College of Agriculture & Natural Resources
Permanent URI for this communityhttp://hdl.handle.net/1903/1598
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
Browse
4 results
Search Results
Item Fate of antimicrobials and nutrients in dairy manure management systems(2018) Schueler, Jenna E; Lansing, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Anaerobic digestion (AD) and composting manure management strategies were explored at the field scale to monitor antimicrobial degradation, nutrient transformations, and optimize mitigation of these pollutants in manure fertilizer to decrease their entry to waterways. Removal of antimicrobials and antimicrobial resistance genes (ARGs) were explored at the bench scale, where AD degraded >85% of antimicrobials. At the field-scale, antimicrobials were not consistently removed, persisting in concentrations up to 34,000 ng/g DW in the AD effluent. The tetM genes were reduced during bench-scale AD suggesting that AD could be an effective treatment for removing tetracycline ARGs from manure. The 100% reduction of sulfadimethoxine antimicrobials during AD did not correspond with Sul1 reduction, illustrating differences in antimicrobial versus gene reductions during manure treatment. Antimicrobials did not degrade significantly during field scale composting, likely due to a shortened composting period (33-days). The field-scale results illuminate limitations of tracking antimicrobials in complex treatment systems.Item INCREASING THE SUSTAINABILITY OF PSYCHROPHILIC SMALL-SCALE ANAEROBIC DIGESTERS(2015) Witarsa, Freddy; Lansing, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The research was aimed at increasing the energy production efficiency of small-scale anaerobic digesters in temperate climates while quantifying their environmental impacts. Biochemical methane potential tests were used to quantify methane (CH4) production from separated and unseparated manure during psychrophilic digestion, and compare CH4 production when pre-incubated alternative inocula (wetland sediment (WS), landfill leachate (LL), mesophilic digestate (MD)) were used. Methanogenic and Archaeal communities were analyzed using T-RFLP and qPCR. At 24 ºC, unseparated manure produced significantly higher (40%) quantity of CH4 than separated manure due to higher volatile solids (VS) content, but differences were insignificant at digestion times of ≤16 days. At lower digestion times, farmers could digest liquid, separated manure without sacrificing CH4 production, but at longer digestion times, the VS in unseparated manure has the time necessary for CH4 conversion. The alternative inocula studies showed that LL inoculum after incubation for 91 days at 25 ºC produced significantly higher quantity (≥20%) of CH4 than MD and WS during digestion at the same temperature, and was not significantly different in CH4 quantity than MD that was incubated and digested at 35 ºC (202 ± 4 L/kg VS). Methanosarcinaceae was dominant in the LL reactor, while the other reactors were abundant in Methanosaetaceae, indicating that inoculum rich in Methanosarcinaceae may be beneficial for starting digestion at lower mesophilic temperature ranges. Longer incubation time generally reduced the inoculum amount needed for batch digestion and prevention of volatile fatty acids accumulation. In batch systems with long digestion time (90 days), MD inoculum from well-established digesters, 35% inoculum to substrate ratio, and 35 ºC operation temperature are recommended for highest CH4 production per unit of digester volume. Additionally, life cycle assessments (LCA) were conducted to compare the sustainability of an unheated Chinese fixed-dome digester with a heated and insulated small-scale plug-flow digester in the US. The LCA showed that the US plug-flow digester was more sustainable than the Chinese fixed-dome system only in climate change category, but contributed negatively towards 17 impact categories. Digester heating and heating infrastructure were the main contributors towards the negative impacts observed in the US plug-flow digester.Item DESIGN AND ECONOMICS OF PLUG-FLOW, SMALL-SCALE ANAEROBIC DIGESTERS FOR TEMPERATE CLIMATES(2011) Klavon, Katherine Heléne; Lansing, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Anaerobic digestion is a manure treatment option that is gaining popularity throughout the world as a result of its multiple environmental and economic benefits. There exists a need for further research to make anaerobic digestion and methane recovery more readily available, cost effective, and manageable to small dairy facilities in the United States. This research analyzes the design and economics of plug flow digesters, modeled after low-cost digesters utilized in the developing world and modified to operate on small to medium-scale farms located in the temperate United States. The objectives of this research are to: 1) Describe the modified design and construction of the research plug flow digesters and analyze the barriers and design challenges to implementing this technology in the United States and 2) Conduct an economic analysis to determine the feasibility of installation and operation of these types of systems in the temperate United States.Item Portable Hyperspectral Imaging Device for Surface Sanitation Verification in the Produce Industry(2011) Wiederoder, Michael; Lo, Y. Martin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Produce processors must clean and sanitize surfaces before production to reduce the risk of foodborne illness. Current surface hygiene verification methods require direct surface sub-sampling at selected locations and a wait time. To augment these methods, a portable hyperspectral imaging device was developed to find potential contaminants in real-time and increase sub-sampling effectiveness. Analysis of hyperspectral fluorescence images showed that fresh-cut produce processing exudates in the regions of 460-540 and 670-680 nm are detectable from background materials, while select cleaning agents are not. The portable single operator imaging system includes a charge coupled device (CCD) camera, tunable optical filter, laptop, light emitting diodes (LED's) for fluorescence excitation, and a touchscreen display. Within a commercial plant, fluorescence imaging identified produce processing residuals following routine cleaning procedures that were not readily visible to the naked eye. These tests demonstrate the system's potential to enhance post-cleaning inspection, and helped improve routine cleaning procedures.