Sustainability
CAAFI's Role
A holistic view of sustainability encompasses environmental, economic, and social performance that enables an activity to be maintained over time. The aviation sector is committed to continuous improvement in performance, including aspects such as emissions, noise, and fuel burn that are relevant to the sustainability of the industry as a whole. The sector recognizes the role of sustainable aviation fuel (SAF) in achieving improved environmental, social, and economic performance. CAAFI® focuses on providing guidance to the aviation sector to ensure that relevant environmental, social, and economic risks and performance metrics are understood and given consideration at every stage of the alternative jet fuel supply chain, including feedstock production, fuels development, evaluation, distribution, and deployment.
Current Status
What is SAF?
To be “sustainable,” the SAF industry must continuously perform in a way that maximizes benefits and minimizes negative impacts among each of three areas: environmental, social, and economic.
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Environmental sustainability considers air and water quality impacts, climate change impacts, land use, biological diversity, and other environmental factors potentially affected by the production and use of SAF.
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Social sustainability involves such considerations as balancing between SAF feedstock and food/ feed/fiber production, land use, rural community engagement and social development, fair trade, energy diversity and security, among other societal factors potentially impacted by the SAF supply chain.
Lastly, economic sustainability largely concerns the sustainability of the SAF industry itself—the commercial viability of feedstock and fuel production, the ability of the industry to attract investors and deliver strong returns on their investments, likeliness of SAF market growth, supply chain efficiency and reliability that airlines can depend on, the potential of the industry to spur job creation and workforce development, SAF price stability, and competitiveness with conventional petroleum-based jet fuel products.
Images used with permission. Credits, right to left, from top: MN Board of Water and Soil Resources; U.S. EPA; Rik Schuiling/Wikimedia Commons/Public Domain; POET-DSM; Wikimedia Commons/Public Domain; United Soybean Board; United Airlines.
Overall, the aviation industry seeks long-term, sustained growth while minimizing environmental and public health impacts. The industry also seeks to ensure a reliable and diversified energy supply. Truly sustainable SAFs can help aviation meet all of these objectives.
How is SAF Evaluated?
Generally, SAF sustainability is evaluated using a regulatory or voluntary evaluative framework that describes a specific set of criteria, for which actual data inputs are audited and certified by a third party. Note that this is in addition to, and separate from, fuel technical qualification for safety and performance, which is described in detail on the CAAFI Fuel Qualification page. A sustainability evaluation is performed for a specific feedstock and fuel production pathway. Some regulatory programs, such as the U.S. EPA’s Renewable Fuel Standard (RFS2), consider representative feedstock and pathway characteristics to estimate sustainability attributes and qualify fuels for their programs. Many others require facility-specific evaluations and associated certifications. These evaluations provide information on performance regarding economic, environmental and social considerations such as greenhouse gas emissions, water quality and use rights, air quality, biodiversity and conservation, community/rural development, food and fuel security, direct and indirect land use change, ratio of energy inputs to outputs, and health and economic impacts on local residents where feedstocks are produced, among many other factors. Regulatory and voluntary sustainability certification schemes require high-quality data to be reviewed by third party auditors on a regular basis to affirm the sustainability attributes and performance of the production system to achieve certification.
Regulatory and policy frameworks such as the RFS2 in the U.S., and the Renewable Energy Directive (RED) in the EU - may include mandates for specific amounts or blend percentages of sustainable alternative fuels, as well as incentives and/or restrictions on how renewable fuels are produced. Many of these regulatory frameworks include specific requirements related to sustainability, such as minimum lifecycle GHG reduction thresholds for fuels, limits on land-use change or conversion, and restrictions on the use of invasive species as feedstock sources. International standards, such as the ISO 13065 Standard (sustainability criteria for bioenergy) provide general guidance on how to perform sustainability evaluations for specific types of bioenergy supply chains.
