Assessing Environmental Impacts of Resource Recovery from Wastewater Treatment and Dairy Manure Management Using Life Cycle Assessment
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Authors
Glover, Callan Jaymes
Issue Date
2022
Type
Dissertation
Language
Keywords
energy recovery , life cycle assessment , manure management , nutrient recovery , resource recovery , sustainability
Alternative Title
Abstract
Manure management and wastewater treatment are responsible for a range of environmental impacts. Expansion of farms into larger, more concentrated operations has increased greenhouse gas emissions and water quality problems related to manure management, particularly for dairy farms. The goal of this work was to evaluate the environmental impacts of a proposed resource recovery system for dairy manure relative to conventional practices and anaerobic digestion through life cycle assessment (LCA). The proposed system for nutrients, energy, and water integrated recovery (NEWIR) consists of hydrothermal carbonization for energy recovery, algae cultivation for nutrient recovery, and membrane distillation (MD) for water recovery. Inventory data were developed from experimental results, modeling, and literature review. LCA results showed that the algae species was an important factor for overall environmental impact from NEWIR. Of the four species evaluated, Spirulina maxima had the highest impact in all categories evaluated due to chemicals required to adjust pH for cultivation. The other three species (Chlamydomonas reinhardtii, Chlorella vulgaris, and Scenedesmus obliquus) did not require chemical inputs and had lower overall environmental impacts, including reduced greenhouse gas and nutrient emissions relative to conventional practices and anaerobic digestion. However, algae cultivation of any species increased water use for manure management above conventional practices, a potential concern in regions facing water scarcity. The results show that resource recovery can help improve greenhouse gas and nutrient emissions from manure management while recovering valuable products, improving overall environmental issues associated with dairy manure. Future research should consider a cost assessment of NEWIR as well as environmental policy to help with implementation of resource recovery systems. A novel wastewater treatment system consisting of a membrane bioreactor-MD (MBR-MD) system was also modeled and analyzed with LCA. The system was designed to produce high-quality water for indirect potable reuse (IPR) and was compared to an established IPR system. Environmental impacts were heavily dependent on the energy requirements for MD; MBR-MD had the best environmental performance when waste heat was used to operate MD. The results of the study show that MBR-MD is an effective potential treatment method for IPR of wastewater from both an operational and environmental perspective.