Biomass losses during short-term storage of bark and recovered wood

Abstract: Storage of biomass is associated with problems like heat development, biomasslosses, and reduction of the fuel quality. Certain processes such as biological- andchemical degradation are responsible for these storage problems. This master’sthesis was carried out at Vattenfall Research and Development AB and is alignedtowards quantifying the biomass losses from short-term storage (1-2 months) ofbark and recovered wood. The biomass was stored in outdoor piles during differentseasons, campaign 1 (summer) and campaign 2 (autumn). Partial covering withtarpaulins of some of the piles were also investigated. The stored biomass wasanalysed for moisture content, ash content and heating value.The biomass losses that were based on the dry matter losses and reduction of thenet heating value of the fuel were limited in the piles of recovered wood. The barkpiles had higher biomass losses due to higher moisture content and smaller particlesize distribution. Storage of moist bark in large piles leads to temperaturedevelopment and subsequently a few percent losses in dry weight. The temperaturedevelopment in the piles of recovered wood is limited and more dependent onambient conditions. No effects of partial covering of the piles were found since thecovering was most likely too small.It was found out that the method of quantifying biomass losses used in this reportneeds to be improved to be able to quantify small biomass losses during short-termstorage, since it is not sensitive enough. The best way to store biomass at a heatingplant for minimal fuel losses is under roof and with as low initial moisture contentand large particle size distribution as possible.