Thesis (Ph.D.)--University of Delaware, 2010. / Principal faculty advisors: James J. Corbett and Jeremy M. Firestone, College of Earth, Ocean, & Environment. Includes bibliographical references.

Thesis (Ph.D.)--Murdoch University, 2005. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (leaves 335-346).

Thesis (LL.M.)--University of Toronto (Canada), 2005. / Includes bibliographical references.

No description available.

This thesis investigates the potential of improved control to reduce greenhouse gas (GHG) emissions resulting from existing wastewater treatment plants (WWTPs), and demonstrates that significant reductions can be achieved without the need for extensive redesign of treatment processes and without increasing operational costs. An emissions model is developed for use in this study, informed by an in-depth analysis of existing state-of-the-art methods and models for estimating GHG emissions, taking into account their suitability for dynamic modelling and WWTP control strategy optimisation. Through the use of local and global sensitivity analysis tools, sources of uncertainty in the modelling of GHG emissions from wastewater treatment are investigated, revealing critical parameters and parameter interactions; these interaction effects have not been considered in previous studies and thus provide a better understanding of WWTP model characterisation. A key finding is that uncertainty in modelled nitrous oxide (N2O) emissions is the primary contributor to uncertainty in total GHG emissions, due largely to the interaction effects of nitrogen conversion modelling parameters. Further local and global sensitivity analysis is used to investigate the effects of adjusting control handle values on GHG emissions, revealing critical control handles and sensitive emission sources for control. This knowledge assists with the following control strategy development and aids an efficient design and optimisation process. Sources with the greatest variance in emissions, and therefore the greatest need to monitor, are also identified. It is found that variance in total emissions is predominantly due to changes in direct N2O emissions and selection of suitable values for wastage flow rate and aeration intensity in the final activated sludge reactor is of key importance. Sets of Pareto optimal operational and control parameter values are derived using a multi-objective genetic algorithm, NSGA-II, with objectives including minimisation of GHG emissions, operational costs and effluent pollutant concentrations, subject to legislative compliance. It is found that multi-objective optimisation can facilitate a significant reduction in GHG emissions without the need for plant redesign or modification of the control strategy layout, but there are trade-offs to consider: most importantly, if operational costs are not to be increased, reduction of GHG emissions is likely to incur an increase in effluent ammonia and total nitrogen concentrations. Alternative control strategies are also investigated and it is concluded that independent control of dissolved oxygen in each aerated activated sludge reactor is beneficial. Optimised solutions are also assessed with respect to their reliability, robustness and resilience, taking into account the effects of influent perturbations and sensor failures on effluent quality and GHG emissions. This reveals that solutions predicted to achieve the most significant reductions in GHG emissions and operational costs under existing design conditions may perform poorly in reality when subject to threats. Dissolved oxygen setpoints which correspond with unacceptable effluent quality reliability and decision variables which should not be considered in future optimisation due to their negative impacts on reliability, robustness and resilience are also identified. Lastly, guidelines for the development of control strategies to reduce GHG emissions are presented. These address GHG emission sources, key control handles and decision variables, choice of control strategy, optimisation and detailed design, and model limitations and uncertainties.

This paper argues that a key mechanism through which greenhouse gas affects growth is via total factor productivity (TFP). We first estimate TFP based on a production function and then estimate the determinants of TFP, paying particular attention to four variables: greenhouse gas, openness of trade, inflation, saving rate ¡@¡@We major results are as follows: 1.In the fixed effect¡GThe impact of greenhouse gas and inflation on TFP to be negative, significant. The impact of openness of trade on TFP to be positive, significant. The impact of saving rate on TFP to be insignificant. 2.The relations between CO2 and TFP have in the degree change, the degree of interplay decreases progressively along with time. 3.The relationship between CO2 and TFP with the countries of OECD is lager than with the countries of Non-OECD. The impact of saving rate on TFP is significant in the countries of OECD, but insignificant in the countries of Non-OECD.

No description available.

