Comprehensive studies have been conducted by several environmental organisations (Hileman, 2009) (Stratton, 2010) (Hileman, 2010) into the complete life cycle impacts of candidate aviation biofuels. Both FT and HRJ fuels have been analysed, with the results of both following. Figure 26 below shows the “well to wake” steps of a biofuel life cycle.
Figure 26 - Biofuel lifecycle steps (Stratton, 2010)
For each step of the lifecycle conducted by (Stratton, 2010), the GHG emissions considered are CO2, CH4 and N2O.For all phases excluding combustion, NOx, SOx and soot are neglected but will be mentioned using flight test data from additional sources.
Many of the biofuels have a “biomass credit” which offsets the CO2emissions released during combustion. As the benefit of biofuels is the ability of the feedstock to absorb the combusted CO2during growth in a “cycle” process, a mechanism is required to consider this. The biomass credit is essentially the “difference between the biomass and fossil fuels in terms of their GHG
emissions” (Stratton, 2010).
The following results were collated from (Stratton, 2010) with the life cycle GHG emissions presented using a metric (g CO2e/MJ) that captures the mass of GHG per unit of energy consumed by the aircraft. The two fuel types to be considered are FT and HRJ fuel. The following feedstocks analysed in (Stratton,
Biomass Co-Product
Recovery & Extraction
Raw Material
Movement ProductionJet Fuel TransportationJet Fuel CombustionJet Fuel Land Change in Land Usage Cultivation Aviation Productivity Other Liquid Fuel Products
2010) and included in this study are listed below in Table 6 together with conventional jet fuel.
Table 6 - Alternative Fuels Considered (Stratton, 2010)
Source Feedstock Recovery Method Processing Method
Final Product
Petroleum ConventionalCrude Crude Extraction Crude Refining JET A1
Natural Gas Natural Gas Natural Gas Extractionand Processing
Gasification, F-T Synthesis and
Upgrading
SPK Jet Fuel (F-T)
Coal Coal Coal Mining
Biomass
Switchgrass Corn Stover
Forest Waste Biomass Cultivation
Biomass – Renewable Oil Soybeans Palm Algae Jatropha Rapeseed
Biomass Cultivation &
Extraction of Plant Oils Hydroprocessing Fuel (HRJ)SPK Jet
Nine categories referring to different life cycle phases and emissions have been analysed, with an overall value of g CO2e/MJ calculated to enable comparisons to be drawn between the different types of aviation fuel.
The nine categories are listed below:
Biomass Credit Combustion
Recovery Well to Tank (WTT) N2O
Feedstock Transport Well to Tank (WTT) CH4
Processing Land Use Change
Fuel Transport
The “well to tank“ category includes all the emissions of N20 and CH4produced from all the phases leading up to but not including combustion. The combustion
category will be complimented with other data obtained from various flight and ground tests to provide a comprehensive evaluation of the environmental merits of each candidate fuel.
With each of the biofuels requiring feedstocks, (Stratton, 2010) formulated several different land use change scenarios to measure the impact when using different types of land masses. Table 7 below details the different scenarios used.
Table 7 - Land Use Scenarios for Candidate Biofuels (Stratton, 2010)
LUC CODE Land Use
Change Scenario 0 Scenario 1
LUC-B Switchgrass None Carbon depleted soils converted toswitchgrass cultivation
LUC-S Soy Oil None Grassland conversion to soybean field
LUC-P Palm Oil None Logged over forest conversion to palmplantation field
LUC-R Rapeseed Oil None Set-aside land converted to rapeseedcultivation
LUC-H Salicornia None Desert land converted to salicorniacultivation field
Figure 27 below displays the results of the PARTNER life cycle study in a graph, highlighting the impact of the various categories on the total life cycle emissions of each fuel.
Figure 27 - Life Cycle GHG Emissions for Alternative Fuels (Derived
2010)
-100 -50
Crude to Conventional JET A1 Natural Gas to FT Fuel Coal to FT Fuel Coal/Switchgrass to FT fuel (LUC Coal/Switchgrass to FT fuel (LUC Soy Oil to HRJ (LUC Soy Oil to HRJ (LUC Palm Oil to HRJ (LUC Palm Oil to HRJ (LUC Rapeseed Oil to HRJ (LUC Rapeseed oil to HRJ (LUC
Jatropha Oil to HRJ Algae to HRJ Salicornia to HRJ (LUC Salicornia to HRJ (LUC Biomass Credit Processing WTT N2O
Life Cycle GHG Emissions for Alternative Fuels (Derived
0 50 100 150
Crude to Conventional JET A1 Natural Gas to FT Fuel Coal to FT Fuel Coal/Switchgrass to FT fuel (LUC-B0) Coal/Switchgrass to FT fuel (LUC-B1) Soy Oil to HRJ (LUC-S0) Soy Oil to HRJ (LUC-S1) Palm Oil to HRJ (LUC-P0) Palm Oil to HRJ (LUC-P1) Rapeseed Oil to HRJ (LUC-R0) Rapeseed oil to HRJ (LUC-R1) Jatropha Oil to HRJ Algae to HRJ Salicornia to HRJ (LUC-H0) Salicornia to HRJ (LUC-H1)
Life Cycle GHG Emissions (g CO2e/MJ )
Biomass Credit Recovery Feedstock Transport
Fuel Transport Combustion
WTT CH4 Land Use Change
Life Cycle GHG Emissions for Alternative Fuels (Derived (Stratton,
150 200
Feedstock Transport Land Use Change
Figure 28 illustrates to same resul
Figure 28 - Total Life Cycle GHG Emissions of Biofuels
Red and Green symbolise increases or decreases in GHG emissions respectively when compared to the baseline JET A1 (black).
Figure 28 summarises the lifecycle impact of each fuel, however the
alone do not determine the suitability of each fuel. Other factors such as feedstock yield and competition with food sources have to be considered. The following section examines FT and HRJ fuel in more detail together with data obtained from ground and flight combustion testing.
0 20 40 60 80 100 120 140 160 180 L C G H G E m is s io n s (g C O 2 e /M J
illustrates to same results as a sum of all nine categories.
Total Life Cycle GHG Emissions of Biofuels (Stratton, 2010)
increases or decreases in GHG emissions respectively when compared to the baseline JET A1 (black).
summarises the lifecycle impact of each fuel, however the
alone do not determine the suitability of each fuel. Other factors such as feedstock yield and competition with food sources have to be considered. The following section examines FT and HRJ fuel in more detail together with data
ound and flight combustion testing.
Fuel Type
ts as a sum of all nine categories.
(Stratton, 2010)
increases or decreases in GHG emissions respectively when
summarises the lifecycle impact of each fuel, however these results alone do not determine the suitability of each fuel. Other factors such as feedstock yield and competition with food sources have to be considered. The following section examines FT and HRJ fuel in more detail together with data