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Voluntary sustainability certification schemes (SCSs) for alternative fuels help provide market assurance of the environmental, social, and economic acceptability of a fuel. This assurance is based on a third-party audit of data demonstrating compliance with sustainability criteria defined by the scheme. The schemes are intended to comprehensively cover all aspects of sustainability, including environmental, social, and economic components, and vary depending on the audience and targeted user. A scheme may be focused on feedstocks (e.g., Bonsucro for sugarcane, Roundtable for Sustainable Palm Oil, Forest Stewardship Council (FSC)), or on the end fuel/product and its entire life cycle or supply chain (e.g., International Sustainability and Carbon Certification (ISCC), Roundtable on Sustainable Biomaterials (RSB)). Some regulatory frameworks accept voluntary certification as a means for demonstrating compliance of renewable alternative fuels with regulatory program. For instance, operators who are certified by an approved voluntary certification scheme accepted under the EU RED can qualify for the mandate under that program. However, many regulatory and voluntary frameworks currently use different indicators and criteria to evaluate sustainability performance of SAF that are not readily comparable.
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​The first globally recognized, sector-wide sustainability approach has been established for international aviation under the United Nations’ International Civil Aviation Organization (ICAO) Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), including requirements for certification by an approved SCS such as ISCC, RSB, or ClassNK, a set of comprehensive sustainability criteria, and supplementary guidance on compliance, the details of which can be found on the ICAO CORSIA Eligible Fuels webpage.
Evaluative Frameworks
The overall goal of most existing alternative fuel mandates and regulations is the deployment of sustainable alternative fuels for surface transportation. These regulatory programs vary in their inclusion or exclusion of alternative jet fuel. Neither the U.S. Renewable Fuel Standard (RFS) nor the European Commission’s Renewable Energy Directive (RED) explicitly include a requirement for alternative jet fuel within their larger fuel mandates. However, both allow jet fuel to count toward their mandates. The California Air Resources Board (CARB) has included SAF in the CA Low Carbon Fuel Standard (LCFS) since January 2019. ICAO CORSIA is strictly aviation focused and includes CORSIA Eligible Fuels options for SAF and fossil-based lower carbon aviation fuels (LCAF).
Existing Alternative Fuel Regulations Affecting SAF
CAAFI Sustainability Focus
CAAFI considers all aspects of sustainability, and is particularly interested in the synergies among environmental performance, economic growth, rural development, job creation, energy supply surety, and social impacts.
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In terms of environmental sustainability, CAAFI has strongly emphasized the importance of sound GHG (LCA) methodology and evaluation. A fuel’s GHG LCA will be critical for its acceptance and use by the aviation sector. In addition to supply surety, energy security, and price stability, the aviation industry’s desire to reduce carbon emissions is a key driver for SAF development and deployment. GHG benefits of alternative jet fuels are measured on a life cycle basis and incorporate emissions from all inputs into the feedstock production and conversion/processing, transport, and use of the fuel. GHG life cycle analysis (LCA) methodologies are well established, but there are still methodological choices that can strongly affect the final LCA value, including the extent of the system boundaries, methods for assigning share of upstream emissions among coproducts, and the inclusion of indirect effects such as indirect land use change. CAAFI seeks to understand how choices in GHG LCA approaches affect results and to advance harmonization in GHG LCA approaches as applied to alternative jet fuel where appropriate. Other sustainability considerations beyond GHG LCA are required to be evaluated for SAF claims under CORSIA.
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Regarding economic sustainability, CAAFI tracks and communicates about ongoing efforts to understand the potential for economic growth, rural job creation, and global competitiveness provided by alternative jet fuels as well as challenges associated with the economic cost of their production.
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To advance social sustainability, CAAFI seeks to educate stakeholders, build relationships within local/regional communities, and consider the effects of development on these communities while improving the quality of life for those all along the supply chain from the farmer to the flyer.
