Environmental concerns about the effect of greenhouse gases have led governments to regulate industrial CO2 emissions, including through emissions caps, trading and penalties, thus creating economic incentives to reduce CO2 emissions. This research focuses on strategies to reduce CO2 emissions from energy systems in the context of the process industries. In the process industries, energy systems consume fuel to generate steam and power for site process units. Improving energy efficiency can reduce costs of energy generation and use, as well as CO2 emissions. This research develops an integrated design and optimisation methodology for energy systems, allowing effective capture and control of carbon dioxide emissions. The first focus of this study is to develop a systematic approach to evaluate combinatorial strategies for reducing CO2 emissions, based on a techno-economic analysis. A conceptual design procedure with hierarchical decision-making is introduced to combine CO2 emissions reduction strategies, accounting for interactions between site components, including the heat exchanger network and utility system. CO2 emissions reduction options considered in development of this procedure include process integration techniques for improving the energy efficiency of the site and fuel switching. The proposed approach considers trade-offs between the economy of energy retrofit and CO2 emissions penalties. Opportunity for reducing the CO2 penalty is included in the economic evaluation of the combined emissions reduction strategies. A mathematical model for simultaneous optimization of emissions reduction strategies is developed. In addition to emissions reduction strategies, options for trading CO2 allowances are considered in the model. The proposed mathematical method applies Mixed Integer Non Linear Programming (MINLP) optimization, which employs a superstructure of the strategies for CO2 reduction. The proposed mathematical model relates the selected options to their operating and capital costs and to their associated CO2 emissions, allowing the optimizer to search for the optimal combination of emissions reduction strategies. While the reduction in CO2 emissions through process integration techniques is based on the existing configuration of a site and the associated structural limitations, integration of Carbon Capture and Storage (CCS) technologies can provide greater mitigation of CO2 emissions from a site. However, important challenges of implementing CCS in the process industries are the energetic and economic impact of the CCS plant on the integrated site. In the second part of this study, these energy-economic issues are explored. The CCS technologies addressed in this thesis include post- and pre-combustion CO2 capture techniques. Simulation of each capture technique is carried out in process simulation software to characterize the energy performance of the CO2 capture plant. Sensitivity analyses are carried out for key parameters of the CO2 capture plant. The relationship between these key parameters and the energy balance of the capture plant is represented using a simple energy performance model for the CO2 capture plant. This model allows the integration of the CO2 capture plant with the site utility system to be explored. Interactions between the utility system and CO2 capture plant are considered. The site utility system, together with the CO2 capture plant, is optimized for minimum operating cost. The proposed procedures are illustrated by application to a case study of a medium-scale oil refinery. The results illustrate that to reduce CO2 emissions, heat integration, utility system optimization and fuel switching provide more cost-effective solutions than integrating CCS technologies. The mathematical model allows more cost-effective solutions to be identified than using sequential, conceptual methods, but the value of the conceptual method for developing insights is also illustrated. The results demonstrate that, depending on the potential of the site for increasing heat recovery and the type of fuel used on site, solutions that combine energy efficiency and fuel switching can provide up to 40% reduction in site CO2 emissions. Integrating a post-combustion CO2 capture plant with the site utility system can provide up to 90 mol% pure CO2 for sequestration; however, the high capital cost of the capture plant reduces the economic performance of the integrated site. The high heat demand of post-combustion CO2 capture for solvent regeneration increases the fuel consumption of the site and its utility system, which in turn reduces the recovery of CO2. The results reveal that pre-combustion CO2 capture can provide opportunities for heat and power generation to improve the techno-economic performance of the overall integrated site.

In this study, the composite of aluminum metal-organic framework MIL-68(Al) and reduced graphene oxide (MA/RG) was synthesized via a one-step solvothermal method, and their performances for pnitrophenol (PNP) adsorption from aqueous solution were systematically investigated. The introduction of reduced graphene oxide (RG) into MIL-68(Al) (MA) significantly changes the morphologies of the MA and increases the surface area. The MA/RG-15% prepared at RG-to-MA mass ratio of 15% shows a PNP uptake rate 64% and 123% higher than MIL-68(Al) and reduced graphene oxide (RG), respectively. The hydrogen bond and pi-pi dispersion were considered to be the major driving force for the spontaneous and endothermic adsorption process for PNP removal. The adsorption kinetics, which was controlled by film-diffusion and intra-particle diffusion, was greatly influenced by solution pH, ionic strength, temperature and initial PNP concentration. The adsorption kinetics and isotherms can be well delineated using pseudo-second-order and Langmuir equations, respectively. The presence of phenol or isomeric nitrophenols in the solution had minimal influence on PNP adsorption by reusable MA/RG composite.

Paid working patterns are currently regulated by governments around the world for a range of social and economic reasons: to increase labour supply and skills; to provide a strong tax base to support an ageing population; to help people reconcile work and family life over increasingly diversified life courses; and to be in line with the general principle of the activating, employment led welfare state. Environmental considerations rarely feature in the design or evaluation of working time policy. Nevertheless, various authors working on policies for sustainable development argue that reductions in average paid working time could lead to environmental benefits: as people work less, they in turn earn less, and so consume less, resulting in lower environmental impacts from lower levels of production of products. This thesis takes this argument as its starting point, and synthesises these distinct perspectives on working time and its regulation to address two key questions: what level of environmental benefits could arise from such reductions in paid working time?; and what are the implications for the design of working time policy? The research addresses these questions, taking the case of greenhouse gas emissions, and the UK and the Netherlands in the early 2000s as case studies. Using household expenditure survey data and data on product emissions intensities, the relationship between paid working time and emissions is analysed at both the household and national levels. At the household level, statistically and substantively significant correlations are found between higher levels of paid work and higher levels of consumption and so greenhouse gas emissions. The effects on emissions of hypothetical changes in the working patterns of the national populations are then modelled. The research estimates that meeting current national objectives to increase labour market participation rates would increase national greenhouse gas emissions by 0.6-0.7%, a cost that might be considered acceptable if it also achieves its aims of reducing income poverty, benefit dependency, and social exclusion. Meanwhile, widespread reductions in average working hours and increased use of career breaks, with corresponding reductions in income, would reduce national emissions. The scenarios modelled (a 20% reduction in the working hours of full time workers, and increasing use of 3 month career breaks) lead to reductions of 3-4.5% in national emissions, with the corresponding increases in “leisure” time, reductions in income inequality, and reduced gender imbalances in the distribution of paid work potentially also improving wellbeing, social cohesion, and gender equality in work and care. The results indicate that environmental factors warrant consideration in the design and evaluation of working time policy, and that challenging but achievable levels of working time reduction could contribute a small but significant share to meeting greenhouse gas emissions targets. Policy instruments would need to address a range of values, attitudes and norms around employment and consumption, as well as employer and situational factors, if substantial working time reduction were to be achieved. Reconciling diverse environmental, social and economic goals also requires careful policy design, particularly for certain demographic groups such as the low income, who would need financial and other support to turn rights to reduce working time into functional freedoms that they could utilise.

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