The composition and pyrolysis characteristics of 60 types of biomass waste from the following six source categories were compared: agricultural residues, woody pruning waste from gardens and lawns, aquatic plant material from eutrophic water bodies, nutshells and fruit peels, livestock manure and residual sludge from municipal wastewater treatment. The yield and physicochemical characteristics of the biochar produced from these feedstocks at 350°C, 500°C and 650°C were also examined. Results of correlation and canonical correspondence analysis between feedstock composition and biochar properties showed that feedstock type played an important role in controlling yield and properties of biochars. The yields of biochar dry ash-free (daf.) basis were positively correlated with cellulose, lignin and lignin/cellulose content of feedstock; and ash content hampered the biochar production. Furthermore, the intensity of correlation between biochar yield and its feedstock composition was improved with pyrolysis temperature and degree of feedstock decomposition. The fixed carbon content in biochar was also negatively influenced by ash content of feedstock, and it increased with increasing pyrolysis temperature when the ash content was below 34.57% in feedstock and decreased when the ash content exceeded. The fixed carbon production in biochar per unit ash-free mass (af.) was positively related to cellulose, lignin and lignin/cellulose content in feedstock, which were same with the yield of biochar (daf.). But on the contrary, the volatiles content in biochar (af.) had negative correlation with these organic constituents. For most feedstocks, the differences in the biochar characteristics among the biomass categories were greater than within any individual category. C/N, H/C and O/C atomic ratio and bulk density of biochar from different types of biomass were also compared. The results will provide guidance for the reutilization of biomass wastes and production of biochar with specified properties for soil amendment applications.

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Metal pollution in soil is an increasing concern. Cadmium poses significant risks to ecosystems, and methodologies for its removal, including adsorption, have been researched. There are several environmentally friendly adsorbing materials (such as Biochar) for Cd removal. In this study, to improve the adsorptive capacity of Cd, coconut and peanut shells were used as raw materials to prepare Biochar at 300 °C and 600 °C. The effects of the pyrolysis temperature and material type on the physicochemical properties of the adsorbents were investigated by elemental analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. Magnesium-loaded BC was synthesized to determine its Cd2+ absorptivity. The adsorption characteristics and mechanisms of Cd2+ in an aqueous phase were studied through batch adsorption experiments. The results demonstrated that the pseudo-second-order kinetics model accurately described the adsorption kinetics of adsorbents of Cd2+. The adsorption behavior of the Cd2+ adsorbent conforms to the single layer adsorption described by the Langmuir model. Adsorption of Cd2+ involves a spontaneous endothermic process. The initial pH of the solution greatly influenced the adsorption of Cd2+ and showed a trend of rapid growth and then slow growth. Thus, magnesium-modified biomass carbon has good potential for applications in pollutant remediation.

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