• Energy Research

Information on vermicomposting with Metaphire posthuma is scanty. This paper, therefore, aims to evaluate the bioconversion efficiency of this species against Eiseniafetida. For comparative analysis, different combinations of municipal solid waste (MSW) and cow dung were used as substrates. The contents of total N and availability of P, K, and Fe increased significantly in both Metaphire and Eisenia systems which was accompanied by substantial reduction in pH and total organic C. Both species exhibited similar levels of urease activity and microbial respiration. Moreover, bioavailability of heavy metals (Pb, Zn, Mn, and Cu) was reduced substantially during vermicomposting, irrespective of the earthworm species. In contrast, each species was distinguished by the enhancement either in microbial biomass C and phosphatase activity (Eisenia) or in humification and fulvic/humic acid C (Metaphire). The overall results suggest that indigenous earthworm, M.posthuma could be utilized as a successful candidate for bioprocessing of toxic wastes.

We present evidence on the short-term differences in airborne pollution levels in terms of weekday/weekend (WD/WN) and weekday/Sunday (WD/Sun) intervals. To this end, we analyzed the hourly data of important pollutants (nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3) and carbon monoxide (CO)) using the data acquired in the Yong-San district of Seoul, Korea from 2009 to 2013. For each week, the pollutant ratio (Rw) was estimated through either WD/WN or WD/Sun. Here, a week is defined as Sunday through Saturday, WD as Monday through Friday and WN as Sunday and Saturday. The WD/Sun Rw geometric means (and range) were 2.02 (0.27–15.5) for NO, 1.29 (0.49–5.7) for NO2 and 0.89 (0.17–7.2) for O3 while the fraction of Rw (WD/Sun) > 1 were 81, 71 and 38%, respectively. NO and CO levels were much higher in October through March (during Autumn and Winter) than April through September (during Spring and Summer), reflecting the potential effect of fuel consumption (e.g., in terms of use patterns of nationwide city natural gas). Thus, we provide a broader interpretation on the occurrence patterns of the major pollutants (e.g., NO, NO2, O3 and CO) in relation to temporal changes in man-made activities.

This work mechanistically investigated the influence of CO2 in the thermo-chemical process of microalgal biomass (Chlorella vulgaris and Microcystis aeruginosa) to achieve a fast virtuous cycle of carbon via recovering energy. This work experimentally justified that the influence of CO2 in pyrolysis of microalgal biomass could be initiated at temperatures higher than 530 °C, which directly led to the enhanced generation of syngas. For example, the concentration of CO from pyrolysis of M. aeruginosa increased up to ∼ 3000% at 670 °C in the presence of CO2. The identified universal influence of CO2 could be summarized by the expedited thermal cracking of VOCs evolved from microalgal biomass and by the unknown reaction between VOCs and CO2. This identified effectiveness of CO2 was different from the Boudouard reaction, which was independently occurred with dehydrogenation. Thus, microalgal biomass could be a candidate for the thermo-chemical process (pyrolysis and gasification).

This study experimentally evidenced that bovine fat could be directly converted into fatty acid methyl esters (FAMEs) without lipid extraction step via thermally assisted in-situ transesterification on a porous material such as SiO2 since providing thermal energy from an external heating source drove pseudocatalytic mechanisms caused by mobility difference between lipid in bovine fat and acyl acceptor. In particular, this study employed dimethyl carbonate (DMC) as an acyl acceptor due to its nontoxicity and economic viability. In order to validate thermal assisted in-situ transesterification, thermal degradation of bovine fat was characterized, which revealed that thermal behavior of lipid in bovine fat was nearly identical to refined lipid. The results also evidenced that bovine fat contains 12.51 wt % impurities. Fatty acid profiles were identical under different transesterification conditions, which provide evidence that the thermal assisted in-situ transesterification should be technically feasible. I...

In this research, efforts were put to demonstrate synergistic interactions between bioenergy generation and wastewater treatment. The extent of such synergistic effect was assessed against wastewater effluents released from the beverage industry through the operation of a membrane-less truncated conical (TC) microbial fuel cell (MFC). A graphite-based reactor was operated for five cycles in batch mode using beverage industry wastewater as an organic substrate. Maximum bioelectricity produced on the fifth operating cycle corresponded to a voltage of 338 mV and a power of 1.14 mW at 100 Ω. The MFC recorded a higher substrate degradation rate (0.84 kg of chemical oxygen demand [COD]/m3-day) accompanied by the development of an electroactive biofilm and polarization behavior (e.g., a reduction in internal resistance from 323 Ω to 197 Ω over five operation cycles). Cyclic voltammetry showed a maximum performance of the biofilm during the fifth cycle (through its enrichment) as interpreted by oxidation and reduction currents of 2.48 and -2.21 mA, respectively. The performance of the proposed MFC was superior to other designs reported previously in both effluent treatment and bioenergy generation. A maximum treatment efficiency of 84.4% (in 385 h) was seen at an organic load (COD) of 3500 mg/L with the specific power yield (0.504 W/Kg of substrate (COD) removal) and volumetric power yield (15.03 W/m3). Our experimental studies support that the proposed system could be upscaled to realize the commercial operation.

