Biomass yield, nutrient removal, and chemical composition of energy cane genotypes in Southeast Brazil

Sugarcane (Saccharum spp.) is the main feedstock for bioethanol production in Brazil. Recently, some breeding programs have focused on energy cane for the enhancement of bioenergy yield in mills operating in the production of second-generation ethanol (2 G-ethanol). However, information on yield, nutritional and chemical composition of energy cane genotypes is still insufficient. Therefore, the objective of this study was to evaluate the biomass production and the amount of nutrients removed by energy cane genotypes under Brazilian field conditions. Between 2016 and 2018, trials were carried out under field conditions in the state of São Paulo, Brazil, throughout the plant cane and first ratoon growing seasons. The experiment was set up in a randomized block design containing 26 energy cane genotypes and two commercial sugarcane varieties. Agronomic and industrial characteristics related to the aboveground biomass (fresh and dry), chemical (sucrose, fiber, Brix, total recoverable sugar, extractives, ashes, lignin, cellulose, and hemicellulose), and nutritional (macro- and micronutrients) composition were evaluated. Some energy cane genotypes presented higher dry biomass yield (∼25%), fiber (∼40%), ashes (∼50%), lower sucrose, total recoverable sugar (∼60% and 50%, respectively), and lower extractives in stalks (∼50%) compared to sugarcane genotypes. The average nutrient requirement per unit of fresh biomass produced (in kg per megagram) for energy cane of two growing seasons was 1.7 N, 0.35 P, 4.2 K, 0.45 Ca, 0.47 Mg, and 0.41 S, while for sugarcane it was 1.3 N, 0.25 P, 3.2 K, 0.28 Ca, 0.30 Mg, and 0.44 S, respectively. For more productive energy cane genotypes, those differences in nutritional demands are even greater. Therefore, higher amounts of fertilizers are required for energy cane genotypes. Moreover, since energy cane genotypes produce less sucrose, its use in industry will only be beneficial as long as their higher fiber content is fully converted into 2 G-ethanol or used for electricity cogeneration.