Abatement of greenhouse gas emitted from ruminants and promotion of biogas energy from animal effluent were comprehensively examined in each anaerobic fermentation reactor and animal experiments. Moreover, the energy conversion efficiency of biomass energy to power generation were evaluated with a gas engine generator or proton exchange membrane fuel cell (PEMFC). To mitigate safely rumen methanogenesis with nutritional manipulation the suppressing effects of some strains of lactic acid bacteria and yeast, bacteriocin, β1-4 galactooligosaccharide, plant extracts (Yucca schidigera and Quillaja saponarea), L-cysteine and/or nitrate on rumen methane emission were compared with antibiotics. For in vitro trials, cumulative methane production was evaluated using the continuous fermented gas qualification system inoculated with the strained rumen fluid from rumen fistulated Holstein cows. For in vivo, four sequential ventilated head cages equipped with a fully automated gas analyzing system were used to examine the manipulating effects of β1-4 galactooligosaccharide, lactic acid bacteria (Leuconostoc mesenteroides subsp. mesenteroides), yeast (Trichosporon serticeum), nisin and Yucca schidigera and/or nitrate on rumen methanogenesis. Furthermore, biogas energy recycled from animal effluent was evaluated with anaerobic bioreactors. Utilization of recycled energy as fuel for a co-generator and fuel cell was tested in the thermophilic biogas plant system. From the results of in vitro and in vivo trials, nitrate was shown to be a strong methane suppressor, although nitrate per se is hazardous. L-cysteine could remove this risk. β1-4 galactooligosaccharide, Candida kefyr, nisin, Yucca schidigera and Quillaja saponarea are thought to possibly control methanogenesis in the rumen. It is possible to simulate the available energy recycled through animal effluent from feed energy resources by making total energy balance sheets of the process from feed energy to recycled energy.
Controlled potential coulometry (CPC) has been developed as an effective analytical tool, in which no calibration is needed for the determination of electroactive species (1,2). Previously, the indirect determination of oxidizing agents, such as nitrite and hydrogen peroxide by controlled potential coulometry using ethylenediaminetetraacetato-ferrous complex or iodide ion as a mediator was carried out and proposed as a concentration step approach for CPC (3)(4)(5)(6). In this case, the determination time is more than 10 min and the slope of the log i vs t curve is about 0.01.In a conventional controlled potential coulometric cell, the working electrode is placed in the electrolytic solution, and the electroactive species have to transfer from the bulk solution to the two-dimensional electrode surface by diffusion or convection. Therefore, if the diffusion of the electroactive species and the electrode reaction can occur in the same three-dimensional space, rapid determination should be carried out.In this work, we intend to describe a novel rapid controlled potential coulometric cell in which a porous carbon felt with chemical activation containing the electrolytic solution is used as a working electrode. In this method, we adopted a concentration-step method in which a given amount of reactant is added to the electrolytic solution at rest a t a given time, then the background current fluctuation caused by the convection of the solution or charging current does not influence the coulometric data.The electroactive species added to the working electrode surface is diffused into the inner part of the felt quickly in a three-dimensional direction, while undergoing the electrode reaction. Therefore, a very fast electrode reaction with the large slope of the log i vs t curve occurs.T o illustrate the present method, iodine and ferricyanide ion are chosen as electroactive species for proving the simplicity and rapidness of our coulometric cell, and the continuous determination of these samples is also described.The reticulated vitreous carbon electrode has been developed by Curran and Strohl as a working electrode in controlled potential coulometry (7), but the determination time is more than 100 s because they used the flow system and not the batch system. EXPERIMENTAL SECTIONA controlled potential coulometric cell was fabricated and a cross section of this cell is shown in Figure 1. Round porous carbon felt (3.8 cm diameter, 3 mm thickness) with chemical activation (8) was used as a working electrode. The chemical activation process is described as follows. Poly(acry1onitrile)-based carbon-fiber felt was baked at 1400 K for 6 h in the oven and oxygen was introduced on the surface of the carbon felt. The ratio of oxygen atom to carbon atom on the surface was determined to be 0.10 by X-ray photoelectron spectroscopy. The carbon felt was placed in the hole of an acrylic resin plate. A 2 mm diameter platinum wire was connected to the carbon felt as a lead wire. The electrolytic solution, 1 M acetic acid containing 5 M KI ...
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