Guayule (Parthenium argentatum) pyrolysis and analysis by PY–GC/MS

Economic and sustainable biofuel production requires high process efficiency. The choice of biomass and the conversion technology employed to produce renewable fuels determine the product yields, fuel quality and consequently the process efficiency. Guayule, a perennial shrub native to the southwestern United States, is currently cultivated as a source of natural rubber latex. However, after latex extraction, about 90% of the crop is used for low value biomass markets or simply goes to waste. Residual biomass from guayule presents an opportunity as a solid fuel resource that is already collected, on-site, and is a suitable ligno-cellulosic conversion feedstock. Using Py–GC/MS, we characterized the starting material of whole guayule shrub (G1) and solid waste streams, including ground bagasse from the industrial latex extraction process (G4), ground whole shrub minus resin (G2), and ground whole shrub minus resin and rubber (G3). These waste streams contain varying amounts of resin and rubber compounds. We measured the energy content of these streams and compared their compositions based on Py–GC/MS pyrograms. Catalytic and non-catalytic pyrolysis reactions were performed. It was found that the stem-derived latex-extracted guayule bagasse (G4) is the material with the most thermochemical energy potential. Whole shrub (G1) is the next in energy content. The gross energy content declined as resin is removed (G2) and further declined with the removal of resin and rubber (G3). The pyrograms showed fragmentation of the biomass polysaccharides and lignin polymers to compounds that have chemical energy, which provides support to the gross energy profiles.