Mercury adsorption from fuel ethanol onto phosphonated silica gel prepared by heterogenous method

Ethanol is one of the most important renewable biofuels contributing to the reduction of negative environmental impacts generated by the worldwide utilization of fossil fuels, and the presence of metal ions in fuel ethanol has significant effect on the performance and the quality of fuel. In the present work, silica gel functionalized by poly(triethylenetetraminomethylenephosphonic acid) SG-Cl-T-P was successfully developed by heterogenous synthesis method, and the adsorption capacity of Hg(II) from fuel ethanol via SG-Cl-T-P was examined. The adsorption isotherms were fitted by the Langmuir model, the Freundlich model and the Dubinin–Radushkevich (D–R) model. Furthermore, the adsorption study was analyzed kinetically. The thermodynamic parameters, including the Gibbs free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) were calculated, they were −3.24 kJ mol⁻¹ (35 °C) , 29.25 kJ mol⁻¹, and 106.20 J K⁻¹ mol⁻¹, respectively.     

Environmental aspects of ethanol derived from no-tilled corn grain: nonrenewable energy consumption and greenhouse gas emissions

Nonrenewable energy consumption and greenhouse gas (GHG) emissions associated with ethanol (a liquid fuel) derived from corn grain produced in selected counties in Illinois, Indiana, Iowa, Michigan, Minnesota, Ohio, and Wisconsin are presented. Corn is cultivated under no-tillage practice (without plowing). The system boundaries include corn production, ethanol production, and the end use of ethanol as a fuel in a midsize passenger car. The environmental burdens in multi-output biorefinery processes (e.g., corn dry milling and wet milling) are allocated to the ethanol product and its various coproducts by the system expansion allocation approach.The nonrenewable energy requirement for producing 1 kg of ethanol is approximately 13.4–21.5 MJ (based on lower heating value), depending on corn milling technologies employed. Thus, the net energy value of ethanol is positive; the energy consumed in ethanol production is less than the energy content of the ethanol (26.8 MJ kg⁻¹).In the GHG emissions analysis, nitrous oxide (N₂O) emissions from soil and soil organic carbon levels under corn cultivation in each county are estimated by the DAYCENT model. Carbon sequestration rates range from 377 to 681 kg C ha⁻¹ year⁻¹ and N₂O emissions from soil are 0.5–2.8 kg N ha⁻¹ year⁻¹ under no-till conditions. The GHG emissions assigned to 1 kg of ethanol are 260–922 g CO₂ eq. under no-tillage. Using ethanol (E85) fuel in a midsize passenger vehicle can reduce GHG emissions by 41–61% km⁻¹ driven, compared to gasoline-fueled vehicles. Using ethanol as a vehicle fuel, therefore, has the potential to reduce nonrenewable energy consumption and GHG emissions.     

A 28-W portable direct borohydride–hydrogen peroxide fuel-cell stack

A 28-W direct borohydride–hydrogen peroxide fuel-cell stack operating at 25 °C is reported for contemporary portable applications. The fuel cell operates with the peak power-density of ca. 50 mW cm⁻² at 1 V. This performance is superior to the anticipated power-density of 9 mW cm⁻² for a methanol–hydrogen peroxide fuel cell. Taking the fuel efficiency of the sodium borohydride–hydrogen peroxide fuel cell as 24.5%, its specific energy is ca. 2 kWh kg⁻¹. High power-densities can be achieved in the sodium borohydride system because of its ability to provide a high concentration of reactants to the fuel cell.     

Solar utility and renewability evaluation for biodiesel production process

A new design concept using solar utility to supply steam and electricity for biodiesel production was proposed. A new indicator, called the renewability index, was then defined and quantified by exergy to evaluate the benefits of substituting fossil fuel utility facilities with solar utility facilities. To reduce the unfavorable environmental impacts of the biodiesel production process, a novel process on an 8000 t a^?1 scale with solar utility facilities was designed and simulated using Aspen Plus. The results show that the amount of fossil fuel consumption saved per year amounts to 1275 t of standard coal and 4676 t of CO₂ release is also eliminated every year. The renewability index of the biodiesel production process with solar utility facilities is 99.9%, 10.5% higher than that with fossil fuel utility facilities. The results reported in this paper indicate that the unfavorable environmental impacts of the biodiesel production process also deserve attention and the impacts can be eliminated by using solar utility facilities.     

