Clone precocity and the use of Helianthus tuberosus L. stems for bioethanol

An experiment was conducted to study the potential of 12 clones of Helianthus tuberosus L. for the production of bioethanol from the stems. Aboveground biomass production and total sugar content of the whole stems were determined at three phenological growth stages: flower bud, full bloom and dry head. The potential of the tubers for bioethanol was determined as well, in order to compare the two possible crop applications. Results showed that the performance of the early clones for the use of the stems was different from the mid-season/late clones. The aboveground biomass production and mean tuber weight of the early clones were lower than for the other clones and the period between the stages of flower bud and dry head much shorter. Stem sugar content of the early clones decreased after the full bloom stage; the trend observed for the other clones was that the decrease happened after the flower bud stage. The final tuber production of the early clones was generally lower. Mid-season/late clones showed a higher potential yield of sugars – and therefore, higher potential for ethanol production – whether they were cropped for the stems or for the tubers. Comparing the values obtained for these two applications of the crop, it was estimated that the potential of the stems of the mid-season/late clones for bioethanol was 38% that of the tubers.