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.
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Item Assessing the uncertainty of emergy analyses with Monte Carlo simulations(2012) Hudson, Amy; Tilley, David R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)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.Item Material and Emergy Cycling in Natural and Human-Dominated Systems(2012) Winfrey, Brandon Kyle; Tilley, David R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)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.Item VALUING FOREST ECOSYSTEM SERVICES IN MARYLAND AND SUGGESTING FAIR PAYMENT USING THE PRINCIPLES OF SYSTEMS ECOLOGY(2012) Campbell, Elliott Thomas; Tilley, David R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Forests provide a multitude of vital benefits to the ecosystems, economies and people of Maryland. Forests regulate atmospheric gas exchange, ameliorate micro-climates, stabilize coastlines and riverbanks, provide wildlife habitat, generate and maintain soils, improve water quality, dampen storm flows, abate air pollution, and provide food, fiber, fuel and shelter. While markets exist to set the price for an economic good like timber, many of the ecosystem services listed above are poorly valued, if at all. This research provides a connection between biophysical and economic methods for evaluating the environment. The hydrology, soil, carbon, air pollution, pollination and biodiversity of a forest are measured from a biophysical standpoint with emergy and converted to dollars using new emergy-to-dollar ratios; termed eco-prices. The functioning of the forest is compared to the most likely alternative land-use (suburbia) and biophysical value is assigned based on this difference. The novel method for assigning value to ecosystem services and the ability to link biophysical evaluation and economic valuation has the potential to be influential in how ecosystem services are incorporated into the economy and used to guide decision making in the future. This research seeks to value ecosystem services provided by forests in Maryland and proposes that an Ecological Investment Corporation (EIC) could be an additional tool for society to direct payments from consumers to land stewards to encourage the production of ecosystem services. To ensure that Maryland forests continue to produce ecosystem services at the current rate, land stewards should receive compensation between $178 and $744 million. On a per capita basis, a resident of Maryland enjoys $850 worth of ecosystem services from the forest as public value. On an area basis, the typical acre of forest in Maryland generates over $2000 of ecosystem services as public value. Based on our compensation estimates for ecosystem services, a land steward should receive a fair payment price of $71 to $298 per year per a typical acre of forest. This research is a step forward for emergy science, providing novel methods for quantifying ecosystem services, calculating ecological debt, and converting renewable emergy flows to dollars.Item Green Facade Energetics(2010) Price, Jeffrey; Tilley, David R; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rising energy costs and a warming climate create the need for innovative, low-carbon technologies that help cool buildings. We constructed four small buildings and instrumented them to measure the cooling effect of a green façade on their south and west walls. The green façade significantly reduced the temperature of the building's ambient air, exterior surface, and interior air, and the heat flux through the vegetated wall. Using a mathematical model, we determined that the whole-building cooling load reduction (1.4 to 28.4%) depended on building construction, green façade placement, and especially whether the windows were covered. An emergy analysis of a south-facing green façade revealed that the total emergy consumed could be balanced by the electricity saved from reduced air conditioning if the cooling load was reduced by at least 14%. With thoughtful design and placement of a green façade it can sustainably and effectively help cool buildings.