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The excessive carbon emissions not only intensify the global climate change, but also seriously restrict the sustainable development of social economy. However, improving industrial carbon emissions efficiency is the most directly effective way to reduce emissions. Therefore, accurate measurement and analysis of carbon emissions efficiency and evolution characteristics of China's industrial system is the basis for China to improve carbon emissions efficiency. Based on this, we adopted energy consumption method and input-output method to calculate and analyze the industrial carbon emissions efficiency and evolution characteristics of China from 2002 to 2015. The results show that (1) If carbon emissions from cement production are ignored and only energy-related carbon emissions are considered, the calculation results of carbon emissions efficiency of heavy industry will be overestimated about 30%. (2) Compared with 2002, China's industrial carbon emissions efficiency increased by about twice in 2015. Specifically, the optimization of carbon emissions efficiency in agriculture, construction, light industry and service industry is very obvious, which has increased by 5.65, 5.00, 4.69 and 4.68 times respectively; The optimization of carbon emissions efficiency in power sector, heavy industry, transportation and chemical industry was obvious, which increased by 2.55, 2.01, 1.86 and 1.47 times respectively; The carbon emissions efficiency of the fossil energy sector has decreased by 0.36 times. (3) The carbon emissions efficiency of various industries has significant differences. Among them, agriculture, service industry, light industry and construction industry are generally industries with higher carbon emissions efficiency, while power sector, fossil energy sector, transportation industry, chemical industry and heavy industry are generally industries with lower carbon emissions efficiency, especially power and fossil energy sectors. Based on these, this paper provides policy implications and scientific evidence for accurately improving carbon emissions efficiency from the perspective of carbon emissions efficiency., Competing Interests: NO authors have competing interests.

Capturing and separating carbon dioxide, particularly using porous carbon adsorption separation technology, has received considerable research attention due to its advantages such as low cost and ease of regeneration. In this study, we successfully developed a one-step carbonization activation method using freeze-thaw pre-mix treatment to prepare high-nitrogen-content microporous nitrogen-doped carbon materials. These materials hold promise for capturing and separating CO2 from complex gas mixtures, such as biogas. The nitrogen content of the prepared carbon adsorbents reaches as high as 13.08 wt%, and they exhibit excellent CO2 adsorption performance under standard conditions (1 bar, 273 K/298 K), achieving 6.97mmol/g and 3.77mmol/g, respectively. Furthermore, according to Ideal Adsorption Solution Theory (IAST) analysis, these materials demonstrate material selectivity for CO2/CH4 (10 v:90 v) and CO2/CH4 (50 v:50 v) of 33.3 and 21.8, respectively, at 1 bar and 298 K. This study provides a promising CO2 adsorption and separation adsorbent that can be used in the efficient purification process for carbon dioxide, potentially reducing greenhouse gas emissions in industrial and energy production, thus offering robust support for addressing climate change and achieving more environmentally friendly energy production and carbon capture goals. [ABSTRACT FROM AUTHOR]

