Modeling and optimization of systems for nutrient recovery from livestock waste

Laburpena

Nutrient pollution of waterbodies is a major worldwide water quality problem. Excessive use and discharge of nutrients can lead to eutrophication of fresh and marine waters, resulting in environmental problems associated with algal blooms and hypoxia, public health issues related to the release of toxins, and freshwater scarcity. Agricultural activities are one of the main contributors to anthropogenic nutrient releases. Focusing on the livestock industry, the releases of nutrients (mainly phosphorus and nitrogen) result from the production of large amounts of organic waste. Particularly, the manure generated in the concentrated animal feeding operations (CAFOs) is a considerable challenge due to the high rates and spatial concentration of the organic waste generated. The abatement of nutrient releases from livestock facilities is a step to address the environmental problem of nutrient pollution. This thesis aims at the holistic assessment of waste treatment processes and management practices for the effective recovery of nutrients from livestock waste. We have performed techno-economic assessments of phosphorus and nitrogen recovery technologies for livestock facilities to determine the systems which implementation in CAFOs is more viable, as well as the potential integration of nutrient recovery technologies with biogas production systems. Based on the information obtained in these studies, a geospatial evaluation of the impact of phosphorus recovery by deploying phosphorus recovery systems at CAFOs in the watersheds of the United States has been carried out. After establishing the most suitable type of processes for phosphorus recovery, a decision-making support tool for the assessment and selection of phosphorus recovery technologies based on technical, economic, and environmental criteria of each CAFO has been developed. Finally, this tool has been used for the design and analysis of incentive policies to promote the implementation of phosphorus recovery processes at CAFOs, including the fair allocation of incentives in limited budget scenarios. These studies are intended to contribute to the development and implementation of sustainable nutrient management strategies at livestock facilities, addressing one of the major water quality problems around the globe, and promoting the transition to a more sustainable paradigm for food production.