Tempering expectations on a novel biofuel tree: Seed and oil yield assessment of pongamia (Millettia pinnata) shows low productivity and high variability

Abstract

Pongamia (Millettia pinnata) has recently gained attention as a novel biofuel feedstock. However, yield levels and dynamics of this largely undomesticated species remain poorly understood. This study addresses the critical lack of scientific evidence by collecting primary seed and oil yield data from 81 pongamia trees across a range of cultivation types in South India, and is the first to explore yield-determining factors using predictive regression models. Our results indicate that annual seed and oil yield for pongamia trees vary widely, generally staying below 2500 kg/ha and 1000 liter/ha, respectively. This current field performance is substantially lower than commonly reported figures in the literature. Furthermore, the study suggests that a complex interplay between genotype, environment and agronomy leads to large spatiotemporal variation in yields, and that this interplay remains poorly understood. Long-term yield monitoring is required to get better insights into realistic yield levels and mechanisms, before labeling pongamia as a significant, stable and profitable source of biofuel feedstock. The paper concludes with a set of hands-on guidelines for pongamia research and harvesting.