Scientists investigate how to produce biofuel for jets from alcohol and vegetable oil

By : Dr. Franyi Sarmiento, Ph.D., Inspenet, March 11, 2022

A group of researchers from the Polytechnic University of Madrid (UPM) in Spain, has carried out an analysis on the efficiency of an integrated biorefinery model to produce biofuels for jet aircraft, which has alcohol and vegetable oil (from waste agricultural oilseed plants) as raw materials. The analysis will also be useful to identify innovations capable of making the process technically, economically and environmentally feasible.

Currently, there are six American Society for Testing and Materials (ASTM)-approved thermochemical pathways for producing biokerosene (petroleum-derived kerosene-compatible aviation biofuel) from renewable feedstocks. However, the routes that have stood out have been those that process cellulosic alcohol (ATJ-SPK) and the hydroprocessing of esters and fatty acids (HEFA-SPK). Nicolás Vela’s doctoral thesis, co-supervised by professors María Jesús García and David Bolonio from the ETSI of Mines and Energy of the Polytechnic University of Madrid (ETSIME), analyzes these routes and assesses the feasibility of biorefinery models for the production of biokerosene as a blend component with conventional kerosene (Jet A1). As raw material, the use of agricultural residues, mainly oilseed crops, was considered.

“Air transport is vital in globalization. Together with an exponential increase in its demand, the efforts to decarbonize the industry and achieve sustainability have been, for now, insufficient. That is why we are working on it”, point out the authors of the study. In the research carried out, the ATJ-SPK process has been analysed, which involves obtaining bioethanol from the lignocellulosic residues of oilseed crops and its subsequent improvement to biokerosene (and green diesel). On the other hand, the HEFA-SPK process, which uses residual vegetable oil and distillate of fatty acids discarded during the refining of crude vegetable oil, has been studied. Both biorefinery models were modeled with AspenPlus chemical engineering process simulation software.

The economic viability of the studied biorefineries has been evaluated through a techno-economic analysis, calculating the investment capital required, the minimum sale price of biokerosene and the most significant economic variables to achieve economic viability. The result, in all cases, shows the need to market co-products, such as lignin, to compete with the sale price of conventional kerosene. With this in mind, the researchers integrated an analysis to optimize the production chain and reduce operating costs, in addition to calculating the associated carbon footprint of the biokerosene produced, performing a life cycle analysis in the SimaPro software.

The results of the evaluation show greenhouse gas emissions lower than those of the production of Jet A1 derived from petroleum. “However, it is necessary to improve ethanol extraction and purification technologies to achieve greater reductions. Likewise, it is essential that hydrogen from renewable sources (such as biogas) be used in the hydrotreatment stages so that the processes are sustainable”, indicate the authors of the study.

The researchers verified, by estimating the physicochemical and thermodynamic properties of the aviation biofuel, that it complies with the current specifications (ASTM D7566 standard), which guarantees the homogeneity of the mixture, the quality of combustion and compliance with safety requirements for storage and transportation of biokerosene.

Finally, a payload calculation in long and medium range flights was carried out to evaluate the performance of biokerosene in particular flight conditions. “The results are encouraging, especially in short-range flight, where biokerosene has been shown to have an advantage over its fossil counterpart,” the researchers conclude.

The latest progress made by Nicolás Vela and his collaborators in this line of research corresponds to a study entitled “Techno-economic and life cycle assessment of triisobutane production and its suitability as biojet fuel,” which was published in the academic journal Applied Energy, as another titled “Biojet fuel production from oleaginous crop residues: thermoeconomic, life cycle and flight performance analysis”, which was published in the academic journal Energy Conversion and Management. (Source: UPM)

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