The P4VP with the molecular weight of 12 K and the molecular weight distribution of 1.2 was synthesized via reversible addition‐fragmentation chain transfer polymerization. Then it was added to the system for the preparation of ZIF‐8 as a surfactant. A special two‐dimensional (2D) sheet was produced because P4VP could promote the lateral growth of ZIF‐8. Additionally, the pyridine group from P4VP chains could complex Au3+ followed by in‐situ reduction under UV light to form the 2D ZIF‐8/P4VP/Au ternary hybrids. The ternary layered ZIF‐8/P4VP/Au hybrids exhibited a good yield for epoxy carbonate of 71 % and the high time‐space yield of 3.22 h−1 in the reaction of carbon dioxide with propylene oxide, which was much higher than 0.425 h−1 of the conventional homogeneous catalyst KI. Besides, the ternary layered ZIF‐8/P4VP/Au showed good stability, the catalytic performance was unchanged after three cycles. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) Zn-MOF-NH 2 /Cu heterojunctions were prepared via in situ photodeposition of Cu NPs on the surface of 2D Zn-MOF-NH 2. The 2D Zn-MOF-NH 2 /Cu (1 wt%) heterojunction exhibited the excellent photocatalytic activity with a CO production rate of 0.76 μmol/h under irradiation of full spectrum light only using H 2 O as a hole sacrificial agent, which is 16.2 and 2.7 times that of bulk Zn-MOF-NH 2 and 2D Zn-MOF-NH 2 nanosheets, respectively. This work provides an insight into design of a highly efficient 2D MOFs-based photocatalysts in catalytic CO 2 reduction. • 2D Zn-MOF-NH 2 nanosheets were prepared by a mild method. • 2D Zn-MOF-NH 2 /Cu heterojunctions have excellent activity in photocatalytic reduction of CO 2. • The CO generation rate of 2D Zn-MOF-NH 2 /Cu (1 wt%) is 16.2 times that of bulk Zn-MOF-NH 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • KOH was impregnated on rice husk KOH-activated carbon, named as DKOH-AC. • DKOH-AC involved both chemi- and physi-sorption when KOH-AC allowed physi-sorption. • CO 2 adsorption on DKOH-AC followed Freundlich and pseudo second order models. • DKOH-AC adsorbed 2.1 mmol/g in an indoor condition. Relatively high indoor CO 2 concentration (greater than 1000 ppm) has a negative impact on human health. In this work, a cost-effective CO 2 adsorbent (DKOH-AC) was developed by impregnating KOH on rice husk-based KOH activated carbon (KOH-AC, 1439 m2/g). KOH can be successfully loaded on the surface of KOH-AC and significantly changed its surface properties. DKOH-AC still remained a considerable surface area (206 m2/g) and showed a similar S micro /S BET ratio. In-situ FTIR analysis confirmed that the major CO 2 adsorption mechanism of KOH-AC was based on physisorption while that on DKOH-AC involved both chemisorption and physisorption. DKOH-AC showed a higher heat of adsorption (34 ∼ 41 KJ/mol) and gas selectivity (16.6) than these of KOH-AC. KOH-AC quickly reached an adsorption equilibrium (about 50 min) as compared to that of DKOH-AC. In addition, DKOH-AC exhibited an excellent adsorption performance of 2.1 mmol/g for a low concentration of CO 2 (2000 ppm ∼ 500 ppm) under indoor conditions. Both the CO 2 adsorption isotherm on KOH-AC and DKOH-AC well followed the Langmuir and Freundlich models. The CO 2 adsorption kinetics on KOH-AC followed the pseudo-first order model whereas that on DKOH-AC obeyed the pseudo-second order model. The adsorption process was controlled by the intraparticle diffusion combined with the film diffusion model. [ABSTRACT FROM AUTHOR]

CO 2 is a reactive gas frequently used for converting biomass or biochar into carbon materials with developed structures at high temperatures. However, at the temperatures (400–700 °C) typically employed for pyrolysis, CO 2 might also involve in pyrolysis and impact properties of the biochar formed, which was investigated in this study with cellulose as feedstock and N 2 or CO 2 as the carrier gas. The results indicated that CO 2 promoted the formation of biochar below 600 °C by suppressing cracking of biochar and enhancing secondary condensation of the volatiles. This reduced the size and abundance of the organics with π-conjugated structures in the bio-oil. CO 2 as an atmosphere produced the biochar with a carbon content higher than that produced in N 2 by 9.96%, and correspondingly the oxygen content was lowered by 36.68% in the biochar, as CO 2 facilitated deoxygenation and dehydrogenation reactions during the pyrolysis. The presence of CO 2 in the pyrolysis also made the biochar more aromatic and thermally more stable, which enhanced both energy yield and energy density of the process. As the heating temperature increases, CO 2 as an atmosphere will significantly affect the evolution of the oxygen-containing function of the biochar surface. [Display omitted] • Impact of CO 2 on properties of biochar in pyrolysis of cellulose was studied. • CO 2 enhances formation of biochar but not the π-conjugated organics in bio-oil. • CO 2 suppresses cracking while enhances secondary condensation of volatiles. • CO 2 facilitates deoxygenation/dehydrogenation to produce carbon-rich biochar. • Evolution of functional groups of biochar is affected by N 2 /CO 2 atmospheres. [ABSTRACT FROM AUTHOR]

