Graduation Year

2018

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Qiong Zhang, Ph.D.

Committee Member

Sarina J. Ergas, Ph.D.

Committee Member

James R. Mihelcic, Ph.D.

Committee Member

Mingyang Li, Ph.D.

Committee Member

John M. Jermier, Ph.D.

Keywords

Climate Change, Energy Intensity Model, Life Cycle Assessment, Renewable Energy

Abstract

Aquaculture had already been distinguished as an important component of global food security and economics. However, aquaculture has expanded at the cost of natural resources and the environment. The vulnerability of the aquaculture industry due to the consequences of global environmental changes and energy price fluctuations has been addressed in various studies. The identification, planning, and implementation of sustainable energy systems are important to ensure the long term economic and environmental sustainability of aquaculture.

This research investigated sustainable energy systems for aquaculture using a life cycle approach, allowing for the identification of the most sustainable energy options under different geographical and economic contexts. This also provides useful insights for the sustainable development of aquaculture with energy systems. The main objectives were to develop a statistical model for energy intensity of aquaculture (Chapter 2) and a user-friendly tool that can assist in the decision making of choosing the sustainable energy systems in aquaculture (Chapter 3), and to investigate the applicability of solar hot water systems for aquaculture (Chapter 4) and the potential improvement of the sustainability performance of aquaculture with energy systems (Chapter 5).

In the first task, the main influencing factors on the energy use of aquaculture were investigated via a statistical analysis method. Results showed that natural trophic level of species, culture technology, culture system intensity, and local climatic conditions are important factors. With the key variables, an energy intensity prediction model was developed and applied to explore an energy efficient growth strategy for global aquaculture. Energy use in future global aquaculture would be significantly reduced with a selective extensification of global aquaculture. Also, climate change with consideration of temperature and precipitation would help reduce the energy use of global aquaculture as warm climate zones are more dominant in major aquaculture producing countries.

In the second task, an MS-Excel based decision support tool was developed to assist the selection of environmentally and economically sustainable energy systems (single source or hybrid sources) in aquaculture. Through a case study, the most sustainable energy options for U.S. aquaponics systems were investigated, considering different geographical and economic contexts in five U.S. states (FL, HI, WA, LA, and ME). Results showed that solar systems (solar photo-voltaic and solar hot water heater) could be the most sustainable energy options for U.S. aquaponics due to their low environmental impacts and economic benefits.

In the third task, results showed that heating strategies, setting (indoor or outdoor), and local climatic conditions played a pivotal role in determining the environmental and economic impacts of solar hot water systems in aquaculture. The lowest environmental impact was found with a 20% heating strategy for outdoor aquaculture systems under hot climate conditions, while the most economical case was found with an 80% heating strategy for indoor aquaculture systems under moderate climate conditions. Further improvements of environmental and economic performances could be achieved with consideration of water source (groundwater and surface) and design (horizontally fixed or optimally tilted solar thermal collector).

In the fourth task, environmental and economic impacts of alternative energy systems were obtained using the tool which was developed in the second task. Results showed that local geographical and weather characteristics, local energy prices, and incentive availability were important parameters to determine the sustainability performance of alternative energy systems in aquaculture. The use of renewable energy was more sustainable than conventional energy systems in the regions where there are favorable geographical conditions, high electricity and fuel prices, and incentives. The use of solar photovoltaic with a thin-film technology was the most sustainable electricity generation options in most states of the U.S., while the use of natural gas boilers was the most sustainable heating options in most states of the U.S. The sustainability performance of the solar photovoltaic systems can be further improved through either a technological advancement or an incentive, while financial support is more effective for solar hot water systems. The application of anaerobic digestion as a backup system in general will reduce the sustainability of hybrid heating system; however, the hybrid biogas-diesel heating system has better sustainability performance compared with a diesel heating system if it is used for medium to large scale fish farms.

This research provides an understanding of energy use characteristics of current aquaculture systems, and insights for the planning of sustainable energy supply systems in aquaculture, considering different growth strategies, effects of climate change, and alternative energy systems with various operational strategies and design factors. Furthermore, the decision-making tool was made to be accessible to fish farmers, state-wide planners, and regulators.

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