Assessing the environmental, economic, and social sustainability of guar and guayule cultivated in the southwest United States

Abstract

Since the mid 20th century, energy consumption has been the main driver of human-induced climate change, rapidly warming the planet’s atmosphere, oceans, and land. These trends have led to growing efforts to develop more sustainable feedstocks to meet increasing energy demands. Guar (Cyamopsis tetragonoloba) and guayule (Parthenium argentatum) are potential feedstocks for renewable fuels; these crops have highly valuable co-products that can enhance their economic viability. Guar and guayule are draught tolerant crops that can be cultivated in the Southwest US. Guar bagasse can be utilized to produce bioenergy, and its co-products include guar gum, a highly valuable chemical used in the food industry as an emulsifier and in the hydraulic fracturing industry as a friction reducer. Guayule bagasse can also be utilized to produce bioenergy, and its valuable co-products include natural rubber and resin, the latter of which can be used to make adhesives, coatings, antifungal agents, and fuels.

To ensure holistic sustainability of these emerging agricultural feedstocks, an array of sustainability tools must be utilized in tandem. This thesis quantifies the three pillars of sustainability - environmental, economic, and social – for guar and guayule and assesses their potential to be integrated into the southwestern bio-economy. Life cycle analysis (LCA) was used to quantify the environmental impacts of guar and guayule, highlighting that irrigation is the main driver of agricultural impacts and thus provides the biggest opportunity for improved agricultural sustainability. Techno-economic analysis (TEA) quantifies the economic impact of guayule rubber production showing irrigation as the main agricultural contributor of economic impacts, while the largest processing contributor is capital/loans. This research is unique in its LCA and TEA approach, where data was collected from field trials and interviews of farmers and researchers were utilized to determine data quality and likelihood. This process produces more robust LCA and TEA results that are more representative of commercial farming practices. Existing social assessment tools were reviewed to determine the most appropriate approach for evaluating social sustainability. Ultimately, social sustainability was assessed by conducting focus groups of guar and guayule farmers and experts to identify social challenges and opportunities. This research aids in providing a clear path for the holistic sustainable development of a bio-economy in the Southwest US for guar and guayule.