Pellets are solid biofuels with a combustion efficiency of 85–90%, low CO₂ emissions and costs, great comfort and versatility. However, the ash generated during combustion can present sintering and fusibility, decreasing boiler efficiency and potentially malfunctioning. Ash composition indexes can be useful to predict observed ash sintering and fusion but require further analysis for a variety of feedstocks. The objective of this work was to determine the effect of the mineral composition of pellet ash from 15 biomasses of forest and agro-industrial sources on observed pellet ash slagging using a laboratory test. The chemical composition of pellets and the indexes B, NaK/B, SiP/CaMg and SiPNaK/CaMg at 550 and 1000 °C were determined. Pearson correlation tests were also performed between cumulative percentages of slag at different sieve sizes. The concentrations of CaO ranged from 4.49 to 65.95%, MgO varied from 1.99 to 17.61%, and the SiO₂ concentration was between 16.11 and 28.24% and 2.19–56.75% at 550 and 1000 °C, respectively. Pellets of forest origin presented a low risk of slag formation, while those from agro-industrial sources showed a high risk of slag formation. The index SiPNaK/CaMg showed the highest correlation (R² > 0.75) to observed slagging using the BioSlag test.

The objectives were to evaluate the energy potential of biomass and pellets produced from five underutilized herbaceous and woody plant species in México and Colombia; characterize pellet quality parameters; and calculate the preliminary production costs and energy requirement during the densification process. Harvest and sawmill residues were obtained for five non-timber and woody plant species. The volatile compounds, ash, and fixed carbon were evaluated, as well as the higher heating value (HHV) and pellet impact resistance (PIR); in addition, lignin, hemicellulose, and cellulose were quantified. The data were analyzed using descriptive statistics, including mean and standard deviation. The volatile compounds ranged from 65.9–77.5%, ash 2.5–17.2%, fixed carbon 5.4–19.9%, HHV 16.4–21.9 MJ kg⁻¹, and PIR (0.6–99.1%). Considerable intra- and inter-specific differences were observed for all the variables, which expanded the options for the selection of biomass sources used in bioenergy production. Biomass processing costs ranged from 675.9 to 679.3 EUR t⁻¹. Optimization of these processes is required to implement more efficient technologies that significantly reduce operating costs in biomass use in biofuel industry. The systematic study of different plant species, both introduced and native, will provide new sources of biomass to produce bioenergy, fertilizers, and other organic inputs.