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Evaluating the sustainability of agricultural systems using life cycle assessment and techno-economic analysis

Date

2021

Authors

Summers, Hailey, author
Quinn, Jason C., advisor
Marchese, Anthony J, committee member
Paustian, Keith, committee member
Willson, Bryan, committee member

Journal Title

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Volume Title

Abstract

In a time of expansive population growth, our global resources have never been so strained; our contributions to a changing climate so significant. The International Panel on Climate Change recently addressed the need for focused effort toward reducing global resource depletion and greenhouse gas emissions (GHGs). As such, special attention has been given to some of the largest GHG emitting sectors in the world: energy, industry, and agriculture. This work focuses on using sustainability analysis to further understand agricultural processes and products, both novel and emerging. To quantify the environmental component of sustainability, life cycle assessment (LCA) is used because it is a well-established method for evaluating processes and products with respect to emissions. Similarly, techno-economic analysis (TEA) is used to understand the economic viability of various processes and products. In harmony, these assessments are used to evaluate the sustainable performance of various agricultural processes and products by identifying pathways to reduce environmental impact while concurrently increasing economic viability. Results enable targeted research to be highlighted that can advance early-stage development toward a sustainable adoption. The dissertation proposal is divided into three topics all with a common theme: Using LCA and TEA to assess the sustainability of, and advance, agricultural systems. A drought tolerant crop currently grown in India, guar, was investigated to understand relative environmental impact and economic viability in the American Southwest compared to existing crops. Guar is cultivated as a source of guar gum, used primarily in hydraulic fracking fluid for shale oil and gas recovery, with demand currently met through importation. Therefore, a feasibility analysis was performed for a domestic guar supply in Arizona and New Mexico using LCA and TEA. The integrated assessment provided insight on environmental and economic performance of guar for comparison to existing crops. Results indicate that environmentally, guar has lower GHGs than many crops currently cultivated in the American Southwest. Economically, guar gum can be produced for less than the five-year average U.S. import price, with minimizing or eliminating irrigation identified as a critical area for further research. A best case scenario and sensitivity analysis are also investigated using LCA and TEA to evaluate early-stage development of adopting guar in the American Southwest. LCA is also a valuable assessment tool for emerging agricultural systems. A detailed LCA was performed for a first-of-its-kind study investigating the GHGs of commercial indoor cannabis cultivation. Since legalization, the cannabis industry has seen substantial growth with many products being cultivated inside industrialized warehouses. An engineering process model was built to track material and energy requirements of a typical indoor cannabis facility which was then translated to GHGs using LCA methodology. Results of a U.S.-wide analysis indicate that indoor cannabis production leads to substantial GHGs regardless of where it is cultivated, with regions such as the Mountain West and Midwestern United States being much more GHG intensive than East or West Coasts. Individual processes that lead to the majority of GHGs are heating, ventilation, and air conditioning (HVAC), high intensity grow lights and the addition of carbon dioxide for increased plant growth rates. Results of this work have informed the industry, consumers, and policymakers of the environmental impact from this practice while providing insight on ways to reduce GHG emissions. Despite LCA and TEA being proven methodologies for assessing novel, emerging and established processes and products, limitations do exist. Particularly, in the context of agriculture, LCA does not traditionally account for water use outside of the emissions associated with procurement and use. In the American Southwest specifically, it is critical to understand water use and associated environmental impact to make informed decisions regarding ecosystem and societal sustainability. Recently, the development of an advanced LCA method, water scarcity footprint (WSF), has enhanced that ability to understand spatial and temporal considerations of freshwater consumption. However, this method is actively emerging and therefore limitations exist, particularly for arid regions where water demand is typically higher than the amount of water available. A novel method was proposed that can improve resolution and decision-making capabilities for freshwater environmental impact when evaluating arid regions. Results include method comparisons that highlight the improved resolution between the developed method and the traditional WSF method. Furthermore, a case study shows variation of the two methods when applied to alfalfa production in the American Southwest that reveals the severity of drought in the region. The proposed method enables improved resolution when considering spatial and temporal freshwater use in arid regions which enhances decision-making capabilities for product development. Throughout this work, traditional and advanced sustainability metrics, LCA, TEA and WSF, were used to understanding the environmental impact and economic viability of various agricultural-related products. Results from these assessments, from novel and existing technology investigation, provide quantifiable results for holistic comparisons and internal process improvement. These results can serve as decision-making tools during the research and development and commercialization stages, all leading toward providing a more sustainable future.

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Subject

cannabis
life cycle assessment
water scarcity
guar
agriculture
techno-economic assessment

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