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What Are the Main Characteristics of Alternative Jet Fuels? 9
Are there examples of drop-in alternative jet fuels?
Synthetic paraffinic kerosene (SPK) is the best example of a drop-in alternative jet fuel. SPK
is considered a drop-in alternative jet fuel because it meets the technical and safety properties of
conventional jet fuel--except for aromatic content. Aromatics are complex hydrocarbon com-
pounds that are required to be present in any jet fuel to some minimal amount (currently 8%).
The existing jet fuel distribution, storage, and handling infrastructure has been designed with
aromatics in mind. Without aromatics, rubber seals in valves and other elements of the jet fuel
supply infrastructure can leak and present unacceptable environmental and safety issues. There-
fore, to be considered as a drop-in alternative jet fuel, SPK must be mixed with conventional
jet fuel so that the resulting blend contains the amount of aromatics mandated by the jet fuel
specification.
To date, blends of up to 50% of two types of SPKs have been approved and certified as drop-
in alternative jet fuel. One type includes SPKs made out of coal, gas, biomass, or municipal solid
waste (MSW) using the Fischer-Tropsch (FT) process. The other type of SPK includes hydro-
processed esters and fatty acids (HEFA) made from plant oils and animal fats. HEFA is also
referred to as hydrotreated renewable jet (HRJ). Both the FT and HEFA processes will be
discussed further in Section 2.3.
What are the blending requirements for alternative jet fuels?
As discussed previously, current approval of alternative jet fuel for use in aircraft requires that
they be blended with conventional jet fuel up to a concentration of 50% alternative jet fuel. As
new processes for producing alternative jet fuels are developed and more experience with the
handling of existing alternative jet fuels is obtained, it is possible that the blending requirements
could be reduced.
Have alternative jet fuels been used in aircraft?
Yes. Jet fuel made from coal using the Fischer-Tropsch process has been in daily use for sched-
uled airline service in South Africa for more than 20 years. The South African energy and chem-
ical company Sasol has produced SPK and other chemicals from locally sourced coal using its
proprietary version of the FT process. When blended up to 50% with conventional jet fuel,
Sasol's SPK was approved for use as commercial jet fuel under the U.K.'s DEFSTAN 91-91 in
1998. Since 1999, this jet fuel blend has been used successfully by commercial airlines in aircraft
refueled at South African airports, and since then South African Airlines has experienced no fuel-
related problems (Roets 2009).
Prior to qualification, there were numerous examples of commercial flight tests using alter-
native jet fuels made with different technologies and feedstocks. A summary of flight demonstra-
tions in commercial aircraft is shown in Table 1. The flight tests showed no significant difference
in the performance of the alternative jet fuel compared to conventional jet fuel.
Since the qualification of HEFA on July 1, 2011, KLM, Lufthansa, and Aeromexico have ini-
tiated commercial service using fuels purchased from U.S. and European sources. These flight
commitments for extended commercial use will prove HEFA fuel's service reliability. Flights by
the airlines Thomson (UK charter operator) and Finnair are imminent.
2.2 Feedstocks for Producing Alternative Jet Fuels
What feedstocks can be used to produce alternative jet fuels?
The two primary sources of feedstock for alternative fuels are fossil fuels and bio-derived
feedstocks. Fossil fuel feedstocks include coal and natural gas. Bio-derived feedstocks include
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10 Guidelines for Integrating Alternative Jet Fuel into the Airport Setting
Table 1. Alternative jet fuel flight demonstrations in commercial aircraft.
