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Biomass valorization for better aviation environmental impact through biocomposites and aviation biofuel
Biomass aviation through aviation
valorization for better environmental impact biocomposites and biofuel
2
Jia Tian Chen 1,2 , Luqman Chuah Abdullah 3 , Paridah Md. Tahir 4 1 Centre of Excellence on Biomass Valorization for Aviation, Institute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, Malaysia; 2Aerospace Malaysia Innovation Centre (AMIC), MIGHT Partnership Hub, Jalan Impact, Cyberjaya, Malaysia; 3Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, Malaysia; 4Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, Malaysia
2.1 2.1.1
Introduction Aviation environmental impact
The expansion of international civil aviation over the past two decades has been significant [1]. Air traffic is accounted by revenue passenger kilometer (RPK), and this has historically doubled every 15 years [2]. The forecast for the next 20 years is an increase between 4.3% and 4.8% in air traffic per year, with the main driver being Asia Pacific in terms of growth percentage [1]. Current global civil aviation accounts for approximately 2% of man-made carbon dioxide (CO2) emissions [3]. In terms of energy consumption in the transportation sector, globally jet fuel contributes 11%, and is projected to increase to 14% within the next 20 years [4]. Other than CO2, an aircraft also emits other greenhouse gases and particles that impact the climate, such as water vapor, nitrogen oxides, sulfur oxides, and soot [5]. Fig. 2.1 shows the RPK, as a representation of air traffic increase, from 1970 to 2010 (Airbus, 2010). According to the International Air Transport Association (IATA), CO2 contribution by the aviation industry may grow by up to 5% by 2050 [6]. However, the environmental impact of air travel is best measured by radiative forcing (RF) effect of its emissions. RF is the measurement of the effect of energy the atmosphere faces due to greenhouse gas emissions, or forcing agents, which triggers a cooling or heating effect expressed in watts per square meter (W/m2) [7]. RF can be uniquely found on flight paths due to the jet engine emissions of nitrogen oxides, sulfur oxides, water vapors, and particulates (like soot). The emission of CO2 is known to be a long-lived greenhouse gas that warms the earth, however, this is not unique only to the aviation industry. An interesting indicator would be water vapor emissions from the jet engines, these emitted vapors form contrails that have atmospheric effects similar to clouds [8,9]. Due Structural Health Monitoring of Biocomposites, Fibre-Reinforced Composites and Hybrid Composites https://doi.org/10.1016/B978-0-08-102291-7.00002-2 Copyright © 2019 Elsevier Ltd. All rights reserved.
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites RPK (trillion) ICAO total traffic
Airbus GMF 2010
10.0
8.0 Air traffic will double in the next 15 years
Air traffic has doubled every 15 years
6.0
4.0 20-year world annual traffic growth 4.8%
2.0
0.0 1970
1980
1990
2000
2010
2020
2030
Figure 2.1 Increase in RPK, as air traffic change, over time and prediction [2].
to the cloud-like effect, contrails absorb and emit thermal infrared radiation leading to positive RF (warming). Contrails can also form into larger forms, known as contrail cirrus, which has a higher RF effect. Fig. 2.2 shows the RF effect of new contrails and the warming effect after formation of larger contrail cirrus clouds [10]. New contrails are clouds that are less than 5 h from jet engine emission, and these account for a positive (warming) RF of the atmosphere by 4.3 mW/m2. However, older contrails that have formed into larger contrail cirrus, will affect the atmosphere eight times more (37.5 mW/m2). Lee et al. have estimated that aviation RF contributes a total increase of the climate by 0.078 W/m2, and this may increase by a factor of four over 2005 levels [9]. 90 45 0 –45
4.3 mW/m2
–90 –180
–90
0
90
180
90 45 0 –45
37.5 mW/m2
–90 –180
–300
–90
–30 –10 –3
0 Longitude –1
1.
90
3. 10. 30.
180
300.
Figure 2.2 Radiative forcing (RF) effects of new contrails (above) and after effects (below) [10].
Biomass valorization for better aviation environmental impact through biocomposites
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In order for the aviation industry’s impact to the environment to be minimal, a global movement spearheaded by Air Transport Action Group (ATAG) in 2008 was put in place. To reduce the environmental footprint, major aviation leaders committed to three targets at the 2008 Aviation and Environment Summit [11]: • • •
Annual fuel efficiency utilization of 1.5% per annum Net carbon emissions cap by 2020 (carbon neutral growth) 50% reduction in net aviation CO2 emissions by 2050 from 2005 levels.
This has led to the International Civil Aviation Organization (ICAO), under the United Nations, to have the aviation industry pledge reduction in its emissions through four pillars of innovation [11]: • • • •
Product Technology Operations and Infrastructure Economic Measures Sustainable Fuel.
Although the aviation industry has had a strong record in decreasing its emissions, the four pillars of innovation are foreseen to enable the industry to reach its 2050 target of 50% net reduction in aviation CO2 emissions, and related greenhouse gasses. The vision of reduction in CO2 emissions by the global aviation industry can be summed up in Fig. 2.3. In Fig. 2.3, it can be seen that technology and biofuels are the two largest contributors to reach 2050’s 50% carbon dioxide reduction goal. The red line represents predicted emissions pending zero action on any of the four pillars, and the green line represents the predicted trajectory toward its 2050 goal. Technology is split into various sectors: (1) aircraft technology, (2) operations, and (3) infrastructure. Improvements in aircraft technology are accounted for by introduction of better aerodynamic
Emissions assuming no action
No action
Aircraft technology (known), operations and infrastructure measures
Carbon-neutral growth 2020
Biofuels and radically new technologies
Gross emissions trajectory
Economic measures
Technology
CO2 Emissions
Operations Infrastructure Biofuels and radical tech CNG 2020
–50% by 2050 Not to scale
2005
2010
2020
2030
2040
2050
Figure 2.3 International Civil Aviation Organization (ICAO) action plan until 2050 (four pillar strategy) [11].
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites
properties into the aircraft, such as wingtips; and weight reduction of the plane, such as increased usage of composite materials, lightweight paints, and lightweight seats. Improvements in operations are targeted at optimized flight paths, fuel savings for takeoff and landing procedures, and weather-based flight paths. Finally, infrastructure is aimed at improvements and modernization of air traffic management systems at airports. The green portion of the action plan, biofuel and radically new technologies, is seen as the major contributor to reach the 50% reduction in CO2 emissions of the industry. While new radical technologies are in development, such as hybrid-electrical propulsion, fuel celledriven environmental control system, and assisted take-off and landing, these technologies are still immature and their effect on the reduction of environmental impact is still in consideration. Biofuel, in this instance,biofuel made for aviation jet fuel grade, is the best contender. Numerous test flights have already been performed globally and its affect in reduction of CO2 emission and improved fuel performance is well recorded [3]. The utilization of jet biofuel and biocomposite contributes to the aviation industry’s reduction in CO2 and improving the sustainability of the industry. Jet biofuel improves fuel performance, lowers soot and CO2 emissions. Biocomposites improve the sustainability factor of a plane, rather than composite fibers derived from nonrenewable sources. Biocomposites have a long development roadmap, and the usage of renewable, sustainable sources is key for implementation onto an aircraft.
