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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).