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In the present study, poly(butylene succinate) (PBSu) and its bionanocomposites containing 1, 2.5, and 5 wt.% biochar (MSP700) were prepared via in situ melt polycondensation in order to investigate the thermal stability and decomposition mechanism of the materials. X-ray photoelectron spectroscopy (XPS) measurements were carried out to analyze the surface area of a biochar sample and PBSu/biochar nanocomposites. From XPS, it was found that only physical interactions were taking place between PBSu matrix and biochar nanoadditive. Thermal stability, decomposition kinetics, and the decomposition mechanism of the pristine PBSu and PBSu/biochar nanocomposites were thoroughly studied by thermogravimetric analysis (TGA) and pyrolysis–gas chromatography/mass spectrometry (Py−GC/MS). TGA thermograms depicted that all materials had high thermal stability, since their decomposition started at around 300 °C. However, results indicated a slight reduction in the thermal stability of the PBSu biochar nanocomposites because of the potential catalytic impact of biochar. Py−GC/MS analysis was employed to examine, in more detail, the thermal degradation mechanism of PBSu nanocomposites filled with biochar. From the decomposition products identified by Py−GC/MS after pyrolysis at 450 °C, it was found that the decomposition pathway of the PBSu/biochar nanocomposites took place mainly via β-hydrogen bond scission, which is similar to that which took place for neat PBSu. However, at higher biochar content (5 wt.%), some localized differences in the intensity of the peaks of some specific thermal degradation products could be recognized, indicating that α-hydrogen bond scission was also taking place. A study of the thermal stability and decomposition pathway of PBSu/biochar bionanocomposites is crucial to examine if the new materials fulfill the requirements for further investigation for mulch films in agriculture or in electronics as possible applications.

Biochar-based column filtration systems (BCFS) for greywater treatment have gained attention in the last decade. However, a review of the state-of-the-art on this subject has not been conducted, leaving the analysis and limitations of the available research still unexplored. This paper reviews the current literature to give insights into the technology and identify new areas of investigation. This study used a systematic review approach to evaluate the documentation relating to the technology's worldwide status, configuration, removal mechanisms, removal efficiency, and water reuse applications. In total, 28 studies were reported in 16 countries including India and Sweden as leading ones. Three filter column configurations were identified: single biochar filter, multilayer filter, and polishing step in the treatment chain. The pollutant removal efficiency of BCFS ranged between 50 and 99%. Treated greywater is reused mainly for non-potable purposes such as toilet flushing, cloth washing, and crop irrigation. Overall, this technology can be a feasible and sustainable alternative for greywater treatment and application in water-scarce regions. However, further research is needed on social perception toward potable water reuse, new feedstocks for biochar production, the scaling-up and long-term assessment, evaluation of additional water microbial indicators, and the modification of biochar to target specific water reuse purposes.

Magnetic carbons can significantly lower the costs of wastewater treatment due to easy separation of the adsorbent. However, current production techniques often involve the use of chlorinated or sulfonated Fe precursors with an inherent potential for secondary pollution. In this study, ochre, an iron-rich waste stream was investigated as a sustainable Fe source to produce magnetic activated biochar from two agricultural feedstocks, softwood and wheat straw. Fe-doping resulted in significant shifts in pyrolysis yield distribution with increased gas yields (+50 %) and gas energy content (+40 %) lowering the energy costs for production. Physical activation transformed ochre to magnetite/maghemite resulting in activated magnetic biochars and lead to a 4-fold increase in the adsorption capacities for two common micropollutants – caffeine and fluconazole. The results show that Fe doping not only benefits the adsorbent properties but also the production process, leading the way to sustainable carbon adsorbents.

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized and standardized. Therefore, the COST Action TD1107 conducted an inter-laboratory comparison, in which 22 laboratories from twelve countries analyzed three different types of biochar for 38 physical-chemical parameters (macro- and micro-elements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data was evaluated in detail using professional inter-laboratory testing software. Whereas intra-laboratory repeatability was generally good or at least acceptable, inter-laboratory reproducibility was mostly not (20% < mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published already, and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.