2.1.2
Sustainable biomass for aviation
Biomass is seen as the next generation source for the aviation industry, as biomass absorbs carbon dioxide, it limits and reduces the aviation industry’s impact. However, caution has to be noted that the biomass has to be sustainable and renewable. Sustainable biomass means no competition with food, no land use change in accordance to sustainability criteria, minimal impact to the environmental/ecosystem, and is renewable (able to be grown), compared to fossil fuel based whose resources are finite. The need for sustainable and renewable biomass sources is best illustrated by Table 2.1. Currently, bioenergy (from biomass) is the world’s largest source of renewable energy, accounting for 14% out of 18% of the renewable energy sector. This places bioenergy at an estimate of 10% of global energy supply. This biomass covers both sustainable and nonsustainable biomass [12]. Of the bioenergy, only 4% of the total
Table 2.1 Comparison of renewable, nonrenewable, sustainable, and nonsustainable Sustainable
Non-sustainable
Renewable
A reliable source that meets annual demand
A renewable source that does not meet demand
Nonrenewable
Producing sufficient sustainable biomass for 10 years only
Supply only lasting for 40 years
Biomass valorization for better aviation environmental impact through biocomposites
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can be considered as biomass usage for biofuel, which includes biodiesel, bioethanol, and biogas. The world’s largest biofuel producers from biomass are South America (largely Brazil), North America, followed by Europe [13]. These energy crops, or biomass, can be sectioned into three generations of biomass feedstock. It is sectioned as such to fundamentally understand the differences between its renewable and sustainable differences. First-generation feedstock are crops such as corn, sugarcane, soybean, vegetable oil, wheat, rapeseed, peanuts, and a number of other food crops. First-generation biofuels are produced directly from these food crops. However, in 2008, it was estimated that if biofuels from first-generation crops were to satisfy 20% of the growing biofuel demand, there will be no crop balances for food. In 2007, the United Nations Food and Agriculture Organization saw world food prices increase by 40% within 12 months, due to the influence of biofuel being derived from feedstock such as sugarcane, corn, rapeseed oil, palm oil, and soybeans [14]. This meant that first-generation biomass was renewable, but not sustainable, for usage of biofuel or for creation of a biocomposite industry. The first-generation debate brought about the need for second-generation feedstock, and later third generation, which are not in direct competition with food. Secondgeneration biofuels are derived from nonfood feedstock, for example, switchgrass, Jatropha, waste vegetable oil, municipal solid waste, lignocellulosic sources, etc. These second-generation sources tends to be grown on marginal lands, land that cannot be used for “edible” crops. Compared to first-generation, second-generation feedstock are processed differently and will require additional processing steps to convert the feed into fuel. Recently, third generation entered into the spotlight as biofuel derived from algae. Third-generation feedstock provides numerous advantages over second and third generation, from a larger array of carbon sources, significantly higher yields, better land efficiency, diversity of algae species for added-value products, good potentials of products, and different methods in cultivation. However, the biggest drawback for algae is the large amount of water and nutrients (nitrogen and phosphorus) to grow them, and the investment costs for large-scale implementation [15]. Combined, biomass feedstock in 2007 was approximated at 47.2 EJ (exajoule) per year; in 2016, this was estimated to be 56 EJ per year. The main driver behind the increase in feedstock availability is the biodiesel and bioethanol industry [16]. This is due to the increase in countries adopting biofuels to improve their greenhouse gas impact, as part of the United Nations Framework Convention on Climate Change.
2.1.3
Biocomposites
A material can be considered a biocomposite when one part of its composition, whether it is its matrix or reinforcements, is derived from natural sources [17]. Biocomposites are made in part, with natural fiber, which can be derived from a plant’s seed, leaf, bast, fruit, and/or stalk. This is limited to such due to the need for cellulose, hemicellulose, and lignin, which is able to form a matrix and is held together in a framework to yield a structured composite shape. The usage of lightweight composite materials, increased utilization of composites on aircraft, and the pending introduction of biocomposites are all contributing factors
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites
toward lowering the weight of an aircraft, and for biocompositesd“greening” the aircraft. With decrease in aircraft weight, fuel savings and reduction of CO2 can be accomplished. The outlook for utilizing biocomposite for aircraft parts is attractive; however, to develop biofibers for aviation requires stringent testing and validation, and the research is not yet mature enough. The limiting factor for now, is the need to treat and process the natural fiber to rival current composite fibers’ properties and component strength. This is accounted by natural fiber’s lack in homogeneity, compared to glass and carbon; it has a higher tendency to absorb moisture; and the compatibility with current resin used in aerospace manufacturing [18]. A method to fast track the implementation of natural fiber into aerospace manufacturing is through hybridization, a mix of conventional glass and/ or carbon fiber with natural fiber; this is currently undergoing prototyping and validation, but is seen as a faster means to market than 100% utilization of natural fiber for aerospace parts [19]. However, natural fibers will inherently be limited to secondgeneration biomass feedstock due to the need for lignocellulose material. The usage of natural fibers like coconut coir, banana stem, pineapple leaves, sugar cane bagasse, kenaf fiber, oil palm empty fruit bunch (EFB), and bamboo fiber has been documented for aerospace part prototyping [18e21].
