Pyrolysis GC/MS analysis of improved guayule genotypes

Authors: Luo, Zinan; Mullen, Charles; Abdel-Haleem, Hussein

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2020
Publication Date: 7/23/2020
Publication URL: https://handle.nal.usda.gov/10113/7045867
Citation: Luo, Z., Mullen, C.A., Abdel-Haleem, H.A. 2020. Pyrolysis GC/MS analysis of improved guayule genotypes. Industrial Crops and Products. 155. Article 112810. https://doi.org/10.1016/j.indcrop.2020.112810.
DOI: https://doi.org/10.1016/j.indcrop.2020.112810

Interpretive Summary: With the growing demand of energy and declining resources for fossil petroleum, discovery of new renewable energy strategies and feedstock is required. The byproducts from guayule shrubs are suitable for conversion to bio-oil and bio-char via pyrolysis, and thus have the potential to serve as a biofuel resource. In addition, because of Southern Texas and Northern Mexico origin, guayule is a good candidate for production in arid and semi-arid regions, which benefits the sustainability of U.S. agriculture systems. This study indicated that pyrolysis byproducts production including non-condensable gases, condensable gases (bio-oil) and bio-char were significantly affected by guayule genotypes and irrigation levels. The observed significant phenotypic variations could lay a foundation for genetic improvement of guayule byproduct production. In order to maintain sustainable agricultural systems, reducing irrigation without impairing guayule productivity is required. This study indicates the significant association between irrigation schedules and guayule pyrolysis byproducts. To increase the genetic gain of guayule byproducts in future breeding programs, testing and selecting for targeted traits of interests in multiple environments or locations are required to detect and select superior breeding lines.

Technical Abstract: In addition to the commonly known use as an alternative source for natural rubber and hypoallergenic latex, guayule could also be a source of resin and bagasse for use in the pharmaceutical and biofuel industries. Pyrolysis is a method to convert guayule biomass into liquid (condensable gas or bio-oil), which can be an intermediate towards production of biofuels and/or renewable chemicals. In this work, six guayule genotypes that were planted under either well-irrigated or reduced-irrigation conditions were pyrolyzed using a pyrolysis gas-chromatography-mass spectrometry instrument (PY-GC/MS). The products included condensable gas, non-condensable gas and bio-char. Within the condensable gases, selected compounds were divided into nine chemical classes including aromatic hydrocarbons, alkyl phenols, guaiacols, syringols, furans, cyclopentenones, acetic acid and acetol, levoglucosan and limonene groups. As a result, significant variations were observed in the major compounds and prominent sub-constituents of condensable gas among the studied guayule genotypes and under irrigation levels. Strong positive correlations were found between irrigation levels and oxygenated condensable gas components derived from cellulose and lignin, although hydrocarbon components derived from the rubber and resin were found to be negatively correlated with irrigation levels. Results indicated that the genetic variations among guayule genotypes can be used to improve its bioenergy potential, and positive correlations observed among pyrolysis byproducts suggest the possibility to improve several byproducts simultaneously in guayule breeding programs. This research gives an insight to breed for guayule as an economic crop with high bioenergy potential for the development of sustainable agriculture.