Electro-dissolution of metal scrap anodes for nickel ion removal from metal finishing effluent

This contribution reports a novel and cost efficient strategy for nickel ion removal from metal finishing effluents by electro-dissolution of scrap aluminium and iron sacrificial anodes. Electro-coagulation of effluent was carried out at 30 mA/cm² current density for 60 min. The nickel ion concentration of electroplating effluent was analysed by Atomic Absorption Spectroscopy. SEM images of iron and aluminium scrap anodes were critically analysed. Parameters such as heavy metal removal, anode dissolution rate with respect to heavy metal removal, reaction kinetics and cost estimation have been elaborately studied. Electro-coagulation at 30 mA/cm² for 60 min using iron and aluminium scrap anodes resulted in 95.9 and 94.1 % nickel ion reduction, respectively, with 0.0094 and 0.0053 g/ppm dissolution rates. The energy consumption for scrap aluminium and iron anodes was 0.0547 kWh/L. Loose internal bonding and spongy surface morphology of used metal scrap render high porosity and active surface area, enhancing reaction rate. Low cost and ready availability of waste scrap makes the process of electro-coagulation economically viable. Thus, the findings from this contribution point decisively at the superiority of waste metal scrap-based anodes for economic and environmentally sustainable heavy metal ion removal from metal finishing effluent.     

Preparation of biochar catalyst with saccharide and lignocellulose residues of corncob degradation for corncob hydrolysis into furfural

This paper presented a novel process for production of furfural by hydrothermal degradation of corncob over biochar catalyst, in which it was prepared with the recycling degradation solution and lignocellulosic solid residues. The biochar catalyst was papered by lignocellulose residues and concentrated saccharide solution, and then impregnated in 0.5 mol/L sulphuric acid at room temperature for 24 h assisted by the ultrasonic vibration. In the system of recycling, 8.8 % lignocellulose residues and 100 % concentrated saccharide solution from corncob hydrolysis have been recycled. Hydrolysis of corncob was carried out at 180 °C for duration of 170 min over the biochar catalyst. The experimental results have shown that the furfural yield of up to 37.75 % and overall corncob conversion rate of 62.00 % could be achieved under optimum operating conditions for the catalysts preparation and the corncob hydrolysis. It is believed that the acid density of 4.27 mmol/g of biochar catalyst makes the SO₃H groups cleave β-1,4 glycosidic linkages effectively and hydrolyze the cellulose and hemicellulose to water-soluble sugars, as well as to facilitate dehydration of xylose to give the product of furfural.     

Mercury flows in a zinc smelting facility in South Korea

To prepare for the international mercury convention, the characteristics of mercury emissions from a zinc smelting facility in South Korea have been reviewed and a material flow analysis (MFA) has been conducted in this research. As inputs into the mercury MFA study, zinc ores and sulfuric acid were examined, whereas wastewater sludge, effluence water, spent catalyst, and emissions from the casting and roasting processes were examined as outputs. Mercury concentrations extracted from end products like zinc ingots, cadmium ingots, and sulfuric acid were then analyzed. Our results showed that the wastewater sludge discharged from the zinc smelting process had a relatively higher concentration of mercury, indicating that the concentration of mercury was further enriched in the wastewater sludge. The wastes discharged through the zinc smelting process should be thoroughly controlled, as results of the MFA showed that approximately 89 % of the mercury contained in the original input was later found in the waste. According to this study, the higher the concentration of mercury within zinc ores at the input stage, the higher is the mercury concentration found in the wastewater sludge at the output stage.     

Life-cycle greenhouse gas emissions and economic analysis of alternative treatments of solid waste from city markets in Vietnam

We utilize life cycle assessment to trace conversion of degradable organic carbon (DOC) contained in organic waste from city markets in Da Nang, Vietnam. Our methodology makes explicit the process of conversion of DOC under aerobic and anaerobic conditions, as well as the balance of nutrients. Greenhouse gas emissions were calculated for six alternative scenarios: (i) anaerobic landfilling (current situation); (ii) semi-aerobic landfilling; (iii) landfill gas capture; (iv) composting; (v) pre-composting before landfill; and (vi) biogas production. We calculate that 1 t of waste in anaerobic landfilling emits 1.70 t CO₂-eq. with life-cycle perspective. Lowest emission occurs in biogas scenario with 0.26 t CO₂-eq./t. Composting occupies an intermediate position with 0.39 t CO₂-eq./t. Likewise, we estimate that cost of emission reduction in solid waste sector of Vietnam is 15.13 US$/t CO₂-eq., given by alternative of composting and taking anaerobic landfilling as reference. On the other hand, if social cost of carbon (SCC) is incorporated lowest cost to treat 1 t of waste is given by composting and semi-aerobic landfilling at discount rate of 5 %. However, using lower discount rates, and consequently higher values of SCC, composting and biogas production become the alternatives with lowest treatment costs.     

Municipal solid waste composition and food loss reduction in Kyoto City

For 35 years, Kyoto City has conducted detailed household waste composition surveys under the guidance of Kyoto University by dividing household waste into approximately 400 categories. In addition, the city has conducted detailed composition surveys of commercial waste generated by businesses. These surveys show that food loss accounts for approximately 40% of total waste, of which leftovers and untouched food account for about 40% in both households and business facilities. Consequently, the annual generation of household and commercial food loss is estimated at about 30,000 tons. Various efforts have been made to reduce waste, including food loss, but further reduction in environmental burden is needed. Thus, Kyoto City revised the ordinance for waste reduction, and in March 2015, formulated a new municipal waste management plan. The plan not only includes the 2Rs (reduce, reuse), but also, for the first time in Japan, sets quantitative targets for reducing food loss. Kyoto City must ensure that the necessary waste reduction measures are clearly explained to the residents and business operators. To ensure that this plan is successful, it is important to clarify concrete actions that residents and business operators should implement, along with their effects.     

