Environmental trade-offs of renewable jet fuels in Brazil: Beyond the carbon footprint

Techno-economic and environmental assessment of renewable jet fuel production in integrated Brazilian sugarcane biorefineries

With jet fuel consumption projected to more than double by 2050, dramatic expansion of sustainable aviation fuel (SAF) use will be essential to meeting the aviation industry goal of achieving carbon neutrality in the same time frame. However, to date, the SAF price has, in part, been responsible for the lack of widespread adoption signaling the need for strong and stable policy. Multiple pathways have been developed and received ASTM approval to convert a variety of feedstocks into SAF, each with strengths and weaknesses that vary with conversion technology, feedstock, and production location. To assist researchers and governments in understanding the role of policy on fuel pricing, a set of harmonized, techno-economic analyses (TEAs) were developed to assess three ASTM-qualified production pathways: hydroprocessed esters and fatty acids (HEFAs), alcohol to jet (ATJ), and Fischer–Tropsch (FT), with multiple feedstock options. These decision support tools were used to assess the minimum selling price (MSP) for fuel distillates. Both mature (nth) plants and first of a kind (pioneer plants) were assessed using TEAs. Existing and proposed U.S. incentives, at both the federal and state levels, were integrated into the tools to determine the impact on the MSP. Considering the existing federal policies, analysis indicated that HEFAs could achieve a SAF price that would be competitive to conventional fuels when using waste lipid feedstocks, making this the most viable near-term option. However, this feedstock for HEFAs is limited and unlikely to support the production of large quantities of SAF. After stacking federal and state programs, SAF produced using FT with municipal solid waste (MSW) has the lowest MSP, although FT forest residuals, FT agricultural residues, ATJ corn ethanol, and HEFAs using second crop oilseeds all approach the historical range of traditional jet fuel prices for nth plants. Pioneer plants are viable for only ATJ corn ethanol; however, FT-MSW is approaching price parity.

Multi-criteria decision analysis for the evaluation and screening of sustainable aviation fuel production pathways

Concerns about environmental impacts and health effects associated with particulate matter emissions of sugarcane production in Brazil have been raised, mainly due to pre-harvest burning of straw in manual harvesting. In consequence, mechanical harvesting without burning has been increasingly adopted. Life cycle studies have assessed environmental impacts of sugarcane and sugarcane products. However, incorporating health effects of particulate matter 2.5 (PM2.5) in a life cycle assessment focusing on evaluating the impacts of increasing use of mechanization has not been conducted. This article compares the life cycle environmental and health impacts (with spatially differentiated characterization factors for PM2.5) of manual and mechanical harvesting of sugarcane in Brazil, and quantifies the health benefits due to the change of harvesting operations. An attributional life cycle assessment (LCA) of manual versus mechanical sugarcane harvesting was conducted to evaluate the impacts of 1 t of sugarcane at the distillery. ReCiPe was applied to characterize impacts at mid-point (i.e., climate change, fossil depletion, ozone depletion, terrestrial acidification, freshwater eutrophication, human toxicity, photochemical oxidant formation, and particulate matter formation) and end point (i.e., human health, ecosystems, and resources). Impacts on climate change were compared considering different soil carbon sequestration scenarios. Characterization factors (CFs) of health effects of PM2.5 for Brazil were calculated differentiating emission sources, population densities, and burdens of disease. At the mid-point, sugarcane production with manual harvesting has higher impacts on photochemical oxidant formation and particulate matter formation mainly due to pre-harvest burning. Mechanical harvesting system may lead to higher impacts on fossil depletion, ozone depletion, and terrestrial acidification resulting from higher use of fertilizers and diesel. Differences of impacts on climate change between two systems vary depending on the soil carbon sequestration scenario. At the end-point level, manual harvesting has higher impacts on human health but lower impacts on resource use. The health effects of PM2.5 vary considerably with population density. Changing from manual to mechanical harvesting close to urban areas leads to a 93% reduction of health effects, while for rural only 15% and for remote areas 5%. When considering average population density, the health effects of PM2.5 of manual harvesting were approximately six times higher than mechanical harvesting. Health effects of PM2.5 calculated with ReCiPe are much lower and may underestimate the effects of primary PM2.5 emissions. The results of this article are an incentive to accelerate the mechanization of sugarcane harvesting in areas with lower mechanization levels (i.e., north-northeast region in Brazil and some rough terrain areas) concerning public health benefits. Meanwhile, manual harvesting with straw burning should only be performed in fields located in rural or remote areas. These results can also contribute to further studies comparing potential benefits of sugarcane culture with alternative crops and guide better decision making at regional development level. Spatially differentiated CFs of PM2.5 calculated in this article may be applied to future studies regarding health effects in the Brazilian context.

