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

Authors: Boateng, Akwasi; Mullen, Charles; McMahan, Colleen; Whalen, Maureen; CORNISH, KATRINA - YULEX CORPORATION

Submitted to: Journal of Analytical & Applied Pyrolysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2009
Publication Date: 9/23/2009
Citation: Boateng, A.A., Mullen, C.A., McMahan, C.M., Whalen, M.C., Cornish, K. 2010. Guayule (Parthenium argentatum)pyrolysis and analysis by PY-GC/MS. Journal of Analytical & Applied Pyrolysis. 87:14-23.

Interpretive Summary: 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. These residues present an opportunity as a solid fuel resource that is already collected, on-site, and is suitable as a liquid transportation fuel conversion feedstock. We characterized several streams of guayule biomass materials in the supply chain of the guayule latex extraction process to establish their bioenergy potential using analytical pyrolysis (thermal decomposition in absence of air) methods with and without the presence of catalyst. The substrates included whole guayule shrub (G1), ground whole shrub without resin (G2), ground whole shrub without resin or rubber (G3), and solid waste streams comprising ground bagasse from an industrial latex extraction process (G4). The sample selection provided an opportunity to evaluate the effect of the varying amounts of resin and rubber compounds in the waste streams on the energy content of the pyrolysis products. We found that the stem-derived latex-extracted guayule bagasse (G4) was the material with the most thermo-chemical energy potential. Whole shrub biomass (G1) was the next in line when it comes to product energy content but the energy content declined as resin was removed (G2) and further declined as resin and rubber was removed (G3). The results of the analysis provide basic data which is useful to the latex extraction industry particularly plant operators who are interested in establishing an integrated biorefinery and also to guayule growers who might want to supply guayule biomass as energy crop.

Technical Abstract: Economic and sustainable biofuel production requires high process efficiency. The choice of biomass and the conversion technology employed to produce renewable fuels determines 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 lignocellulosic 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.