Life cycle analysis of retrofitting with high energy efficiency air-conditioner and fluorescent lamp in existing buildings

Life cycle analysis of mercury in discarded low energy efficiency fluorescent lamps (36 W) and of HCFC in air-conditioners (12,000 Btu) removed from service has been conducted in this study. The objective was to find out the environmental impact (EDIP 1997 category, waste evaluation) of the products that appear in the waste stream as a result of facility upgrades. The scope of the study starts from retrofitting of the lamps and air-conditioners through recycling and disposal. For a 36 W fluorescent lamp, the bulk waste 1.64E-5 kg, hazardous waste 1.11E-4 kg, radioactive waste 1.09E-9 kg, and slag-ash 6.02E-7 kg occurred at the end of life of the retrofitting cycle. For a 12,000 Btu air-conditioner, the bulk waste 0.58 kg, hazardous waste 0.11 kg, radioactive waste 0.0002 kg, and slag-ash 0.01 kg also occurred at the end of life of the retrofitting cycle. These small amounts become important when viewed at the country level. These quantities imply that the policy makers who deal with hazardous waste should be aware of this waste-generating characteristic before issuing any pertinent policy. Consideration of this characteristic and planning for appropriate waste management methods at the beginning stage will reduce any future problem of contamination by the hazardous waste.Life cycle Hazardous waste Energy conservation

Spatial and Temporal Variation of NDVI in Response to Climate Change and the Implication for Carbon Dynamics in Nepal

Nepal is a country of contrast, with varying altitude, climate and vegetation from the top of high mountains to the tropical forest in low lands. The terrestrial vegetation has rapidly been altered by climate change in Nepal. The spatial and temporal evolution of vegetation and its linkage to climatic variables were analyzed using the Normalized Difference Vegetation Index (NDVI) obtained from Advanced Very High Resolution Radiometer (AVHRR) sensors. A linear regression model and Sen’s slope method were used to estimate NDVI trends and the Pearson correlation between NDVI and climatic variable, i.e., temperature and precipitation were calculated to identify the role of climate in vegetation changes. The carbon dynamics were also measured using a biomass carbon density estimation model. Results showed that NDVI experienced an overall increasing trend in Nepal from 1982–2015. The NDVI significantly increased at the rate of 0.0008 year−1 (p < 0.05) with seasonal variation of 0.0004 year−1, p > 0.05; 0.0007 year−1, p < 0.05; 0.0008 year−1, p < 0.05 and 0.0007 year−1, p > 0.05 in winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. The NDVI relative change ratio (RCR) was 6.29% during last 34 years in Nepal. The correlation between NDVI and temperature was significantly positive (r = 0.36, p = 0.03), but there was a negative correlation with precipitation (r = −0.21, p = 0.28). Altogether, 82.20% of the study areas showed a positive correlation with temperature in which 34.97% was significant and 69.23% of the area had a negative correlation (16.35% significant, p < 0.05) with precipitation. In addition, NDVI-based carbon estimation showed that Nepal’s forest total carbon stock is 685.45 × 106 t C (i.e., an average of 115.392 t C/ha) with an annual carbon sequestration rate of 0.10 t C/ha from 1982–2015. The results suggest that NDVI variation is more sensitive to temperature than precipitation and it is valuable to measure carbon dynamics in Nepal

Comparative study of zinc oxide nanocomposites with different noble metals synthesized by biological method for photocatalytic disinfection of Escherichia coli present in hospital wastewater

