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Comparison of traceable methods for determining the calorific value of non-conventional fuel gases
(2016)
Energy-content measurements by direct methods (such as calorimetry) are used to validate the indirect method (from gas composition obtained by gas chromatography) which is generally adopted by grid operators for on-site gas control. A primary reference gas calorimeter and three field calorimeters were used for the first time to measure accurately the energy content of non-conventional gases (biogas and coal mine methane). The gas mixtures for this study were prepared by gravimetry and comprised three binary mixtures containing carbon dioxide and (up to 80 mol-%) methane, three ternary mixtures containing carbon dioxide, (up to 70 mol-%) methane and (up to 0.3 mol-%) hydrogen sulphide as well as a ten-component mixture with a methane content of approximately 64 mol-% which represents a typical coal mine methane. Associated uncertainty calculations were developed for each instrument and are presented here. Traceability of the measurements to the SI units is ensured in reference calorimetry, as calibration is accomplished by electrical simulation based on the Joule effect in order to obtain the heat capacity of the entire system. The results obtained with the four calorimeters are compared with each other and also with results calculated from the indirect method that is based on gas chromatography. Uncertainties (k = 2) between 0.07 and 0.49% for the reference gases were obtained with the reference calorimeter, while uncertainties for the field calorimeters range between 0.18 and 2.48% for the same mixtures. Compared to the usual standard deviation observed by gas chromatography for a multicomponent gas mixture of about 1%, it is demonstrated that the calorimetric method, although rarely used for non-conventional gases before, is appropriate for energy-content measurements of gases originating from renewable energy sources.
Emerging infectious diseases (EIDs) have contributed significantly to the current biodiversity crisis, leading to widespread epidemics and population loss. Owing to genetic variation in pathogen virulence, a complete understanding of species decline requires the accurate identification and characterization of EIDs. We explore this issue in the Western honeybee, where increasing mortality of populations in the Northern Hemisphere has caused major concern. Specifically, we investigate the importance of genetic identity of the main suspect in mortality, deformed wing virus (DWV), in driving honeybee loss. Using laboratory experiments and a systematic field survey, we demonstrate that an emerging DWV genotype (DWV-B) is more virulent than the established DWV genotype (DWV-A) and is widespread in the landscape. Furthermore, we show in a simple model that colonies infected with DWV-B collapse sooner than colonies infected with DWV-A. We also identify potential for rapid DWV evolution by revealing extensive genome-wide recombination in vivo. The emergence of DWV-B in naive honeybee populations, including via recombination with DWV-A, could be of significant ecological and economic importance. Our findings emphasize that knowledge of pathogen genetic identity and diversity is critical to understanding drivers of species decline.
The Sponsorship Programme for the Testing of Manufactured Nanomaterials (further referred to as “the Testing Programme”) was concluded in March 2013, and the publication of the dossiers via the OECD website (www.oecd.org/science/nanosafety) started in June 2015. As indicated in the “Guidance manual for the testing of manufactured nanomaterials: OECD’s sponsorship programme”, after conclusion of the Testing Programme a next step is to consider “the status, need for, and coordination of further test development”. Parallel to concluding the final stages of the Testing Programme, a series of workshops have taken place, in which for different topics the applicability of existing OECD test guidelines for nanomaterials was discussed and the need for new ones analysed. One workshop focussed on physico-chemical methods, addressing in detail the relevance of each physico-chemical endpoint proposed in the Testing Programme for the regulation of nanomaterials. The methods were discussed in more general terms. However, as most of the proposed endpoints are new to the OECD Test Guidelines Programme, a much more detailed evaluation of the applied methods would
be highly relevant.
To this extent,the Netherlands volunteered to lead an initial detailed evaluation of the applicability of the test methods applied to determine the physico-chemical properties of different types of nanomaterials in the Testing Programme. This initial focus on physico-chemical properties was prompted by the essential need for an adequate and complete characterisation of nanomaterials to enable a further evaluation of their (toxicological) properties.
A number of experts from several delegations volunteered to review and evaluate the methods applied to determine the physico-chemical properties of the nanomaterials in the Testing Programme.