Lignocellulosic biomass is an important and abundant source of renewable energy. However, difficulties in transportation and handling cause issues with the commercialization of its use, due to its low bulk density and tendency to rot if not stored properly. Thermochemical pretreatment through a process of wet torrefaction increases the mass and energy density of a biomass, as well as increases its hydrophobicity, makes it easier to store, transport, and handle. Researchers at the University of Nevada, Reno have developed an improved and more efficient method of wet torrefaction (also known as thermal hydrolysis or hydrothermal carbonization) with a reaction time of less than 5 minutes.
Our researchers have developed methods of wet torrefaction with optimized reaction conditions so that the process can be completed in 1-5 minutes. This is a significant improvement to the conventional method which may take several hours. Wet torrefaction is the process of treating biomass with hot compressed water in an inert atmosphere, also known as hydrothermal pretreatment or carbonization, where gas, water solubles, and a carbonized solid product or biochar (also known as hydrochar) are produced. The produced biochar can be used directly as fuel or can be formed into pellets for easier transportation and handling. The biomass is reacted in a reaction chamber with an inert atmosphere, such as purged with a non-reactive gas such as nitrogen, where the chamber maintains an optimal temperature and pressure to keep the water at a condensed state and to increase the energy density of the biomass. In our method, the lignin contained within the biomass is minimally degraded, therefore effective amounts remain to act as a binder for pellets. The liquid used in the reaction may also be recycled where soluble components can precipitate and deposit on back on biochar, and when the reagent is acidic, it may be used to catalyze further wet torrefaction reactions. Desirable products including sugars and substituted furans can be separated for other processes. Any other source of cellulosic biomass may be used in this process, including woody plants, microorganisms such as yeasts, and wet waste materials including wastewater sludge.
- Wet torrefaction is more efficient in increasing mass and preserving energy density, as compared to dry torrefaction
- Our process of wet torrefaction has a reduced reaction time of 5 minutes or less
- Our process may utilize any form of lignocellulosic or cellulosic biomass
- Drying the biomass prior to treatment is not needed, unlike (dry) torrefaction, saving substantially on energy.