Bioenergy technologies for carbon abatement

In this paper, bioenergy technologies (BETs) are presented as potential carbon abatement opportunities substituting fossil fuel or traditional (less efficient) biomass energy systems. Cost of energy (produced or saved) of BETs is compared with fossil fuel and traditional biomass energy systems to estimate the incremental cost (IC). The IC of carbon abatement for each of the selected BETs (in $ kWh⁻¹ or $ GJ⁻¹) is estimated using the carbon emission (tC kWh⁻¹ or tC GJ⁻¹) reduction obtained by substituting fossil fuel and traditional biomass alternatives. The abatement costs are estimated and compared for ten combinations of BETs (with seven technology alternatives) substituting conventional technologies. The analysis indicates that out of the ten project cases six have negative ICs in the range of −37 to −688 $ tC⁻¹ and four have positive ICs in the range of 52–162 $ tC⁻¹ mitigation. The negative ICs indicate that the suggested alternatives are cheaper than the original technologies. Thus, results indicate that the chosen BETs are cost-effective mitigation opportunities and are currently aggressive candidates under Clean Development Mechanism.     

Performance of simulated flexible integrated gasification polygeneration facilities,Part B: Economic evaluation.

This paper investigates the economics of integrated gasification polygeneration (IG-PG) facilities and assesses under which market conditions flexible facilities outperform static facilities. In this study, the facilities use Eucalyptus wood pellets (EP), torrefied wood pellets (TOPS) and Illinois #6 coal as feedstock to produce electricity, FT-liquids, methanol and urea. All facilities incorporate CCS. The findings show production costs from static IG-PG facilities ranging between 12 and 21 €/GJ using coal, 19–33 €/GJ using TOPS and 22–38 €/GJ using EP, which is above the average market prices. IG-PG facilities can become competitive if capital costs drop by 10%–27% for coal based facilities. Biomass based facilities will need lower biomass pellet prices or higher CO₂ credit prices. Biomass becomes competitive with coal at a CO₂ credit price of 50–55 €/t CO₂. Variations in feedstock, CO₂ credit and electricity prices can be offset by operating a feedstock flexible IG-PG facility, which can switch between coal and TOPS, thereby altering its electricity production. The additional investment is around 0.5% of the capital costs of a dedicated coal based IG-PG facility. At 30 €/t CO₂, TOPS will be the preferred feedstock for 95% of the time at a feedstock price of 5.7 €/GJ. At these conditions, FT-liquids (gasoline/diesel) can be produced for 15.8 €/GJ (116 $/bbl). Historic records show price variations between 5.7 and 7.3 €/GJ for biomass pellet, 1.0–5.6 €/GJ for coal and 0–32 €/t CO₂. Within these price ranges, coal is generally the preferred feedstock, but occasionally biomass is preferred. Lower biomass prices will increase the frequency of switching feedstock preference from coal to biomass, raising the desire for flexibility. Of the three investigated chemicals, an IG-PG facility producing FT-liquids benefits the most from flexibility. Our study suggests that if the uncertainty in commodity prices is high, a small additional investment can make flexible IG-PG facilities attractive.     

Opportunity of metallic interconnects for ITSOFC: Reactivity and electrical property

Iron-base alloys (Fe–Cr) are proposed hereafter as materials for interconnect of planar-type intermediate temperature solid oxide fuel cell (ITSOFC); they are an alternative solution instead of the use of ceramic interconnects. These steels form an oxide layer (chromia) which protects the interconnect from the exterior environment, but is an electrical insulator. One solution envisaged in this work is the deposition of a reactive element oxide coating, that slows down the formation of the oxide layer and that increases its electric conductivity. The oxide layer, formed at high temperature on the uncoated alloys, is mainly composed of chromia; it grows in accordance with the parabolic rate law (k_p = 1.4 × 10⁻¹² g² cm⁻⁴ s⁻¹). On the reactive element oxide-coated alloy, the parabolic rate constant, k_p, decreases to 1.3 × 10⁻¹³ g² cm⁻⁴ s⁻¹. At 800 °C, the area-specific resistance of Fe–30Cr alloys is about 0.03 Ω cm² after 24 h in laboratory air under atmospheric pressure. The Y₂O₃ coating reduces the electrical resistance 10-fold. This indicates that the application of Y₂O₃ coatings on Fe–30Cr alloy allows to use it as an interconnect for SOFC.     

