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Year 2012

Volume 3, Issue 4 October - December 2012

Abstract: Electricity from solar photovoltaics (PV) is gaining attention in Thailand, since the Ministry of Energy set forth targets to produce 25% of its electricity from renewable sources by 2021. Monocrystalline PV (mc-Si), the most energy-conversion efficient type photovoltaic module, is widespread as a solar technology in Thailand. Understanding the potential greenhouse gas emission reductions is increasingly important for evaluating renewable energies. This paper evaluates different parameters from a life cycle perspective that affect climate change mitigation. The primary objectives are to quantify the different life cycle effects on resulting greenhouse gas (GHG) emissions for electricity produced by mc-Si panels for grid-connected systems in Thailand. The study considers the effects of energy efficiency measures, location of production, installation, building-integrated options, and climatic effects. A life cycle assessment suggested that monocrystalline panels can generate electricity with approximately ten times fewer GHG emissions than Thailand’s average electricity mix. The inclusion of building-integrated applications reduces the life cycle impact even further by a factor of 3. With potential for significant GHG emission reductions, mc-Si PV grid-connected electricity production can serve as a possible climate change mitigation strategy for Thailand. This paper outlines the ways that different parameters can alter life cycle GHG emission results.

Keywords: life cycle thinking, monocrystalline PV, climate change mitigation, Thailand.
(125 K)
Abstract: The effects of cropping changes from upland maize to flooded rice cultivation on soil organic carbon (SOC) were studied. Three treatments of field experiments; continuous maize (M treatment), continuous paddy rice (R treatment) and maize-rice rotation (RM treatment) were made. Cropping change from maize to flooded rice resulted in an increase in soil bulk density and SOC content when compared to that of maize-rice rotation and continuous maize. The total SOC after two croppings was 16.50, 20.88 and 19.35 ton C ha-1 in the M, R and RM treatments, respectively. The effects of these short-term cropping changes were observed at both the aggregate level and in the humic substances of soil organic matter. The majority of SOC (ca. 65%) was present in association with the macro-aggregate (>250 m), of which the fraction size of 250-500 m contained the highest carbon concentration. After two croppings, the 13C values of SOC and humic substances were shifted towards the 13C values of rice straw when soil was incorporated with rice straw. The shift of 13C values towards maize straw’s 13C values was also observed in cases when maize straw was incorporated into soil. The results demonstrate that a shift from upland maize to flooded rice could enhance soil carbon sequestration, and decomposition and incorporation of organic materials (maize and rice straw) into SOC and humic substances (himic acid, fulvic acid and humin) was detectable within a short time period.

Keywords: Soil organic carbon, cropping change, natural 13C abundance, soil aggregate, humic substances.
(169 K)
Abstract: In this study, a novel bio-based adsorbent was developed for CO2 adsorption. Palm shell activated carbons were immersed in chitosan solutions at the concentrations between 0.1-2 g/L under agitation. A series of chitosan impregnated activated carbon was obtained: 0.12-0.98 wt% chitosan. The chitosan impregnated activated carbon that was the most suitable for CO2/H2 separation was the one impregnated with 0.1 g/L chitosan solution yielding 0.12 g chitosan per one hundred gram activated carbon. A lab-scale pressure swing adsorption process using the modified activated carbon as the adsorbent (adsorption pressure of 4 bar and the feed flowrate of 2 L/min 50-50 mixture of H2 and CO2 for a period of 2 min) yielded ultra pure H2 for 8 cycles before the breakthrough of CO2, while only 3 cycles were achieved with the native activated carbon. The chitosan impregnated activated carbon that was the most suitable for CO2/CH4 separation was the one impregnated with 2 g/L chitosan solution yielding 0.76 g chitosan per one hundred gram activated carbon. The lab-scale adsorption process using the modified activated carbon as the adsorbent yielded ultra pure CH4 for 3 cycles before the breakthrough of CO2, while only 1 cycle was achieved with the native activated carbon. For the CO2/N2 dynamic adsorption of 0.12 wt% CHI/AC, 100% nitrogen was achieved for 1-8 cycles. For the CO2/N2 dynamic adsorption of 0.76 wt% CHI/AC, 100% nitrogen was achieved for 1-9 cycles.