2.1.4
Jet biofuel
Global Kerosene Jet A-1 production and demand is approximately 80 billion gallons litre per year, or 302.8 billion liters per year [22]. To understand the magnitude of jet biofuel required globally, taking into account the mandates by various countries, a 2%e3% global replacement with jet biofuel will equate to roughly 6.06e15.14 billion liters per year. According to ICAO, the United States, Canada, China, Japan, the European Union, and Indonesia have implemented a jet biofuel mandate between 2% and 3% of their annual consumption. This is the result of the aviation industry’s pledge back in 2008 with ATAG, and in 2017 marks the introduction of a carbontrading scheme by ICAO known as Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) [23]. The CORSIA scheme will go into its pilot phase in 2020, and will see the implementation (a global market-based measure) of trading “emissions” units. Aircraft operators will be required to pay for any CO2 emission growth at their 2020 levels (reported). The amount of CO2 to be offset by 2025 is in the range of 142e174 million tons of CO2 emissions. The price of carbon is also estimated from a low 6e10 USD/ton of CO2-eq to a high estimate of 20e33 USD/ ton CO2-eq. To produce jet biofuel sustainably, the feedstock has to be sustainable (second or third generation) and the process to convert has to be certified. Under the ASTM: D7566 “Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbon” [24], only five processes have been certified under international standards that govern Kerosene Jet A-1 usage on board an aircraft. Synthesized hydrocarbon from biomass is in essence jet biofuel. Conventionally, Kerosene Jet A-1 is certified under ASTM: D1655 “Standard Specification for Aviation Turbine Fuel,” without any synthetic hydrocarbons [25]. In order to produce synthetic hydrocarbons, or jet
Biomass valorization for better aviation environmental impact through biocomposites
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biofuel, the five processes are: (1) Fischer-Tropsch Synthetic Kerosene with Aromatics (SKA), (2) Fischer-Tropsch Synthetic Paraffinic Kerosene, (3) Hydroprocessed Esters and Fatty Acids, (4) Alcohol-to-Jet, and (5) Direct Sugar to Hydrocarbon/Synthetic Isoparaffin. These were recognized and certified in 2009 (FT-SPK), 2011 (HEFA), 2016 (ATJ), and 2014 (DSHC/SIP). All FT fuels are able to be blended up to 50%, HEFA fuel is also up to 50%, DSHC/SIP can be blended up to 10%, and finally ATJ up to 30% blend. A simplified process flow can be seen in Fig. 2.4 of the various jet biofuel processes [26]. Conventional Kerosene Jet A-1 (via MEROX process) composition is approximately 21% aromatics, 25% paraffin, 11% isoparaffin, and 43% cycloparaffin. Compared to fuel derived from HEFA; 10% paraffin, 90% isoparaffin; FT derived, 3% paraffin, 88% isoparaffin, 9% cycloparaffin; and lastly, DSHC derived is >95% isoparaffins. The difference in composition is noticeable and, therefore, is unable to fully (100%) substitute conventional Kerosene Jet A-1, and requires blending instead. Asides from these five processes, there are numerous other, not yet certified, pathways that utilize second-generation and third-generation feedstock to yield jet biofuel. Most notably are hydrotreated depolymerized cellulosic jet, catalytic hydrothermolysis, hydrothermal liquefaction, synthesized aromatic kerosene, and synthesized kerosene. Utilization of jet biofuel is a reality, and efforts are underway worldwide to push for adoption. This is needed to understand the performance and benefits of jet biofuel.
Vegetable oil, used cooking oil, fat
Hydroprocessing
50%
Hydrothermal liquefaction Algae
Pyrolysis
Bio-oil
Gasification
Fischer-tropsh synthesis
Syngas
50%
Lignocellulose Gas fermentation
Alcohol synthesis
Hydroprocessing
Alternative jet fuel
Hydrolysis Waste gas CO, CO2, H2
Olefins Glucose
Hydrocarbons
Alcoholic fermentation
Dehydration & oligomerization
Alcohols 30%
Sugar & starch
Fermentation
Farnesane
10%
Biological process
Chemical process
Thermal process
Feedstock
Intermediate product
= ASTM certified (maximum blending level indicated)
Figure 2.4 Simplified process flow of certified processes to produce jet biofuel [26].
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites KLM / skyNRG Alaska /hawaї bioenergy
Airbus / air canada / biofuelnet
Core jetfuel
Advanced biofuel flighpath SAFUG NARA
Lufthansa / GEVO Airbus / rostec
aireg
BA/solena
NEWbio
NISA
Bioport holland
Airbus / ENN
lufthansa / solena ASCENT
United / altair
Farm to fly CAFFI
Itaka
INAF
Bioqueroseno
GE / D’arcinoff Qatar univ. biofuel project
Cathay / fulcrum
MSBRC SEASAFI
Airbus / malaysia Qatar airways / byogy Green aviation initiative
BBP GOL / boeing
Virgin / lanzatech
QSAFI
GOL / amyris-total Arg. national initiative
Boeing / SSA / SKYNRG
AISAF
Virgin / skyNRG
Avianca / byogy Quantas / solena Stakeholders action group
Projects
Airlines /fuel producers
Figure 2.5 Global activity map of jet biofuel, test flights by airlines and aerospace industry [11].
Fig. 2.5) is a world map of various activity on jet biofuel test flights, production, and projects [11]. Some of the efforts have been summarized in the table below to link the relationship between the airline, jet biofuel producer, its feedstock and process utilized, and contractual ties (Table 2.2). To replace 2%e3% with jet biofuel of current global aviation jet fuel demand, a total of roughly 6e15 billion liters per year is required. This demand is currently not met by any jet biofuel producers around the world, and only a handful of countries around the world have implemented mandates on jet biofuel. However, through rigorous testing and analysis, it is a known fact that jet biofuel combustion process is cleaner and more efficient than conventional Kerosene Jet A-1. Jet biofuel offers customization beyond the ability of conventional Kerosene Jet A-1, as the production of Kerosene Jet A-1 is in harmony with other products derived from crude oil, i.e., gasoline/petrol, diesel, and petroleum products. Jet biofuel processes enable a certain level freedom of conversion and equilibrium reaction. For example, most synthetic kerosene-grade fuel offers more straight chain chemical groups than conventional jet fuel, which limits the soot formation during combustion in the jet engines. Cleaner burn, limited soot formation will mean increased engine performance, easier maintenance cycles, and better fuel efficiency. Stability of the fuel also increases through the introduction of more cyclic components within the fuel, without a decrease in fuel performancedjet biofuel is able to be tailored. The lack of aromatics in synthetic kerosene is an advantage, as aromatics do not provide clean combustion and encourage soot formation, unlike Kerosene Jet A-1, where aromatics are still in abundance. Aromatics are heavy molecules, with limited hydrogen, and therefore limited energy content. Aromatics increase the fuel density without offering
Biomass valorization for better aviation environmental impact through biocomposites
Table 2.2 Overview of airlines that have agreements with jet biofuel producers Airline
Producer
Feedstock-pathway
Description
United Airlines
AltAir
HEFA
AltAir production capacity from 2016, 15 million gallons at a 30:70 blend, purchase agreement.
Cathay Pacific
Fulcrum Bioenergy
MSW-FT
Long-term supply agreement for fuel from municipal solid waste, located in Nevada. Supply starting from 375 million gallons (US) over 10 years (2% of Cathay’s annual fuel consumption). Airline strategy to achieve carbon neutral growth by 2020.
Southwest Airlines
Red Rock Biofuels
Forest residues e FT
Supply agreement for 3 million gallons per year.
GOL (Brazil)
UOP/AmyrisTotal
HEFA e inedible corn oil and used cooking oil/. SIPsugarcane
Target blending of 1% of biofuel in 2016, achieved 200 flights with 4% mixture for World Cup (92,000 L of HEFA UOP fuel). SIP achieved first flight in September 2014.
Oslo Airport
Neste Oil
NESTE e NEXBTL
First airport in the world to introduce jet biofuel.
Air France
Amyris-Total
SIP-Sugarcane
1 year series of weekly flights between Toulouse and Paris, using 10% blend, completed in September 2015.
