Energy and economic performances of stump and roots removal of eucalyptus for bioenergy

Abstract Traditional logistics of residue removal is expensive and energy demanding, such as the procedures adopted for removing remaining stumps on forest biomass production. When considered as a biomass source, stumps can contribute to minimizing problems related to the restriction of the use of the area in terms of the use of the machines and operational quality, bringing economic and energy benefits or at least, avoiding costs. Therefore, this study aimed at evaluating the operational, economic and energy viability of a mechanized-harvesting system for collection of eucalyptus stumps. So, data related to the work capacity of the equipment were obtained by means of a time and motion of mechanized operations of stumps removal, carrying, processing, and transportation. A model was used to evaluate scenarios and to identify the critical variables. Results showed that the mechanized system used for stumps and roots removal, is operationally and economically viable and provides higher energy performance for this biomass. Total energy input (EI) of the system was 14.3 GJ ha−1, energy intensity 406.8 MJ t−1, EROI was 28.2 for 33 MJ MJ−1 and 4.0 for 4.3 MJ MJ−1 year−1 and a positive energy balance of 434.3 MJ ha−1. The final cost of producing of eucalyptus stump chips was 37.87 USD t−1, savings of USD 2.13 t-1 were obtained for the additional biomass. Restrictions for using this system refer to the minimum area and transportation distance. Additionally, variations in productivity, market price of biomass, and field operational capacity would affect the economic viability of this alternative.