The CO conversion rate and conversion efficiency were greatly enhanced by homogeneous dielectric barrier discharges generated in our experiment. Influence of CaO-BO-SiO glass addition on dielectric properties and microstructures of CaSrTiO were investigated for the purpose of discerning the effect of dielectric barrier material on the dielectric barrier discharge performance so as to improve the CO conversion rate and conversion efficiency. It was found that considerable grain boundaries on the dielectric barrier surface serving as charge trapping sites contribute a great many charges during plasma generation. And low resistance of the dielectric barrier surface distributes the charges effectively. More importantly, when the gap of the discharge is narrowed down, the surface charges on the dielectric barrier will play a dominant role during the discharge. As a result, for the 5.0 wt% glass addition, the CO conversion rate and conversion efficiency reached the maximum values of 48.71 % and 1.14 W/%, respectively. [ABSTRACT FROM AUTHOR]

• Mechanism of CO2 adsorption on biomass derived carbon was explained using DFT methods. • Building the relationship between nucleophilicity and adsorption capacity of biochar. • Carboxyl and diketone groups are the most active O-containing sites. • TG-MS experiments proved the effect of nucleophilicity group of biochar on CO 2 adsorption. CO 2 adsorption is an important issue for sustainable development today. In this study, zigzag edge and armchair edge cluster models containing oxygen-containing groups were established, and the interaction with CO 2 molecules was calculated based on Density functional theory. The results indicated that the carboxyl and diketone groups have the CO2 adsorption capacity. The relationship between CO 2 adsorption performance and nucleophilicity of O-containing groups was established. A subsequent TG-MS experiment also proved that the introduction of nucleophilic group can promote interaction between CO 2 and carbon surface. [ABSTRACT FROM AUTHOR]

As a critical intermediate substance or a target product, CO plays a vital role in the chemical looping processes. The control of CO conversion is significant since chemical looping processes with various target products have different requirements for CO content. In the present work, the CO oxidation behaviors with different oxygen species were investigated experimentally and theoretically with Ca-substituted lanthanum ferrite (LaFeO 3) as the oxygen carrier to regulate the CO conversion. The results showed that the CO 2 yield increased significantly when the adsorbed oxygen species was removed, suggesting that the lattice oxygen was the active oxygen species. It was consistent with the calculation result that the energy barrier of CO oxidation with lattice oxygen was lower than that with surface adsorbed oxygen. Moreover, the CO 2 yield increased with the increase of Ca concentration, indicating that Ca doping was favorable for lattice oxygen migration and further promoted CO oxidation. [Display omitted] • The Ca doping in LaFeO 3 promotes the migration of lattice oxygen and further enhances CO conversion. • The CO oxidation by COOH-mediated mechanism is more favored than the direct CO oxidation with single oxygen ion. • Removal of surface adsorbed oxygen can expose more active sites on the surface. • The active oxygen species is lattice oxygen of oxygen carriers for CO oxidation in chemical looping processes. [ABSTRACT FROM AUTHOR]