Key Topics
Sustainability Benefits of Alternative Jet Fuels
CAAFI seeks to leverage synergies among environmental, social, and economic sustainability for SAF production, including:
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Local Air Quality Benefits
Emissions from aircraft impact human health, climate, and local air quality. Particulate matter (PM) and sulfur oxides (SOx) are linked to “higher incidences of asthma, cancer, cardiovascular disease, stroke, and premature mortality, especially in communities directly surrounding airports where the bulk of emissions from air travel take place” (Clearing the Air: The Public Health Benefits of Meeting the SAF Grand Challenge – Third Way). Numerous measurement studies have shown that jet engines burning SAF or fuels with lower aromatic and sulfur content can reduce aircraft engine PM emissions compared to conventional, fossil-based jet fuels. Specifically, emissions of black carbon, or “soot”, and those derived from sulfur dioxide are curtailed. Based on these studies, biobased fuels show a reduction of PM number by up to 90% and of mass by 60-85% total. , (The non-CO2 climate co-benefit of SAF and other fuels with low aromatic and sulfur content - IATA). According to a study by Third Way, replacement of jet fuel with SAF by 2050 could prevent over 3,000 premature deaths, reduce asthma, cardiovascular disease and other non-fatal illnesses as well as reducing asthma and cardiovascular disease.​​​
From Hileman, 2022 CBGM presentation, slide 12: PowerPoint Presentation
While CO2 may be the most significant greenhouse gas emitted from aircraft, other non-CO2 impacts from aviation, including from the formation of condensation trails (contrails), also affect climate. Contrails are trails of ice crystals formed from water vapor emitted from aircraft engines that condense and freeze onto naturally occurring particles and those emitted from the aircraft in cold and humid conditions at high altitude, seen as white, line-shaped clouds behind aircraft.
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Although recent engine technology has made progress in reducing these emissions, most of today’s jet engines emit soot particles. Soot contributes to the formation of the ice crystals that make up contrails and impact the climate. Research suggests that aviation-induced cloudiness, or cirrus clouds caused by persistent contrails from aircraft, is estimated to be the largest contributor to warming by non-CO2 emissions, but with large uncertainties in the magnitude of the warming. The contrails are short-lived and dependent on the geographical location, altitude, and time of day and year in which they form and persist. Contrails are not formed on all flights, and instead only when certain atmospheric conditions, including temperature and humidity levels, are present. Studies have found that only a small number of flights are responsible for most of the contrail climate warming.
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Contrails from SAF may be more frequent, since they produce more water vapor, but have lower sulfur and particulate matter that may lead to less ice crystal formation and reduced lifetime. Altering fuel composition by removing or reducing aromatics, naphthalenes, and sulfur from conventional jet fuels to reduce PM emissions is being considered as a strategy to help reduce air transportation’s non-CO2 impacts, and such benefits can also be accomplished through the use of SAF. Additionally, research has suggested that using SAF selectively to flights at times of day or in seasons with high likelihood of contrail formation may mitigate contrails, albeit with management and logistical complications, but this has not been demonstrated on a commercial scale
Sources:
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Overview of the National Jet Fuels Combustion Program – Aerospace Research Central
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The non-CO2 climate co-benefit of SAF and other fuels with low aromatic and sulfur content - IATA
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Clearing the Air: The Public Health Benefits of Meeting the SAF Grand Challenge – Third Way
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Understanding and Addressing Aviation’s Non-CO2 Climate Impacts – Airlines for America
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Economic and Social Benefits for Local and Rural Communities
There are economic and social opportunities connected with the deployment of SAF, including rural job creation and increased revenue for farmers. For society as a whole, SAF production contributes to a vibrant bioeconomy that has a $210.4 B impact annually, supporting over 50,000 direct jobs and nearly 650,000 total jobs. Third Way analyses suggest that deployment of SAF to meet the SAF Grand Challenge targets could lead to support of approximately 100,000 jobs annually.
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At the farm level, SAF production can have beneficial effects not only on farmer revenue, but also on ecosystem services. Bioenergy cover crops can protect and water soil quality and reduce runoff/improve water quality while generating farmer revenue in a season that normally does not provide a saleable crop. CAAFI is very interested in opportunities to leverage payment programs that promote environmentally beneficial projects as an additional revenue stream for SAF feedstock producers. Such programs could provide greater economic benefits fostering economic and social sustainability for SAF feedstock producers. To learn more about CAAFI’s interests in this area, go to the Feedstocks page.
