Comparison of pretreatment methods for wheat straw densification by life cycle assessment study

Abstract

<abstract> <bold>Abstract.</bold> Compaction and pelletization methods increase biomass bulk density and energy density, making the bulk biomass easy to handle, transport and utilize. Abundant amounts of wheat straw biomass are produced every year in the world. This paper presents a life cycle analysis assessment (LCA) study to compare five different pretreatment methods during wheat straw pelletization. System boundary was defined from transporting wheat straw bale in the field to the pelletizing plant and pellets transported to the customer. Steam explosion treatment (SE), microwave alkaline treatment (MA), binder addition (BD), radiofrequency alkaline treatment (RF) and torrefaction (TF) have potential as pretreatment method prior to pelletization. A description for each pretreatment method in the pelletization system is presented in this paper. The Simapro software for LCA study incorporating Ecoinvent database and literature data was used to conduct this study. The environmental impact for each pretreatment method was evaluated. Global warming potential, acidification, eutrophication, human toxicity, marine aquatic ecotoxicity, ozone layer depletion, abiotic depletion, fresh water aquatic ecotoxicity, photochemical oxidation, and terrestrial ecotoxidation were considered as environment impact indicators against which each pretreatment method for wheat straw pelletization was evaluated. The results revealed that binder addition especially involving the addition of wood waste has lower environmental impact compared to the control case (no treatment system option) and the other pretreatment options. Steam explosion (SE) and radiofrequency (RF) pretreatment methods had the more negative environmental impacts if these were to be adopted in wheat straw pelletization system compared to the control case and other options (MA, BD and TF).