Airline or
Engine Fuel
Date Other Aircraft Feedstock Technology Source
Maker Producer
Sponsor
Feb Rolls- Fischer-
Airbus A380 Shell Natural gas Airbus 2011
2008 Royce Tropsch
Dec Air New B747- Rolls- Warwick
UOP Jatropha HEFA
2008 Zealand 300 Royce 2009
Jan B737- Jatropha,
Continental GE/CFMI UOP HEFA DOE 2009
2009 800 algae
Camelina,
Jan Japan B747- Pratt & Mecham
UOP Jatropha, HEFA
2009 Airlines 300 Whitney 2008
algae
Oct A340- Rolls- Fischer- Qatar
Qatar Shell Natural gas
2009 600 Royce Tropsch Airways 2011
Nov B747- North Sea
KLM GE UOP Camelina HEFA
2009 400 Group 2011
Apr Fischer-
United A319 IAE Rentech Natural gas Kuhn 2009
2010 Tropsch
Nov
TAM A320 CFMI UOP Jatropha HEFA Karp 2010
2010
Apr InterJet
A320 CFMI UOP Jatropha HEFA Gross 2011
2011 (Mexico)
June Rolls-
Honeywell G450 UOP Camelina HEFA Chatzis 2011
2011 Royce
June
Boeing B747-8 GE UOP Camelina HEFA Lane 2011
2011
Palm oil,
July
Lufthansa A321 CFMI Neste Oil rapeseed, HEFA Reals 2011
2011
animal fats
July B737- Used
KLM CFMI Dynamic Fuels HEFA KLM 2011
2011 800 cooking oil
July SkyNRG Used
Finnair A319 CFMI HEFA Mroue 2011
2011 cooking oil
Aug B777- Aeromexico
Aeromexico GE ASA Jatropha HEFA
2011 200 2011
Sept Thomson Rolls- Used Thompson
B757 SkyNRG HEFA
2011* Airways Royce cooking oil 2011
Bom-
Porter Bombardier
2012* bardier PWC UOP Camelina HEFA
Airlines 2010
Q400
Advanced
2012* Azul Embraer GE Amyris Sugarcane FRJ
Biofuels 2009
B747- Pratt & Stanway
2013* Air China UOP Jatropha HEFA
400 Whitney 2010
*Announced as of August 31, 2011
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What Are the Main Characteristics of Alternative Jet Fuels? 11
plant oils, animal fats, crop residues, woody biomass, municipal solid waste, and other organic
material. Each has relative strengths and weaknesses. Following is a brief overview of each
potential feedstock and the most important considerations for each.
1) Fossil fuels
Coal and natural gas can be used to make alternative jet fuel with the Fischer-Tropsch process
(see Section 2.3). Because of availability, transportation systems, and developed markets, coal
and natural gas can support production in commercial quantities.
a) Sources and availability
Ample supplies of coal and natural gas at low per-unit costs support large rates of extraction
for sustained periods of time. Costs and methods for extraction are well known, and large un-
tapped deposits exist in the United States.
b) Economics and logistics
Coal and natural gas have well-developed markets, supply chains, pricing mechanisms, and
risk management tools such as financial derivatives to hedge against volatility in the price of the
commodities. Existing pipeline and rail transportation systems are cost effective and cheaper
than truck transportation for transporting coal and natural gas; however, alternative jet fuel pro-
cessing facilities would need to be located in proximity to existing transportation infrastructure
in order to take advantage of this cost advantage. Construction of new rail lines and pipelines
would likely compromise the economic viability of any alternative jet fuel project.
c) Environmental considerations
If not properly mitigated, the life-cycle greenhouse-gas (GHG) footprint of alternative jet fuels
from fossil fuel feedstocks can be two to three times that of conventional jet fuel (see Box 1 and
Section 2.4 for more details on life-cycle GHG analysis). These results depend to a great extent
Box 1. Brief introduction to life-cycle greenhouse gas analysis.
Life-cycle analysis (LCA) of GHGs estimates the amount of greenhouse gases (e.g.,
CO2) released in the full life cycle of an alternative fuel (see Section 2.4 for a more
complete discussion). This includes emissions from the production, distribution,
and combustion of an alternative fuel, including extraction; inputs to production
such as tillage, planting, and harvesting biomass feedstocks; processing and con-
version; transportation; and storage. It is a cradle-to-grave estimate of all GHG
emissions from the production of the fuel.
A key concept in life-cycle GHG analysis is land use change (see Section 4 for more
information on land use). Land use change can lead to indirect GHG emissions. For
example, increased demand for feedstocks that compete for land with the exist-
ing food and feed production chain (e.g., corn, soybeans) may lead to conversion
of unused land, such as grassland or forests, to agriculture production. This can
result in an increase in CO2 emissions that would be included in the life-cycle GHG
analysis. Thus, LCA results can show a significant increase in GHG emissions for
alternative fuels made from renewable feedstocks because of indirect land use
change. Inclusion of indirect land use changes in life-cycle analysis is currently a
controversial and politically charged debate.
