Submitted to: Fuel
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2015
Publication Date: 1/1/2016
Publication URL: https://handle.nal.usda.gov/10113/61638
Citation: Boateng, A.A., Elkasabi, Y.M., Mullen, C.A. 2016. Guayule (parthenium argentatum) pyrolysis biorefining: fuels and chemicals contributed from guayule leaves via tail gas reactive pyrolysis. Fuel. 163:240-247.
Interpretive Summary: The guayule desert shrub is grown in the southwestern United States, for the purposes of extracting valuable natural rubber from its stems for use in tires and other products. We used the leaves from the guayule plant, which are not utilized for rubber recovery, as feedstock for pyrolysis, a thermal process for conversion of biomass to liquids which can be used for renewable fuels or chemical purposes. We employed the process developed at ARS called tail gas reactive pyrolysis (TGRP) which uses a reactive gas atmosphere instead of an inert one, which is normally used for pyrolysis. Similar to our previous work in converting residuals from the guayule stem (termed ‘guayule bagasse’), a stable high-quality oil was produced from pyrolysis of guayule leaves. However, the oil from the guayule leaves is characterized as containing unique chemicals that were either found in deficient amounts or not found at all in the guayule bagasse oil. The research reported herein may be beneficial to guayule producers and the US tire and latex manufacturing companies who are looking to produce valuable products from the whole guayule shrub.
Technical Abstract: Guayule (Parthenium argentatum), a woody desert shrub cultivated in the southwestern United States, is a source of natural rubber and organic resins that promises to revolutionize the tire and rubber industry. Some 20,000 kg ha-1 yr-1 is reported to be harvested worldwide and expected to grow due to renewed interest in guayule to replace imported Hevea rubber. We have recently reported the use of guayule bagasse, the residual biomass after latex extraction, as feedstock in a pyrolysis process that employs a reactive gas environment to formulate a special intermediate bio-oil product that is easily distillable and readily synthesized to hydrocarbon (drop-in) fuels. This submission reports on the use of the same pyrolysis process for the leaves of the guayule plant and the array of fuels and chemicals that the leaves can contribute to a co-located guayule biorefinery at a latex plant that could utilize the entire biomass residue value chain. The composition of the guayule leaves is different than the bagasse, with the main differences being lower resin content along with higher ash (>16 wt%) and higher nitrogen (2.6 wt%, dry ash free, daf) contents resulting from the higher concentration of the plant proteins (16.4 wt% (daf)). Since the former two components have exhibited a drastic influence on pyrolysis product distribution in the past, it was incumbent upon us to explore whether the resin content would provide additional synergistic effects and influence product selectivity pathways to bio-based chemicals. We found that the combined effect of the tail gas reactive pyrolysis process, the proteinaceous nature of the guayule leaf and resin combine to create a complex mechanism that results in an interesting bio-oil intermediate product from which a slew of fuel and commodity chemical compounds can be synthesized upon mild upgrading.