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®’s Sustainability Team 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.

What is Sustainable AJF?

To be “sustainable,” the AJF industry must continuously perform in a way that maximizes benefits and minimizes negative impacts among each of these areas. 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 AJF. Social sustainability involves such considerations as balancing between AJF feedstock and food, feed, and fiber production, land use, rural community engagement and social development, fair trade, energy diversity and security, among other societal factors potentially impacted by the AJF supply chain. Lastly, economic sustainability largely concerns the sustainability of the AJF 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 AJF market growth, supply chain efficiency and reliability that airlines can depend on, the potential of the industry to spur job creation and workforce development, AJF price stability, and competitiveness with conventional petroleum-based jet fuel products.

collage of environmental photos showing the intersection of three concepts: Environmental Sustainability (air quality, climate, water quality and quantity, soil quality, land use, and biodiversity), Social Sustainability (fair trade, resource conservation, energy security, food security, rural development, and social acceptability), and Economic Sustainability (commercial viability, return on investment, prices stability, supply chain efficiency and reliability, workforce availability, and market growth potential)

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 Soy Bean 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 diverse energy supply. Truly sustainable AJFs can help aviation meet all of these objectives.

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How is AJF Sustainability Evaluated?

Generally, AJF 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. In the alternative jet fuel industry and for CAAFI’s purposes, a sustainability evaluation will most often be performed for a specific feedstock, fuel producer, and/or for a broader fuel production pathway. 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.

Rating System: Criteria and Indicators (Government Regulations, Intenational Standards, and Other Requirements), Inputs (Primary and Secondary Data, Audit Evidence, and Supplier Reps. and Certs.), and Rating System Operator (Company/Group of Companies, Industrial Sector or Trade Association, Government Agency, and Independent/Other Organization) go into Analysis/Modeling and Conformity Assessment which become Ouputs (LCA Study, Supplier Certification, Supplier's Declaration of Conformity, Product Label, and Sustainability Product Declaration)

This schematic shows the various stakeholders involved in the use of a sustainability rating system and how data are fed into the system and audited to provide a rating or evaluation. Reproduced with permission from a report by Futurepast (2012) produced for the FAA.

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Evaluative Frameworks

There are multiple regulatory/policy and voluntary frameworks that define and require evaluation of sustainability for alternative fuels. Regulatory and policy frameworks may include mandates for specific amounts or blend percentages of sustainable alternative fuels—such as the EPA’s Renewable Fuel Standard (RFS2) in the U.S., and the Renewable Energy Directive (RED) in the EU, 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.

Voluntary sustainability certification schemes for alternative fuels help provide market assurance of the environmental, social, and economic acceptability of a fuel and can 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)). Regulatory or voluntary sustainability certification schemes require high-quality data to be reviewed by third party auditors on a regular basis to affirm the performance of the production system.

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 AJF that are not readily comparable. A globally-recognized approach for sustainable AJF evaluation will likely be defined by the forthcoming Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). CORSIA represents a commitment among the airline industry to reducing the carbon footprint of international flights, through global market-based measures including the use of sustainable AJF. CORSIA sustainability requirements are expected to be an umbrella standard accepting multiple regulatory and/or voluntary sustainability certification schemes, similarly to the current approach used by the EU for the RED (see framework scheme comparison table, below).

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Existing Alternative Fuel Regulations Affecting AJF

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 AJF in the CA Low Carbon Fuel Standard (LCFS) since January 2019.

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Voluntary Certification Schemes

Voluntary certification schemes are intended to provide assurance to fuel purchasers, government entities, and other stakeholders that a given fuel is considered sustainable. 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. For example, the Global Bioenergy Partnership (GBEP), an international sustainability scheme, is intended for use at the governmental level to assess the performance of an entire sector or industry, whereas CAAFI’s focus is on those schemes focused specifically on feedstock and fuel supply chains and pathways.

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Chain of Custody for AJF

Drop-in AJFs 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 AJF 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.

There are three main types of CoC mechanisms commonly used to track AJF:

  1. physical segregation
  2. mass-balance, and
  3. book-and-claim.

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 AJF molecules have entered a specific fuel tank, to a more general need to ensure that AJF has entered the supply chain overall.

In the physical segregation CoC approach, certified AJF 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 AJF 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 AJF 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 AJF.

graphic of Physical Segregation: Feedstock to Production to Alternaive Fuel to Transport to Blending to Airport Storage to Aircraft

Graphic reproduced with permission from ACRP Research Report 165.

