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PubMed2005

Determination of the energy potential of gases produced in the pyrolysis processes of the vegetal carbon manufacture industry.

In this work, a pyrolysis plant located in Valverde de Leganes, Badajoz (SW Spain) was studied. At present, only the solid phase obtained by pyrolysis finds an application as domestic fuel. In order to analyze the feasibility of a further energetic exploitation of the plant under study, the gases flowing through the chimneys were collected at different times throughout the pyrolysis process. Next, they were characterized and quantified by gas chromatography, the energy potential of each of the gases being determined. According to the results obtained in this study, a total energy potential of 5.6 x 10(7) MJ (i.e., 1.78 MW(t)) might be generated yearly. Hence, considering an overall process yield equal to 20%, up to 358 KW(e) would be produced. This power would supply enough electric energy to the industry, the remaining being added to the common electric network.

Bioelectric Energy Sources↗
PubMed2005

Fixed-bed catalytic pyrolysis of cotton-seed cake: effects of pyrolysis temperature, natural zeolite content and sweeping gas flow rate.

Catalyzed pyrolysis of cotton-seed cake was studied under different experimental conditions. Variables investigated were pyrolysis temperature, zeolite content and sweeping gas flow rate. Experiments were carried out isothermally. Liquids, gases and char were obtained as products of pyrolysis. The distributions of these products were determined for various contents (1, 5, 10, 20 wt.% of raw material) of zeolite at four different pyrolysis temperatures. The maximum liquid yield obtained was 30.84% at a pyrolysis temperature of 550 degrees C with a sweeping gas flow rate of 100 cm(3) min(-1) in the presence of clinoptilolite (20% based on raw material) as catalyst. The pyrolytic and catalytic liquid products were analysed in detail to determine the predominant chemical classes and the identities of the major compounds present.

Bioelectric Energy Sources↗
PubMed2006

Pyrolysis of triglyceride materials for the production of renewable fuels and chemicals.

Conversion of vegetable oils and animal fats composed predominantly of triglycerides using pyrolysis type reactions represents a promising option for the production of renewable fuels and chemicals. The purpose of this article was to collect and review literature on the thermo-chemical conversion of triglyceride based materials. The literature was divided and discussed as (1) direct thermal cracking and (2) combination of thermal and catalytic cracking. Typically, four main catalyst types are used including transition metal catalysts, molecular sieve type catalysts, activated alumina, and sodium carbonate. Reaction products are heavily dependant on the catalyst type and reaction conditions and can range from diesel like fractions to gasoline like fractions. Research in this area is not as advanced as bio-oil and bio-diesel research and there is opportunity for further study in the areas of reaction optimization, detailed characterization of products and properties, and scale-up.

Bioelectric Energy Sources↗
PubMed2005

Versatile bioelectronic interfaces based on heterotrifunctional linking molecules.

Bioelectronic interfaces that allow dehydrogenase enzymes to communicate with electrodes have potential applications such as biosensors and biocatalytic reactors. A major challenge in creation of such bioelectronic interfaces is to orient the enzyme, its cofactor, and an electron mediator properly with respect to the electrode in order to achieve efficient, multistep electron transfer. This paper describes a versatile, new method that uses cysteine, an inexpensive, branched amino acid having sulfhydryl, amino, and carboxyl functional groups, to achieve such orientation. This approach provides greater flexibility in assembling complex bioelectronic interfaces than previously reported approaches that bind the enzyme, cofactor, and mediator in a linear chain. Cysteine was attached to a gold electrode through the sulfhydryl groups, to the electron mediator toluidine blue O (TBO) through the carboxyl group, and to the cofactor (e.g., NAD(P)+) through the amino group. Cyclic voltammetry, impedance spectroscopy, chronoamperometry and quartz crystal microbalance gravimetry were used to demonstrate the sequential assembly steps and the electrical activity of the resulting bioelectronic interface.

Alcohol Dehydrogenase↗
PubMed2006

Biomembranes for fuel cell electrolytes employing anhydrous proton conducting uracil composites.