The aviation industry contributes to more than 2% of global human-induced CO2-emissions, and it is expected to increase to 3% by 2050 as demand for aviation grows. As the industry is still dependent on conventional jet fuel, an essential component for a carbon-neutral growth is low-carbon, sustainable aviation fuels, for example alternative drop-in fuels with biobased components. An optimization model was developed for the case of Sweden to examine the impacts of carbon price, blending mandates and penalty fee (for not reaching the blending mandate) on the production of renewable jet fuel (RJF). The model included biomass gasification-based Fischer–Tropsch (FT) jet fuel, Power-to-Liquid (PTL) jet fuel through the FT route and Hydrothermal liquefaction (HTL)-based jet fuel. Thus, this study aims at answering how combining different policies for the aviation sector can support the production of RJF in Sweden while reducing greenhouse gas (GHG) emissions. The results demonstrate the importance of implementing policy instruments to promote the production of RJF in Sweden. The blending mandate is an effective policy to both promote RJF production while reducing emissions. The current level of the penalty fee is not sufficient to support the fuel switch to RJF. A higher blending mandate and carbon price will accelerate the transition towards renewable and sustainable fuels for the aviation industry.

The aviation industry’s efforts to reduce carbon emissions have driven the rapid development and scale-up of sustainable aviation fuels (SAFs). SAFs have the potential to significantly reduce CO2 lifecycle emissions by up to 80% in comparison to Jet A and other conventional fossil-derived jet fuels. For multiple logistical and practical reasons, it is preferable to ensure that SAFs are ‘essentially identical’ (also referred to as ‘drop-in SAF’) to conventional jet fuel in terms of their performance, durability and compatibility with existing hardware systems. Because the majority of SAFs are not identical (non-drop-in) to conventional jet fuel, they have not been approved for use in their neat (100%) form. Instead, these non-identical SAFs are named synthetic blend components (SBC) as they are blended with conventional fuels to different extents per ASTM D7566-23a. It should be noted that there are on-going efforts to develop non-drop in SAF specifications to broaden their proliferation and maximise the aviation industries’ ability to reduce CO2 lifecycle emissions. One very important area of focus is the compatibility of SAFs with engine and fuel system seals, specifically understanding the dynamics of elastomeric seals. To address this, a novel approach has been developed to measure seal dynamics in flowing fuel. This technique has been applied to study the dynamic seal behaviour of four industrially relevant elastomer seals commonly employed in aviation fuel systems. The study involved three test fuels: (i) conventional fossil-derived Jet A, neat hydroprocessed esters and fatty acids (HEFA) SAF, and neat alcohol to jet (ATJ) SAF. Notably, both HEFA and ATJ fuels contain 0% aromatics, in contrast to Jet A, which typically contains around 17% aromatics by volume. The novel fuel-elastomer test rig used in this study was designed to simulate a practical scenario in which fuel flows through the inner surface of a pre-loaded static O-ring. The results of these tests demonstrate that the behaviour of different nitrile elastomers is unique to their formulation, and in all cases, the behaviour in HEFA and ATJ SAF differs significantly from that in Jet A. However, new fuel approval tests may only list one type of elastomer for evaluation, for example the ‘Fit-for-Purpose’ test in ASTM D4054-22 Tier 2 lists one specific nitrile. The findings of this study highlight the complexities of fuel-elastomer interactions within nominally identical chemical families and emphasise the potential risks of assessing compatibility based on tests conducted with a single member of a chemical family.

