Abstract
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. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 8 : 1199-1208)
Highlights
Global warming, due to an increase in the atmospheric concentration of greenhouse gases, is an important issue (Takahashi and Young, 2002)
Methanogens in the rumen are hydrogenotrophic bacteria which carbon dioxide is reduced with hydrogen though the acetotrophic methanogens in the biogas system generate the methane from acetic acid, formic acid, methanol, and the methylamine, etc
From the results of anaerobic fermentation trials of cow manure in the biogas reactors, 300 L pure methane equivalent to 11.85 MJ can be collected per each kg DM of manure
Summary
Due to an increase in the atmospheric concentration of greenhouse gases, is an important issue (Takahashi and Young, 2002). Methane is an important greenhouse gas, second only to carbon dioxide in its contribution to global warming, due to its high absorption ability of infrared in radiation from the sun (IPCC, 1994). Methanogens in the rumen are hydrogenotrophic bacteria which carbon dioxide is reduced with hydrogen though the acetotrophic methanogens in the biogas system generate the methane from acetic acid, formic acid, methanol, and the methylamine, etc. Whilst rumen methanogenesis must be, reduced to abate greenhouse effect, the potential energy of effluent should be recycled as a useful alternative energy source to reduce fossil energy consumption. The present paper deals with some nutritional options using some probiotics and natural compounds compared with antibiotics to abate methane emission from farm animals, especially ruminants and the recycling rate of the potential energy of effluent as a fuel source of a cogenerator and fuel cell
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