Changes in Composition and Structure of Water Hyacinth Based on Various Pretreatment Methods

The deconstruction of cellulose, hemicellulose, and lignin has varying effects on lignocellulosic biomass. To understand and evaluate these effects it is important to conduct compositional and structural analyses. In this study, the effect of different pretreatments on the composition and structure of water hyacinth (WH) was investigated. The pretreatment methods investigated were acid, alkali, ionic liquid (IL), and microwave-alkali. The structural analysis was completed before and after the pretreatment using scanning electron microscopy. In addition, the biomass recovery rate was measured to evaluate the composition of the WH biomass. Based on the results, all pretreatment methods effectively disrupted the crystalline structure and enhanced the digestibility of the WH through increasing the cellulose and hemicellulose content and reducing the lignin content. The acid pretreatment resulted in high cellulose digestibility while the microwave-alkali pretreatment destroyed only the lignin structure of the WH. The alkali and IL pretreatments increased the cellulose and hemicellulose content of the WH. The highest recovery rate was obtained via IL pretreatment. The acid, microwave-alkali, and alkali pretreatments had the second, third, and fourth highest recovery rates, respectively. This study showed that the biomass recovery rate, compositional makeup, and structural analysis are important to use WH for bioenergy production.