The controls of proton transfer through membranes involve fundamental properties of chemical energy conversion in industrial devices as well as living systems. In particular, ion-exchange membranes are generally used as superior proton conductors for polymer electrolyte fuel cells (PEFC) due to the fluidic nature of water, although the cell operation above the boiling point (>100 degrees C) has been considered to provide a higher efficiency and an easier humidity management. We show that biomembranes consisting of uracil and chitin phosphate have large anhydrous proton conductivities over a wide temperature range from room temperature to 160 degrees C with sufficient thermal stabilities. Water-free conductivities exceeding 10(-3) S cm(-1) have been obtained in the elastic polymeric material, and the fuel cell employing the biomembrane as an electrolyte exhibited a stable current generation under non-humidified H2/O2 conditions at 160 degrees C.

Bioelectric Energy Sources↗
PubMed2006

Biofuel cells and their development.

This review considers the literature published since 1994 on microbial and enzymatic biofuel cells. Types of biofuel cell are classified according to the nature of the electrode reaction and the nature of the biochemical reactions. The performance of fuel cells is critically reviewed and a variety of possible applications is considered. The current direction of development of biofuel cells is carefully analysed. While considerable chemical development of enzyme electrodes has occurred, relatively little progress has been made towards the engineering development biofuel cells. The limit of performance of biofuel cells is highlighted and suggestions for future research directions are provided.

Bacteria↗
PubMed2006

Direct methanol biocatalytic fuel cell--considerations of restraints on electron transfer.

In this paper structure and operational principles of a novel type direct methanol biocatalytic fuel cell (DMBFC) system is introduced. In addition observed restraints in the energy generation are discussed. The operational principle of the biofuel cell is enzymatic breakdown of methanol by methanol dehydrogenase (MDH) from Methylobacterium extorquens at the anode. The terminal electron acceptor at the cathode is potassium permanganate. Performance characteristics of the system are the following: open circuit voltage 1.4 V, power density 0.25 mW/cm2 and current density 0.38 mA/cm2 at the operating voltage of 0.67 V, and a continuous operation time of 2 weeks. A biofuel cell usually requires an electrochemically active reagent, a mediator, to ensure effective transfer of the electrons from the activity centre of the enzyme to the electrode. Inactivation of the mediator was found to restrict the electron transfer. Moreover, the rate of inactivation was found to increase in fuel cell conditions. The half-life of TMPD was observed to be maximum 5 days compared to 10 days in normal conditions. Experiments showed that addition of 0.2% w/w of aluminium dioxide into the anodic graphite paste stabilized the mediator.

Alcohol Oxidoreductases↗
PubMed2006

Microfluidic biofuel cells: the influence of electrode diffusion layer on performance.

Microfluidic biofuel cells exploit the lack of convective mixing at low Reynolds number to eliminate the need for a physical membrane to separate fuel from oxidant. This paper demonstrates how the length and spacing of electrodes within a microchannel, and thus thickness of the diffusion layer, affects the performance of a microfluidic biofuel cell. It was found that splitting a single electrode into two (or more) smaller electrodes and separating them by a distance equal to three times their length prevents the continuous increase in thickness of a diffusion layer. This change results in a 25% increase in maximum power density compared to a single electrode device with identical electroactive area. Furthermore, we found that the maximum current density of a microfluidic biofuel cell operated with different electrode configurations (i.e., length of cathode) closely matches that predicted by theory.

Bioelectric Energy Sources↗
PubMed2006

Biofuel cells--recent advances and applications.

In 2006, the journal Biosensors and Bioelectronics published a special issue devoted exclusively to biofuel cells, including several research papers and an extensive review of the field [Bullen, R.A., Arnot, T.C., Lakeman, J.B., Walsh, F.C., 2006. Biosens. Bioelectron.]. Within this review a brief description will firstly be given of the history of biofuel cells together with coverage of some of the major historical advances. The review is intended, however, to largely concentrate on and give an overview of the advances made in recent years in this area together with a discussion surrounding the practical application of biofuel cells. There are several classes of biofuel cells: we shall firstly discuss the recent advances in biofuel cells that convert chemical fuels to produce electrical power by use of catalytic enzymes. This will be followed by a section on similar cells where micro-organisms rather than enzymes are used to convert the fuel to energy. Thirdly we shall consider hybrid biofuel cells that combine the utilisation of photochemical chemistries and biological systems for the generation of electricity. Finally we will discuss some of the proposed uses of biofuel cells together with a short consideration of future research possibilities and applications of these systems.

