Life cycle assessment of production of black locust logs and straw pellets for energy purposes

In recent years, black locust has been receiving special attention as a potential energy crop. Conversely, straw, which constitutes a waste product, is mainly used for energy purposes. The aim of this study was to perform the Life Cycle Assessment of straw pellet and black locust logs production. The environmental effects were investigated according to the Ecoindicator’99 and Global Warming Potential 100a methods. The single score for the functional unit of black locust logs equals 5.47 Pt, and for cereal straw pellets is between 23.37 and 30.49 Pt. The minor value of the indicator for wood results from higher density and net calorific value, which in this study was equal to 17.72 MJ/kg for black locust and 14.9 MJ/kg for cereal straw pellets. Moreover, greenhouse gas emission was calculated and equals 94.7 kgCO_2eq for black locust logs and between 365.9 and 588.3 kgCO_2eq for cereal straw pellets. Obtained results allow to compare the processes of biomass production. Black locust logs have a smaller potential of affecting the environment than pellets due to lower energy intensity of the production process, especially lower electricity consumption. Furthermore, logistic improvement may significantly decrease the environmental impact of discussed products. Novelty or Significance: The presented study includes the comparison of two biomass products (cereal straw pellets and black locust logs) based on the Life Cycle Assessment of their production. The originality of the comparison is based both on the detailed inventory and the applied impact assessment method (Ecoindicator'99). The broadened scope of the study allowed for the assessment of both production of materials and pellets, which brings the novel contribution into the existing state of knowledge pertaining to the biomass life cycle described by points of Ecoindicator and greenhouse gas emission.