In recent decades, the accelerating economic and social developments have led to exponentially increasing emissions of carbon dioxide (CO2) into the atmosphere. As a result, much research efforts have been directed toward more effective measures for the carbon capture and storage (CCS). In this review, we first briefly described the general background on the various techniques available for the abatement of CO2 emissions worldwide. Then, we provided an in-depth discussion regarding the two comparable control technologies, i.e., the amine- vs. ammonia-based capture approaches; ammonia has lower energy costs than monoethanolamine (MEA). The applicability of each method was described further with an emphasis on their advantages and disadvantages. We also briefly discussed the available options for post-absorption processing such as recovery of absorbed CO2, compression, and storage. Many immobilized amines as adsorbents can only be regenerated a few times or are a ‘once-through process’. This may deplete the global supply of those materials if CCS is scaled up in excess of Mton CO2 captured per year. Ideally, the captured CO2 should be isolated from the atmosphere indefinitely and/or photochemically reduced (either biologically or industrially). Finally, we explored future challenges in this field of study to envision and suggest more optimized solutions.

In this study, wind conditions and its energy potential have been assessed by conducting a Weibull analysis of the wind speed data (over the period of 2002-2011) measured from a port city (Mongla) and an isolated island (Sandwip) in Bangladesh. The monthly mean wind speed at Mongla ranged from 1.60 m/s (December) to 2.47 m/s (April). The monthly values of Weibull shape parameter (k) were from 1.27 to 2.53. In addition, the values of the scale parameter (c) and the monthly wind power density ranged from 1.76 to 2.79 m/s and 3.95 to 17.45 W/m2, respectively. The seasonal mean wind speed data varied from 1.72 (fall) to 2.29 m/s (spring) with the wind power density from 5.33 (fall) to 14.26 W/m2 (spring). In the case of Sandwip, the results were comparable to those of Mongla, but moderate reductions in all the comparable variables were observed. The wind data results of these two areas have been compared with those of eight other locations in the world with respect to wind power generation scale. According to this comparison, the wind power generation scale for Mongla and Sandwip was adequate for stand-alone small/micro-scale applications such as local household consumption, solar-wind hybrid irrigation pumps, and battery charging.

This work confirmed that dominant microalgal strain in the eutrophic site (the Han River in Korea) was Microcystis aeruginosa (M. aeruginosa) secreting toxins. Collected and dried microalgal biomass had an offensive odor due to microalgal lipid, of which the content reached up to 2±0.2wt.% of microalgal biomass (dry basis). This study has validated that the offensive odor is attributed to the C3-6 range of volatile fatty acids (VFAs), which was experimentally identified by the non-catalytic transformation of triglycerides (TGs) and free fatty acids (FFAs) in microalgal biomass into fatty acid methyl esters (FAMEs). In particular, this study mechanistically investigated the influence of CO2 in the thermal destruction (i.e., pyrolysis) of hazardous microalgal biomass in order to achieve dual purposes (i.e., thermal disposal of hazardous microalgal biomass and energy recovery). The influence of CO2 in pyrolysis of microalgal biomass was identified as 1) the enhanced thermal cracking behaviors of volatile organic compounds (VOCs) from the thermal degradation of microalgal biomass and 2) the direct gas phase reaction between CO2 and VOCs. These identified influences of CO2 in pyrolysis of microalgal biomass significantly enhanced the generation of CO: the enhanced generation of CO in the presence of CO2 was 590% at 660°C, 1260% at 690°C, and 3200% at 720°C. In addition, two identified influences of CO2 (i.e., enhanced thermal cracking and direct gas phase reaction) occurred simultaneously and independently. The identified gas phase reaction in the presence of CO2 was only initiated at temperatures higher than 500°C, which was different from the Boudouard reaction. Lastly, the experimental work justified that exploiting CO2 as a reaction medium and/or chemical feedstock will provide new technical approaches for controlling syngas ratio and in-situ air pollutant control without using catalysts.