Bioelectric Energy Sources↗
PubMed2006

A biofilm enhanced miniature microbial fuel cell using Shewanella oneidensis DSP10 and oxygen reduction cathodes.

A miniature-microbial fuel cell (mini-MFC, chamber volume: 1.2 mL) was used to monitor biofilm development from a pure culture of Shewanella oneidensis DSP10 on graphite felt (GF) under minimal nutrient conditions. ESEM evidence of biofilm formation on GF is supported by substantial power density (per device cross-section) from the mini-MFC when using an acellular minimal media anolyte (1500 mW/m2). These experiments demonstrate that power density per volume for a biofilm flow reactor MFC should be calculated using the anode chamber volume alone (250W/m3), rather than with the full anolyte volume. Two oxygen reduction cathodes (uncoated GF or a Pt/vulcanized carbon coating on GF) were also compared to a cathode using uncoated GF and a 50mM ferricyanide catholyte solution. The Pt/C-GF (2-4% Pt by mass) electrodes with liquid cultures of DSP10 produced one order of magnitude larger power density (150W/m3) than bare graphite felt (12W/m3) in this design. These advances are some of the required modifications to enable the mini-MFC to be used in real-time, long-term environmental power generating situations.

Bioelectric Energy Sources↗
PubMed2006

Direct electron transfer with yeast cells and construction of a mediatorless microbial fuel cell.

The direct electron transfer exhibited by the yeast cells, Hansenula anomala has been demonstrated using the electrochemical technique cyclic voltammetry by immobilizing the microorganisms by two different methods viz., physical adsorption and covalent linkage. The analysis of redox enzymes present in the outer membrane of the microorganisms has been carried out in this work. This paper demonstrates that yeast cells with redox enzymes present in their outer membrane are capable of communicating directly with the electrode surface and contribute to current generation in a mediatorless biofuel cells. The efficiency of current generation has been evaluated using three anode materials.

Bioelectric Energy Sources↗
PubMed2006

Challenges in biocatalysis for enzyme-based biofuel cells.

Enzyme-based biofuel cells are attracting attention rapidly partially due to the promising advances reported recently. However, there are issues to be addressed before biofuel cells become competitive in practical applications. Two critical issues are short lifetime and poor power density, both of which are related to enzyme stability, electron transfer rate, and enzyme loading. Recent progress in nanobiocatalysis opens the possibility to improve in these aspects. Many nano-structured materials, such as mesoporous media, nanoparticles, nanofibers, and nanotubes, have been demonstrated as efficient hosts of enzyme immobilization. It is evident that, when nanostructure of conductive materials are used, the large surface area of these nanomaterials can increase the enzyme loading and facilitate reaction kinetics, and thus improving the power density of biofuel cells. In addition, research efforts have also been made to improve the activity and stability of immobilized enzymes by using nanostructures. It appears to be reasonable to us to expect that progress in nanostuctured biocatalysts will play a critical role in overcoming the major obstacles in the development of powerful biofuel cells.

Bioelectric Energy Sources↗
PubMed2004

Biotechnological applications of hydrogenases.

Hydrogenases have found use in a variety of biotechnological applications, including biohydrogen production, wastewater treatment, the prevention of microbial-induced corrosion and the generation and regeneration of NADP cofactors. In the future, advances in genome mining and screening techniques are likely to identify new hydrogenases for novel applications.

Bacteria↗
PubMed2006

Microbial fuel cells: novel microbial physiologies and engineering approaches.

The possibility of generating electricity with microbial fuel cells has been recognized for some time, but practical applications have been slow to develop. The recent development of a microbial fuel cell that can harvest electricity from the organic matter stored in marine sediments has demonstrated the feasibility of producing useful amounts of electricity in remote environments. Further study of these systems has led to the discovery of microorganisms that conserve energy to support their growth by completely oxidizing organic compounds to carbon dioxide with direct electron transfer to electrodes. This suggests that self-sustaining microbial fuel cells that can effectively convert a diverse range of waste organic matter or renewable biomass to electricity are feasible. Significant progress has recently been made to increase the power output of systems designed to convert organic wastes to electricity, but substantial additional optimization will be required for large-scale electricity production.