KLM
SkyNRG
HEFA-used cooking oil
18 weekly intercontinental flight from Amsterdam to Aruba, using 20% blend of biofuels made from used cooking oil.
Lufthansa
Neste Oil
HEFA-used cooking oil
Part of Project burnFAIR.
SAS (Norwegian)
SkyNRG Nordic
HEFA-used cooking oil
Airport-based biofuel supply facilities in Norway and Sweden.
Virgin
Lanzatech/ Swedish biofuels
Waste gases e alcohol to Jet
In pipeline to be used.
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites
(a)
(b)
(c)
(d)
Figure 2.6 Experimentation with Kerosene Jet A-1 and various synthetic aviation fuel with a Rolls-Royce combustion rig [30]. Description of a to d can be seen in the paragraph below.
the added boost of energy density [27e29]. Experiments on soot/coke formation were performed, and the results can be seen in Fig. 2.6. Experimentation performed by Pucher et al. [30], in the figure above. (a) is with conventional Kerosene Jet A-1, (b) is with 2% fatty acid methyl esters (FAME) mixture with conventional Kerosene Jet A-1, (c) is with 50% synthetic Kerosene Jet A-1 blended with conventional fuel, and (d) is with 100% synthetic Kerosene Jet A1. These fuels were combusted in a Rolls Royce T-56-A-15 combustion rig to mimic a typical jet engine. As seen, the vast difference is between (a and d), with 100% synthetic Kerosene Jet A-1 there is a vast difference in soot/coke formation at the fuel nozzle and igniter plug, an almost absence of coke formation. However, blended fuel (b and c) still saw significant coke formation, with (c) flaring betterdinjector holes are relatively clear compared to (b and a) [30]. From a CO2 standpoint, jet biofuel production has been compared with conventional Kerosene Jet A-1. In this study [31], vegetable oil using HEFA process was used to compare with Kerosene Jet A-1 (MEROX process). The results can be seen in the graph in Fig. 2.7. Vegetable oil conversion with HEFA can yield between 20% and 73% better CO2eq/MJ compared to Kerosene Jet A-1. However, current HEFA fuel is more expensive to produce compared to Kerosene Jet A-1. A study by Massachusetts Institute of Technology (MIT) used a discounted cash flow rate of return approach (DCFROR)
Biomass valorization for better aviation environmental impact through biocomposites
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Jet A1 Pure vegetable oil from rape seed Hydrotreated vegetable oil from palm oil* Hydrotreated vegetable oil from palm oil Hydrotreated vegetable oil from sunflower Hydrotreated vegetable oil from rape seed 0
10
20
30
40
50
60
70
80
90
(gCO2eq/MJ)
Figure 2.7 Conventional Jet A-1 production compared with HEFA-based jet biofuel production on CO2 emissions per MJ [31].
[29], HEFA fuel best scenario cost was 2.2 times more expensive than Kerosene Jet A1 (MEROX), with its worst case scenario being up to 2.6 times more expensive, where Kerosene Jet A-1 fuel price is approximately USD 1.82/gal (USD 0.48/L).
2.2
Summary
Biomass valorization is needed for a better aviation environmental footprint and this can be accomplished by biocomposites and jet biofuel. The key to enabling the aviation industry to adopt biomass-derived products is for the biomass to be sustainable and renewable. Sustainability of the feedstock and its abundance is needed to support a growing aviation industry sustainably, while ensuring the safety standards that the industry is known for. First-generation biomass is not known for its sustainability, due to its competition with food. Biocomposites therefore need to utilize secondgeneration sustainable feedstock, however, development of biocomposites is currently limited to its ability to treat and process natural fibers to rival its glass and carbon fiber (fossil-derived) counterparts. The development of biocomposites is much watched by the aviation industry, which sees it as an integral part to “green” the industry’s carbon footprint, and the lightweight properties of composite are needed to meet the industry’s goal of reduction in CO2 emissions. However, biocomposites are still not mature enough to be adopted by the industry, however, hybridization (mixing biocomposites with conventional composites) is seen as a means to fast track the ability to introduce biocomposites into the market for aviation. Lastly, for jet biofuel, the maturity is gaining ground with up to five certified pathways/methods to produce jet biofuel. However, like with biocomposites, the source needs to be sustainable and be sufficiently abundant to supply a very large global demand (at least 6 billion liters annually for global consumption) for jet biofuel. The costs to produce synthetic fuel are still high, as seen with recent studies, but development of the jet biofuel is not at a dead end. Reduction of production price is still hopeful, coupled with the inherent increase in fossil fuels, the price will eventually be competitive. Still, with movements of CORSIA and the aviation industry, the cost of jet biofuel remains high, even in the face of a growing industry, the considerable operational benefits jet biofuel can offer, and the corresponding environmental benefits.
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites
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[21] Haris MY, Laila D, Zainudin ES, Mustapha F, Zahari R, Halim Z. Preliminary review of biocomposites materials for aircraft radome application. Key Eng Mat 2011;471e472: 563e7. [22] Davidson C, Newes E, Schwab A, Vimmerstedt L. An Overview of aviation fuel markets for biofuels stakeholder. Technical Report NREL/TP-6A20e60254. National Renewable Energy Laboratory; July 2014 [Internet] Available from: http://www.nrel.gov/docs/. [23] Carbon Market Watch. The CORSIA: ICAO’s market based measure and implications for Europe. Carbon Market Watch; October 2016. Available from: https:// carbonmarketwatch.org. [24] ASTM. ASTM D 7566, standard specification for aviation turbine fuels csynthesized hydrocarbon. 2016. version revision a. [25] version revision a ASTM D 1655 “standard specification for aviation turbine fuels”. 2016. Available from:, https://www.astm.org/. [26] El Takriti S, Pavlenko N, Searle S. Mitigating international aviation emissions, risks and opportunities for alternative jet fuels. The International Council on Clean Transportation; March 2017. [27] Edwards T, Maurice LQ. Surrogate mixtures to represent complex aviation and rocket fuels. J Prop Power 2001;17:461e6. [28] Bisio A. Aircraft fuels e energy, technology and the environment1. John Wiley and Sons Inc.; 1995. p. 257e9. [29] Coordinating Research Council Inc. Handbook of aviation fuel properties. CRC report No. 635. 3rd ed. 2004. [30] Pucher G, Allan W, Poitras P. Emissions from a gas turbine sector rig operated with synthetic aviation and biodiesel fuel. J Eng Gas Turbine Power 2010;133(11). [31] Malina R. HEFA and FT jet fuel cost analyses. MIT; November 2012.
