Wood-based ash landfilling is increasing issue not only in Latvia but in the whole world as more biomass is used for energy production. Utilization of wood burning waste as fertilizer is already used worldwide, but there is lack of information about chemical composition of wood ash obtained from Latvia plants, so the aim of this study was to determine chemical composition and analyse possible utilization options of wood-based ash from Latvia plants. Therefore wood ash samples from 53 companies were collected, sieved and chemical composition of samples was determined. It was concluded that within higher capacity of furnace more coarse fraction of wood ash was observed which is less valuable as fertilizer. Wood ash is good liming material consisting alkali compounds and other biogenic elements but also heavy metals, which are pollutants and could cause environmental problems.

The main aim of this paper is to fuzzify the kinetic parameters, which have crisp nature, in order to obtain the realistic and accurate results. In the present study, the variance, upper limit of ‘dE’ and the frequency factor are assumed to be fuzzy numbers. The Gaussian distribution is considered as the distribution function, f (E), of Distributed Activation Energy Model (DAEM). The membership and the non-membership functions are evaluated by the trapezoidal fuzzy number. Thermo-analytical data has been found experimentally with the help of TGA/DTG analysis. The approximated solution of DAEM is obtained with the help of asymptotic expansion.