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12 Guidelines for Integrating Alternative Jet Fuel into the Airport Setting
on the efficiency of the process to convert coal or natural gas to alternative jet fuel. However,
there are ways to reduce the GHG footprint. For example, carbon capture and sequestration
(CCS) technology could be employed to capture and permanently store CO2 during the produc-
tion process (see Section 2.3). In addition, using biomass in addition to coal can reduce the GHG
footprint of the overall process.
d) Advantages
Fossil fuel feedstocks are abundant and available at relatively low cost. Their large-scale avail-
ability is an advantage for FT plants, which tend to be very large (and expensive to build) in order
to benefit from economies of scale.
e) Disadvantages
Fossil fuel feedstocks may have a potentially unacceptable life-cycle GHG footprint if not mit-
igated properly. Possible mitigation strategies include the use of CCS technology and use of bio-
mass as a co-feedstock for the FT process. FT plants tend to be very large and capital intensive.
For example, a typical FT plant could process 1 to 2 billion gallons per year (GPY) and cost
several billion dollars to build. For comparison, the average size of the top 100 U.S. petroleum
refineries is 2.5 billion GPY (EIA 2011). In addition, since there are not many commercial-scale
examples in operation, it is difficult to evaluate their economics of production.
2) Oils and fats
Plant oils and animal fats can be used as feedstocks for making alternative jet fuels via hydro-
processing (see Section 2.3).
a) Sources and availability
Many different plant oils can be used to make alternative jet fuel. These include nonfood oils
such as Camelina, Jatropha, pennycress, and algae, and food oils such as soybean and canola.
Some of these oils are currently produced at commercial or semicommercial scales in the
United States. Others have not yet reached such large scales of production. Research is ongoing
to improve the oil content (yields) and other characteristics that are advantageous to alternative
jet fuel production. Animal fats (tallow), frying oils, and greases may also be used to produce
alternative jet fuel.
Nonfood oils are promising potential feedstocks with attractive characteristics. Algae are
adaptable, grow very quickly, and have higher oil content than other alternative fuel feedstocks.
Jatropha, an oilseed plant historically grown in tropical areas, has high concentrations of oil and
can be grown in poor-quality soils not suitable for traditional agricultural crops. Pennycress
and Camelina have high oil content and have the potential to be grown without competing for
land availability with traditional crops.
Tallow and other fats are generally considered waste products, so these materials are more
economically attractive than refined plant oils; however, the current poor refining quality may
require additional processing or additives.
b) Economics and logistics
Feedstock is expected to be the largest cost component in the production of alternative jet fuel
from plant oils. Some plant oils that could potentially support commercial-scale production of
alternative jet fuel, such as soybean oil, are already expensive to produce. In addition, because
soybean and other plant oils are also used for human and animal consumption and in the pro-
duction of biodiesel, competition for this feedstock is likely to keep prices high. Therefore, there
is great interest in alternative oilseed feedstocks such as Jatropha, pennycress, and Camelina that
can be produced at a lower cost.
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What Are the Main Characteristics of Alternative Jet Fuels? 13
Soybean oil and other oilseed feedstocks have well-developed markets, available risk manage-
ment tools, and well-developed supply chains. Alternative oil feedstocks such as algae and
Jatropha may be able to be integrated into the existing transportation infrastructure. Markets,
pricing mechanisms, risk management tools, and contract and supply chain considerations
would all have to be developed for algae, Jatropha, and other feedstocks not currently produced
at commercial scale. Transportation and storage of tallow can be expensive, requiring heated
tanks at a minimum of 65°C to thwart the growth of bacteria and enzymatic activity.
c) Environmental considerations
Alternative jet fuels from plant oils and fats may have a lower life-cycle GHG footprint com-
pared to conventional jet fuel; however, the life-cycle GHG footprint of alternative jet fuels from
plant oils is very dependent on land use. If the plant oil is grown on existing cropland, the land-
use change impact may be limited; however, if forest needs to be cleared to grow the plant oil,
the land-use impact would be significant. Plant oils that can grow in fallow or marginal lands,
such as Jatropha and Camelina, can avoid some of these concerns.
d) Advantages
Some plant oils are available in commercial quantities and have developed markets, supply
chains, and transportation systems. Some alternate feedstocks have great potential. Some strains
of algae have the potential to produce more than 30 times the amount of oil per acre per year
than any other plant currently used to produce alternative fuels. The relatively small size of HEFA
facilities makes co-location near airports possible.
e) Disadvantages
All current oil-based alternative jet fuels struggle with high costs. Improving the productivity
of growing oil plants is critical to achieve competitive costs for alternative jet fuel. Feedstock costs
make up 80% or more of the cost of these fuels. The U.S. Department of Agriculture (USDA) has
programs to improve yields that are similar to food crop yield improvement programs. Similarly,
current production yields for algae are not yet commercially viable and are still in the research
stage. Fuels derived from edible plant oils could be considered to compete with food supplies (see
Section 4.1 for more information on the food-versus-fuel question).
