Emissions related to aviation have during the last decades become an important topic of discussion. Besides carbon dioxide ($CO_2$) which is the major pollutant from air travel, other gas emissions such as hydrocarbons ($HC$), nitrogen oxides ($NO_x$), carbon monoxide ($CO$) and sulfur oxides ($SO_x$) also need to be investigated. The work within this field has traditionally been challenged by the fact that aircraft emission calculations often required engine proprietary data which usually is difficult to obtain. However, in recent years other methods have been developed and this report investigates one such method, namely The Boeing Fuel Flow Method 2. The analysis is carried out on an ATR 72-500 turboprop aircraft flying at $13000$ feet from Visby to Bromma, Sweden. The method uses continuous data of fuel flow and altitude together with estimated emission index data at sea level for the specific engine to estimate the amount of emissions emitted during the flight. From this it was possible to determine the levels of $HC$,$NO_x$,$CO$, $CO_2$ and $SO_x$ emitted during the different stages of flight. There was a clear trend that $HC$ and $CO$ emissions were the highest at low fuel flow levels, i.e. at low power, while $NO_x$ increased with increasing fuel flow. Emission levels of $CO_2$ and $SO_x$ were found to be proportional to fuel flow. In addition, two alternative trajectories at $10000$ and $24000$ feet were studied. When comparing the $10000$ feet route with the original $13000$ feet route the the level of $NO_x$, $CO_2$ and $SO_x$ were unaffected while $HC$ and $CO$ decreased as the period of high fuel flow were shortened. In the $24000$ feet route the levels of $HC$, $CO$ and $SO_x$ were unaffected while the level of $CO_2$ and $NO_x$ decreased. This decrease can be explained by the lowered fuel flow rate as air resistance is significantly lower at $24000$ feet compared to $13000$ feet.

Sustainable aviation fuels are one of the proposals that the aviation industry is adopting to reduce its impact on the environment. These are obtained by applying chemical processes to biological and non-biological resources, and their main objective is to replace conventional (fossil-derived) aviation fuel in their entirety. There are currently seven approved production pathways and two co-processing processes. Understanding the real impact of these fuels on the amount of emissions produced by an aircraft along a trajectory is essential to further develop sustainable proposals and regulations. So to understand how the use of these fuels affects total emissions, the model developed by Boeing to estimate aircraft emissions has been adapted to sustainable aviation fuels using the Lower Heating Value as a proposal throughout this project. The methodology has been applied to a real flight between Stockholm Airport and Bordeaux Airport. Four different scenarios, characterized by varying fuel blends, have been studied: exclusive use of kerosene, 10% sustainable fuel blend, an equal 50% blend of each fuel, and sustainable fuel only. The analysis has been performed for five different types of non-conventional fuels; Shell FT-SPK, Sasol FT-SPK, UOP HEFA-SPK, Coconut HEFA-SPK and Hevo ATJ-SPK. At large, two trends have been detected in the effect of these fuels on total emissions; some types of SAF have increased CO and HC emissions and reduced NOx emissions compared to kerosene, and others whose behavior has been the reverse. In addition, the percentage of fuel used has an impact on total emissions. It can be concluded that no non-conventional fuel type among those studied has been found to produce a reduction in all types of emissions, however, given that their life cycle is circular, they do contribute to making the aviation sector more sustainable by reducing CO2. The results can help to better understand the impact of this type of fuel, as well as provide valuable information for decision-making in the implementation of sustainable strategies in the aviation industry. / Hållbara flygbränslen är en av de förslag som flygindustrin antagit för att minska sin påverkan på miljön. Dessa bränslen framställs genom att tillämpa kemiska processer på biologiska och icke-biologiska resurser, och deras främsta mål är att helt ersätta konventionellt (fossilbaserat) flygbränsle. För närvarande finns det sju godkända produktionsvägar och två sambehandlingsprocesser. För att förstå den verkliga påverkan av dessa bränslen på mängden utsläpp som produceras av ett flygplan längs en bana är det nödvändigt att vidareutveckla hållbara förslag och regler. För att förstå hur användningen av dessa bränslen påverkar totala utsläpp har modellen utvecklats av Boeing för att uppskatta flygutsläpp anpassats till hållbara flygbränslen genom att använda lägre värmevärde som förslag i hela detta projekt. Metoden har tillämpats på en verklig flygning mellan Stockholms flygplats och Bordeaux flygplats. Fyra olika scenarier, karakteriserade av varierande bränsleblandningar, har studerats: enbart användning av flygbränsle, 10% hållbar bränsleblandning, en jämn fördelning av 50% av varje bränsle, och enbart hållbart bränsle. Analysen har utförts för fem olika typer av icke-konventionella bränslen; Shell FT-SPK, Sasol FT-SPK, UOP HEFA-SPK, Coconut HEFA-SPK och Hevo ATJ-SPK. Generellt sett har två trender observerats beträffande dessa bränsles effekter på totala utsläpp; vissa typer av hållbara bränslen har ökat CO- och HC-utsläppen och minskat NOx-utsläppen jämfört med flygbränsle, medan andra har haft motsatt beteende. Dessutom har procentandelen bränsle som används en påverkan på totala utsläpp. Det kan dras slutsatsen att ingen av de studerade icke-konventionella bränsletyperna har visat sig minska alla typer av utsläpp. Men med tanke på att deras livscykel är cirkulär bidrar de till att göra flygsektorn mer hållbar genom att minska CO2. Resultaten kan hjälpa till att bättre förstå denna typ av bränsles påverkan och tillhandahålla värdefull information för beslutsfattande vid införandet av hållbara strategier inom flygindustrin.