Methane storage in molecular nanostructures

We survey various molecular structures which have been proposed as possible nanocontainers for methane storage. These are molecular structures that have been investigated through either experiments, molecular dynamics simulations or mathematical modelling. Computational simulation and mathematical modelling play an important role in predicting and verifying experimental outcomes, but both have their limitations. Even though recent advances have greatly improved computations, due to the large number of atoms and force field calculations involved, computational simulations can still be time consuming as compared to an instantaneous mathematical modelling approach. On the other hand, underlying an ideal mathematical model, there are many assumptions and approximations, but such modelling often reveals the key physical parameters and optimal configurations. Here, we review methane adsorption for three conventional nanostructures, namely graphite, single and multi-walled carbon nanotubes, and nanotube bundles (including interstitial and groove sites), and we survey methane adsorption in other molecular structures including metal organic frameworks. We also include an examination of minimum binding energies, equilibrium distances, gravimetric and volumetric uptakes, volume available for adsorption, as well as the effects of temperature and pressure on the adsorption of methane onto these molecular structures.     

Carbon trading: Current schemes and future developments

This paper looks at the greenhouse gas (GHG) emissions trading schemes and examines the prospects of carbon trading. The first part of the paper gives an overview of several mandatory GHG trading schemes around the world. The second part focuses on the future trends in carbon trading. It argues that the emergence of new schemes, a gradual enlargement of the current ones, and willingness to link existing and planned schemes seem to point towards geographical, temporal and sectoral expansion of emissions trading. However, such expansion would need to overcome some considerable technical and non-technical obstacles. Linking of the current and emerging trading schemes requires not only considerable technical fixes and harmonisation of different trading systems, but also necessitates clear regulatory and policy signals, continuing political support and a more stable economic environment. Currently, the latter factors are missing. The global economic turmoil and its repercussions for the carbon market, a lack of the international deal on climate change defining the Post-Kyoto commitments, and unfavourable policy shifts in some countries, cast serious doubts on the expansion of emissions trading and indicate that carbon trading enters an uncertain period.     

Is e-reading environmentally more sustainable than conventional reading?

Technology is changing the way we read, with printed material being replaced by electronically published text such as e-books and e-newspapers. Although digitally published texts offer some advantages over printed material in terms of cost and ease of access, it is not immediately clear whether e-reading is environmentally a more sustainable alternative to conventional reading. Therefore, this paper reviews the literature and compares the environmental impacts of the two reading alternatives, taking a life cycle approach. The review of various studies indicates that there are large variations in the impacts for e-readers as well as the printed material, mainly owing to different assumptions. Nevertheless, the results of this work indicate clearly that e-reading can only be environmentally sustainable at very high usage rates, as manufacturing of e-readers has relatively high environmental impacts.     

Microbial spoilage of Solanum tuberosum L. tubers in Nigeria

Studies were carried out to investigate the microorganisms associated with the spoilage of Solanum tuberosum tubers in 6 states of Nigeria. Microbial spoilage was found to be caused by Fusarium solani, Rhizopus oryzae, R. stolonifer, Erwinia sp., Aspergillus niger and Alternaria longipes. The spoilage caused by the first 4 organisms was the most important with F. solani producing the highest percentage loss in potato tubers. The effect of temperature on the growth of 4 of the spoilage organisms in liquid culture and on spoilage of tuber is presented and discussed.     

Mycoflora of post-harvest maize and wheat grains and the implication of their contamination by molds

Thirteen fungi including toxigenic Aspergillus nidulans and A. clavatus were isolated from the grains. The isolated fungi grew well at 25–30 °C. A. clavatus and A. nidulans were grown in liquid maize yeast extract medium and wheat yeast extract medium. Both fungi produced amylases on the two media and on the basal medium at 30 °C. During incubation more total reducing sugars were detected in maize grains than in wheat while non-reducing sugars were detected than reducing sugars in both grains. A. clavatus showed highest amylase activities at 25–30 °C and at a pH 7–8 while 30 °C and pH 6.0 were the optimum conditions for highest amylase activities of A. nidulans. During incubation with both fungi a decrease in the protein and carbohydrate contents of both grains was recorded while more fat was accumulated in the grains.     

Fruit rots of Capsicum annuum L. and C. frutescens L. in Nigeria. Part III. Effect of post-harvest infection by two Fusaria species on a few nutrients

The effects of temperature on rot infections produced by Fusarium oxysporum and F. equiseti on the sugars and ascorbic acid levels in pepper fruits were investigated. There was a gradual decrease to a total loss of ascorbic acid in infected fruits (at 25 °C) with increase in incubation period (14 days). In infected fruits stored at 30 °C during the 8 days of incubation, a total loss of this acid was also recorded. There were fluctuations in the levels of reducing sugars in diseased fruits stored for 8 days at different temperatures while a gradual decrease in amount of sugars was recorded in infected fruits at a temperature of 25 °C during 14 days of incubation.     

Life cycle sustainability assessment of electricity options for the UK

The UK electricity mix will change significantly in the future. This provides an opportunity to consider the full life cycle sustainability of the options currently considered as most suitable for the UK: gas, nuclear, offshore wind and photovoltaics (PV). In an attempt to identify the most sustainable options and inform policy, this paper applies a sustainability assessment framework developed previously by the authors to compare these electricity options. To put discussion in context, coal is also considered as a significant contributor to the current electricity supply. Each option is assessed and compared in terms of its economic, environmental and social implications, using a range of sustainability indicators. The results show that no one technology is superior and that certain trade‐offs must be made. For example, nuclear and offshore wind power have the lowest life cycle environmental impacts, except for freshwater ecotoxicity for which gas is the best option; coal and gas are the cheapest options (£74 and 66/MWh, respectively, at 10% discount), but both have high global warming potential (1072 and 379 g CO₂ eq./kWh); PV has relatively low global warming potential (88 g CO₂ eq./kWh) but high cost (£302/MWh), as well as high ozone layer and resource depletion. Nuclear, wind and PV increase some aspects of energy security: in the case of nuclear, this is due to inherent fuel storage capabilities (energy density 290 million times that of natural gas), whereas wind and PV decrease fossil fuel import requirements by up to 0.2 toe/MWh. However, all three options require additional installed capacity for grid management. Nuclear also poses complex risk and intergenerational questions such as the creation of 10.16 m³/TWh of nuclear waste for long‐term geological storage. Copyright © 2012 John Wiley & Sons, Ltd.     

Flat controller design for hardware-cost reduction in polar-axis photovoltaic systems

Initial costs of solar-photovoltaics have remained a significant factor contending against the wide-spread utilization of solar energy. The paper demonstrates that the concept of differential flatness could be used to design controllers for a polar-axis solar tracker that would enable reduction in hardware costs. Key results show that, the implementation of trajectories of motion in the controller can reduce the drive power requirement and associated photovoltaic (PV) cost by about 31%, and enable the use of smaller drive motors with a possible 25% reduction in drive motor costs; and that the implementation of sensorless control in the polar-axis tracking system is able to further lead to sensor cost elimination.