Herein, we described a finding in the CO 2 hydrogenation reaction: by just altering the support interface types in Cu-based catalysts, selectivity could be totally reversed. CH 3 OH selectivity on Cu/ZnO-MgO catalyst was about 80%, whereas CH 4 selectivity on Cu/ZnO-CoO catalyst was around 98%. [Display omitted] • A new method for constructing multiple interface types was proposed. • CZM showed CH 3 OH selectivity, while CZC exhibited CH 4 selectivity. • Strength of basicity site at support interface can affect product selectivity. • The adsorption position of H 2 COO* on catalysts is key for CO 2 hydrogenation products. Growing interest has been shown in controlling the selectivity of CO 2 hydrogenation to produce specific compounds and fuels with additional value. However, it is challenging to selectively generate target products due to the complexity and diversity of the products in CO 2 hydrogenation reaction. Herein, we reported a finding in the CO 2 hydrogenation reaction: selectivity could be totally reversed by just altering support interface types on Cu-based catalysts. Cu/ZnO-MgO catalysts showed high CH 3 OH selectivity, while Cu/ZnO-CoO catalysts exhibited good selectivity of CH 4. According to in-depth characterization, varied basicity sites most likely as results of the different support interface types. Density functional theory (DFT) calculations pointed that support interface types altered the adsorption position of H 2 COO* on catalysts and affect the adsorption and activation of intermediates, and thus resulted in noticeably varied product selectivity. This study demonstrated the value of regulating CO 2 hydrogenation selectivity via support interface types on Cu-based catalysts, which can aid in the rational design of catalysts for not only CO 2 hydrogenation but also other significant reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Leaching of the valuable metals and utilizing carbon residue from spent lithium-ion batteries. • K 2 CO 3 impregnated carbon utilized as an adsorbent for indoor CO 2 capture. • An investigation of the reaction mechanism for CO 2 adsorption on supported K 2 CO 3 under humid condition. • At low CO 2 concentrations, the CO 2 adsorption capacity for K 2 CO 3 /carbon ranged from 5.1 to 7.3 wt% Recycling and reusing the carbon-residues (i.e., graphite), as well as recovering valuable metals by leaching from spent lithium-ion batteries, is environmentally and economically significant. In particular, since a large amount of spent lithium-ion batteries (LIBs) will be generated along with the rapid growth of electric vehicles (EVs), research on recycling carbon-residues from LIB anodes is urgently needed. Herein, the battery powder (BP) was obtained from spent lithium-ion batteries (LIBs) through physical-pyrolysis and sieving. Chemical composition analysis confirmed that the battery used in this work was composed of NCM cathode with high-nickel content and graphite anode material. The average particle size of the obtained BP was 87 μm. In order to obtain the residue having high concentration of carbon, the metal extraction was applied using an HCl solution. As a result, metals (Li, Ni, Co, Mn, Al, Cu, and Fe) in the final remnant were found to be less than 2%, and carbon was found to have a purity of 97% or more. The obtained BP was tested as both the adsorbent and support for indoor CO 2 capture. Various activation treatments were examined to enhance the textural properties of BP. BP-K (K 2 CO 2 impregnated BP) adsorbents were prepared, and their CO 2 adsorption performances were evaluated with CO 2 adsorption isotherms, thermogravimetric analysis (TGA), and 0.1 m 3 chamber (CO 2 IR analyzer) at low CO 2 level (1000–2000 ppm). Through XRD and FT-IR analyses, the adsorption mechanism between K 2 CO 3 and CO 2 under moisture-containing indoor air conditions was confirmed to depend on chemisorption in the following reaction pathway: R1–R3(K 2 CO 3 (s) + H 2 O (g) + CO 2 (g) ⇋ 2KHCO 3 (s) (R1), K 2 CO 3 (s) + 1·.5H 2 O(g) ⇋ K 2 CO 3 ·1·.5H 2 O(s) (R2), K 2 CO 3 ·1·.5H 2 O(s) + CO 2 (g) ⇋ 2KHCO 3 (s) + 0·.5H 2 O(g)(R3)). The adsorption working capacities of the recycled BP-K adsorbents were remained relatively constant during four consecutive cycles. [ABSTRACT FROM AUTHOR]

CO 2 and H 2 O are two important activators in production of activated carbon (AC) via physical activation method. They could oxidize the carbonaceous species in biochar or biomass via varied mechanisms and might also impact environments as well as the pore structures and evolution of functionalities of AC in different ways. In this study, the activations of the biochar from pyrolysis of cellulose with H 2 O, CO 2 or mixed H 2 O/CO 2 were performed. The results demonstrated that H 2 O as an activator led to higher weight loss than that of CO 2 during the activation, originating from its higher efficiency for oxidation of the aliphatic structures in biochar to –OH and their further removal via deoxygenation or dehydration. Activation with CO 2 made the AC more oxygen-rich, due to the retainment of abundant oxygen-containing functionalities, which suppressed further oxidation of carbon species and led to formation of main micropores. The higher capability of H 2 O for deoxygenation made the AC more carbon-rich with much more developed pore structures as well as higher proportion of mesopores and thus the superior capability for adsorption of phenol. In addition, during the activation in either CO 2 or H 2 O, the unsaturated aldehyde/ketone and C-O-C structures was thermally more stable than lactones, saturated aliphatic acids and aliphatic aldehydes. The life cycle analysis (LCA) suggested that CO 2 activation showed lower impact on environment by reducing emissions and consumption of fossil fuel. [Display omitted] • Carbon yield is lower in activation of biochar from cellulose in H 2 O than in CO 2. • CO 2 makes activated carbon (AC) O-rich, due to lower capability for deoxygenation. • AC obtained with H 2 O has more developed pore structure of mesopores than with CO 2. • C C–C O and C–O–C on AC are more stable than saturated lactones/acids/aldehydes. • LCA indicates that CO 2 activation shows lower impact on environment. [ABSTRACT FROM AUTHOR]