Life cycle assessment of a Brassica carinata bioenergy cropping system in southern Europe

The energetic and environmental performance of production and distribution of the Brassica carinata biomass crop in Soria (Spain) is analysed using life cycle assessment (LCA) methodology in order to demonstrate the major potential that the crop has in southern Europe as a lignocellulosic fuel for use as a renewable energy source.The Life Cycle Impact Assessment (LCIA) including midpoint impact analysis that was performed shows that the use of fertilizers is the action with the highest impact in six of the 10 environmental categories considered, representing between 51% and 68% of the impact in these categories.The second most important impact is produced when the diesel is used in tractors and transport vehicles which represents between 48% and 77%. The contribution of the B. carinata cropping system to the global warming category is 12.7 g CO₂ eq. MJ⁻¹ biomass produced. Assuming a preliminary estimation of the B. carinata capacity of translocated CO₂ (631 kg CO₂ ha⁻¹) from below-ground biomass into the soil, the emissions are reduced by up to 5.2 g CO₂ eq. MJ⁻¹.The production and transport are as far as a thermoelectric plant of the B. carinata biomass used as a solid fuel consumes 0.12 MJ of primary energy per 1 MJ of biomass energy stored. In comparison with other fossil fuels such as natural gas, it reduces primary energy consumption by 33.2% and greenhouse gas emission from 33.1% to 71.2% depending on whether the capacity of translocated CO₂ is considered or not.The results of the analysis support the assertion that B. carinata crops are viable from an energy balance and environmental perspective for producing lignocellulosic solid fuel destined for the production of energy in southern Europe. Furthermore, the performance of the crop could be improved, thus increasing the energy and environmental benefits.     

Development of a miniaturized polymer electrolyte membrane fuel cell with silicon separators

The fabrication process and electrochemical characterization of a miniaturized PEM fuel cell with silicon separators were investigated. Silicon separators were fabricated with silicon fabrication technologies such as by photolithography, anisotropic wet etching, anodic bonding and physical vapor deposition (PVD). A 400 μm × 230 μm flow channel was made with KOH wet etching on the front side of a silicon separator, and then a 550 nm gold current collector and 350 nm TiN_x thin film heater were respectively formed on the front side and the opposite side by PVD. Two separators were assembled with the membrane electrode assembly (MEA) having a 4 cm² active area for the single cell. With pure hydrogen and oxygen under atmospheric pressure without humidification, the performance of the single fuel cell was measured. A single cell operation led to generation of 203 mW cm⁻² at 0.6 V at room temperature, which corresponded to 360 mW cm⁻³ in terms of volumetric fuel cell power density, with 20 ccm of gas flow rate of hydrogen and oxygen at the inlet.     

Analysis of stationary fuel cell dynamic ramping capabilities and ultra capacitor energy storage using high resolution demand data

Current high temperature fuel cell (HTFC) systems used for stationary power applications (in the 200–300 kW size range) have very limited dynamic load following capability or are simply base load devices. Considering the economics of existing electric utility rate structures, there is little incentive to increase HTFC ramping capability beyond 1 kWs⁻¹ (0.4% s⁻¹). However, in order to ease concerns about grid instabilities from utility companies and increase market adoption, HTFC systems will have to increase their ramping abilities, and will likely have to incorporate electrical energy storage (EES). Because batteries have low power densities and limited lifetimes in highly cyclic applications, ultra capacitors may be the EES medium of choice. The current analyses show that, because ultra capacitors have a very low energy storage density, their integration with HTFC systems may not be feasible unless the fuel cell has a ramp rate approaching 10 kWs⁻¹ (4% s⁻¹) when using a worst-case design analysis. This requirement for fast dynamic load response characteristics can be reduced to 1 kWs⁻¹ by utilizing high resolution demand data to properly size ultra capacitor systems and through demand management techniques that reduce load volatility.     

