The effects of Cu(II) ion as an additive on NH3 loss and CO2 absorption in ammonia-based CO2 capture processes

Chemical CO2 absorption is one of the most cost- and energy-intensive processes in carbon capture and storage (CCS) technology. Among various absorption processes, ammonia-based processes attract much attention, due to many benefits: high CO2 absorption rate and low energy consumption for ammonia regeneration. Ammonia-based processes, however, have a problem to be solved for practical implementation due to the high vapor pressure of ammonia, which incurs ammonia loss during regeneration. In this study, the effect of Cu(II) ion as an additive on NH3 loss and CO2 absorption was investigated to examine the potential of Cu(II) ion to enhance the economic performance of ammonia-based processes. Continuous operations were conducted with and without the addition of Cu(II) ion. The results showed that the addition of Cu(II) ion noticeably decreased NH3 loss in the regeneration process due to the complexation of copper and ammonium ions, i.e., [Cu(NH3)(4)](2+). The Cu(II) addition also increased the CO2 absorption capacity in the absorption process because ammonia concentration remained higher. In conclusion, Cu(II) ion can be used to reduce ammonia make-up cost and to enhance CO2 absorption performance in ammonia-based CO2 capture processes. (C) 2012 Elsevier B.V. All rights reserved.11sciescopu

Potentials of macroalgae as feedstocks for biorefinery

Macroalgae, so-called seaweeds, have recently attracted attention as a possible feedstock for biorefinery. Since macroalgae contain various carbohydrates (which are distinctively different from those of terrestrial biomasses), thorough assessments of macroalgae-based refinery are essential to determine whether applying terrestrial-based technologies to macroalgae or developing completely new technologies is feasible. This comprehensive review was performed to show the potentials of macroalgae as biorefinery feedstocks. Their basic background information was introduced: taxonomical classification, habitat environment, and carbon reserve capacity. Their global production status showed that macroalgae can be mass-cultivated with currently available farming technology. Their various carbohydrate compositions implied that new microorganisms are needed to effectively saccharify macroalgal biomass. Up-to-date macroalgae conversion technologies for biochemicals and biofuels showed that molecular bioengineering would contribute to the success of macroalgae-based biorefinery. It was concluded that more research is required for the utilization of macroalgae as a new promising biomass for low-carbon economy. (C) 2012 Elsevier Ltd. All rights reserved.11sciescopu

Eco-Design of a Wastewater Treatment System Based on Process Integration

Because almost all industrial plants have wastewater treatment systems, eco-design of the systems is an effective way to reduce environmental impacts and economic costs of industry sectors. The eco-design using biobjective optimization has, however, a limitation due to the subjective weighting on the two objectives. The objective of this study is to eco-design existing wastewater treatment systems based on process integration by converting biobjective to single objective problems. For the mathematical optimization model, an objective function is formulated by monetizing environmental impacts to external costs and summing the external and economic costs. Mass balances and constraints are formulated to reflect the superstructure model and real situations. Two case studies are performed to verify the developed model. The eco-design outcomes are compared to their respective economic cost- and environmental impact-minimized designs. This comparison shows that the developed model optimizes the trade-offs between the biobjectives. This study can be applied to reduce environmental impacts and economic costs of other process systems

Effect of technology convergence for tablet PC on potential environmental impacts from heavy metals

<p>The technology convergence integrating multiple devices into a single one is now a distinct trend in electronic industry. This trend can lead to a decrease in the use of rare and toxic heavy metals due to resource sharing, or an increase due to the application of new and auxiliary technology. This study investigates the effect of technology convergence for tablet PC on hazardous waste, resource depletion, and toxicity potentials from heavy metals in electronic devices, considering how many single devices (i.e., netbook computer, electronic dictionary, mp3 player, digital camera, cell phone, and vehicle GPS system) can be displaced by a tablet PC depending on users. The hazardous waste potential from heavy metals is examined with existing U.S. federal and California state regulations, and the resource depletion and toxicity potentials from heavy metals are evaluated based on life cycle impact assessments. The potentials of a specific tablet PC are compared to the total of those of displaced single products. Overall, the tablet PC has lower hazardous waste, resource depletion, and toxicity potentials from heavy metals. However, in case the tablet PC displaces only two or three single devices, it requires more gold, molybdenum, and vanadium. Therefore, technology convergence should take into account materials consumption and user behavior to develop more sustainable products.</p

System optimization for eco-design by using monetization of environmental impacts: a strategy to convert bi-objective to single objective problems

Eco-design is an essential way to reduce the environmental impacts and economic cost of processes and systems, as well as products. Until now, the majority of eco-design approaches have employed multi-objective optimization methods to balance between environmental and economic performances. However, the methods have limitations because multi-objective optimization requires decision makers to subjectively assign weighting factors for objectives, i.e., environmental impacts and economic cost. This implies that, depending on decision makers&apos; preference and knowledge, different design solutions can be engendered for the same design problem. Thus, this study proposes an eco-design method which can generate a single design solution by developing mathematical optimization models with a single-objective function for environmental impacts and economic cost. For the formulation of the single-objective function, environmental impacts are monetized to external cost by using the Environmental Priority Strategies. This enables the tradeoffs between environmental impacts and economic cost in the same unit, i.e., monetary unit. As a case study, the proposed method is applied to the eco-design of a water reuse system in an industrial plant. This study can contribute to improving the eco-efficiency of various products, processes, and systems. (C) 2012 Elsevier Ltd. All rights reserved.11sciescopu

Environmental benefits of seaweed biomass as a bioenergy feedstock

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