Investigating utility level of waste disposal methods using multicriteria decision-making techniques (case study: Mazandaran-Iran)

Journal of Material Cycles and Waste Management - Regardless of collection and disposal systems of wastes, which are the main causes of pollution in cities and villages, attention to the health and...     

Developing a sustainable agro-system for central Nepal using reduced tillage and straw mulching

In Nepal, soil erosion under maize (Zea mays) agro-ecosystems is most critical during the pre-monsoon season. Very few field experiments have been conducted on reduced tillage and rice straw (Oryza sativa) mulching, although these conservation approaches have been recommended. Thus, a five replicate field experiment was established in 2001 at Kathmandu University (1500 m above sea level) on land with 18% slope to evaluate the efficiency of reduced tillage and mulching on soil and nutrient losses and maize yield. The results showed non-significant differences among conservation approaches on runoff and maize yield. Mulching and reduced tillage significantly lowered annual and pre-monsoon soil and nutrient losses compared to conventional tillage. Soil organic matter (SOM) and nitrogen losses associated with eroded sediment were significantly higher in conventional tillage. However, due to limited availability and high opportunity cost of rice straw, reduced tillage would be a better option for soil and nutrient conservation without sacrificing economic yield in upland maize agro-ecosystems.     

Two-dimensional modeling of torrefaction of a large biomass particle

A two-dimensional (2-D) model is developed to predict the torrefaction behavior of a large wet biomass particle. Although one-dimensional (1-D) model is found to be adequate for L/D ≥ 6, the necessity of using 2-D model at lower L/D ratios and higher torrefaction temperature is established. Errors up to 18% are observed in predicted mass fractions between 1-D and 2-D models. The center temperatures differed more, up to 96%, between z = 0 and z = L/2 in 2-D model which is not captured by the 1-D model. The model predictions agree well with the experimental results of the present authors and others. The evolution of the temperature profile is found to govern the mass fraction profile. At higher reactor temperature, three distinct zones are visible in the contour plots: peripheral fully torrefied zone, intermediate torrefying zone, and core with unreacted virgin biomass zone. Simulation studies show the formation of two symmetric annular hot spots at the ends, which move inward axially and subsequently merge at the center, the rate being faster for smaller L/D ratio. However, 1-D model does not provide such insight. The effects of reactor temperature, particle size, the residence time, and the initial moisture content on the torrefaction behavior are investigated.     

Evaluation of Extracted Chitosan from Portunus Pelagicus for the Preparation of Chitosan Alginate Blend Scaffolds

In recent years there is a growing need in generating a biocompatible and cost effective porous scaffold for tissue engineering purposes. Therefore, this study focused on conversion of the shell waste of locally available crab variety P.pelagicus (Blue swimming crab) into the chitosan scaffold. As the poor mechanical strength of chitosan limits its usage in tissue engineering, it was blended with alginate. The scaffolds were prepared by the freeze gelation method which requires less time and minimum energy, with fewer residual solvent and easier to scale up. To the best of our knowledge there are no reports on scaffold preparation from the extracted chitosan, blended with alginate by freeze gelation method. The biological properties of chitosan-alginate scaffolds (Cts–Alg) were evaluated and compared with those of chitosan scaffolds. The prepared scaffolds were characterized by SEM, swelling property, in vitro enzymatic degradation, and hemo, biocompatibility properties. Chitosan-alginate scaffolds had an average pore size of 40 μm and tensile strength of 0.564 ± 0.0.018 % MPa. Its swelling ratio was 27.5 ± 0.28 %, with mass loss percentage of 10 ± 0.33 % after 4 weeks of degradation. It has exhibited good hemocompatible properties too. Mouse fibroblast 3T3 cells were able to adhere and proliferate well in the blended scaffold. All these results indicated that chitosan-alginate scaffold is a suitable alternative substitute for tissue engineering.     

Usefulness of automated chromatography for rapid fetal blood analysis for second trimester prenatal diagnosis of β-thalassemia

Prenatal diagnosis of β-thalassemia is now ideally done in the first trimester of pregnancy by chorionic villus tissue DNA analysis. Nevertheless, fetal blood analysis in the second trimester is required either when the mutation in both parents cannot be characterised or when the couple comes late for investigations. We evaluated the usefulness of analysis of fetal blood on the Biorad Variant Hemoglobin Testing System using the β-thalassemia short programme in comparison with the conventional globin biosynthesis in 58 pregnancies. The β/α biosynthesis ratios in 13 homozygous fetuses ranged from 0 to 0.03 and the adult hemoglobin (HbA) levels by automated chromatography varied from 0% to 0.4%. The normal or heterozygous fetuses had β/α ratios of >0.04 and HbA levels ranging from 2.1% to 10.6%. In 17 fetuses we also correlated the β gene mutations with the predicted genotypes using automated high-performance liquid chromatography (HPLC). Follow-up of 18 unaffected fetuses using the Variant System at birth showed a significant increase in HbA levels. Copyright © 2002 John Wiley & Sons, Ltd.     

Understanding the multifunctionality in Cu-doped BiVO4 semiconductor photocatalyst

A visible light-induced, Cu-doped BiVO_4 photocatalyst was synthesized by a microwave hydrothermal method. The photocatalytic efficiency was investigated in the degradation of model water pollutants like Methylene Blue(dye) and ibuprofen(pharmaceuticals), as well as the inactivation of Escherichia coli(bacteria). The Cu-doped BiVO4 samples showed better efficiency than undoped BiVO_4, and the 1 wt.% Cu-doped BiVO_4 sample showed the best efficiency. The degradation of Methylene Blue reached 95%, while the degradation of ibuprofen reached 75%, and the inactivation of E. coli reached 85% in irradiation with visible light. The appearance of additional absorption band shoulders and widening of the optical absorption in the visible range makes the prepared powder an efficient visible light-driven photocatalyst. Moreover, the formation of an in-gap energy state just above the valance band as determined by density functional theory(DFT) first principle calculation, facilitates the wider optical absorption range of the doped system. Similarly, this in-gap energy state also acts as an electron trap, which is favorable for the efficient separation and photoexcited charge carriers' transfer process. The formation of oxygen vacancies due to doping also improved the separation of the charge carrier, which promoted the trapping of electrons and inhibited electron hole recombination, thus increasing the photocatalytic activity. No decrease in the efficiency of the 1 wt.% Cu-doped BiVO_4 photocatalyst in the degradation of ibuprofen over three consecutive cycles revealed the stability of the photocatalyst towards photocorrosion. These findings highlight the multifunctional applications of Cu-doped BiVO_4 in wastewater containing multiple pollutants.