Survey on readability of online information for upgrading understandability of biomass energy technology

Waste management contributes to renewable energy such as biodiesel production from processes of various types of biomass including vegetable oils, animal fats, and waste of edible oil. Successful waste management effort is influenced by people concern about benefit of waste management including for renewable energy from biomass. It involves their understanding initiated by literacy on biomass energy. To help increase literacy on waste recycle and biomass energy technology, we study readability of online information regarding biomass energy in Indonesian language (Bahasa Indonesia). Indonesia is considered as one of biomass-rich country with a little utilization for energy. The readability is studied by combining two approaches: measurement by readability standard and survey on readability confirming measurement by the standard. This study focuses on the confirmation survey readability standard measured on biomass online information in Indonesian language. In the survey, 19 online text materials were read by respondents and they were asked to give their impression whether the texts are easy or difficult to understand. From this study, what factors influence understandability of text information are shown. The results could be a guidance for preparing text information to raise people concern on waste recycle and renewable energy in general.     

Recycling of biodiesel fuel wastewater for use as a liquid fertilizer for hydroponics

Wastewater is discharged during washing processes in the production of biodiesel fuel (BDF) using alkaline catalysts. It can be recycled as a liquid fertilizer for hydroponics by adding essential components for plant growth. The effects of the liquid fertilizer on plant growth were investigated. Liquid fertilizer containing a smaller amount of the BDF wastewater had a similar effect on plant growth as the standard nutrient solutions. This result reveals that BDF wastewater can be recycled for use as a liquid fertilizer for hydroponics. However, fertilizer with a larger amount of the BDF wastewater showed poor and varied plant growth due to the growth of microorganisms in the contaminated wastewater. Hence, when BDF wastewater becomes contaminated during storage, sterilization is necessary to recycle it as a liquid fertilizer. Moreover, contamination during storage should be avoided for successful recycling.     

Life cycle assessment of biodiesel fuel production from waste cooking oil in Okayama City

A life cycle assessment (LCA) is performed to make clear of the actual environment impacts from conversation of waste cooking oil (WCO) to biodiesel fuel (BDF) in Okayama. A scenario analysis is carried out based on different participation rate of residents who separate WCO from general waste, corresponding to different BDF utilisation rate in transportation system. Sub scenarios complying with different gas emission standards regarding vehicles are designed as well. Afterwards, life cycle impact assessment is conducted to focus on global warming, acidification, and urban air pollution. Overall improvement of almost all kinds of life cycle inventories is significant when diesel is replaced with BDF, demonstrating that a shift from WCO-to-incineration to WCO-to-BDF is more beneficial. Under carbon neutral, compared to base scenario (S0), about 746.05 ton CO₂ emission will be reduced annually in the scenario with 100 % BDF utilisation in vehicles (S4). Meanwhile, total external cost in three environmental impacts (EI) sharply reduces by 51.90 %, showing much economic sustainability in S4. Moreover, the manufacturing cost for producing one litter WCO-to-BDF is 97.32 Yen. Sensitivity analysis shows that the gas emission standard regarding vehicles had much bigger effect on EI than BDF manufacturing process in this research.     

Spatial simulation and LCA evaluation on the plastic waste recycling system in Tianjin

With the rapid economic development in China, the amount of plastic waste (PW) generated has greatly increased and much of the waste is currently not treated. To reduce greenhouse gas (GHG) emissions from recycling of PW, we estimated the PW flow and considered methods to improve the household PW recycling system in Tianjin by adjusting processes during transportation and establishing a PW recycling factory in Zi’ya Industrial Park. The goal of the study was to identify reasonable improvements for the recycling system and clarify the environmental load. Geographic information system (GIS) technology was used to simulate transport processes for comparing GHG emissions from the transport processes between the present case and an improved case. Life cycle assessment (LCA) was used to compare GHG emissions between a projected scenario and a baseline scenario. Estimated GHG emissions during transport processes in the improved case were reduced by about 12,197 t CO₂ eq per year compared to the present case, equivalent to about 65.9 % of the total emissions in the present case. GHG emissions in the projected scenario were about 101,738 t CO₂ eq less per year than the baseline scenario, equivalent to about 75.5 % of the total emissions in the baseline scenario.     

Formation of persistent chlorinated aromatic compounds in simulated and real fly ash from iron ore sintering

Effects of carbon concentration and Cu additive in simulated fly ash (SFA) and real fly ash (RFA) on the formation of polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo-p-dioxins (PCDDs), chlorobenzenes, and polychlorinated biphenyls which were all regarded as persistent chlorinated aromatics in iron ore sintering were investigated. In the annealing process of SFA with various carbon contents, the yield of chlorinated aromatics and the I-TEQ obtained their maximum at 10 wt% carbon content. Active carbon in SFA acted as the carbon source as well as an adsorbent which led to higher production of PCDD/F in solid phase at 10 wt% carbon content. The increase of carbon content will be beneficial on the formation of 2,3,7,8-Chloro-substituted PCDF compared with 2,3,7,8-Chloro-substituted PCDD. In addition, the CuCl₂·2H₂O was a much more powerful catalyst in the formation of chlorinated aromatic compounds compared with elementary Cu, since it served as both a catalyst and a chlorine donor. However, the RFA behaved similarly with SFA with elementary Cu in the formation of chlorinated aromatic compounds. The effect of carbon content and copper additives on formation of 2,3,7,8-chloro-substituted congeners displayed similar characteristics with the tetra- to octa-PCDD/F isomers and even the total PCDD/Fs.