• CAB-PILs showed excellent catalysis performance for CO 2 cycloaddition reaction. • Cycloaddition mechanism were investigated by experimental and DFT methods. • The Lewis base site of CAB-PILs is the CO2 adsorption center. • Lewis base and Bronsted acid sites have a synergistic effect. Conjugate acid-base bi-functional PILs (CAB-PILs) with carboxylate and carboxyl branches were synthesized and used as catalysts for the cycloaddition reaction of glycidol with CO 2. Two functional ionic monomers, 3-(carboxymethyl)-1-vinyl-1H-imidazol-3-ium chloride (CEImCl) and 2-(1-vinyl-1H-imidazol-3-ium-3-yl) acetate (CCIm), were introduced into the CAB-PILs skeleton. In this case, we proved the excellent characteristics of the catalyst containing both Lewis base and Bronsted acid sites for converting CO 2 to cyclic carbonate under mild conditions. The catalyst showed good reusability and remained excellent activity after five reaction cycles. Combined with XPS, FTIR and DFT calculations, it is proved that the CCIm ionic monomer not only play the role of CO 2 absorption center, but also has synergistic effect with CEImCl in CAB-PILs to promote cycloaddition reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reactions of volatile and biochar fill pores via forming carbon deposit on biochar. • Aliphatic of cellulose are more reactive than phenolics of lignin with biochar. • Volatile-char interaction consumes aldehydes/ketones and π-conjugated organics. • Volatile-char interaction dominate pore formation instead of activation with H 2 O/CO 2. • Interaction aids deoxygenation, forming C-rich biochar of higher energy yield. CO 2 and H 2 O are commonly used oxidants for activation of carbonaceous feedstock, which are also major products in biomass pyrolysis. The heated CO 2 and H 2 O from pyrolysis might be used directly to activate biochar without cooling down. This was investigated in a reactor with dual fixed beds with biochar on the bottom and biomass feedstock (poplar sawdust, cellulose, or lignin) of the same origin on top. The CO 2 and H 2 O together with the volatiles generated at 700 °C from the top bed passed through the lower-bed biochar for activation. The results indicated that, except for CO 2 and H 2 O, the volatiles from pyrolysis of upper-bed biomass were highly reactive with the lower-bed biochar, especially for the cellulose-derived aliphatic volatiles. This formed carbonaceous deposit and enhanced the yield of biochar at expense of the volatiles (i.e. aldehydes/ketones and heavy organics of large π-conjugated structures), leading to lower yields of bio-oil. The carbonaceous deposit formed via cracking and/or polymerization filled the pores and substantially decreased the surface specific area by 99.9 % for sawdust-biochar, 87.4 % for cellulose-biochar, and 33.1 % for lignin-biochar. The volatile-char interaction, instead of the activation with CO 2 and H 2 O, dominated the pore development of biochar. Additionally, the interaction of volatiles with biochar enhanced deoxygenation, producing the carbon-rich biochar of higher heating value and energy yield. [ABSTRACT FROM AUTHOR]

CO 2 can be used to activate biomass for production of activated carbon at high temperatures (usually above 700 °C). At typical pyrolysis temperatures, CO 2 might also involve in biomass pyrolysis, which was investigated via pyrolysis of lignin at temperatures from 400 to 700 °C in N 2 and CO 2 atomsphere, respectively. The results suggested that CO 2 interfered with the pyrolysis process, facilitating formation of bio-oil and biochar but not gases via suppressing further gasification of volatiles. This reserved more mono-ring phenolics in bio-oil and also formed more heavier phenolics through secondary condensation routes. As for biochar, CO 2 enhanced the aromatization process, generating the carbon-rich biochar of higher heating value. The in-situ characterization of the functionalities of biochar during pyrolysis suggested that CO 2 accelerated removal of the aliphatics like -OH, -C-H, C O, and C-O-C. This rendered the biochar of hydrophobic surface but less fragmentized structures than that obtained in N 2. [Display omitted] ● CO 2 interferes with formation of volatiles and biochar in lignin pyrolysis. ● CO 2 enhances the formation of biochar and bio-oil at the expense of gases. ● CO 2 suppress cracking of volatiles into gas but promotes secondary condensation. ● CO 2 aids removal of aliphatic structures, making biochar of hydrophobic. ● CO 2 promotes aromatization, producing carbon-rich biochar of higher energy yield. [ABSTRACT FROM AUTHOR]

