The reason for the sudden demand is that used cooking oil can now be used to produce sustainable aviation fuel, or SAF.Used cooking oil is the main substance used for production, but research is underway to identify other viable waste sources.Estimates suggest that replacing conventional jet fuel with SAF would reduce industry-wide emissions by approximately 80 percent.But a major plant is now under construction in Singapore that would have an annual production capacity of one million tons, about five times the current global total of 200,000.They are currently building a plant in Sakai City, Osaka, that will have a production target of approximately 30,000 tons in three years."