Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2018
Authors
Calle Nilsson Henrik Ramebäck Callum Aidan Stephen Hill Mehrdad ArshadiAbstract
The self-heating of wood fuel pellets is a well-recognised problem causing fire incidents in the storage of the pellets as well as severe intoxication of workers by elevated carbon monoxide and carbon dioxide levels and oxygen depletion. Possible factors contributing to the self-heating are considered to be autoxidation and microbiological activity, while the role and contribution to the temperature rise caused by the heat of condensation from water vapour condensing during fast changes in the relative air humidity is less investigated. Using Dynamic Vapour Sorption, the water uptake was measured at 25 °C when increasing the RH from 40 to 80% using 35 fuel pellet samples covering a broad variation in pellet raw materials and process equipment found in Europe (both pilot and industrial scale). The equilibrium total water uptake and speed of the uptake were determined. Total water uptake was 4.56% (range 3.69–6.86%) with no systematic difference found related to the scale of production (industry as compared to pilot plant). In addition, the variations within larger groups of raw material (pine, spruce and pine/spruce mixtures) were relatively small, and the mean water uptake did not differ significantly between these groups. An estimation of the overall potential heat release (when raising the RH% from 40 to 80%) made from the experimental results, taking the early fast water uptake process into consideration (2 h counting for half the total uptake), showed that a heat release of 47 kJ/kg of pellets (range 12–63 kJ/kg) and a potential temperature increase of 45 °C is possible. This estimation clearly demonstrates that the heat of condensation released during water condensation in a pellets silo or in a pellets pile should be expected to be a major contributing factor to initiating temperature rise incidents. In addition, such a temperature increase is expected to assist the initiation of, and to increase the speed of autoxidation of fatty acids and other compounds in the material that will further contribute to a temperature rise. Thus, the results in this study have the potential to improve the basis for modelling the self-heating process in pellet silos/storage and to predict the status of a certain pellet batch by presenting a broad basis for expected variation in the important parameters (specific heat capacity CP and thermal conductivity λeff) influencing the process, and thus aid in taking preventive actions like venting or shifting the pellets to another silo/pile to reduce risk for self-heating and possible fire.
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Authors
Ievina SturiteAbstract
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Many nonlinear methods of time series analysis require a minimal number of observations in the hundreds to thousands, which is not always easy to achieve for observations of environmental systems. As a result, finite size effects often hamper proper interpretation of the results; the estimation of the correlation dimension, Lyapunov exponents or KolmogorovSinai entropies, to name a few, is plagued by huge uncertainties. Eddy Covariance (EC) measurements of the carbon exchange between the atmosphere and vegetation provide a noticeable exception. The turbulent wind fields transporting carbon dioxide to the surface layer show variability over a large range of spatiotemporal scales, and their quantification demand a high temporal resolution, typically at 20 Hz. This generates very long time series even for short measurement periods; usually, the raw data are aggregated to carbon cycle observables, like Gross Primary Productivity (GPP) or Net Ecosystem Exchange (NEE) at half-hourly time steps. In this presentation, we investigate the high-resolution raw data of 3D wind speed and CO2 concentrations measured at a young forest plantation in Southeast Norway since July 2018. After introducing the EC technique and the Integrated Carbon Observation System (ICOS), we present results of complexity analysis, Tarnopolski diagrams, q-Entropy and Hurst analysis, and Empirical Mode Decomposition. This provides insights into not only whether the young forest stand is actually a source or sink of carbon, but also when, how and how strong carbon uptake and release are taking place at the site, and the nature of dynamics of carbon fluxes across this system boundary in general.
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The Norwegian per capita sales of wine have more than doubled over the past 20 years, while the sales of sprits and beer have declined. These changes are likely to be the effect of changes in economic, demographic, and attitudinal factors as well as the availability of wine. We estimated age-period-cohort (APC) logit models using data from a large repeated cross-sectional survey over the period 1991–2015. The estimation results indicate substantial effects of the APC variables as well as income, availability, and attitudes. The model was used to simulate wine consumption over the life cycle in different birth cohorts. The simulation results indicate that wine consumption frequency increases by age, and younger cohorts are expected to increase their consumption frequencies more than older cohorts, which suggests an increased wine consumption over time.
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http://www.sterf.org/Media/Get/2978/annual-report-2017
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No abstract has been registered