Rich Cu-ZnO interfaces play a significant role in Cu/ZnO catalysts for CO 2 hydrogenation to methanol. However, the low methanol selectivity and catalytic stability of reported Cu/ZnO catalysts mainly ascribe to the reduction of Cu-ZnO interfaces, which caused by the agglomeration of Cu nanoparticles. Herein, Cu/ZnO catalysts (named Cu x ZnO-MOF-74–350) with rich Cu-ZnO interfaces were prepared by using Cu-Zn bimetallic metal organic framework (MOFs)-templated strategy (x is the feeding ratios of Cu/Zn). Especially, CuZnO-MOF-74–350 catalyst exhibited high methanol selectivity of about 80% at a CO 2 conversion of 7.5%, and had long-term durability for 100 h at 190 ºC under 4.0 MPa. The great catalytic performance mainly resulted from rich interfaces, which were conducive to the adsorption of CO 2 and the formation of intermediate. This study provides a novel strategy for optimizing the activity of catalysts in the view of the regulation of interface. [Display omitted] • A novel Cu/ZnO catalyst was constructed by Cu-Zn bimetallic MOFs-templated strategy for CO 2 hydrogenation to methanol. • CuZnO-MOF-74–350 catalyst was characterized by uniform dispersion of Cu and Zn elements and rich Cu-ZnO interfaces. • CuZnO-MOF-74–350 catalyst exhibited high CO 2 adsorption capacity and strength, and strong reducibility. • CuZnO-MOF-74–350 catalyst showed good catalytic performance with high CH 3 OH selectivity and had long-term durability. [ABSTRACT FROM AUTHOR]

• Chlorella sp. was able to grow in a broad range of CO 2 levels (5–30%). • The highest biomass productivity (0.033 g L−1 d−1) was achieved at 15% CO 2. • ALA was dominant PUFA and reached 50.11% under 30% CO 2. • Under 15% CO 2 , SFA content increased to 31.91%, which enhanced CN value to 38.07. • Bio-oil quality was better under air due to higher hydrocarbon and lower acid. Nowadays, biological mitigation of carbon dioxide (CO 2) by means of microalgae is one of the promising approaches, as biomass can be used to produce renewable fuels such as biodiesel and crude bio-oil. In this study, the growth of Desmodesmus sp. in response to different CO 2 levels (ambient air, 5%, 10%, 15%, 20%, 25%, 30%, and 35% CO 2) was studied, and then the suitability of the biomass for bio-oil and biodiesel production was evaluated. The studied strain was able to grow efficiently in a broad range of elevated CO 2 (5–30%, v/v), suggesting its suitability for CO 2 mitigation. The highest specific growth rate (0.769 d−1) and biomass productivity (0.033 g L−1 d−1) were achieved at 15% CO 2 ; therefore, the concentration of 15% CO 2 was selected as the optimum. Alpha-Linolenic acid (ALA) was the dominant polyunsaturated fatty acids (PUFAs) in studied Desmodesmus strain, and its content increased from 31.82% under ambient air to 41.94% and 50.11% under 15% CO and 30% CO 2 , respectively, suggesting a key role of ALA in response to CO 2 elevation. Using fatty acid methyl ester (FAME) profiles of cultures in different CO 2 conditions, biodiesel parameters such as cetane number (CN), saponification value (SV), iodine value (IV), long chain saturation factor (LCSF), oxidative stability (OS), higher heating value (HHV) and degree of unsaturation (DU) were estimated. Overall, the lipid extract was not suitable for biodiesel production due to high PUFA content ranging between 52.91% and 71.14%. Under optimum CO 2 (15%), saturated fatty acids (SFAs) content increased to 31.91% and PUFA content reduced to 52.91%. This could significantly improve the CN to 38.07, which was 11% and 13% higher than the air and 30% CO 2. Pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) was used to analyze the potential of microalgal biomass for bio-oil production upon CO 2 changes. The pyrolysate contained 40–47% acid content due to the high content of fatty acids. The pyrolysate quality declined under 15% CO 2 due to the higher accumulation of acidic and nitrogen-containing compounds and reduced hydrocarbon proportion. In conclusion, the optimum CO 2 could enhance biodiesel parameters such as CN, but demonstrated negative effects on bio-oil quality. [ABSTRACT FROM AUTHOR]