Mitigation of greenhouse gas emissions by adopting anaerobic digestion technology on dairy,sow and pig farms in Finland

The impact of anaerobic digestion (AD) technology on mitigating greenhouse gas (GHG) emissions from manure management on typical dairy, sow and pig farms in Finland was compared. Firstly, the total annual GHG emissions from the farms were calculated using IPCC guidelines for a similar slurry type manure management system. Secondly, laboratory-scale experiments were conducted to estimate methane (CH₄) potentials and process parameters for semi-continuous digestion of manures. Finally, the obtained experimental data were used to evaluate the potential renewable energy production and subsequently, the possible GHG emissions that could be avoided through adoption of AD technology on the studied farms. Results showed that enteric fermentation (CH₄) and manure management (CH₄ and N₂O) accounted for 231.3, 32.3 and 18.3 Mg of CO₂ eq. yr^?1 on dairy, sow and pig farms, respectively. With the existing farm data and experimental methane yields, an estimated renewable energy of 115.2, 36.3 and 79.5 MWh of heat yr^?1 and 62.8, 21.8 and 47.7 MWh of electricity yr^?1 could be generated in a CHP plant on these farms respectively. The total GHG emissions that could be offset on the studied dairy cow, sow and pig farms were 177, 87.7 and 125.6 Mg of CO₂ eq. yr^?1, respectively. The impact of AD technology on mitigating GHG emissions was mainly through replaced fossil fuel consumption followed by reduced emissions due to reduced fertilizer use and production, and from manure management.     

Supply curves of reed canary grass (Phalaris arundinacea L.) in Västerbotten County,northern Sweden,under different EU subsidy schemes

A partial equilibrium model with a break-even price approach was used to create supply curves for the energy crop reed canary grass (Phalaris arundinacea L.) (RCG) in Västerbotten County in northern Sweden. The impact of the European Union's (EU) Common Agricultural Policy (CAP) on the supply curves was studied by comparison of three different scenarios. Supply curves were created including agricultural subsidies under the current subsidy scheme, the Commission's proposal for a new subsidy scheme for implementation in 2004, and without subsidies. The geographical distribution of the potential supply was determined by the use of GIS tools. Under the current subsidy scheme, the lowest RCG farmgate fuel price would be 56 SEK MWh⁻¹. A RCG production equalling 360 GWh could be available at that fuel price level. Under the proposed subsidy scheme of 2004, a farmgate fuel price of 99 SEK MWh⁻¹ is required for RCG production amounting to 910 GWh. In the scenario where no subsidies are disbursed, the lowest break-even price would be 115 SEK MWh⁻¹. In all scenarios, a biofuel feedstock production from RCG equivalent to 1.3 TWh could be available at a farmgate fuel price of 116 SEK MWh⁻¹. The RCG supply would be concentrated in the coastal area of the county, which has the most developed infrastructure and the highest population density, thus providing a nearby market for the fuel.     

Surface modified Nafion® membrane by ion beam bombardment for fuel cell applications

The interfacial structure between an electrolyte membrane and an electrode catalyst layer plays an important role in determining performance of proton exchange membrane fuel cell (PEMFC) since the electrochemical reactions produce electricity occur on the interfaces that are in contact with hydrogen or oxygen gas, so-called three phase boundaries. To improve performance of the PEMFC by enlarging effective area of the interfaces, surface of Nafion^® 115 membrane was roughened by Ar⁺ ion beam bombardment before being coated with a catalyst ink to form the electrode layer. With increasing ion dose density from 0 to 1 × 10¹⁷ ions cm⁻², roughness and hydrophobicity of the membrane surface increased, which could be favored for a high-performance PEMFC. In fuel cell tests, the single cell using Nafion^® membrane bombarded at an ion dose density of 10¹⁶ ions cm⁻² exhibited maximum power density of 0.62 W cm⁻², which was two times higher than that of the single cell employing untreated Nafion^® 115 membrane, i.e. 0.30 W cm⁻².     

