Waste cooking oil offers a viable alternate to cut carbon emissions by aircraft: Study

As India prepares to meet the internationally mandated obligations for adopting cleaner aviation fuel by 2027, a new study has found that blending waste cooking oil with aviation fuel can significantly reduce carbon emissions.

Researchers at the Department of Aerospace Engineering, Indian Institute of Technology, Kharagpur investigated the result of blending neat Jet A-1, a kerosene based fuel used in aircraft, and neat fried cooking oil, methyl ester (FCOME). Blends with 10 percent, 20 percent, 30 per cent, 40 per cent and 50 per cent by volume of FCOME were used.

“FCOME shows approximately 37 percent reduced carbon monoxide (CO) emissions but a slight increase in nitrogen oxides (NOx) when compared to neat Jet A-1,” the researchers reported.

“Among blends, 10 percent FCOME and 90 percent Jet A-1 can be considered as an environmentally friendly fuel, as it has reduced both CO and NOx emissions, but overall, a blend with 20 percent FCOME will have optimum performance in all aspects,” the researchers said.

The research, titled ‘Combustion Study of Fried Cooking Oil Methyl Ester for Potential Additive to Aviation Fuel,’ was published in Elsevier’s Fuel, an international peer reviewed journal, on April 6.

FCOME was created in-house by the researchers from waste fried cooking oil through chemical processes. True color flame images, emission spectra, average flame temperature, average exit temperature and NOx and CO emissions were thoroughly investigated and compared for all test fuel samples.

The analysis of physico-chemical properties showed that the density, viscosity and surface tension of FCOME were 12 percent, 4.5 times and 23 percent, respectively, greater than Jet A-1.

According to industry estimates, India produces about 25–30 lakh tonnes of used cooking oil annually. Most of it comes from commercial food operators and households, creating a substantial yet mostly underutilised, resource for producing biodiesel.

With an annual consumption of around 2,700 crore liters of cooking oil every year, India has the potential to produce around 110 crore liters of biodiesel annually, which is being done through the government’s Repurpose Used Cooking Oil (RUCO) initiative.

The physical and chemical requirements of bio blends for diesel used in road transport and jet fuel for aircraft, however, are different due to the vast difference in the type of engines as well as the characteristics of the two fuels. Hence, the processing of blends for the two would have to be done separately.

The use of bio blends for aircraft engines, known as sustainable aviation fuel (SAF), at present is in a nascent stage in India, with some trials carried out by the Indian Air Force as well as commercial operators. Bio-jet fuel is derived from non-edible oils like Jatropha and agricultural residue.

India’s roadmap for the use of SAF to reduce carbon emissions in the aviation sector, calls for one percent blend by 2027 and five per cent by 2030, with a long-term goal of 20 per cent. The annual consumption of aviation fuel in India is 900–950 crore liters. According to projections, India will require at least 70 crore liters of SAF by 2030. The excess production capacity of SAF from all sources also offers the potential of export.