Further reading [1] ATAG. Air Transport Action Group. Fact sheet: delivering fuel efficiency. ATAG; 2016 [Internet] Available from: http://www.atag.org/component/.
valorization for better environmental impact biocomposites and biofuel
2
Jia Tian Chen 1,2 , Luqman Chuah Abdullah 3 , Paridah Md. Tahir 4 1 Centre of Excellence on Biomass Valorization for Aviation, Institute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, Malaysia; 2Aerospace Malaysia Innovation Centre (AMIC), MIGHT Partnership Hub, Jalan Impact, Cyberjaya, Malaysia; 3Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, Malaysia; 4Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, Malaysia
2.1 2.1.1
Introduction Aviation environmental impact
The expansion of international civil aviation over the past two decades has been significant [1]. Air traffic is accounted by revenue passenger kilometer (RPK), and this has historically doubled every 15 years [2]. The forecast for the next 20 years is an increase between 4.3% and 4.8% in air traffic per year, with the main driver being Asia Pacific in terms of growth percentage [1]. Current global civil aviation accounts for approximately 2% of man-made carbon dioxide (CO2) emissions [3]. In terms of energy consumption in the transportation sector, globally jet fuel contributes 11%, and is projected to increase to 14% within the next 20 years [4]. Other than CO2, an aircraft also emits other greenhouse gases and particles that impact the climate, such as water vapor, nitrogen oxides, sulfur oxides, and soot [5]. Fig. 2.1 shows the RPK, as a representation of air traffic increase, from 1970 to 2010 (Airbus, 2010). According to the International Air Transport Association (IATA), CO2 contribution by the aviation industry may grow by up to 5% by 2050 [6]. However, the environmental impact of air travel is best measured by radiative forcing (RF) effect of its emissions. RF is the measurement of the effect of energy the atmosphere faces due to greenhouse gas emissions, or forcing agents, which triggers a cooling or heating effect expressed in watts per square meter (W/m2) [7]. RF can be uniquely found on flight paths due to the jet engine emissions of nitrogen oxides, sulfur oxides, water vapors, and particulates (like soot). The emission of CO2 is known to be a long-lived greenhouse gas that warms the earth, however, this is not unique only to the aviation industry. An interesting indicator would be water vapor emissions from the jet engines, these emitted vapors form contrails that have atmospheric effects similar to clouds [8,9]. Due Structural Health Monitoring of Biocomposites, Fibre-Reinforced Composites and Hybrid Composites https://doi.org/10.1016/B978-0-08-102291-7.00002-2 Copyright © 2019 Elsevier Ltd. All rights reserved.
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites RPK (trillion) ICAO total traffic
Airbus GMF 2010
10.0
8.0 Air traffic will double in the next 15 years
Air traffic has doubled every 15 years
6.0
4.0 20-year world annual traffic growth 4.8%
2.0
0.0 1970
1980
1990
2000
2010
2020
2030
Figure 2.1 Increase in RPK, as air traffic change, over time and prediction [2].
to the cloud-like effect, contrails absorb and emit thermal infrared radiation leading to positive RF (warming). Contrails can also form into larger forms, known as contrail cirrus, which has a higher RF effect. Fig. 2.2 shows the RF effect of new contrails and the warming effect after formation of larger contrail cirrus clouds [10]. New contrails are clouds that are less than 5 h from jet engine emission, and these account for a positive (warming) RF of the atmosphere by 4.3 mW/m2. However, older contrails that have formed into larger contrail cirrus, will affect the atmosphere eight times more (37.5 mW/m2). Lee et al. have estimated that aviation RF contributes a total increase of the climate by 0.078 W/m2, and this may increase by a factor of four over 2005 levels [9]. 90 45 0 –45
4.3 mW/m2
–90 –180
–90
0
90
180
90 45 0 –45
37.5 mW/m2
–90 –180
–300
–90
–30 –10 –3
0 Longitude –1
1.
90
3. 10. 30.
180
300.
Figure 2.2 Radiative forcing (RF) effects of new contrails (above) and after effects (below) [10].
Biomass valorization for better aviation environmental impact through biocomposites
21
In order for the aviation industry’s impact to the environment to be minimal, a global movement spearheaded by Air Transport Action Group (ATAG) in 2008 was put in place. To reduce the environmental footprint, major aviation leaders committed to three targets at the 2008 Aviation and Environment Summit [11]: • • •
Annual fuel efficiency utilization of 1.5% per annum Net carbon emissions cap by 2020 (carbon neutral growth) 50% reduction in net aviation CO2 emissions by 2050 from 2005 levels.
This has led to the International Civil Aviation Organization (ICAO), under the United Nations, to have the aviation industry pledge reduction in its emissions through four pillars of innovation [11]: • • • •
Product Technology Operations and Infrastructure Economic Measures Sustainable Fuel.
Although the aviation industry has had a strong record in decreasing its emissions, the four pillars of innovation are foreseen to enable the industry to reach its 2050 target of 50% net reduction in aviation CO2 emissions, and related greenhouse gasses. The vision of reduction in CO2 emissions by the global aviation industry can be summed up in Fig. 2.3. In Fig. 2.3, it can be seen that technology and biofuels are the two largest contributors to reach 2050’s 50% carbon dioxide reduction goal. The red line represents predicted emissions pending zero action on any of the four pillars, and the green line represents the predicted trajectory toward its 2050 goal. Technology is split into various sectors: (1) aircraft technology, (2) operations, and (3) infrastructure. Improvements in aircraft technology are accounted for by introduction of better aerodynamic
Emissions assuming no action
No action
Aircraft technology (known), operations and infrastructure measures
Carbon-neutral growth 2020
Biofuels and radically new technologies
Gross emissions trajectory
Economic measures
Technology
CO2 Emissions
Operations Infrastructure Biofuels and radical tech CNG 2020
–50% by 2050 Not to scale
2005
2010
2020
2030
2040
2050
Figure 2.3 International Civil Aviation Organization (ICAO) action plan until 2050 (four pillar strategy) [11].
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites
properties into the aircraft, such as wingtips; and weight reduction of the plane, such as increased usage of composite materials, lightweight paints, and lightweight seats. Improvements in operations are targeted at optimized flight paths, fuel savings for takeoff and landing procedures, and weather-based flight paths. Finally, infrastructure is aimed at improvements and modernization of air traffic management systems at airports. The green portion of the action plan, biofuel and radically new technologies, is seen as the major contributor to reach the 50% reduction in CO2 emissions of the industry. While new radical technologies are in development, such as hybrid-electrical propulsion, fuel celledriven environmental control system, and assisted take-off and landing, these technologies are still immature and their effect on the reduction of environmental impact is still in consideration. Biofuel, in this instance,biofuel made for aviation jet fuel grade, is the best contender. Numerous test flights have already been performed globally and its affect in reduction of CO2 emission and improved fuel performance is well recorded [3]. The utilization of jet biofuel and biocomposite contributes to the aviation industry’s reduction in CO2 and improving the sustainability of the industry. Jet biofuel improves fuel performance, lowers soot and CO2 emissions. Biocomposites improve the sustainability factor of a plane, rather than composite fibers derived from nonrenewable sources. Biocomposites have a long development roadmap, and the usage of renewable, sustainable sources is key for implementation onto an aircraft.
