The research was conducted with the goal to determine the variability of the quality parameters of the wood chips produced from the most favorable raw material (energy roundwood), and in the most controllable operational conditions (pellet factory), as the first step in identifying opportunities to optimize the wood chips’ quality monitoring. Four raw material types were tested: fir/spruce and beech debarked energy roundwood, as well as energy wood with bark of the same species. Sampling was conducted during six consecutive months along with laboratory testing, all according to the HRN EN ISO standards for solid biofuels. Interpretation of the results was done in relation to deviation from the first sampling results (as an indicator of the possibility to retain the quality of wood chips), and repeatability and reproducibility set in the standards (as an indicator of acceptable variability). The influence of the species and debarking process on the wood chips’ quality was analyzed as well. Relative deviation from the first sampling as well as the quality class change pointed moisture content as a normative property with the lowest possibility to retain initial values over the six-month period. Ash content results indicated a strong possibility to maintain the initial ash content class in the majority of the samples. In just three cases, the results of ash content were outside the reproducibility limits with first sampling as a reference. Gross calorific value results pointed only four samples outside the reproducibility limits with the first sampling results are set as a reference. Wood species influenced gross calorific value and the median value of the particle size distribution and debarking showed a significant positive effect on the moisture content reduction as well as on the ash content reduction. Presented findings are indicative for the investigated raw materials, however for the general conclusion on the subject of wood chips normative properties variation, various raw material types will have to be examined in further research.

The global demand to reduce CO2 emissions has led large industrial pollutants, particularly power generation and metallurgical sectors, to search for alternatives to traditional fossil fuels like coal. Wood pellets have emerged as a recognized cleaner alternative. Yet, pellets fall short of coal key properties, notably in calorific value and storage stability. By subjecting the feedstock for wood pellet production, namely woody biomass, to thermal pre-treatments like torrefaction or steam explosion, these limitations can be mitigated. These treatments reduce moisture content, increase energy density, and enhance storage stability, making the wood pellets producedfrom thermally treated feedstock more similar to coal and compatible with existing coal infrastructure. While these pre-treatments offer potential energy savings and other benefits along the process of pellet production and supply chain, they might also necessitate significant capital investments. This review provides a concise overview of thermal pre-treatment technologies, necessary parameters, their impact on treated woody biomass, as well as final characteristics of treated woody biomass.