• Energy Research
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• 12. Responsible consumption close
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Background and Objective: In recent years, management and disposal of municipal solid waste has become a global problem and the most important environmental concern. Anaerobic digestion is a cost-effective solution for treatment of both solid waste and wastewater. The aim of this study was to investigate the positive or negative effects of calcium chloride content in anaerobic digestion process of municipal solid waste and leachate on biogas production. Materials and Methods: Experiments with 8 levels of calcium chloride on co-digestion of municipal solid waste and leachate were investigated in 500 ml digesters under mesophilic conditions in a completely randomized design with three replications. Reactors with a ratio of substrate to inoculum of 2 (on VS basis) were operated and the volume of the biogas was measured daily. Volatile and total solids, carbon/nitrogen of waste, COD, BOD and heavy metals were measured by following APHA. Results: The results of the experiment showed that the pH was decreased with increasing calcium chloride concentration. The highest amount of cumulative biogas production was obtained in CaCl2 of 2 g/L with the highest VS and TS reduction. Higher concentrations of CaCl2 (≥3 g/L) caused a reduction in the degradability of volatile and total solids and, as a result, a decreased performance of the digester. Conclusion: The results clearly confirmed that the addition of calcium chloride was an effective solution to improve biodegradability in co-digestion of the MSW and leachate and consequently to reduce the total and volatile solids and to increase the amount of‌ biogas.

Introduction: Identifying the effect of energy consumption, economic growth and foreign trade on CO2 emissions have been studied at both national and international levels. However, there have been very few researches on the effect of financial and banking development on the CO2 emissions, especially in Iran. So, this study aimed to cover this research gap. Methods: This study was a time-series analyses over the period of 1971-2011. In order to investigate about existence of a long-run co-integration relationship between CO2 emissions and banking development indicators in Iran, long-run coefficients were estimated by Autoregressive Distributed Lag (ARDL) and Dynamic Ordinary Least Squares (DOLS) approaches. Moreover, to carry out the econometric tests Microfit (5.0) and Eviews (9.0) software were used. Results: Findings showed that the ratio of domestic credit to private sector by banks to GDP (Banking Development Indicator) reduces CO2 emissions in Iran. In addition, results confirm with theories and other empirical studies showed that energy consumption has positive and significant effect on CO2 emissions in long-run. Conclusion: The government can help to improve environment quality by establishing a strong policy making on credit to firms by banking system. Because in this framework firms to receive credit from banking system are required codified programs to reduce negative outcomes of energy consumption and this lead to a less CO2 emissions in long-run.

Background and Objective: Solid waste management has always been one of the major challenges of large cities. Conversion of waste to energy in the form of biogas is known to be an appropriate solution. The aim of this study was to investigate the effect of total solids (TS) content and alkaline pretreatment on biogas production from municipal solid waste (MSW). Materials and Methods: Experiments were done in 1 L glass bottles at 37 °C with different TS contents (5, 10, and 15%), each in 3 replications based on a completely randomized design. Comparison of means was used for interpretations of the result. The volume of the produced biogas, the amount of methane, and changes in pH were measured on a daily basis. In order for better mixing, the digesters were manually shaken for 30 seconds every day. TS, volatile solids (VS), carbon and nitrogen of the feedstock were determined according to APHA standard methods. Results: The highest methane yield and VS reduction was observed in 5% TS. Therefore, this TS was chosen for alkaline pre-treatment. The results showed that pre-treatment with NaOH significantly improved biodegradability of MSW. In 25 days, the production of biogas was 30.38% higher than that of the untreated digester. The highest methane yield was 83.35 mL/g TS and 132 mL/g TS from the control and the pretreated digesters, respectively. Conclusion: The results of the lab experiments showed that the TS of 5 % and the alkaline pre-treatment, significantly improved biodegradability of MSW and consequently increased biogas and methane yield.