Pei-Te Chiueh

Efficient decomposition of perfluorocarboxylic acids in aqueous solution using microwave-induced persulfate.

The microwave-hydrothermal decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water with persulfate (S(2)O(8)(2-)) at 60, 90, and 130 degrees C was examined to develop an effective technology for treating PFOA pollution. S(2)O(8)(2-) is an efficient oxidant for degrading PFOA even at the room temperature of 27 degrees C. Higher temperature accelerates the PFOA decomposition rate, but an extremely high temperature (130 degrees C) will lead to the formation of significant amounts of radical oxidants that are released rapidly to consume most remaining persulfate thus causing a lower mineralization efficiency. The solution pH value is another important factor to influence the degradation rate; there is almost no PFOA decomposition reaction under alkaline conditions. The decomposition rate in acidic conditions is 1.1-7.4 times faster than in alkaline condition. Additionally, the proposed method is also effective in decomposing other PFCA species such as the C2-C7 perfluoroalkyl groups.

Microwave-hydrothermal decomposition of perfluorooctanoic acid in water by iron-activated persulfate oxidation

The microwave-hydrothermal decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in aqueous solution using persulfate activated by zero-valent iron (ZVI) at 60 and 90 degrees C was examined. The results of laboratory study reveal that when PFOA is treated with 5mM persulfate (PS) and ZVI at 90 degrees C for 2h, 67.6% of PFOA is effectively decomposed to form shorter-chain perfluorinated carboxylic acids (PFCAs) and fluoride ions, with 22.5% defluorination efficiency. Introducing ZVI into the PFOA solution with PS addition will lead to synergetic effect that accelerates the PFOA decomposition rate, and reduces the reaction time. ZVI not only decomposes PFOA, but also releases ferrous ions to lower the activation energy of PS while forming sulfate free radicals at a lower reaction temperature. The combined use of ZVI and persulfate will lead to significant savings in energy consumption and reduction of process time.

Pyrolysis of biomass by thermal analysis-mass spectrometry (TA-MS).

The kinetic parameters such as pre-exponential factor and activation energy of hemicellulose, cellulose, and lignin were well determined by the linear regressions of selected, sufficient thermogravimetric data, and close to literature values. The pyrolysis of biomass can be divided into four stages. There was only drying in the zeroth stage (<150°C). In the first stage (150-250°C), some light hydrocarbons were produced with the early pyrolysis of biomass. The biomass was mainly pyrolyzed in the second stage (250-500°C) with higher reaction rates than those of other stages. The productions of H(2) and CO(2) in the third stage (>500°C) may be able to be the evidence of self-gasification of char existing at higher temperatures.

A sequential method to analyze the kinetics of biomass pyrolysis

The kinetics of biomass pyrolysis was studied via a sequential method including two stages. Stage one is to analyze the kinetics of biomass pyrolysis and starts with the determination of unreacted fraction of sample at the maximum reaction rate, (1-α)(m). Stage two provides a way to simulate the reaction rate profile and to verify the appropriateness of kinetic parameters calculated in the previous stage. Filter paper, xylan, and alkali lignin were used as representatives of cellulose, hemicellulose, and lignin whose pyrolysis was analyzed with the assumption of the orders of reaction being 1, 2, and 3, respectively. For most of the biomass pyrolysis, kinetic parameters were properly determined and reaction rate profiles were adequately simulated by regarding the order of reaction as 1. This new method should be applicable to most of the biomass pyrolysis and similar reactions whose (1-α)(m) is acquirable, representative, and reliable.

Microwave torrefaction of rice straw and pennisetum.

Microwave torrefaction of rice straw and pennisetum was researched in this article. Higher microwave power levels contributed to higher heating rate and reaction temperature, and thus produced the torrefied biomass with higher heating value and lower H/C and O/C ratios. Kinetic parameters were determined with good coefficients of determination, so the microwave torrefaction of biomass might be very close to first-order reaction. Only 150W microwave power levels and 10min processing time were needed to meet about 70% mass yield and 80% energy yield for torrefied biomass. The energy density of torrefied biomass was about 14% higher than that of raw biomass. The byproducts (liquid and gas) possessed about 30% mass and 20% energy of raw biomass, and they can be seen as energy sources for heat or electricity. Microwave torrefaction of biomass could be a competitive technology to employ the least energy and to retain the most bioenergy.