Economically efficient biomass production is crucial to lift the microalgal circular bioeconomy requiring low production cost with higher biomass and value-added products. In this study, Micractinium sp. YACCYB505 was cultured at different illuminations (1600, 2400, 3200 lux) and CO 2 conditions (up to 10%) to evaluate biomass productivity and accumulation of macromolecules (lipid, carbohydrate and protein). The product optimization study was conducted to analyze individual variables of environmental factors by using a Box-Behnken design. Highlight intensity (3200 lux) and 5% CO 2 aeration maximized biomass productivity on 11th day of microalgal harvest. Microalgal lipid accumulation indicated positive impact on increased CO 2 aeration and light intensity treatment. Similarly, a considerable amount of protein content (9%) was increased at higher CO 2 aeration but raised light intensity had a negative impact on protein biosynthesis. Significant carbohydrate content reduction was observed with increased light intensity and CO 2 aeration. The overall results proved that increased CO 2 concentration (10%) and light intensity (3200 lux) enhanced lipid accumulation (32%) and biomass productivity in Micractinium sp., which provides potential to achieve a sustainable, cost-effective biomass and value-added products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Steps with O and Ca at the edges are the best termination for SO 3 adsorption. • Adsorption energy has a remarkable increase at edge sites on step surface. • Coordination of O and Ca at edges affect SO 3 adsorption. • Pre-adsorption of SO 3 or SO 2 at neighboring sites increases SO 3 adsorption energy. • SO 3 adsorption is more stable than the adsorption of SO 2 and CO 2 at edge sites. With the application of high-sulfur coal and oxy-fuel combustion in power plants, the formation of SO 3 in flue gas has strongly enhanced. Hence, the removal of SO 3 has received growing attention. Within this context, SO 3 sorption using calcium-based sorbents is an interesting approach. In this study, we analyzed the steps on a CaO surface and examined their influence on the adsorption of SO 3 molecules using density function theory calculations. The results indicate that steps with O and Ca atoms at the edges are the most stable terminations and also the best terminations for SO 3 adsorption. SO 3 molecules bind to O CaO sites by S SO3 atoms and weak bonds between Ca and O SO3 are formed. At edge sites, the adsorption energy of SO 3 , SO 2 and CO 2 shows a remarkable increase compared to that on a flat surface, whereas it decreases at the top site nearby the edge. The adsorption energy of SO 3 is also affected by the O CaO that interacts with S SO3 and the Ca near the O CaO. Interestingly, the SO 3 adsorption energy can increase if an SO 3 , SO 2 or CO 2 molecule previously adsorbed at a neighboring site. SO 3 adsorption is more stable than SO 2 and CO 2 absorption on step surface and has an advantage in competitive adsorption with SO 2 or CO 2. The calculation results thus indicate that the formation of a step surface could be an effective method to enhance SO 3 sorption on calcium-based sorbents. [ABSTRACT FROM AUTHOR]