Binary zinc oxide (ZnO) nanocomposites with different noble metals, silver (Ag) and ruthenium (Ru), were prepared from an aqueous leaf extract of Callistemon viminalis. The biosynthesized photocatalysts were characterized and examined for their photocatalytic disinfection against Escherichia coli isolated from hospital wastewater. The influence of the different noble metals showed a difference in physicochemical characteristics and photocatalytic efficiency between Ag–ZnO and Ru–ZnO. The photocatalytic degradation of methylene blue and photocatalytic disinfection were found to be in the order Ag–ZnO > Ru–ZnO > ZnO. The photocatalytic disinfection of Ag–ZnO reached a 75% reduction in 60 min, compared to 34 and 9% reductions of Ru–ZnO and ZnO, respectively. The kinetic reaction rate for the photocatalytic disinfection of Ag–ZnO was found to be 2.8 times higher than that of Ru–ZnO. The outstanding photocatalytic activity of Ag–ZnO over Ru–ZnO was attributed to higher crystallinity, greater UVA adsorption capacity, smaller particle size, and the additional antimicrobial effect of Ag itself. The C. viminalis-mediated Ag–ZnO nanocomposites can be a potential candidate for photocatalytic disinfection of drug-resistant E. coli in hospital wastewater. HIGHLIGHTS Biosynthesis and characterization of two zinc oxide-based nanocomposites with silver and ruthenium were presented.; Photocatalytic disinfection of Escherichia coli present in hospital wastewater was demonstrated.; The influence of different noble metals (silver and ruthenium) on the characteristics and photocatalytic efficiency were discussed.

Syngas production from rubberwood biomass in downdraft gasifier combined with wet scrubbing: investigation of tar and solid residue

Production of synthesis gas by gasification is still a challenge due to the tar in the synthesis gas (syngas). This tar needs to be eliminated by appropriate methods before using the syngas as a fuel. Moreover, the solid residue after gasification also needs to be properly managed or destroyed. Therefore, the aim of this study was to investigate tar and solid residue generated by gasification of rubberwood biomass, including rubberwood chips (RWC), rubberwood pellets (RWP), rubberwood unburned char (UBC), and their blends, in a downdraft gasifier. Waste vegetable oil (WVO) and water were used as scrubbing media. Properties of the biomass samples were characterized by proximate and ultimate analysis, as well as for the higher heating value. The downdraft gasifier was operated at 850 °C and equivalence ratio (ER) of 0.25. The concentrations of tar in syngas both before and after passing through the wet scrubber were determined. Chemical compounds in the tar were analysed by GC-MS. The solid residue remaining after gasification was separated into biochar and ash. The biochar was characterized by CHNS/O analyser, FTIR, SEM, and for the iodine number. The compounds in ash were determined by XRF. The results show that biomass type and scrubbing media affected the tar removal efficiency. Scrubbing syngas with WVO had better tar removal efficiency than scrubbing with water. The highest tar removal efficiency with WVO was 82.16%. The tar sample consisted of complex compounds as indicated by GC-MS, and these compounds depended on type of biomass feedstock. The solid residue obtained after gasification process contained biochar (unburned carbon) and ash. Some biochars can be used as solid fuels, depending on carbon content and energy content. The biochar also had a highly porous structure based on SEM imaging, and a high iodine number (930-1134 mg/g). The biochar contained the functional groups OH, C-O, and C-H, as indicated by FTIR. CaO, K2 O, SiO2 , and MgO were the major components in ash. The spent WVO, biochar, and ash need to be properly managed or utilized for sustainable gasification operations, and these results support that pursuit

Characteristics of Carbon from Chitin-coated LiFePO4 and its Performance for Lithium Ion Battery

A LiFePO4 battery is the best device for energy storage. Batteries are currently being developed for higher capacity using novel materials. Carbon is one material that can be used to improve the properties of LiFePO4 batteries. The chitin produced from shrimp shell is a viable material that can be transformed into organic carbon. The chitin is revealed to be an element of 36.6 wt% carbon (C). Carbon is formed of small crystallites comprising electrode composite with a uniform carbon coating that can improve the electrochemical activation for LiFePO4/C composites. When the electrochemical reaction was operated at 1.2 V, the flow rate was increased 80%. The average charge-discharge capacities were 100 and -100 mAh/g, respectively, while the average energy density over a period of 20 cycles was 336 Wh/kg (maximum ~350 Wh/kg). Therefore, organic carbon can be used to remarkably improve the properties of LiFePO4 batteries with low-cost materials