Microwave pyrolysis of rice straw: products, mechanism, and kinetics.

Rice straw is an abundant resource for the production of biofuels and bio-based products. How to convert the recalcitrant lignocellulose effectually is a critical issue. The objective of this study was to investigate the products, mechanism, and kinetics of rice straw pyrolysis by using microwave heating. The highest energy densification ratio of solid residues was achieved at the microwave power level of 300 W. The atomic H/C and O/C ratios of solid residues were much lower than those of rice straw. The primary components of gaseous product were CO, H2, CO2, and CH4, whose molecular fractions were 57%, 21%, 14%, and 8%, respectively. The more gaseous product and the less solid residues were obtained at higher microwave power levels, while the liquid production remained the same and showed a maximum of about 50 wt.%. The kinetic parameters of rice straw pyrolysis were increased with increasing microwave power level.

Correlation between land-use change and greenhouse gas emissions in urban areas

Urban areas are the main sources of greenhouse gas (GHG) emissions. Previous studies have identified the effectiveness of better urban design on mitigating climate change and land-use patterns in cities as important factors in reducing GHG by local governments. However, studies documenting the link between land-use and GHG emissions are scant. Therefore, this study explores the driving forces of land-use change and GHG emission increments in urban areas and investigates their correlations. The study area, Xinzhuang, is a satellite city of Taipei that has rapidly urbanized in the past few decades. Twenty-one potential variables were selected to determine the driving forces of land-use change and GHG emission increments by binomial logistic regression based on the investigation data of national land use in 1996 and 2007. The correlation of land-use change and GHG increments was examined by Spearman rank-order analysis. Results of logistic regression analysis identified that population and its increasing density rate are main driving forces on both land-use change and GHG increments. The Spearman rank correlation matrix indicates that fluctuating urbanization level is significantly correlated with the increase of total GHG emissions, the emissions of residence, commerce, and transportation sectors in neighborhoods; and the emissions of residence and transportation sectors seem closely connected to current urbanization level. The findings suggest that relationships among land-use, urbanization, and GHG emissions in urban areas vary greatly according to residence and transportation characteristics. Land-based mitigation may provide the most viable mechanism for reducing GHG emissions through residence and transportation sectors.

Life cycle assessment of biochar cofiring with coal.

This study used life cycle assessment software SimaPro 7.2 and impact assessment model IMPACT 2002+ to evaluate the environmental impact and benefits of a biochar cofiring supply chain used for electricity generation. The biochar was assumed to be produced by rice straw torrefaction and the case study was located in Taoyuan County, Taiwan. This supply chain may provide impact reduction benefits in five categories (aquatic ecotoxicity, terrestrial ecotoxicity, land occupation, global warming, and non-renewable energy) but cause higher impacts than coal firing systems in other categories. Damage assessment of cofiring systems indicated that damage to human health was higher while the damage categories of ecosystem quality, climate change, and resources were lower. Carbon reduction could be 4.32 and 4.68metric tons CO2eq/ha/yr at 10% and 20% cofiring ratios, respectively. The improvement of electricity generation efficiency of cofiring systems may be the most important factor for reducing its environmental impact.

Implications of biomass pretreatment to cost and carbon emissions: Case study of rice straw and Pennisetum in Taiwan

The purpose of this study was to explore the impact of feedstock collection and torrefaction pretreatment on the efficiency of a biomass co-firing system. Considering the transformation of existing municipal solid waste incinerators, several scenarios in which biomass supply chains depend on centralised pretreatment and transportation alternatives are presented. The cost, net energy output, and greenhouse gas effects of these scenarios were analysed using a spreadsheet model. Based on the Taoyuan County case in Taiwan, the mitigation costs of carbon emissions for rice straw and Pennisetum are 77.0

A GIS-based system for allocating municipal solid waste incinerator compensatory fund

/Mg CO(2) and 63.8