Bioenergy production from forest resources offers opportunities to reduce greenhouse gas (GHG) emissions associated with fossil fuel use, reduce non-renewable energy consumption, and provide investment and employment in the forestry sector. These opportunities, however, must be considered within the broader contexts of forest systems. Of particular interest is how bioenergy opportunities impact carbon storage within the forest. This thesis develops a method to integrate life cycle assessment and forest carbon analysis approaches to quantify the total GHG emissions associated with forest bioenergy. Bioenergy production and utilization decisions are then investigated to evaluate opportunities to increase GHG mitigation performance. An accounting method is developed to evaluate the impact of emissions timing on the cost-effectiveness of GHG emissions reductions from biomass-based electricity generation. Applying the integrated life cycle assessment/forest carbon analysis method to a case study of forest bioenergy production in Ontario reveals significant reductions in forest carbon associated with bioenergy production. Wood pellet production from standing trees or harvest residues (displacing coal in electricity generation) would increase total GHG emissions over periods of approximately 40 and 15 years, respectively. Ethanol production (displacing gasoline) would increase GHG emissions throughout the 100-year model period if produced from standing trees; emissions would increase over a period of approximately75 years if produced from harvest residues. Strategic ethanol production decisions (e.g., process energy source, co-location with other processes, co-product selection) can improve GHG mitigation. Co-production of biomass pellets with ethanol performs best among co-product options in terms of GHG emissions; co-location with facilities exporting excess steam and biomass-based electricity further increases GHG mitigation performance. Delayed GHG reductions due to forest carbon impacts the cost of GHG emissions reductions associated with electricity production from forest biomass. Cost-effectiveness is heavily dependent on the time horizon over which global warming impacts are measured and influences the ranking of biomass electricity pathways (biomass co-firing is the most cost-effective pathway between 2020 and 2100; biomass cogeneration is the most cost-effective pathway beyond year 2100). The accounting tools and methods developed within this thesis will to help inform decision-makers in the responsible development of forest bioenergy opportunities and associated policies.

Bioenergy production from forest resources offers opportunities to reduce greenhouse gas (GHG) emissions associated with fossil fuel use, reduce non-renewable energy consumption, and provide investment and employment in the forestry sector. These opportunities, however, must be considered within the broader contexts of forest systems. Of particular interest is how bioenergy opportunities impact carbon storage within the forest. This thesis develops a method to integrate life cycle assessment and forest carbon analysis approaches to quantify the total GHG emissions associated with forest bioenergy. Bioenergy production and utilization decisions are then investigated to evaluate opportunities to increase GHG mitigation performance. An accounting method is developed to evaluate the impact of emissions timing on the cost-effectiveness of GHG emissions reductions from biomass-based electricity generation. Applying the integrated life cycle assessment/forest carbon analysis method to a case study of forest bioenergy production in Ontario reveals significant reductions in forest carbon associated with bioenergy production. Wood pellet production from standing trees or harvest residues (displacing coal in electricity generation) would increase total GHG emissions over periods of approximately 40 and 15 years, respectively. Ethanol production (displacing gasoline) would increase GHG emissions throughout the 100-year model period if produced from standing trees; emissions would increase over a period of approximately75 years if produced from harvest residues. Strategic ethanol production decisions (e.g., process energy source, co-location with other processes, co-product selection) can improve GHG mitigation. Co-production of biomass pellets with ethanol performs best among co-product options in terms of GHG emissions; co-location with facilities exporting excess steam and biomass-based electricity further increases GHG mitigation performance. Delayed GHG reductions due to forest carbon impacts the cost of GHG emissions reductions associated with electricity production from forest biomass. Cost-effectiveness is heavily dependent on the time horizon over which global warming impacts are measured and influences the ranking of biomass electricity pathways (biomass co-firing is the most cost-effective pathway between 2020 and 2100; biomass cogeneration is the most cost-effective pathway beyond year 2100). The accounting tools and methods developed within this thesis will to help inform decision-makers in the responsible development of forest bioenergy opportunities and associated policies.

Thesis (M.Env.Sc.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1999. / Bibliography: leaves 120-124.