Progress in the development of a high-power,direct ethylene glycol fuel cell (DEGFC)

We recently reported on a high-power nanoporous proton-conducting membrane (NP-PCM)-based direct methanol fuel cell (DMFC) operated with triflic acid. However, accompanying the advantages of methanol as a fuel, such as low cost and ease of handling and storage, are several pronounced disadvantages: toxicity, high flammability, low boiling point (65 °C) and the strong tendency to pass through the polymer-exchange membrane (high crossover). The focus of this work is the development of a high-power direct ethylene glycol fuel cell (DEGFC) based on the NP-PCM. Ethylene glycol (EG) has a theoretical capacity 17% higher than that of methanol in terms of Ah ml⁻¹ (4.8 and 4, respectively); this is especially important for portable electronic devices. It is also a safer (bp 198 °C) fuel for direct-oxidation fuel cell (DOFC) applications. Maximum power densities of 320 mW cm⁻² (at 0.32 V) at 130 °C have been achieved in the DEGFC fed with 0.72 M ethylene glycol in 1.7 M triflic acid at 3 atm at the anode and with dry air at 3.7 atm at the cathode. The cell platinum loading was 4 mg Pt cm⁻² on each electrode. The overpotentials at the cathodes and at the anodes of the DEGFC and DMFC were measured, compared and discussed.     

Effects of sputtering parameters on the performance of electrodes fabricated for proton exchange membrane fuel cells

One way to alleviate the emission of air pollutants and CO₂ due to burning fossil fuels is the use of fuel cells. Sputter deposition techniques are good candidates for the fabrication of electrodes used for proton exchange membrane fuel cells (PEMFCs). Input power and sputtering-gas pressure are two important parameters in a sputtering process. However, little is known about the effects of these sputtering parameters on the performance of PEMFC electrodes. Therefore, this study applied a radio frequency (RF) magnetron sputter deposition process to prepare PEMFC electrodes and investigated the effects of RF power and sputtering-gas pressure in electrode fabrication on electrode/cell performance. At a Pt loading of 0.1 mg cm⁻², the electrode fabricated at 100 W, 10⁻³ Torr was found to exhibit the best performance mainly due to its lowest kinetic (activation) resistance (dominating the cell performance) in comparison to those fabricated by 50 and 150 W at 10⁻³ Torr, as well as by 10⁻⁴ and 10⁻² Torr at 100 W. In the tested ranges, the control of sputtering-gas pressure seems to be more critical than that of RF power for the activation loss. In addition to electrochemically active surface area, electrode microstructure should also be responsible for electrode/cell polarization, particularly the activation polarization.     

Eucalyptus gunnii: A possible source of bioenergy?

Eucalypts are widely grown throughout the world for timber, essential oil, fuel, biomass and cut foliage. In experiments in University College Dublin (UCD), Eucalyptus gunnii yielded an average dry weight of 4.74 kg per plant per annum, equivalent to 12.59 t dm ha⁻¹. The average calorific values of 17.60 MJ kg⁻¹ (leafy material) and 17.09 MJ kg⁻¹ (woody material) are less than the values reported for other species of Eucalyptus.     

Quantitative appraisal and potential analysis for primary biomass resources for energy utilization in China