2.1.2
Sustainable biomass for aviation
Biomass is seen as the next generation source for the aviation industry, as biomass absorbs carbon dioxide, it limits and reduces the aviation industry’s impact. However, caution has to be noted that the biomass has to be sustainable and renewable. Sustainable biomass means no competition with food, no land use change in accordance to sustainability criteria, minimal impact to the environmental/ecosystem, and is renewable (able to be grown), compared to fossil fuel based whose resources are finite. The need for sustainable and renewable biomass sources is best illustrated by Table 2.1. Currently, bioenergy (from biomass) is the world’s largest source of renewable energy, accounting for 14% out of 18% of the renewable energy sector. This places bioenergy at an estimate of 10% of global energy supply. This biomass covers both sustainable and nonsustainable biomass [12]. Of the bioenergy, only 4% of the total
Table 2.1 Comparison of renewable, nonrenewable, sustainable, and nonsustainable Sustainable
Non-sustainable
Renewable
A reliable source that meets annual demand
A renewable source that does not meet demand
Nonrenewable
Producing sufficient sustainable biomass for 10 years only
Supply only lasting for 40 years
Biomass valorization for better aviation environmental impact through biocomposites
23
can be considered as biomass usage for biofuel, which includes biodiesel, bioethanol, and biogas. The world’s largest biofuel producers from biomass are South America (largely Brazil), North America, followed by Europe [13]. These energy crops, or biomass, can be sectioned into three generations of biomass feedstock. It is sectioned as such to fundamentally understand the differences between its renewable and sustainable differences. First-generation feedstock are crops such as corn, sugarcane, soybean, vegetable oil, wheat, rapeseed, peanuts, and a number of other food crops. First-generation biofuels are produced directly from these food crops. However, in 2008, it was estimated that if biofuels from first-generation crops were to satisfy 20% of the growing biofuel demand, there will be no crop balances for food. In 2007, the United Nations Food and Agriculture Organization saw world food prices increase by 40% within 12 months, due to the influence of biofuel being derived from feedstock such as sugarcane, corn, rapeseed oil, palm oil, and soybeans [14]. This meant that first-generation biomass was renewable, but not sustainable, for usage of biofuel or for creation of a biocomposite industry. The first-generation debate brought about the need for second-generation feedstock, and later third generation, which are not in direct competition with food. Secondgeneration biofuels are derived from nonfood feedstock, for example, switchgrass, Jatropha, waste vegetable oil, municipal solid waste, lignocellulosic sources, etc. These second-generation sources tends to be grown on marginal lands, land that cannot be used for “edible” crops. Compared to first-generation, second-generation feedstock are processed differently and will require additional processing steps to convert the feed into fuel. Recently, third generation entered into the spotlight as biofuel derived from algae. Third-generation feedstock provides numerous advantages over second and third generation, from a larger array of carbon sources, significantly higher yields, better land efficiency, diversity of algae species for added-value products, good potentials of products, and different methods in cultivation. However, the biggest drawback for algae is the large amount of water and nutrients (nitrogen and phosphorus) to grow them, and the investment costs for large-scale implementation [15]. Combined, biomass feedstock in 2007 was approximated at 47.2 EJ (exajoule) per year; in 2016, this was estimated to be 56 EJ per year. The main driver behind the increase in feedstock availability is the biodiesel and bioethanol industry [16]. This is due to the increase in countries adopting biofuels to improve their greenhouse gas impact, as part of the United Nations Framework Convention on Climate Change.
2.1.3
Biocomposites
A material can be considered a biocomposite when one part of its composition, whether it is its matrix or reinforcements, is derived from natural sources [17]. Biocomposites are made in part, with natural fiber, which can be derived from a plant’s seed, leaf, bast, fruit, and/or stalk. This is limited to such due to the need for cellulose, hemicellulose, and lignin, which is able to form a matrix and is held together in a framework to yield a structured composite shape. The usage of lightweight composite materials, increased utilization of composites on aircraft, and the pending introduction of biocomposites are all contributing factors
24
Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites
toward lowering the weight of an aircraft, and for biocompositesd“greening” the aircraft. With decrease in aircraft weight, fuel savings and reduction of CO2 can be accomplished. The outlook for utilizing biocomposite for aircraft parts is attractive; however, to develop biofibers for aviation requires stringent testing and validation, and the research is not yet mature enough. The limiting factor for now, is the need to treat and process the natural fiber to rival current composite fibers’ properties and component strength. This is accounted by natural fiber’s lack in homogeneity, compared to glass and carbon; it has a higher tendency to absorb moisture; and the compatibility with current resin used in aerospace manufacturing [18]. A method to fast track the implementation of natural fiber into aerospace manufacturing is through hybridization, a mix of conventional glass and/ or carbon fiber with natural fiber; this is currently undergoing prototyping and validation, but is seen as a faster means to market than 100% utilization of natural fiber for aerospace parts [19]. However, natural fibers will inherently be limited to secondgeneration biomass feedstock due to the need for lignocellulose material. The usage of natural fibers like coconut coir, banana stem, pineapple leaves, sugar cane bagasse, kenaf fiber, oil palm empty fruit bunch (EFB), and bamboo fiber has been documented for aerospace part prototyping [18e21].