Keywords: Modified activated carbon, chitosan, impregnation, biohydrogen, biogas, flue gas, purification.
(509 K)
Abstract: Anaerobic treatment of molasses stillage generated from an ethanol production plant was investigated in a two phase semi-continuously stirred tank reactor (semi-CSTR) operated under mesophilic conditions (37°C). Molasses stillage used in this study was a highly polluted wastewater having 150-200 g L-1chemical oxygen demand (COD), 146.48 g L-1 total solid (TS) and 110 g L-1 suspend solid (VSS). Furthermore, this wastewater contained a high amount of potassium, calcium and magnesium (9.6–9.9, 5.6–6.0 and 0.9–1.5 g L-1, respectively). The two phase semi-CSTR was operated at an organic loading rate (OLR) of 1.2–3.54 kg COD m−3 day-1 and a hydraulic retention time (HRT) of 140-40 days. The results showed that the average methane yield obtained was 0.3 m3 CH4 kg-1 CODremoved with 65% CH4 in biogas. The COD removal efficiency decreased from 97% to 68% with an increase in OLR. When the system had been operated for 90 days or at OLR of 3.71 kg COD m−3 day-1 and HRT of 38 days, the accumulation of solid was observed in the reactors. The concentration of SS in the first and second phase reactors was 20 and 27.55 g L-1, respectively. These concentrations increased by 2.49 and 3.43 times, respectively, compared to the initial solid concentration of each reactor. The ratios of VSS to SS of the second phase reactor decreased significantly while those of the first phase reactor were not significant. The ratios of VSS to SS of the first and second phase reactors decreased from 0.98 to 0.92 and 0.98 to 0.68, respectively. The solid in the first phase reactor consisted of mostly SS coming from influent feed whereas that in the second phase reactor consisted of inert material. The inert material was generated by the precipitation of calcium because of a high alkalinity inside the reactor. The average concentrations of calcium in the solid of the first and second phase reactors were 136.9 and 1,712 mg kg-1, respectively. The specific methanogenic activity of the sludge in the second phase reactor decreased from 0.155 to 0.004 g CODCH4 g-1 VSS day-1. The COD removal efficiency of the system dropped to 58%. The volatile acid to alkalinity ratio of the second phase reactor was higher than 0.4.

Keywords: Anaerobic digestion, Ethanol wastewater, Molasses stillage, Solid accumulation, Two phase CSTR.
(136 K)
Abstract: The authors compare distributions of annual mean wind speed during 1961–2099 at altitudes of 30–100 m above ground level (AGL) in Central Japan based on several available databases. Wind speed fields are statistically interpolated in time and space using three existing databases: the 333-m resolution local wind field database in Central Japan during 2001–2002 (GWA333), the global reanalysis ECMWF during 1957–2001 (ERA40), and the global multi-model database during 2000–2100 (CMIP3) under the SRES A1B scenario. The interpolated data is validated by available surface observation conducted by the Japan Meteorological Agency, and we confirm that the interpolation shows good agreement with the observations. Results show that domain-averaged wind speeds in 2099 evaluated by the statistical interpolation exceed the wind speeds in 2001 evaluated by GWA333 by about 0.48 m/s at 30 m AGL. Over the coastal and mountainous regions, the wind speed at 30 m AGL increase from 8 m/s in 2001 to 10 m/s in 2099. The gradual increase of the surface wind speed might be completed until the early 21st century. It is concluded that if global warming advances according to the IPCC A1B scenario, the surface wind speed, namely, the wind energy resource in Central Japan is expected to increase gradually during the early 21st century.

Keywords: average wind speed, wind energy, global warming.
(670 K)
Abstract: An extensively used non-steroidal anti-inflammatory drug (NAID) diclofenac (DCF) is reported to be present in the environment. Several adverse effects have been reported due to presence of DCF and hence it should be removed from the environment. Among several treatment methods, classic Fenton oxidation is found to be an effective process for the removal of organic contaminants. In the present study, the effect of initial DCF concentration and pseudo second order rate constants of DCF degradation are evaluated by Fenton oxidation process. Percent DCF reduction and percent Chemical Oxygen Demand (COD) removal are measured as the objective parameters to be maximized. At the optimum conditions, for 31.43 x 10-3 mM of initial DCF concentration, 74.25 percent DCF reduction and 72.80 percent COD removal are observed in 240 minutes reaction time. The pseudo second order rate constants are 206.95 M-1S-1 for 31.43 x 10-3 mM and 75.55 M-1S-1 for 157.17 x 10-3 mM initial concentration of DCF. The Fenton oxidation process is the most effective in degradation of DCF in water.

Keywords: AOPs; COD removal; Diclofenac degradation; Fenton oxidation; Kinetic studies.
(118 K)

ISSN: 1906-4918
Frequency: Quartery
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