Characterization and potential applications of solid particles produced at a biomass gasification plant

Biomass gasification processes generate large amounts of solid. The aim of this work is to characterize the particles produced at a demonstration scale downdraft multi-stage gasification plant running on pinewood. The results have been used to understand their formation mechanism, evaluate potential applications and determine their hazardousness to human health and the environment. Chemical, physical, morphological and textural analyses suggest that most of the particles are formed via gas phase condensation reactions, with a very limited proportion resulting from direct carbonization of the original biomass feedstock. This is confirmed by a very limited micropore structure, surface area and adsorption capacity, making the particles unsuitable for use as an adsorbent in gas and water treatment applications. The particles exhibit superior fuel properties in terms of carbon content, heating value and thermal stability, which may be associated with the high temperatures at which they are generated. Due to their biomass origin, the particles contain a high proportion of calcium, potassium, magnesium and other plant micronutrients that could be beneficial if the material is used for soil conditioning and fertilizing. Regarding particle size distribution, most of the particles fitted in the range between 100 and 250 μm, with only 0.5 wt% smaller than 30 μm. This is too large for a carbon black surrogate but minimizes health risks associated with exposure to the lower regions of the respiratory tract. The concentration of biologically active PAH is sufficiently low to represent no hazard to the environment or human health.