Bacterial Physiological Phenomena↗
PubMed2004

Analysis of microbial diversity in oligotrophic microbial fuel cells using 16S rDNA sequences.

Molecular ecological techniques were applied to analyze the bacterial diversity of two oligotrophic microbial fuel cells (MFCs) enriched using river water or artificial wastewater (AWW) as fuel. Denaturing gradient gel electrophoresis (DGGE) of the PCR amplified 16S rDNA showed that different microbial communities were present in the two MFCs and these were different from the river sediment used to initiate the enrichment. Nearly complete 16S rDNA was amplified and sequenced. Over 80% of the clones were Proteobacteria. Betaproteobacteria were the dominant clones (46.2%) in MFCs fed with river water, and about 64.4% of the clones in MFCs fed with AWW were Alphaproteobacteria. Actinobacteria were found only in the MFC fed with AWW, and Deltaproteobacteria, Acidobacteria, Chloroflexi and Verrucomicrobia in the MFC fed with river water. Many clones were related to uncultured bacteria, some with homology less than 95%, indicating that many novel bacteria were enriched in the oligotrophic MFCs.

Actinobacteria↗
PubMed2004

Spatial assessment of the economic feasibility of short rotation coppice on radioactively contaminated land in Belarus, Ukraine, and Russia. II. Monte Carlo analysis.

A Monte Carlo analysis of two sequential GIS-embedded submodels, which evaluate the economic feasibility of short rotation coppice (SRC) production and energy conversion in areas contaminated by Chernobyl-derived (137)Cs, was performed to allow for variability of environmental conditions that was not contained in the spatial model inputs. The results from this analysis were compared to the results from the deterministic model presented in part I of this paper. It was concluded that, although the variability in the model results due to within-gridcell variability of the model inputs was considerable, the prediction of the areas where SRC and energy conversion is potentially profitable was robust. If the additional variability in the model input that is not contained in the input maps is also taken into account, the SRC production and energy conversion appears to be potentially profitable at more locations for both the small scale and large scale production scenarios than the model predicted using the deterministic model.

Bioelectric Energy Sources↗
PubMed2004

Spatial assessment of the economic feasibility of short rotation coppice on radioactively contaminated land in Belarus, Ukraine, and Russia. I. Model description and scenario analysis.

The economic feasibility of short rotation coppice (SRC) production and energy conversion in areas contaminated by Chernobyl-derived (137)Cs was evaluated taking the spatial variability of environmental conditions into account. Two sequential GIS-embedded submodels were developed for a spatial assessment, which allow for spatial variation in soil contamination, soil type, and land use. These models were applied for four SRC production and four energy conversion scenarios for the entire contaminated area of Ukraine, Belarus, and Russia and for a part of the Bragin district, Belarus. It was concluded that in general medium-scale SRC production using local machines is most profitable. The areas near Chernobyl are not suitable for SRC production since the contamination levels in SRC wood exceed the intervention limit. Large scale SRC production is not profitable in areas where dry and sandy soils predominate. If the soil contamination does not exceed the intervention limit and sufficient SRC wood is available, all energy conversion scenarios are profitable.

Bioelectric Energy Sources↗
PubMed2005

Nongovernmental valorization of carbon dioxide.

Carbon dioxide (CO2) is considered the largest contributor to the greenhouse gas effect. Most attempts to manage the flow of CO2 or carbon into our environment involve reducing net emissions or sequestering the gas into long-lived sinks. Using CO2 as a chemical feedstock has a long history, but using it on scales that might impact the net emissions of CO2 into the atmosphere has not generally been considered seriously. There is also a growing interest in employing our natural biomes of carbon such as trees, vegetation, and soils as storage media. Some amelioration of the net carbon emissions into the atmosphere could be achieved by concomitant large withdrawals of carbon. This report surveys the potential and limitations in employing carbon as a resource for organic chemicals, fuels, inorganic materials, and in using the biome to manage carbon. The outlook for each of these opportunities is also described.

Bioelectric Energy Sources↗