Sorption enhanced gasification of biomass is a novel technology for high purity H 2 production and simultaneous carbon negative emission. The effect of CaO on the H 2 production process was normally qualitatively explained. To quantitatively study the enhancing mechanism of CaO, the sorption enhanced gasification of cellulose for H 2 rich syngas production was carried out in a fixed-bed pyrolysis-gasification system, the amount of CO 2 absorbed, the carbon conversion rate of volatiles as well as the changes in the role of CaO under different gasification conditions were quantitatively studied. The results showed that CaO acted as a CO 2 absorbent and/or a catalyst depending on the gasification temperature. It functioned as both a CO 2 absorbent and a catalyst at lower temperatures of 550–700 °C, and a maximum amount of CO 2 absorbed by CaO was achieved at 550 °C as 189.88 ml/g cellulose, CaO catalyzed the volatiles gasification to produce more H 2 and achieve more sufficiently conversion with increasing temperature. While when the gasification temperature ≥750 °C, CaO acted only as a catalyst. The optimized condition for sorption enhanced pyrolysis-gasification of cellulose was of gasification temperature of 650 °C and of mass ratio of CaO/cellulose of ≥4, under which the actual carbon conversion rate of volatiles achieved ∼90 wt.%. [Display omitted] • Sorption enhanced pyrolysis-gasification of cellulose for H 2 production was studied. • CaO acted as an absorbent and/or a catalyst depending on gasification temperature. • Maximum CO 2 absorbed by CaO was 189.88 ml/g cellulose at 550 °C during gasification. • The gasification rate, CO 2 absorption and catalysis of CaO were optimized at 650 °C. • A carbon conversion rate of ∼90 wt.% was achieved at 650 °C with CaO/cellulose of 4. [ABSTRACT FROM AUTHOR]

Reducing carbon dioxide (CO 2) emissions has been a hot research topic in recent years. The integration of microalgae cultivation using CO 2 from power plants and factories has been introduced as an environmentally friendly approach. However, strains with high biomass productivity are required to achieve a sustainable integrated platform. Improving photosynthesis is critical to increase both biomass productivity and CO 2 sequestration efficiency. The improvement of photosynthesis is often attained by enhancing the efficiency of enzymes that are involved in CO 2 fixation, reducing the antenna size to avoid energy loss, extending the photosynthetically active radiation range to broaden the light utilization capacity, increasing CO 2 assimilation by replacing the existing carbon fixation pathway with more efficient pathways and enzymes, and reducing the release of captured CO 2. Implementation of these modifications is achievable via transformation and gene editing. The transformation of the new gene constructs into microalgae has been discussed as an extremely challenging task in the past decade. In recent studies, the digestion of the microalgae cell wall, as one of the main barriers of transformation, has been recommended as a promising approach. Moreover, the emergence of preassembled Cas9 protein-gRNA ribonucleoproteins that do not require vector constructs has been suggested as an efficient approach for gene editing. This review comprehensively describes the potential strategies that enhance microalgae CO 2 fixation, provides insight into current limitations and gaps, and proposes future perspectives. Image 1 • Improving microalgae strains can lead to a viable platform mitigating CO 2 and produce biomass. • Photosynthetic pathways can be engineered to consume more and release less CO 2. • Degradation of cell wall enhances the delivery of gene-editing tools into microalgae. • Using preassembled RNP instead of vectors, and gene delivery by electroporation showed promising results. • Adaptive laboratory evolution (ALE) can be considered as a substitute for genetic engineering. [ABSTRACT FROM AUTHOR]

In this study, the effect of char preparation temperature on the interactions between cellulose volatiles and acid-washed sawdust char was investigated experimentally on a fixed-bed pyrolysis system. The results indicated that significant volatile-char interactions did exist at the pyrolysis temperature of 500 °C as evidenced by the great changes in the composition and distribution of pyrolysis products. The oxygen-containing functional groups as well as the aromatic ring systems in the char both acted as active sites during the volatile-char interactions. The changes in chemical structure of biochar caused by the different preparation temperatures would notably affect the final products of cellulose pyrolysis. Meanwhile, the acid-washed sawdust char was still found to participate in the reaction process, lower temperature chars would have higher reactivities, and an obvious weight loss of char was also observed after interactions. In addition, volatile-char interactions significantly increased the yields of non-condensable gases, especially those of CO and CO 2 , while decreased the yield of condensable vapors. The introduction of biochar into cellulose pyrolysis could promote the ring scission of pyranoses as well as the decarbonylation/decarboxylation and dehydration reactions, thus caused the yields of anhydrosugars and monoaromatic compounds decreased and the yields of light ketones and acids increased. Image 1 • Effect of char preparation temperature on volatile-char interactions was studied. • O-containing groups and aromatic ring systems in char both acted as active sites. • Char participated in the reactions with an obvious weight loss after interactions. • Interactions enhanced non-condensable gas yield and reduced condensable vapor yield. • Char promoted ring scission of pyran and decarbonylation and dehydration reactions. [ABSTRACT FROM AUTHOR]