• Energy Research
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A biodiesel wastewater treatment technology was investigated for neutral alkalinity and COD removal by microbial fuel cell. An upflow bio-filter circuit (UBFC), a kind of biocatalyst MFC was renovated and reinvented. The developed system was combined with a pre-fermented (PF) and an influent adjusted (IA) procedure. The optimal conditions were operated with an organic loading rate (OLR) of 30.0 g COD/L-day, hydraulic retention time (HRT) of 1.04 day, maintained at pH level 6.5-7.5 and aerated at 2.0 L/min. An external resistance of circuit was set at 10 kΩ. The purposed process could improve the quality of the raw wastewater and obtained high efficiency of COD removal of 15.0 g COD/L-day. Moreover, the cost of UBFC system was only US$1775.7/m3 and the total power consumption was 0.152 kW/kg treated COD. The overall advantages of this invention are suitable for biodiesel wastewater treatment.

Ethanol is an attractive alternative fuel because it is a renewable bio-based resource and it is oxygenated, thereby providing the potential to reduce particulate emissions in compression-ignition engines. In this review the properties and specifications of ethanol blended with diesel fuel are discussed. Special emphasis is placed on the factors critical to the potential commercial use of these blends. These factors include blend properties such as stability, viscosity and lubricity, safety and materials compatibility. The effect of the fuel on engine performance, durability and emissions is also considered. The formulation of additives to correct certain key properties and maintain blend stability is suggested as a critical factor in ensuring fuel compatibility with engines. However, maintaining vehicle safety with these blends may entail fuel tank modifications. Further work is required in specifying acceptable fuel characteristics, confirming the long-term effects on engine durability, and ensuring safety in handling and storing ethanol-diesel blends.

Microalgae are considered to be a potential alternative to terrestrial crops for bio-energy production due to their relatively high productivity per unit area of land. In this work we examined the amount of dissolved organic matter exuded by algal cells cultured in photobioreactors, to examine whether a significant fraction of the photoassimilated biomass could potentially be lost from the harvestable biomass. We found that the mean maximum amount of dissolved organic carbon (DOC) released measured 6.4% and 17.3% of the total organic carbon in cultures of Chlorellavulgaris and Dunaliella tertiolecta, respectively. This DOM in turn supported a significant growth of bacterial biomass, representing a further loss of the algal assimilated carbon. The release of these levels of DOC indicates that a significant fraction of the photosynthetically fixed organic matter could be lost into the surrounding water, suggesting that the actual biomass yield per hectare for industrial purposes could be somewhat less than expected. A simple and inexpensive optical technique, based on chromophoric dissolved organic matter (CDOM) measurements, to monitor such losses in commercial PBRs is discussed.

Increasing energy demand and depleting fossil fuel sources have intensified the focus on biofuel production. Microalgae have emerged as a desirable source for biofuel production because of high biomass and lipid production from waste water source. In this study, five microalgae were isolated from effluents of Nisargruna biogas plants. These isolates were identified based on morphology and partial 18S and 23S rRNA gene sequences. Growth and lipid accumulation potential of these microalgae were investigated. One isolate, Chlorella sp. KMN3, accumulated high biomass (1.59 ± 0.05 g L(-1)) with moderate lipid content (20%), while another isolate Monoraphidium sp. KMN5 showed moderate biomass accumulation of 0.65 ± 0.05 g L(-1) with a very high (35%) lipid content. The fatty acid methyl esters mainly composed of C-16:0, C-18:0, C-18:1 and C-18:2. This observation makes these microalgae immensely potential candidate for biodiesel production using the effluent of a biogas plant as feed stock.

This article presents the application of microwave-induced pyrolysis to total recovery of resources and energy from rice straw. The microwave power and particle size of feedstock were both key parameters affecting the performance of microwave-induced pyrolysis. Under 400-500W microwave power, the reduction of fixed carbon in the biomass was significant. From the experimental results of specific surface area, zeta potential, and Cu2+ adsorption, the applications of solid residues in the water and wastewater treatment could be expected. The major compositions in gaseous product were H2, CO2, CO, CH4 of 55, 17, 13, 10vol.%, respectively. The high H2 content might imply that microwave-induced pyrolysis of biomass waste has the potential to produce the H2-rich fuel gas. Alkanes, polars, and low-ringed polycyclic aromatic hydrocarbons were three primary kinds of compounds in the liquid product.

The relationship between anode microbial characteristics and electrochemical parameters in microbial fuel cells (MFCs) was analyzed by time-course sampling of parallel single-bottle MFCs operated under identical conditions. While voltage stabilized within 4days, anode biofilms continued growing during the six-week operation. Viable cell density increased asymptotically, but membrane-compromised cells accumulated steadily from only 9% of total cells on day 3 to 52% at 6weeks. Electrochemical performance followed the viable cell trend, with a positive correlation for power density and an inverse correlation for anode charge transfer resistance. The biofilm architecture shifted from rod-shaped, dispersed cells to more filamentous structures, with the continuous detection of Geobacter sulfurreducens-like 16S rRNA fragments throughout operation and the emergence of a community member related to a known phenazine-producing Pseudomonas species. A drop in cathode open circuit potential between weeks two and three suggested that uncontrolled biofilm growth on the cathode deleteriously affects system performance.

The effect of trace elements (TEs) addition and NaOH pretreatment on the anaerobic digestion of rice straw was investigated in batch tests. Co, Ni and Se were added to the raw rice straw at different dosages. The NaOH pretreatment was applied to the rice straw both alone and in combination with the addition of TEs, in order to evaluate potential synergistic effects of the pretreatment and the TEs supplementation on the biogas production yields. The results obtained showed that the alkaline pretreatment was more effective than the TEs addition in increasing the cumulative biogas production, causing a 21.4% enhancement of the final biomethane yield, whereas the increase due to TEs dosing was not statistically significant. The analysis of volatile fatty acids (VFAs) confirmed that the NaOH pretreatment resulted in a higher production of VFAs, indicating an increased hydrolysis, while TEs addition did not cause significant changes in the VFA concentrations.

As one of the most abundant biomass resources, crop stalks are great potential feedstock available for anaerobic digestion (AD) to produce biogas. However, the specific physical properties and complex chemical structures of crop stalks form strong barriers to efficient AD bioconversion. To overcome these problems, many efforts have been made over the past few years. This paper reviewed recent research in the evolving field of anaerobic bioconversion of crop stalks and was focused on three critical aspects affecting AD performance: various pretreatment methods and their effects on the improvement of crop stalk biodegradability, determination of specific AD operation parameters for crop stalks, and development of AD technologies. Finally, recommendations on the future development of crop stalk AD were proposed.