As the largest agricultural country, China has abundant biomass resources, but the distribution is scattered and difficult to collect. It is essential to estimate the biomass resource and its potential for bioenergy utilization in China. In this study, the amount of main biomass resources for possible energy use and their energy utilization potential in China are analyzed based on statistical data. The results showed that the biomass resource for possible energy use amounted to 8.87 × 10⁸ tce in 2007 of which the crops straw is 1.42 × 10⁸ tce, the forest biomass is 2.85 × 10⁸ tce, the poultry and livestock manure is 4.40 × 10⁷ tce, the municipal solid waste is 1.35 × 10⁶ tce, and the organic waste water is 6.46 × 10⁶ tce. Through the information by thematic map, it is indicated that, except arctic-alpine areas and deserts, the biomass resource for possible energy use was presented a relatively average distribution in China, but large gap was existed in different regions in the concentration of biomass resources, with the characteristics of East dense and West sparse. It is indicated that the energy transformation efficiency of biomass compressing and shaping, biomass anaerobic fermentation and biomass gasification for heating have higher conversion efficiency. If all of the biomass resources for possible energy use are utilized by these three forms respectively, 7.66 × 10¹² t of biomass briquettes fuel, 1.98 × 10¹² m³ of low calorific value gas and 3.84 × 10¹¹ m³ of biogas could be produced, 3.65 × 10⁸ t to 4.90 × 10⁸ t of coal consumption could be substituted, and 6.12 × 10⁸ t to 7.53 × 10⁸ t of CO₂ emissions could be reduced. With the enormous energy utilization potential of biomass resources and the prominent benefit of energy saving and emission reduction, it proves an effective way to adjust the energy consumption structure, to alleviate the energy crisis, to ensure the national energy security and to mitigate the global warming trend.     

Embodied energy analysis of adobe house

In this paper an attempt has been made to develop a simple methodology to calculate embodied energy of the adobe house at Solar Energy Park, Indian Institute of Technology Delhi, New Delhi (28°35′N, 77°12′E) and its effect on the environment. The special feature of the adobe house is that, the whole house is constructed by using low energy intensive materials like soil, sand cow dung, etc. The embodied energy involved in construction of main structure, foundation, flooring, finishes, furniture, maintenance and electric work are 102 GJ, 214 GJ, 55 GJ, 5 GJ, 18 GJ, 59 GJ and 4 GJ, respectively. It is seen that the embodied energy involved in the maintenance of the adobe house (12% of total embodied energy) is significant. It has been found that approximately 370 GJ energy can be saved per year. The energy pay back time (EPBT) for the adobe house is 1.54 years. By using low energy intensive materials the mitigation of CO₂ in the environment is reduced by an amount 101 tonnes/year. The adobe house is more environmentally friendly house in comparison to conventional buildings.     

Influence of pore structure on electric double-layer capacitance of template mesoporous carbons

The behavior of two types of mesoporous carbons with different pore structures (i.e. unimodal and bimodal) as electrode material in an electrochemical double-layer capacitor has been analyzed. The carbon samples were prepared using mesostructured silica materials (MSM) as templating agents. The unimodal mesoporous carbon has a BET surface area of 1550 m² g⁻¹, and a pore volume of 1.03 cm³ g⁻¹; the porosity is mainly made up of structural mesopores of ca. 3 nm that exhibit a narrow pore size distribution (PSD). The bimodal carbon shows larger surface area (1730 m² g⁻¹) and larger pore volume (1.50 cm³ g⁻¹); the porosity is composed of two types of mesopores: structural (size around 3 nm) and complementary (size around 16 nm) mesopores. Both carbons show a disordered 3-D pore structure. Heat treatments at high temperatures (1000 °C) for long times (11 h) do not significantly change the pore structure with respect to the two synthesised carbons (800 °C). From the synthesized and heat-treated carbons, electrodes were processed as composites in which the carbons, polivinilidene fluoride (PVDF) and carbon black (CB) were the components. The effect of the heat treatment and relative CB content on specific capacitance, energy density and power density were studied. We found a specific capacitance of 200 F g⁻¹ for low current density (1 mA cm⁻²) and 110 F g⁻¹ for high current density (150 mA cm⁻²). Moreover, the curve of the specific capacitance versus current density shows three regimes, which are related to the three types of pore: micropores, structural mesopores and complementary mesopores. An energy density of 3 Wh kg⁻¹ at a power density of 300 W kg⁻¹ was obtained in some particular cases.     

Improving the stability of direct-methane solid oxide fuel cells using anode barrier layers

Solid oxide fuel cells (SOFCs) were characterized with methane as the fuel, both with and without an inert porous layer placed between the anode and the fuel stream. For a given set of operating conditions, SOFCs were stable without coking above a critical current density. The barrier layer decreased the critical current density, e.g. from 1.8 to <0.6 A cm⁻² at 800 °C. This much-increased stable operating range is discussed in terms of mass transport through the barrier layer.