Tallow-based oils enjoy a steady if limited supply, but storage and transportation issues may
constrain their use as a feedstock. Furthermore, their limited supply may constrain their use on
a large-scale commercial basis.
3) Biomass feedstocks
Biomass feedstocks are generally divided into three categories: energy crops (e.g., switchgrass),
agricultural residues (e.g., corn stover), and woody biomass (e.g., wood chips). The potential sup-
ply of biomass is substantial, although there are considerable constraints related to its bulk. Bio-
mass can be used with the Fischer-Tropsch process to produce alternative jet fuel (see Section 2.3).
a) Sources and availability
Energy crops are grown specifically and primarily for biofuels, including alternative jet fuel.
Switchgrass, Miscanthus, energy cane, wheatgrass, and bluestem are potential energy crops. Agri-
cultural residues such as corn stover and wheat straw are other promising sources of biomass
feedstock for alternative jet fuel production. Woody biomass and by-products are also potential
feedstocks. The lumber, mill, pulp, and paper industries have long burned woody by-products as
a source of energy and consume most available supplies. Recent declines in these industries, how-
ever, are driving down the costs of woody biomass and spurring interest in its use for producing
alternative jet fuel.
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14 Guidelines for Integrating Alternative Jet Fuel into the Airport Setting
b) Economics and logistics
Energy crops need to be grown on marginal lands not appropriate for traditional agriculture
production in order to keep feedstock costs low. Absent production on marginal lands, energy
crops will have to compete for land use with current agriculture production activities and pro-
vide a return to producers at least equal to current production. Agriculture residues such as corn
stover and wheat straw have an economic advantage over dedicated energy crops because they
are by-products of corn and wheat production. Even though the production costs of agricultural
residues are already covered by existing revenues, producers will likely require additional incen-
tives as compensation for harvest, collection, and transportation costs. Furthermore, agricultural
residues have soil quality benefits such as nutrient cycling and moisture retention; accordingly,
not all agriculture residues could be collected.
There are many challenges associated with the use of dedicated energy crops and agriculture
crop residues as alternative fuel feedstock. No established markets exist, and contracting and sup-
ply chain considerations would have to be resolved before producers would be willing to supply
either a dedicated energy crop or agricultural residues.
The huge quantities of biomass required to support commercial-scale operations make trans-
portation and logistical issues very challenging. Densification and pretreatment techniques to
address these issues are being studied. Woody biomass not currently utilized for other products
and processes, such as harvest residues, faces logistical challenges similar to crop residues and
energy crops due to low bulk density.
c) Environmental considerations
Land use can have a bearing on the life-cycle GHG footprint of alternative jet fuels made from
biomass feedstocks. In order to prevent competing uses for land, dedicated energy crops will
need to be grown on land that is marginal for traditional agriculture. What constitutes marginal
land, what crops would be grown, and the practicality of production of dedicated energy crops
will vary regionally. Research is ongoing to identify how much marginal land is available. Research
on cultivation, yield, and production economics of various potential dedicated energy crops is
also ongoing. Assuming no changes in land use, the life-cycle GHG footprint of alternative jet
fuels from biomass can be less than that of conventional jet fuels.
d) Advantages
Energy crops may be able to grow on land not suitable for traditional agriculture, are adapt-
able to various soils and climates, and integrate well with conventional agriculture. The use of
marginal land for energy crops eliminates the competition with land for traditional agriculture
commodities, reduces production costs, and avoids food-versus-fuel concerns. Agriculture residues
may be available in sufficient quantities to potentially support a commercial conversion facility.
Corn stover and wheat straw have the greatest potential as low-cost, first-generation biomass
feedstocks.
e) Disadvantages
Logistical and transportation challenges are a major impediment. Because of their low energy
density, very large amounts of biomass feedstocks are required to feed production facilities.
Handling this bulky material can be expensive and uneconomical outside of a 50-mile
radius from the production facility. Market, supply chain, contracting, transportation, and
logistical infrastructure need to be developed. Furthermore, there are concerns about how
much forest and other residue can be extracted for fuel production without adverse impacts
(SAFNW 2011b).