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The deployment of SAF also provides opportunities for U.S. domestic fuel production and export to global markets, enhancing competitiveness of the U.S. in the energy arena.
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Range and Maintenance Benefits
The higher energy mass density of some SAFs can enable aircraft to move payloads longer distances for the same mass of fuel. Other performance enhancements may also be possible, such as increased equipment longevity due to lower radiative heat loading and other favorable SAF characteristics. CAAFI is seeking information and data on this topic and would welcome your input at info@caafi.org.
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Food and Fuel
There has been widespread concern that a widely scaled-up biofuel industry could lead to reduced food availability due to use of food crops for biofuel production and/or growth of non-edible biofuels feedstocks on land historically used for food production, exacerbating food insecurity and driving up food prices (see a brief history here). This conflict is often termed “food versus fuel.” However, other analyses suggest there may be positive synergies between food production and biofuel production when both are done well. By providing more revenue stream opportunities for farmers, by enhancing traditional food crop production (e.g., through the use of bioenergy-related cover crops and multicropping) and by enabling the development of infrastructure and acquisition of agricultural inputs to enhance overall production in a given region, sustainable SAF production may be able to enhance food production, thus shifting the debate from “food versus fuel” to “food and fuel.”
Tradeoffs/Challenges/Risks with SAF Production
CAAFI recognizes that there are environmental, social, and economic risks associated with feedstock and fuel production. The assurance of sustainability through certification or other means is intended to mitigate those risks. CAAFI’s Alternative Jet Fuel Environmental Sustainability Overview is intended to provide airlines with an understanding of the kinds of sustainability analyses commonly considered when evaluating alternative fuels and to provide common background for SAF stakeholders to discuss environmental sustainability issues and concerns. The document provides basic information about various environmental sustainability considerations relevant to SAF production and some of the metrics used to evaluate them, as well as an analysis of where risk of environmental sustainability issues resides along the alternative jet fuel supply chain (see table below). However, the actual impacts of any given step in the supply chain of a given feedstock or process will depend on the details of feedstock cultivation, collection, transport, processing, and distribution.
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CAAFI also recognizes that there can be tradeoffs among various aspects of environmental, social, and economic performance, and that often fuels may perform well in one area while raising concern in others. For example, there has been significant scrutiny on the tradeoffs between energy production and water use and quality. This has been termed the “Water-Energy Nexus” by the Department of Energy. While the challenge of maintaining water supply and quality while also producing energy is not unique to alternative fuels, the use of irrigation to generate bioenergy crops can pose the risk of significant impacts in water-stressed regions, necessitating informed planning and decision making.
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Another significant sustainability challenge is that many of the high productivity, low input, and broad environmental tolerance characteristics sought in biofuel feedstocks may also be strong predictors of invasion risk by non-native species. Invasive species spread into natural ecosystems, edging out native species and disrupting ecosystem services, costing billions of dollars annually in control and eradication efforts. An analysis has shown that U.S. bioenergy-related programs and regulations do not have a consistent approach to addressing invasive species risk in biofuel production, indicating that the community should maintain awareness of this issue when evaluating new feedstocks and opportunities.
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Such tradeoffs must be considered when evaluating the suitability and sustainability of SAF feedstocks and processes for a given location. The matrix below provides an assessment of the potential risks for various environmental impacts across the SAF supply chain. For environmental sustainability, CAAFI considers most of the risk to be associated with feedstock production, indicating that both proactive management and vigilance are required to overcome these risks to maintain environmental quality and to enhance environmental performance of SAFs over time.
Impact Matrix showing potential for direct environmental impacts across the alternative jet fuel supply chain for selected environmental sustainability indicators.
Drop-in SAFs are anticipated to have a carbon benefit over petroleum-based jet fuel in many cases (e.g., see PARTNER Project 28 Report on GHG LCA for alternative jet fuels). However, for an operator or airline to receive credit for the carbon benefit of SAF under any regulatory or voluntary carbon emissions reduction scheme, there needs to be a structured, transparent, and effective accounting system in place to demonstrate that the fuel was produced according to defined requirements and that only one party receives the credit. Such accounting mechanisms are called “Chain of Custody” or CoC systems, and provide an unbroken tracking of the production, transfer, and use of a product. Chain of custody systems need to be auditable and enforceable to ensure that the accounting system is accurate, verifiable, and fair.
