Agnieszka Korus

Phytoremediation is a sustainable approach for the remediation of heavy metal–contaminated soils; however, the management of contaminated biomass generated during this process remains an insufficiently addressed challenge. Such biomass constitutes a secondary waste stream that may release mobile pollutants and pose environmental risks. In this study, an integrated ecotoxicological assessment framework was applied to evaluate phytoremediation-derived biomass and its transformation products obtained via pyrolysis. Two types of woody biomass with different heavy metal contents and their corresponding biochars produced at 700 °C were investigated. A multitrophic battery of bioassays combining direct exposure assays using terrestrial organisms (higher plants, Eisenia fetida, and soil microbial activity) with leachate-based assays using aquatic organisms (Lemna minor, Daphnia magna, and Aliivibrio fischeri) was applied. Untreated biomass exhibited high to extreme toxicity in aquatic systems (toxic units, TU >100) and significant phytotoxic effects. Pyrolysis substantially reduced contaminant mobility and ecotoxicity of leachates, resulting in lower toxicity (TU typically <15) and no significant effects on plant growth, earthworm survival, or soil microbial functional diversity. Residual toxicity was linked to elevated pH and trace amounts of thermally generated organic substances. These results demonstrate that pyrolysis effectively reduces the environmental risk of contaminated biomass and supports the use of multitrophic ecotoxicological testing for safe waste valorization within circular economy strategies.

Thermally activated biochar catalysts from straw, eucalyptus, and sewage sludge were prepared under eight gasification conditions and evaluated for catalytic toluene decomposition relevant to syngas reforming. Steam treatment and high burn off levels promoted pore widening, whereas CO2 activation preserved the microporous structure of the samples. Notably, mesopore formation was influenced more by the precursor than by the gasification conditions. High-temperature gasification improved thermal oxidation stability as well as thermal and electrical conductivity. Sewage sludge-derived biochars, characterized by high inorganic content and low total porosity, exhibited stable but moderate toluene conversion (0.6–0.3 over 60 min). In contrast, lignocellulosic biochars achieved higher initial conversion (up to 0.9) but deactivated more rapidly due to pore accessibility limitations. Multivariate statistical analysis (principal component analysis and Spearman’s correlation) identified microporosity, electrical and thermal conductivity as key parameters governing initial catalytic activity, while mesoporosity became critical during prolonged reaction, highlighting structure–performance relationships in biochar-based catalysts.

Urban tree-management operations generate substantial amounts of woody biomass that often remain underutilized despite their potential value as a local renewable fuel. This study investigates the possibility of using woodchips and sawdust delivered from municipal tree-cutting activities as boiler fuel, with a specific focus on how fuel moisture, particle size, and natural-fiber packaging influence combustion performance and emission characteristics. In collaboration with a municipal greenery-cutting company, representative batches of biomass were collected, characterized through proximate and ultimate analyses, and combusted in a small-scale boiler. Unlike conventional densification routes (pelletization/briquetting), the proposed approach uses combustible natural-fiber packaging to create modular ‘macro-pellets’ from minimally processed urban residues. The study quantifies how this low-energy packaging concept affects emissions and boiler efficiency relative to loose chips/sawdust at two moisture levels. The results demonstrate that packaging the fuel in jute bags markedly improved performance for both woodchips and sawdust by stabilizing the fuel bed, enhancing air distribution, and reducing emissions of incomplete combustion products. Boiler efficiency increased from approximately 60% for raw unpackaged fuels to 71–75% for the dried and jute-packaged variants. The findings highlight that simple preprocessing steps—drying and packaging in natural-fiber bags—can substantially enhance the energy recovery potential of urban green waste, offering a practical pathway for integrating municipal biomass residues into a sustainable fuel.