Sample methods in Solid Biofuels
The provision of high quality is prerequisite for biofuel in order to gain the confidence of the customer. On this basis, he BIONORM project worked out a quality assurance system for solid bio fuels to help their development in the bio fuel market. The system was based on extensive work on sampling and testing to improve existing sampling and testing procedures. The samples of solid biofuels may be taken from different places such as from the place where the raw material grows, from production plants, from deliveries or from stock. The methods of sampling and sample reduction are significant with regard to testing methods of fuel properties in order to ensure that the required fuel properties are met. In the context of the BIONORM project, the bias introduced from different sampling methods was assessed and the number and size of increments needed to provide a representative sample was defined. A number of experiments were carried out for four important kinds of fuels (sawdust, GROT, pellets, straw-bales). This included the testing of physical-mechanical fuel characteristics (for e.g. moisture content and bulk density) as well as chemical fuel properties (among other elements particularly sulphur, chlorine and nitrogen content). These experiments showed that all methods gave results, which justify their practical use and their inclusion in European standardization. Moreover, BIONORM outlined the usefulness of a range of practical sample reduction methods, indicating the preferred methods in each of the experiments carried out. However, it was found that for the determination of moisture, sample reduction should be avoided. In addition, due to the variations introduced when reducing the sample size, laboratory staff should check the variability they achieve with the sample reduction methods used. The results of the project will directly contribute to European standardization activities in the field of solid biofuels. In addition, they indicate the necessity for further similar research on more materials as well as on other sampling methods issues, such as the frequency of sampling.
