Bacterial community structure in experimental methanogenic bioreactors and search for pathogenic clostridia as community members.

Microbial conversion of organic waste or harvested plant material into biogas has become an attractive technology for energy production. Biogas is produced in reactors under anaerobic conditions by a consortium of microorganisms which commonly include bacteria of the genus Clostridium. Since the genus Clostridium also harbors some highly pathogenic members in its phylogenetic cluster I, there has been some concern that an unintended growth of such pathogens might occur during the fermentation process. Therefore this study aimed to follow how process parameters affect the diversity of Bacteria in general, and the diversity of Clostridium cluster I members in particular. The development of both communities was followed in model biogas reactors from start-up during stable methanogenic conditions. The biogas reactors were run with either cattle or pig manures as substrates, and both were operated at mesophilic and thermophilic conditions. The structural diversity was analyzed independent of cultivation using a PCR-based detection of 16S rRNA genes and genetic profiling by single-strand conformation polymorphism (SSCP). Genetic profiles indicated that both bacterial and clostridial communities evolved in parallel, and the community structures were highly influenced by both substrate and temperature. Sequence analysis of 16S rRNA genes recovered from prominent bands from SSCP profiles representing Clostridia detected no pathogenic species. Thus, this study gave no indication that pathogenic clostridia would be enriched as dominant community members in biogas reactors fed with manure.

Biogas production: current state and perspectives.

Anaerobic digestion of energy crops, residues, and wastes is of increasing interest in order to reduce the greenhouse gas emissions and to facilitate a sustainable development of energy supply. Production of biogas provides a versatile carrier of renewable energy, as methane can be used for replacement of fossil fuels in both heat and power generation and as a vehicle fuel. For biogas production, various process types are applied which can be classified in wet and dry fermentation systems. Most often applied are wet digester systems using vertical stirred tank digester with different stirrer types dependent on the origin of the feedstock. Biogas is mainly utilized in engine-based combined heat and power plants, whereas microgas turbines and fuel cells are expensive alternatives which need further development work for reducing the costs and increasing their reliability. Gas upgrading and utilization as renewable vehicle fuel or injection into the natural gas grid is of increasing interest because the gas can be used in a more efficient way. The digestate from anaerobic fermentation is a valuable fertilizer due to the increased availability of nitrogen and the better short-term fertilization effect. Anaerobic treatment minimizes the survival of pathogens which is important for using the digested residue as fertilizer. This paper reviews the current state and perspectives of biogas production, including the biochemical parameters and feedstocks which influence the efficiency and reliability of the microbial conversion and gas yield.

Citation success of different publication types: a case study on all references in psychology publications from the German-speaking countries (D-A-CH-L-L) in 2009, 2010, and 2011.

Scientometric data on the citation success of different publication types and publication genres in psychology publications are presented. Data refer to references that are cited in these scientific publications and that are documented in PSYNDEX, the exhaustive database of psychology publications from the German-speaking countries either published in German or in English language. Firstly, data analyses refer to the references that are cited in publications of 2009 versus 2010 versus 2011. With reference to all cited references, the portion of journal articles ranges from 57 to 61 %, of books from 22 to 24 %, and of book chapters from 14 to 15 %, with a rather high stability across the three publication years analysed. Secondly, data analyses refer to the numbers of cited references from the German-speaking countries, which are also documented in PSYNDEX. These compose about 11 % of all cited references indicating that nearly 90 % of the references cited are of international and/or interdisciplinary publications not stemming from the German-speaking countries. The subsample shows the proportion of journal articles, books, and chapters, and these are very similar to the percentages identified for all references that are cited. Thirdly, analyses refer to document type, scientific genre, and psychological sub-discipline of the most frequently cited references in the psychology publications. The frequency of top-cited references of books and book chapters is almost equal to that of journal articles; two-thirds of the top-cited references are non-empirical publications, only one-third are empirical publications. Top-cited references stem particularly from clinical psychology, experimental psychology, as well as tests, testing and psychometrics. In summary, the results point to the fact that citation analyses, which are limited to journal papers, tend to neglect very high portions of references that are cited in scientific publications.

Production and energetic use of biogas from energy crops and wastes in Germany.

The production of biogas for reducing fossil CO2 emissions is one of the key strategic issues of the German government and has resulted in the development of new process techniques and new technologies for the energetic use of biogas. Progress has been made in cultivating energy crops for biogas production, in using new reactor systems for anaerobic digestion, and in applying more efficient technologies for combined heat and power production. Recently, integration of fuel cells within the anaerobic digestion process was started, and new technologies for biogas upgrading and conversion to hydrogen were tested. This article describes the trends in Germany for achieving more efficient energy production.