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Dissertation Defenses

Doctoral students who have an upcoming dissertation oral defense are posted here. So why not take this opportunity to learn about the research that our graduate students are doing!

Dissertation Defense for Allison Leach


Department Contact Email: allison.leach@unh.edu

Defense Title: Addressing the nitrogen challenge: Footprint tools and on-farm solutions

Defense Date and Time: 11/30/18 1:00 pm

Defense Location: Demeritt 240

Defense Advisor: Dr. John Aber

Defense Abstract: Nitrogen management presents a unique dilemma: We must use reactive nitrogen to grow our food and sustain life on earth, but excess reactive nitrogen that accumulates in the environment contributes to a cascade of negative impacts to human and ecosystem health. Addressing this nitrogen challenge will require a suite of solutions. This dissertation presents and explores three nitrogen management strategies: 1) The first ever integrated carbon and nitrogen footprint tool for campus sustainability management; 2) Exporting compost to improve a farm’s nitrogen efficiency; and 3) Methods for reducing gas emissions from aerated static pile heat recovery composting.

The campus nitrogen footprint tool helps campuses track, manage, and reduce their nitrogen pollution. However, nitrogen pollution is just one way campus activities impact the environment; it is important to assess environmental impacts together to identify management strategies and avoid trade-offs. In this paper, the development and methodology behind the first ever integrated carbon and nitrogen footprint tool for campuses is presented. Comparisons of campus carbon and nitrogen footprints show that the footprints correlate strongly, and scenario analyses indicate benefits to both footprints from a range of management strategies. Integrating the carbon and nitrogen footprints into a single tool for campuses will facilitate more comprehensive and integrated management of campus sustainability.

A major source of nitrogen pollution is food production, and specifically animal production. As dairy farms become more concentrated and generate more by-products, novel waste management strategies are needed to reduce nitrogen pollution and promote nutrient recycling. Aerated static pile (ASP) heat recovery composting is a manure management method that processes by-products, generates a stable soil amendment, and captures heat. In this study, the potential for ASP heat recovery composting as a nitrogen management strategy was explored at the University of New Hampshire Organic Dairy Research Farm, which is home to the only commercial-scale ASP heat recovery compost facility for research. First, the effect of an ASP heat recovery compost facility on the farm’s overall nitrogen budget was assessed. The nitrogen budget of the farm was quantified, and a compost export scenario found that the farm’s nitrogen efficiency would be improved by exporting compost. Then, compost gas emissions (ammonia, carbon dioxide, methane) were measured for the first time at an ASP heat recovery compost facility and management strategies were recommended to reduce greenhouse gas and ammonia emissions from composting.


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