The content and emission factors of heavy metals in biomass used for energy purposes in the context of the requirements of international standards

The aim of this work was to study the content of seven heavy metal factors within different biomasses. The potential environmental effects associated with the release of these elements into the atmosphere were also studied by determining the emission factors for each of biomass. 31 samples of biomass which were classified into four groups, i.e.: wood biomass, herbaceous biomass, fruit biomass and aquatic biomass and analyzed with use of ICP-OES spectrometer. Performed results were analyzed in the context of the requirements of international standards, described in the EN ISO 17225:2014. Higher heavy metal contents than the limits described in the EN ISO 17225:2014 standard were detected within some of the studied biomass samples. Importantly, this is also related to the products available on the market, i.e., wood pellets or wood chips. Among the detected trace elements, the largest limit exceedance was for lead (wood chips from a rubber tree, pomace oil and palm kernel shells) and arsenic (Sea Balls). The highest emission factors were determined for the herbaceous, fruit and aquatic biomass. However, the wood chips studied were characterized by relatively high emission factors for each heavy metal. A comparison of the emission factors calculated for the studied biomass samples and for coal revealed that the total emission of heavy metals during the combustion of wood pellets and wood chips was lower than that calculated for hard coal.