With limited additional waste oil available, the industry in the U.S. is relying on purpose-grown soy and corn to drive near-term growth. “Purpose-grown crops could constitute the majority of the supply within six to 10 years,” estimated Adam Klauber, who oversees sustainability and digital supply chains at World Energy, an SAF producer.

To qualify as SAF, fuels produced from these crops need to emit no more than 50 percent of the emissions from fossil jet fuel. Many in the industry say they do, but the researchers argue that assessment rests on faulty accounting.