A mass-balance CoC approach allows the physical commingling of AJF 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 AJF 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 AJF and 300,000 gallons of conventional jet fuel would indicate a 25% mass-balance of AJF 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 AJF. Mass-balance CoC allows tracking of certified AJF 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 of Mass-Balance: conventional resource flow (Feedstock to Production to Conventional Fuel) and alternative resource flow (Feedstock to Production to Alternative Fuel) join together to create a mix of certified and non-certified (Transport to Blending to Airport Storage to Aircraft)

Graphic reproduced with permission from ACRP Research Report 165.

Finally, in a book-and-claim CoC approach, the sustainability attributes of a given quantity of AJF 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 AJF, 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 AJF to participate in the sustainable fuels market and meet regulatory compliance by purchasing sustainable AJF 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 AJF 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 AJF is not counted more than once.

graphic of Book-and-Claim: Certified Alternative steps (Feedstock to Production to Alternative Fuel) are 'sustainability attributes decoupled from physical product (Transport to Blending to Airport Storage steps); usually conveyed to end-user (Aircraft)'

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.

Click here for a PDF showing the sustainability elements included in these regulatory and voluntary sustainability schemes.

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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.

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. The aviation industry’s desire to reduce carbon emissions is a key driver for AJF 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 may become critical requirements for AJF purchases as CORSIA comes into effect.

Regarding economic sustainability, CAAFI tracks and communicates about ongoing efforts to understand the potential for economic growth provided by alternative jet fuels as well as challenges associated with the economic cost of their production.

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.

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Sustainability Benefits of Alternative Jet Fuels

CAAFI seeks to leverage synergies among environmental, social, and economic sustainability for SAF production, including:

Local Air Quality Improvement and Greenhouse Gas Emissions Reduction
A key driver for industry interest in alternative jet fuels is the potential to reduce air quality impacts and GHG emissions from aviation, particularly given the sector’s commitments to carbon neutral growth in international aviation starting in 2020 and the desire to reduce particulate and sulfur oxide emissions to improve local air quality. Some AJF pathways produce fuels with low or no aromatics, and all currently qualified pathways exhibit reduced sulfur content, resulting in reductions in particulate formation. Therefore, GHG emission and air quality benefits are often synergistic.

Environmental Performance and Economic and Social Benefits for Local and Rural Communities
Opportunities include rural job creation, increased revenue for farmers, the use of bioenergy cover crops to protect soil quality while generating farmer revenue and enhancing production of some primary crops such as wheat, and improving water quality. CAAFI is very interested in opportunities to leverage payment programs that promote environmentally beneficial projects as an additional revenue stream for AJF feedstock producers. Such programs could provide greater economic benefits and therefore, foster economic and social sustainability for AJF feedstock producers. To learn more about CAAFI’s interests in this area, go to the Feedstocks page.

Range and Maintenance Benefits
The higher energy mass density of some AJFs 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 AJF characteristics. CAAFI is seeking information and data on this topic and would welcome your input at

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 AJF production may be able to enhance food production, thus shifting the debate from “food versus fuel” to “food and fuel.”

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Tradeoffs/Challenges/Risks with AJF 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 AJF stakeholders to discuss environmental sustainability issues and concerns. The document provides basic information about various environmental sustainability considerations relevant to AJF 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.

CAAFI also recognizes that there can be tradeoffs among various aspects of environmental, social, and economic performance, and that often fuels may be high performing 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.

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. A recent analysis has summarized these risks and 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.

Such tradeoffs must be considered when evaluating the suitability and sustainability of AJF feedstocks and processes for a given location. The matrix below provides an assessment of the potential risks for various environmental impacts across the AJF 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 AJFs over time.

Impact Matrix showing potential for direct environmental impacts across the alternative jet fuel supply chain for selected environmental sustainability indicators

Impact Matrix showing potential for direct environmental impacts across the alternative jet fuel supply chain for selected environmental sustainability indicators.

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Voluntary Sustainability Certification Schemes

This list does not imply endorsement of any products or organizations. It may not be exhaustive. Please let us know if you are aware of others by emailing us at

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Chain of Custody Resources

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Sustainability and Fuel Readiness

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GHG LCA Analyses and Methodologies

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Other Tools and Resources

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