2.1.4
Jet biofuel
Global Kerosene Jet A-1 production and demand is approximately 80 billion gallons litre per year, or 302.8 billion liters per year [22]. To understand the magnitude of jet biofuel required globally, taking into account the mandates by various countries, a 2%e3% global replacement with jet biofuel will equate to roughly 6.06e15.14 billion liters per year. According to ICAO, the United States, Canada, China, Japan, the European Union, and Indonesia have implemented a jet biofuel mandate between 2% and 3% of their annual consumption. This is the result of the aviation industry’s pledge back in 2008 with ATAG, and in 2017 marks the introduction of a carbontrading scheme by ICAO known as Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) [23]. The CORSIA scheme will go into its pilot phase in 2020, and will see the implementation (a global market-based measure) of trading “emissions” units. Aircraft operators will be required to pay for any CO2 emission growth at their 2020 levels (reported). The amount of CO2 to be offset by 2025 is in the range of 142e174 million tons of CO2 emissions. The price of carbon is also estimated from a low 6e10 USD/ton of CO2-eq to a high estimate of 20e33 USD/ ton CO2-eq. To produce jet biofuel sustainably, the feedstock has to be sustainable (second or third generation) and the process to convert has to be certified. Under the ASTM: D7566 “Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbon” [24], only five processes have been certified under international standards that govern Kerosene Jet A-1 usage on board an aircraft. Synthesized hydrocarbon from biomass is in essence jet biofuel. Conventionally, Kerosene Jet A-1 is certified under ASTM: D1655 “Standard Specification for Aviation Turbine Fuel,” without any synthetic hydrocarbons [25]. In order to produce synthetic hydrocarbons, or jet
Biomass valorization for better aviation environmental impact through biocomposites
25
biofuel, the five processes are: (1) Fischer-Tropsch Synthetic Kerosene with Aromatics (SKA), (2) Fischer-Tropsch Synthetic Paraffinic Kerosene, (3) Hydroprocessed Esters and Fatty Acids, (4) Alcohol-to-Jet, and (5) Direct Sugar to Hydrocarbon/Synthetic Isoparaffin. These were recognized and certified in 2009 (FT-SPK), 2011 (HEFA), 2016 (ATJ), and 2014 (DSHC/SIP). All FT fuels are able to be blended up to 50%, HEFA fuel is also up to 50%, DSHC/SIP can be blended up to 10%, and finally ATJ up to 30% blend. A simplified process flow can be seen in Fig. 2.4 of the various jet biofuel processes [26]. Conventional Kerosene Jet A-1 (via MEROX process) composition is approximately 21% aromatics, 25% paraffin, 11% isoparaffin, and 43% cycloparaffin. Compared to fuel derived from HEFA; 10% paraffin, 90% isoparaffin; FT derived, 3% paraffin, 88% isoparaffin, 9% cycloparaffin; and lastly, DSHC derived is >95% isoparaffins. The difference in composition is noticeable and, therefore, is unable to fully (100%) substitute conventional Kerosene Jet A-1, and requires blending instead. Asides from these five processes, there are numerous other, not yet certified, pathways that utilize second-generation and third-generation feedstock to yield jet biofuel. Most notably are hydrotreated depolymerized cellulosic jet, catalytic hydrothermolysis, hydrothermal liquefaction, synthesized aromatic kerosene, and synthesized kerosene. Utilization of jet biofuel is a reality, and efforts are underway worldwide to push for adoption. This is needed to understand the performance and benefits of jet biofuel.
Vegetable oil, used cooking oil, fat
Hydroprocessing
50%
Hydrothermal liquefaction Algae
Pyrolysis
Bio-oil
Gasification
Fischer-tropsh synthesis
Syngas
50%
Lignocellulose Gas fermentation
Alcohol synthesis
Hydroprocessing
Alternative jet fuel
Hydrolysis Waste gas CO, CO2, H2
Olefins Glucose
Hydrocarbons
Alcoholic fermentation
Dehydration & oligomerization
Alcohols 30%
Sugar & starch
Fermentation
Farnesane
10%
Biological process
Chemical process
Thermal process
Feedstock
Intermediate product
= ASTM certified (maximum blending level indicated)
Figure 2.4 Simplified process flow of certified processes to produce jet biofuel [26].
26
Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites KLM / skyNRG Alaska /hawaї bioenergy
Airbus / air canada / biofuelnet
Core jetfuel
Advanced biofuel flighpath SAFUG NARA
Lufthansa / GEVO Airbus / rostec
aireg
BA/solena
NEWbio
NISA
Bioport holland
Airbus / ENN
lufthansa / solena ASCENT
United / altair
Farm to fly CAFFI
Itaka
INAF
Bioqueroseno
GE / D’arcinoff Qatar univ. biofuel project
Cathay / fulcrum
MSBRC SEASAFI
Airbus / malaysia Qatar airways / byogy Green aviation initiative
BBP GOL / boeing
Virgin / lanzatech
QSAFI
GOL / amyris-total Arg. national initiative
Boeing / SSA / SKYNRG
AISAF
Virgin / skyNRG
Avianca / byogy Quantas / solena Stakeholders action group
Projects
Airlines /fuel producers
Figure 2.5 Global activity map of jet biofuel, test flights by airlines and aerospace industry [11].
Fig. 2.5) is a world map of various activity on jet biofuel test flights, production, and projects [11]. Some of the efforts have been summarized in the table below to link the relationship between the airline, jet biofuel producer, its feedstock and process utilized, and contractual ties (Table 2.2). To replace 2%e3% with jet biofuel of current global aviation jet fuel demand, a total of roughly 6e15 billion liters per year is required. This demand is currently not met by any jet biofuel producers around the world, and only a handful of countries around the world have implemented mandates on jet biofuel. However, through rigorous testing and analysis, it is a known fact that jet biofuel combustion process is cleaner and more efficient than conventional Kerosene Jet A-1. Jet biofuel offers customization beyond the ability of conventional Kerosene Jet A-1, as the production of Kerosene Jet A-1 is in harmony with other products derived from crude oil, i.e., gasoline/petrol, diesel, and petroleum products. Jet biofuel processes enable a certain level freedom of conversion and equilibrium reaction. For example, most synthetic kerosene-grade fuel offers more straight chain chemical groups than conventional jet fuel, which limits the soot formation during combustion in the jet engines. Cleaner burn, limited soot formation will mean increased engine performance, easier maintenance cycles, and better fuel efficiency. Stability of the fuel also increases through the introduction of more cyclic components within the fuel, without a decrease in fuel performancedjet biofuel is able to be tailored. The lack of aromatics in synthetic kerosene is an advantage, as aromatics do not provide clean combustion and encourage soot formation, unlike Kerosene Jet A-1, where aromatics are still in abundance. Aromatics are heavy molecules, with limited hydrogen, and therefore limited energy content. Aromatics increase the fuel density without offering
Biomass valorization for better aviation environmental impact through biocomposites
Table 2.2 Overview of airlines that have agreements with jet biofuel producers Airline
Producer
Feedstock-pathway
Description
United Airlines
AltAir
HEFA
AltAir production capacity from 2016, 15 million gallons at a 30:70 blend, purchase agreement.
Cathay Pacific
Fulcrum Bioenergy
MSW-FT
Long-term supply agreement for fuel from municipal solid waste, located in Nevada. Supply starting from 375 million gallons (US) over 10 years (2% of Cathay’s annual fuel consumption). Airline strategy to achieve carbon neutral growth by 2020.
Southwest Airlines
Red Rock Biofuels
Forest residues e FT
Supply agreement for 3 million gallons per year.
GOL (Brazil)
UOP/AmyrisTotal
HEFA e inedible corn oil and used cooking oil/. SIPsugarcane
Target blending of 1% of biofuel in 2016, achieved 200 flights with 4% mixture for World Cup (92,000 L of HEFA UOP fuel). SIP achieved first flight in September 2014.
Oslo Airport
Neste Oil
NESTE e NEXBTL
First airport in the world to introduce jet biofuel.
Air France
Amyris-Total
SIP-Sugarcane
1 year series of weekly flights between Toulouse and Paris, using 10% blend, completed in September 2015.
