, savings per ton of sugarcane are more significant than in
the other evaluated routes.
6.4 Final Remarks
The potential of biofuels to mitigate climate change and reduce dependency on fossil fuels is involved in an intense controversy, as its real benefits are significantly
constrained by local geographic factors, technology of production, background
assumptions, and methodological parameters of LCA. Major sources of uncertainty
are data inventory, selection of allocation procedures, system boundaries, and functional unit. An LCA was conducted to discuss the source of uncertainty in LCA and
to evaluate the GHG emission and NRE consumption category impacts of sugarcane ethanol production and utilization in Brazil within a 2030 horizon.
The results suggest that ethanol carriers effectively yield GHG and NRE savings,
both in the production and operation stages. In the production stage, a key advantage is the recovery of sugarcane byproducts, straw, and bagasse, either to maximize
the production of ethanol or to prioritize the generation of electricity. The former
has lower direct emissions, but the latter results in GHG and energy credits as generated surplus electricity displaces grid electricity in Brazil. In the operation stage, the
use of ethanol either in conventional, ethanol-dedicated, or flexible-fuel vehicles
results in negligible GHG emission and NRE consumption, as ethanol is admitted to
be a carbon-neutral renewable fuel.
The integrated WTW analysis discloses the overall benefits of ethanol carriers.
Applying both a product-based and feedstock-related FU, ethanol shows gains in
terms of GHG emission and NRE consumption, but results have dual interpretation
according to which FU is selected. When applying a VKT as FU and system expansion approach, the enhanced electricity route reveals higher credits. On the contrary,
a ton of sugarcane FU indicates that the enhanced ethanol pathway brings more
advantages. This implies that the better process choice depends on the purpose and
evaluation criteria.
6 The Effect of Biofuel Production on Greenhouse Gas Emission Reductions