J.C. Quinn, H.M. Summers, E. Sproul, C. Seavert, J. Robbs, S. Khanal, V. Mealing, A.E. Landis, N. Fan, O. Sun
Colorado State University,
Keywords: guar gum, techno-economics, life cycle assessment
Summary:Drought represents a significant risk for agricultural producers in the American Southwest. A potential method for lowering this risk is introducing high-value crops that are drought tolerant. One particular crop, Guar (Cyamopsis tetragonoloba) is gaining increased attention as it is known for being drought tolerant and also has added benefit of being nitrogen-fixing. Guar is a legume used to produce guar gum which is a thickening and stabilizing agent for a wide variety of products. One of the primary applications for guar gum is as an additive for hydraulic fracking fluid used in the recovery of shale oil and gas. Currently, the United States imports the majority of guar gum from India and Pakistan. Previous publications highlight the physical ability to cultivate Guar in the United States, yet minimal information can be found regarding the economic viability or environmental impact of domestically cultivating and processing Guar into guar gum. The limited amount of previous research focuses on cultivation outside the United States and does not include a conversion facility for generating guar gum from the harvested Guar crop. Based on these shortcomings, this work had two primary objectives. First, develop detailed system models for cultivation, harvest, transport and processing of Guar to accurately capture the material and energy needs of producing guar gum in the arid southwestern United States. Second, use the system model’s material and energy inventory to inform an integrated economic and environmental analyses evaluating the feasibility of implementing this process. The economic analysis performed includes a full farm analysis in which guar is partially adopted to the farm as well as the capital and operational expenditures of operating a thirty year bioprocessing facility. These costs are used to determine the minimum selling price of guar gum needed to recover all the production costs with a fixed internal rate of return. The environmental analysis accounted for cradle-to-gate emissions of the entire growth, transport and conversion process of obtaining guar gum. Resulting emissions were categorized into ten impact categories to investigate largest contributors and highlight areas for improved reduction efforts. Baseline results for the integrated analysis show a minimum guar gum selling price of $4.72 per kilogram while obtaining a co-product credit for protein-rich animal feed from Guar germ at $0.44 per kilogram. Total costs are divided amongst agriculture and processing to determine contribution to overall minimum selling price. Within agriculture, the highest costs are attributed to irrigation and equipment replacement costs whereas the bioprocessing facility showed the highest costs resulting from labor and capital investment. Environmental results from the integrated analysis show that practices within the farm, including irrigation, land preparation and harvest, account for the vast majority of burden across all impact categories. Sensitivity results highlight the need for focused research within irrigation as minor reductions show significant impact in both economic and environmental results. Future work includes tradeoff investigation through scenario analysis to find methods for reducing cost and environmental impact simultaneously.