KLM
SkyNRG
HEFA-used cooking oil
18 weekly intercontinental flight from Amsterdam to Aruba, using 20% blend of biofuels made from used cooking oil.
Lufthansa
Neste Oil
HEFA-used cooking oil
Part of Project burnFAIR.
SAS (Norwegian)
SkyNRG Nordic
HEFA-used cooking oil
Airport-based biofuel supply facilities in Norway and Sweden.
Virgin
Lanzatech/ Swedish biofuels
Waste gases e alcohol to Jet
In pipeline to be used.
27
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Structural Health Monitoring of Bio-, Fibre-Reinforced Composites and Hybrid Composites
(a)
(b)
(c)
(d)
Figure 2.6 Experimentation with Kerosene Jet A-1 and various synthetic aviation fuel with a Rolls-Royce combustion rig [30]. Description of a to d can be seen in the paragraph below.
the added boost of energy density [27e29]. Experiments on soot/coke formation were performed, and the results can be seen in Fig. 2.6. Experimentation performed by Pucher et al. [30], in the figure above. (a) is with conventional Kerosene Jet A-1, (b) is with 2% fatty acid methyl esters (FAME) mixture with conventional Kerosene Jet A-1, (c) is with 50% synthetic Kerosene Jet A-1 blended with conventional fuel, and (d) is with 100% synthetic Kerosene Jet A1. These fuels were combusted in a Rolls Royce T-56-A-15 combustion rig to mimic a typical jet engine. As seen, the vast difference is between (a and d), with 100% synthetic Kerosene Jet A-1 there is a vast difference in soot/coke formation at the fuel nozzle and igniter plug, an almost absence of coke formation. However, blended fuel (b and c) still saw significant coke formation, with (c) flaring betterdinjector holes are relatively clear compared to (b and a) [30]. From a CO2 standpoint, jet biofuel production has been compared with conventional Kerosene Jet A-1. In this study [31], vegetable oil using HEFA process was used to compare with Kerosene Jet A-1 (MEROX process). The results can be seen in the graph in Fig. 2.7. Vegetable oil conversion with HEFA can yield between 20% and 73% better CO2eq/MJ compared to Kerosene Jet A-1. However, current HEFA fuel is more expensive to produce compared to Kerosene Jet A-1. A study by Massachusetts Institute of Technology (MIT) used a discounted cash flow rate of return approach (DCFROR)
Biomass valorization for better aviation environmental impact through biocomposites
29
Jet A1 Pure vegetable oil from rape seed Hydrotreated vegetable oil from palm oil* Hydrotreated vegetable oil from palm oil Hydrotreated vegetable oil from sunflower Hydrotreated vegetable oil from rape seed 0
10
20
30
40
50
60
70
80
90
(gCO2eq/MJ)
Figure 2.7 Conventional Jet A-1 production compared with HEFA-based jet biofuel production on CO2 emissions per MJ [31].
[29], HEFA fuel best scenario cost was 2.2 times more expensive than Kerosene Jet A1 (MEROX), with its worst case scenario being up to 2.6 times more expensive, where Kerosene Jet A-1 fuel price is approximately USD 1.82/gal (USD 0.48/L).
2.2
Summary
Biomass valorization is needed for a better aviation environmental footprint and this can be accomplished by biocomposites and jet biofuel. The key to enabling the aviation industry to adopt biomass-derived products is for the biomass to be sustainable and renewable. Sustainability of the feedstock and its abundance is needed to support a growing aviation industry sustainably, while ensuring the safety standards that the industry is known for. First-generation biomass is not known for its sustainability, due to its competition with food. Biocomposites therefore need to utilize secondgeneration sustainable feedstock, however, development of biocomposites is currently limited to its ability to treat and process natural fibers to rival its glass and carbon fiber (fossil-derived) counterparts. The development of biocomposites is much watched by the aviation industry, which sees it as an integral part to “green” the industry’s carbon footprint, and the lightweight properties of composite are needed to meet the industry’s goal of reduction in CO2 emissions. However, biocomposites are still not mature enough to be adopted by the industry, however, hybridization (mixing biocomposites with conventional composites) is seen as a means to fast track the ability to introduce biocomposites into the market for aviation. Lastly, for jet biofuel, the maturity is gaining ground with up to five certified pathways/methods to produce jet biofuel. However, like with biocomposites, the source needs to be sustainable and be sufficiently abundant to supply a very large global demand (at least 6 billion liters annually for global consumption) for jet biofuel. The costs to produce synthetic fuel are still high, as seen with recent studies, but development of the jet biofuel is not at a dead end. Reduction of production price is still hopeful, coupled with the inherent increase in fossil fuels, the price will eventually be competitive. Still, with movements of CORSIA and the aviation industry, the cost of jet biofuel remains high, even in the face of a growing industry, the considerable operational benefits jet biofuel can offer, and the corresponding environmental benefits.
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Biomass valorization for better aviation environmental impact through biocomposites
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[21] Haris MY, Laila D, Zainudin ES, Mustapha F, Zahari R, Halim Z. Preliminary review of biocomposites materials for aircraft radome application. Key Eng Mat 2011;471e472: 563e7. [22] Davidson C, Newes E, Schwab A, Vimmerstedt L. An Overview of aviation fuel markets for biofuels stakeholder. Technical Report NREL/TP-6A20e60254. National Renewable Energy Laboratory; July 2014 [Internet] Available from: http://www.nrel.gov/docs/. [23] Carbon Market Watch. The CORSIA: ICAO’s market based measure and implications for Europe. Carbon Market Watch; October 2016. Available from: https:// carbonmarketwatch.org. [24] ASTM. ASTM D 7566, standard specification for aviation turbine fuels csynthesized hydrocarbon. 2016. version revision a. [25] version revision a ASTM D 1655 “standard specification for aviation turbine fuels”. 2016. Available from:, https://www.astm.org/. [26] El Takriti S, Pavlenko N, Searle S. Mitigating international aviation emissions, risks and opportunities for alternative jet fuels. The International Council on Clean Transportation; March 2017. [27] Edwards T, Maurice LQ. Surrogate mixtures to represent complex aviation and rocket fuels. J Prop Power 2001;17:461e6. [28] Bisio A. Aircraft fuels e energy, technology and the environment1. John Wiley and Sons Inc.; 1995. p. 257e9. [29] Coordinating Research Council Inc. Handbook of aviation fuel properties. CRC report No. 635. 3rd ed. 2004. [30] Pucher G, Allan W, Poitras P. Emissions from a gas turbine sector rig operated with synthetic aviation and biodiesel fuel. J Eng Gas Turbine Power 2010;133(11). [31] Malina R. HEFA and FT jet fuel cost analyses. MIT; November 2012.
Further reading [1] ATAG. Air Transport Action Group. Fact sheet: delivering fuel efficiency. ATAG; 2016 [Internet] Available from: http://www.atag.org/component/.