DRUM Collection: Environmental Science & Technology Theses and Dissertations

Assessing the uncertainty of emergy analyses with Monte Carlo simulations

2013-04-10T02:33:35Z

Title: Assessing the uncertainty of emergy analyses with Monte Carlo simulations Authors: Hudson, Amy Abstract: Crop production systems were used to show the presence and propagation of uncertainty in emergy analyses and the effect of source variance on the variance of the yield unit emergy value (UEV). Data on energy/masses and UEVs for each source and yield were collected from the emergy literature and considered as inputs for the Monte Carlo simulation. The inputs were assumed to follow normal, lognormal, or uniform probability distributions. Using these inputs and a tabular method, two models ran Monte Carlo simulations to generate yield UEVs. Supplemental excel files elucidate the Monte Carlo simulations' calculations. The nitrogen fertilizer UEV and net topsoil loss energy were the inputs with the largest impact on the variance of the yield's UEV. These two sources also make the largest emergy contributions to the yield and should be the focus of a manager intent on reducing total system uncertainty. The selection of a statistical distribution had an impact on the yield UEV and thus these analyses may need to remain system- or even source- specific.

ENVIRONMENTAL SUSTAINABILITY AND WASTE TREATMENT CAPABILITIES OF SMALL-SCALE ANAEROBIC DIGESTION SYSTEMS

2013-02-07T04:00:47Z

Title: ENVIRONMENTAL SUSTAINABILITY AND WASTE TREATMENT CAPABILITIES OF SMALL-SCALE ANAEROBIC DIGESTION SYSTEMS Authors: Moss, Andrew Robert Abstract: Anaerobic digestion is a common form of waste treatment and energy production throughout the world, and in the United States the number of agricultural digesters is increasing at a rate of approximately 10% annually. As the number of digesters grows, efforts to assess the environmental cost of their installation and the potential utility of their by-products are required. This research investigates the relative environmental sustainability of small-scale digesters treating dairy manure in the U.S. and human waste in Haiti, and explores the biogas potential and nutrient transformations resulting from the anaerobic digestion of dairy manure. Specifically, the objectives of the research are: 1) to conduct an eMergy analysis on the two digestion systems to assess the effect of waste source, climate, and infrastructure on system sustainability; and 2) to provide an overview of waste treatment and energy production options for agricultural digesters treating dairy manure in the United States.

Material and Emergy Cycling in Natural and Human-Dominated Systems

2013-02-07T03:36:17Z

Title: Material and Emergy Cycling in Natural and Human-Dominated Systems Authors: Winfrey, Brandon Kyle Abstract: In order to address how emergy cycles with material in systems, the following work uses three studies that 1) explores the reasons why emergy should follow cycles, 2) shows how emergy should be allocated to cycling material within a system, and 3) shows how emergy can be simulated dynamically in systems that cycle material. The first study investigated how waste flows from its production process, through some transformation in a treatment system, and into the environment, which must use resources to absorb the waste's residual available energy that went untreated by the treatment system. This study showed that much work was required by the environment to return constituents in waste to background levels. Waste treatment systems for two different wastewater types and three different scenarios of treatment were compared using this new methodology and a novel index. Passive treatment systems performed better with regards to the new index, using less purchased emergy and more renewable emergy. The second study examined how emergy can be allocated to cycles within systems that have internal material flows as a large component (i.e., forest ecosystem and farms). Three study sites were evaluated that cycled phosphorus at similar levels internally. The natural system recycled the same amount of mass but required less emergy to do so because purchased emergy was not required for the forest to recycled emergy. In the farms, NPP of crops, and thus recycling phosphorus, required substantial purchased inputs. The third study adapted a previous minimodel with two storages of material, one low quality and one higher quality. The low quality material storage was open to material input and output and the overall system was open to energy input and output. Response variables of this model were compared to the previous model and to previous rules for simulating dynamics of emergy cycles within systems. This model showed that a system open to material inputs and outputs could accumulate more material while proportionately less emergy flows in. Consequently, emergy becomes "diluted" by increased material accumulation in systems that are open to material as those closed to material have higher steady state emergy cycling.

FATE AND TRANSPORT OF NITROGEN AT A DEEP ROW BIOSOLIDS APPLICATION HYBRID POPLAR TREE FARM

2013-02-11T16:50:47Z

Title: FATE AND TRANSPORT OF NITROGEN AT A DEEP ROW BIOSOLIDS APPLICATION HYBRID POPLAR TREE FARM Authors: Maimone, Diana Abstract: This study evaluates deep row applied biosolids as a nutrient source for hybrid poplar trees grown on a gravel mine reclamation site in Brandywine, Maryland from November 2003 to April 2009. The study included biosolids application rates of 386, 773, and 1,159 dry Mg/ha (172, 345, and 517 dry ton/ac.) and hybrid poplar tree densities of 0, 716, and 1,074 trees/ha (0, 290, and 435 trees/ac.). Soil water samples taken from suction lysimeters located 15 - 120 cm (6 - 48 in.) vertically below the biosolids were analyzed for total ammoniacal-nitrogen (TAN) and nitrate-nitrogen (NO₃-N). The majority (96.3%) of NO₃-N values were less than EPA drinking water MCL of 10 mg/L. No NO₃-N values within the tree plots exceeded 2 mg/L. The TAN concentrations increased with application rates, but decreased with distance from the biosolids, except there was no difference between 60 cm (24 in.) and 120 cm (48 in.).