Approximately 21.2 billion of carbon has to be reduced for achieving Fly Net Zero. The International Air Transport Association has targeted the production of sustainable aviation fuel (SAF) to be 449 billion liters by the year of 2050. The feedstock supply by then is going to be problematic. This study compares the SAFs produced through two different route: Hydroprocessed Esters and Fatty Acids (HEFA), derived from triglyceride-based oil and Alcohol-to-Jet (ATJ) derived from alcohol. The HEFA SAF is produced from palm oil feedstock, and ATJ SAF is produced from ethanol and butanol (named ATJ-e and ATJ-b). Firstly, the properties of the two produced fuel products are measured and both compared with conventional jet fuel based on ASTM specifications, including density and viscosity with various temperatures, auto-ignition temperature, smoke point, flash point, cetane number, heating value, and distillation temperature. Secondly, the combustion behaviors of HEFA and ATJ SAFs, including the spray characteristics and ignition behaviors, are also examined and compared. In addition, the combustion behaviors of five different blendings (0 %, 25 %, 50 %, 75 %, 100 %) with HEFA and ATJ SAFs are tested.

A kinetic study on the blending behavior of sustainable and conventional aviation fuels: Soot formation processes

Multi-objective optimization for sustainable renewable jet fuel production: A case study of corn stover based supply chain system in Midwestern U.S.

Global biorenewable development strategies for sustainable aviation fuel production

Comparison of three different analytical protocols for 2019 updated D2425 method for renewable jet fuel product certification analysis

Both Fischer-Tropsch (FT) and Hydroprocessed Esters and Fatty Acids (HEFA) Synthetic Paraffinic Kerosine (SPK) fuels are considered as leading alternative replacements for conventional jet fuel. To satisfy the requirements of Civil Aviation Authorities (CAA), their drop-in incorporations have been subjected to a rigorous certification process. To reach the ambitious incorporation targets, new routes for biofuels incorporation may need to emerge, involving optimizing the production processes and the blending strategies. This paper focuses on a new strategy for incorporating HEFA, allowing the process yield to be optimised.One of the major steps limiting the process yield for HEFA remains the isomerisation that allows production of a biofuel with very good cold flow properties. But this step introduces a substantial decrease of the overall yield (fuel component per kg of starting material) due to the production of light compounds, unsuitable for conventional jet fuel. In this work relaxing the freezing point requirement for the neat HEFA component (by decreasing the severity of the isomerisation step) is proposed in order to minimize the production of less valuable light compounds. This strategy could lead to a significant additional biofuel yield with respect to the oil compared to a process making a better freeze point component. This allows the land surface area necessary for HEFA feedstock cultivation to be reduced for a given amount of bio-jet fuel produced.

Recent advancements in catalytic conversion pathways for synthetic jet fuel produced from bioresources

Socioeconomic effects of aviation biofuel production in Brazil: A scenarios-based Input-Output analysis

<div class="section abstract"><div class="htmlview paragraph">The paper presents an extensive assessment of the hygroscopic characteristics of a number of alternative jet fuel blends. These are blended with conventional Jet A-1 to conform with current aviation standards at a 50:50 ratio by volume, except for DSHC (Direct Sugar to Hydrocarbon), which is blended at 10% DSHC and 90% Jet A-1. Given the lack of information available on the water solubility of alternative jet fuels, an effective analysis of experimental data about this characteristic in six different alternatives was performed. These included four ASTM approved alternatives (two Fischer-Tropsch (FT) synthetics from coal and natural gas, one HEFA (Hydroprocessed Esters and Fatty Acids) derived from camelina and DSHC. An extra two alternatives currently under consideration for ASTM approval were also tested; ReadiJet and an ATJ (Alcohol to Jet). Water solubility-temperature curves were created and compared to the Jet A-1 reported in the CRC (Coordinating Research Council) Handbook of Aviation Fuel Properties. All samples were subjected to a temperature range of −20°C to 50°C, significantly wider than that illustrated in recent studies and the CRC Handbook. The preliminary results suggest that the alternative fuel blends followed a different pattern to the CRC Jet A-1 for water solubility at different temperatures. Unlike the conventional fuels, the curves did not fit an exponential trend. The preliminary results need to be verified to assert confidence in the results with further testing. The results for the water absorption between −20°C and 50°C for each alternative blend were measured and it was found that DSHC:Jet A-1 absorbed the most water, and ReadiJet:Jet A-1 the least. Further work is planned to validate the trends observed.</div></div>