Life cycle greenhouse gas analysis of biojet fuels with a technical investigation into their impact on jet engine performance

Abstract

Life cycle emissions Engine/aircraft performance Thermodynamics Numerical modelling a b s t r a c t Biojet fuels have been claimed to be one of the most promising and strategic solutions to mitigate aviation emissions. This study examines the environmental competence of BioSynthetic Paraffinic Kerosene (Bio-SPKs) against conventional Jet-A, through development of a life cycle GHG model (ALCEmB e Assessment of Life Cycle Emissions of Biofuels) from "cradle-grave" perspective. This model precisely calculates the life cycle emissions of the advanced biofuels through a multi-disciplinary study entailing hydrocarbon chemistry, thermodynamic behaviour and fuel combustion from engine/aircraft performance, into the life cycle studies, unlike earlier studies. The aim of this study is predict the "cradle-grave" carbon intensity of Camelina SPK, Microalgae SPK and Jatropha SPK through careful estimation and inclusion of combustion based emissions, which contribute z70% of overall life cycle emissions (LCE). Numerical modelling and non-linear/dynamic simulation of a twin-shaft turbofan, with an appropriate airframe, was conducted to analyse the impact of alternative fuels on engine/aircraft performance. ALCEmB revealed that Camelina SPK, Microalgae SPK and Jatropha SPK delivered 70%, 58% and 64% LCE savings relative to the reference fuel, Jet-A1. The net energy ratio analysis indicates that current technology for the biofuel processing is energy efficient and technically feasible. An elaborate gas property analysis infers that the Bio-SPKs exhibit improved thermodynamic behaviour in an operational gas turbine engine. This thermodynamic effect has a positive impact on aircraft-level fuel consumption and emissions characteristics demonstrating fuel savings in the range of 3e3.8% and emission savings of 5.8e6.3% (CO 2 ) and 7.1e8.3% (LTO NOx), relative to that of Jet-A.

Review of life‐cycle greenhouse‐gas emissions assessments of hydroprocessed renewable fuel (HEFA) from oilseeds

“…Carbon dioxide makes up the majority of combustion emissions and is considered to be carbon neutral for biofuels, as this GHG is sequestered from the atmosphere during crop growth. However, some LCAs have considered the effect of non‐CO 2 combustion emissions, namely NO x and particulate matter, on radiative forcing 13,22 . Life‐cycle assessments of both diesel and jet fuel were included because the potential sources of methodological variability affect both fuels equally, and the life cycles are very similar up to final use.…”

“…Greater confidence in the life‐cycle GHG emissions of HEFA fuel, along with a host of economic and political factors, may aid the adoption of HEFA fuel in Canada, one of the world's top producers of canola 3 . Between 2008 and 2016, there were at least 13 LCAs published on HEFA fuels derived from canola, camelina, or carinata 4–16 …”

Recent development in studies of alternative jet fuel combustion: Progress, challenges, and opportunities

“…Therefore, bio-jet (HRJ) fuels are widely considered by the aviation industry to be one of the primary means to reduce its carbon footprint. Recently, Lokesh et al [14] has predicted the -cradle-grave‖ carbon intensities of several bio-jet fuels using a life cycle GHC model. Their results revealed that bio-jet fuels derived from camelina, micro-algae, and jatropha deliver 70%, 58%, and 64% of life cycle emissions savings, respectively, relative to Jet A-1.…”

Environmental impact assessment of wheat straw based alkyl polyglucosides produced using novel chemical approaches

“…34 To precisely predict the quantity of CO 2 contained within the by-product biochar, the following factors must be first defined. 32 These factors have been indicated and the figures assumed for each of the factors have been presented below:…”