Understanding the dependence of biochar properties on different types of biomass

Owing to the diversity of biomasses and many variables in pyrolysis process, the property of biochar from varied biomass feedstock or even same biomass could differ significantly. Since the property of biochar governs the further application of biochar, this review paid particular attention to the correlation between the nature of biomass feedstock and the specifications of biochar in terms of yield, elemental composition, pH, functionalities, heating value, pore structures, morphologies, etc. The property of the biochar from the pyrolysis of cellulose, hemicellulose, lignin, woody biomass (pine, mallee, poplar, acacia, oak, eucalyptus and beech), bark of woody biomass, leaves of woody biomass, straw, algae, fruit peels, tea waste was compared and summarized. In addition, the differences of the biochar of these varied origins were also analyzed. The remaining questions, about the correlation of biomass nature with biochar characteristics, to be further investigated are analyzed in detail. The deduced information about the relationship of the nature of biochar and biomass feedstock as well as key pyrolysis parameters is of importance for further development of the methods for tailoring or production of the biochar of desirable properties. The results from this study could be interesting technically and commercially for the technology developer using biochar as the source of carbon in different applications.

The Capture and Transformation of Carbon Dioxide in Concrete: A Review

Concrete is one of the most commonly used engineering materials in the world. Carbonation of cement-based materials balances the CO2 emissions from the cement industry, which means that carbon neutrality in the cement industry can be achieved by the carbon sequestration ability of cement-based materials. Carbon dioxide is a symmetrical molecule and is difficult to separate. This work introduces the important significance of CO2 absorption by using cement-based materials, and summarizes the basic characteristics of carbonation of concrete, including the affected factors, mathematical modeling carbonization, and the method for detecting carbonation. From the perspective of carbon sequestration, it mainly goes through carbon capture and carbon storage. As the first stage of carbon sequestration, carbon capture is the premise of carbon sequestration and determines the maximum amount of carbon sequestration. Carbon sequestration with carbonization reaction as the main way has been studied a lot, but there is little attention to carbon capture performance. As an effective way to enhance the carbon sequestration capacity of cement-based materials, increasing the total amount of carbon sequestration can become a considerably important research direction.

Fe-Catalyzed CO2 Adsorption over Hexagonal Boron Nitride with the Presence of H2O

The energy barrier of CO₂ chemically adsorbed on hexagonal boron nitride (h-BN) is relatively big. In order to cut down the energy barriers and facilitate fast adsorption of CO₂, it is necessary to apply catalysts as a promoter. In this study, single-atom iron is introduced as the catalyst to reduce the energy barriers of CO₂ adsorbed on pure/doped h-BN. Through density functional theory calculations, catalytic reaction mechanisms, stability of single-atom iron fixed on adsorbents, CO₂ adsorption characteristics, and features of thermodynamics/reaction dynamics during adsorption processes are fully investigated to explain the catalytic effects of single-atom iron on CO₂ chemisorption. According to calculations, when CO₂ and OH^- get into activated states (i.e., CO₂^•- and ^•OH) with the help of single-atom iron, their chemical activities will be promoted to a large degree, which makes the transition state (TS) energy barrier of HCO₃^- to decrease by 92.54%. In the meantime, it is proved that single-atom iron could be stably fixed on doped h-BN with the binding energy larger than 2 eV to achieve sustainable catalysis. With the presence of single-atom iron, TS energy barriers of CO₂ adsorbed on h-BN with the presence of H₂O decreased by 94.39, 78.87, and 30.63% over pure h-BN, 3C-doped h-BN, and 3N-doped h-BN, respectively. In the meantime, thermodynamic analyses indicate that TS energy barriers are mainly determined by element doping and temperatures are a little beneficial to the reduction of TS energy barriers. With the above aspects combined, the results of this study could supply crucial information for massively and quickly capturing CO₂ in real industries.