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CoC mechanisms commonly used to track SAF:
Chain of Custody for SAF
CoC approach:
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Book-and-Claim
Finally, in a book-and-claim CoC approach, the sustainability attributes of a given quantity of SAF are documented in a certificate once the fuel is produced. These certificates or credits can then be sold/traded to credit buyers that may claim renewable fuel credits associated with the produced SAF, even if they themselves do not actually consume the fuel. This arrangement allows the certified fuel to be locally inserted into the conventional fuel supply chain (reducing logistics and delivering sustainability benefits) while allowing distant entities lacking readily accessible sustainable SAF to participate in the sustainable fuels market and meet regulatory compliance by purchasing sustainable SAF production credits from the fuel producer. The leading example of an alternative fuels book-and-claim system is the U.S. RFS program, which is supported by a Renewable Identification Number (RIN) trading market. Because book-and-claim does not require physical separation between certified SAF and non-certified conventional fuel, it does not in of itself require a separate dedicated transport or distribution infrastructure. However, because no fuel accompanies the certificate, additional oversight may be needed to ensure that a given unit of SAF is not counted more than once.
Graphic reproduced with permission from ACRP Research Report 165.
The table below summarizes some of the key elements of three alternative fuel mandates and several example voluntary certification schemes including their inclusion of jet fuel, a few key methodological aspects of the GHG LCA accounting, and a summary of sustainability aspects covered as part of qualification of fuels for the mandate. Note that in the U.S., many sustainability elements are addressed in other laws not specific to biofuel production. For example, in the U.S., the Clean Air Act and Clean Water Act address air quality and water quality for industrial facilities, respectively. These are not reflected in the table below. Note that CAAFI does not endorse or promote any specific sustainability schemes; those shown below are simply examples.
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CoC approach:
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Mass-Balance
A mass-balance CoC approach allows the physical commingling of SAF with non-certified conventional fuel across shared transport, storage, and distribution infrastructure. The quantity of certified fuel is tracked as it moves along the supply chain to ensure that only the original amount of certified SAF transported is credited once the blended fuel reaches its final destination. For example, a blended jet fuel shipment that includes 100,000 gallons of certified SAF and 300,000 gallons of conventional jet fuel would indicate a 25% mass-balance of SAF in that total shipment (400,000 gallons). Accordingly, the recipient of the fuel shipment would be informed that they may only take credit for 100,000 of certified SAF. Mass-balance CoC allows tracking of certified SAF molecules in the fuel supply as they move across each segment of the supply chain. Such tracking can enable the traceability of feedstocks and fuels for other sustainability criteria as well.
Graphic reproduced with permission from ACRP Research Report 165.
CoC approach:
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Physical Segregation:
The type of CoC approach used depends on the level of tracking required, which may range from needing to ensure that a specific set of SAF molecules have entered a specific fuel tank, to a more general need to ensure that SAF has entered the supply chain overall.
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In the physical segregation CoC approach, certified SAF remains physically separated from non-certified (i.e., conventional) fuel from its point of production all the way to the airport and/or aircraft. This tracking method is clear-cut and may make sense when the SAF production facility is located on or near an airport. However, it does require dedicated transport and storage infrastructure to keep certified and non-certified fuels separate. Because drop-in SAF is fungible with petroleum-based jet fuel and does not compromise performance or equipment, segregation of product all the way to the aircraft may not be necessary and may add costs for the industry due to the additional infrastructure requirements. Furthermore, once a fuel has been blended and has met the specification to be used under ASTM D7566, the fuel is automatically considered to be standard jet fuel under ASTM D1655. Therefore, the aviation sector is likely to focus on other CoC approaches or a mix of approaches as the most appropriate fit for drop-in SAF.
Graphic reproduced with permission from ACRP Research Report 165.
