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Thermosetting polymers are used in a wide range of applications due to their robust mechanical strength and superior flame retardancy. Despite these technical benefits, recycling of thermosetting polymers has been challenging because of their crosslinking nature. Moreover, their disposal through conventional methods (landfill and combustion) poses environmental concerns, such as microplastics and air pollutants. To address these issues, this study introduces a thermo-chemical disposal platform for thermosetting polymer wastes that employs carbon dioxide (CO 2 ) as a reactive medium. In this work, melamine-formaldehyde was used as model compound of thermosetting polymers. In single-stage pyrolysis, it was revealed that CO 2 plays a crucial role in controlling in the compositional matrices of pyrolytic gases, liquid products, and wax. These compositional changes were attributed to the homogeneous reactions between CO 2 and the volatile compounds released from the thermolysis of MF. To enhance the thermal cracking of the MF, a double-stage pyrolysis process was tested, which increased the production of pyrolytic gases and eliminated wax formation. However, the slow kinetics governing the reactivity of CO 2 limits the occurrence of homogeneous reactions. A nickel-based catalyst was used to accelerate reaction kinetics. The catalytic pyrolysis under CO 2 conditions led to substantial increases in syngas (H 2 and CO) production of 880% and 460%, respectively, compared with double-stage pyrolysis. These findings demonstrate that thermosetting polymer wastes can be valorized into gaseous fuels through thermo-chemical process, and CO 2 enhances the recovery of energy and chemicals. Therefore, this study presents an innovative technical platform to convert thermosetting polymer wastes and CO 2 into syngas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

[Display omitted] • Cryogenic CO 2 capture and storage (CCS) reduces power generation efficiency penalty. • Power consumption during natural gas liquefaction decreases by up to 67.17%. • Liquefied natural gas (LNG) supply chain with cryogenic CCS reduces energy waste. • Natural gas liquefaction and regasification are integrated based on cryogenic CCS. • The exergy efficiency in the LNG supply chain is increased from 18.18 to 46.39%. Natural gas combined cycle power plants generate substantial amounts of CO 2. Also, since natural gas is produced in limited sites, the liquefied natural gas (LNG) supply chain consumes considerable energy in transporting natural gas overwide. Herein, advanced natural gas liquefaction and regasification processes using an LNG supply chain with cryogenic CO 2 capture and storage (CCS) are proposed using Aspen Plus® V11. This solves three significant problems associated with conventional LNG supply chains. First, through the utilization of LNG cold energy, the cryogenic CCS process reduces the efficiency penalty of power generation from 14.34 to 4.45%. Second, solid CO 2 from cryogenic CCS is used as an additional cold source in the natural gas liquefaction process by conveying it to the liquefaction site via the returning LNG ship. As a result, the power consumption in the refrigerant cycle is reduced by up to 67.17% than single mixed refrigerant (SMR) process. Finally, the LNG supply chain with cryogenic CCS minimizes the sustained energy waste between the natural gas liquefaction and regasification stages owing to the geographical separation. LNG cold energy from the regasification stage is utilized in the form of solid CO 2 in the CCS and liquefaction stages. Consequently, the exergy efficiency in the overall LNG supply chain increases from 18.18 to 46.39%. The findings of this study can potentially provide environmentally friendly design guidelines for various LNG processes that use LNG cold energy in CCS and natural gas liquefaction. [ABSTRACT FROM AUTHOR]

Power-to-methane (PtM) coupled with renewables requires an energy buffer to ensure a steady and flexible operation. Liquid CO 2 energy storage (LCES) is an emerging energy storage concept with considerable round-trip efficiency (53.5%) and energy density (47.6 kWh/m3) and can be used as both an energy and material (i.e., CO 2) buffer in the PtM process. Integration of LCES with the PtM process realizes co-production of methane and electricity, supports peak shaving of the power grid, and enhances profitability via the sale of electricity at peak hours. This study aims to design, optimize, and comprehensively evaluate the techno-economic performance of the PtM-LCES process using a renewable power mix of solar and wind. A process scheduling model is formulated to understand the impacts of storage sizing and power allocation on the process performance. Then, artificial neural network-based surrogate optimization was performed to establish a cost-optimal design. Investigation at Kramer Junction, California, found that the production cost of methane was 161.6 €/MWh with an efficiency of 76.2% and a renewables penetration of 78.7%. This cost could be reduced by improving LCES's performance and considering electricity price arbitrage in areas with high electricity prices. The electricity price arbitrage and improvement of LCES's performance could lower the cost to 83.8 and ∼60 €/MWh, respectively. Moreover, zero or negative carbon emissions can be achieved if the renewables penetration can be increased to 91.5%. Results indicate that the PtM-LCES process is both energy efficient and economically viable, through which renewable methane can be cost-competitive with fossil natural gas. • Power-to-Methane coupled with renewables via liquid CO 2 energy storage. • Process flexible operation achieved by a bidirectional connection with the grid. • Energy- and cost-efficient production of methane in a continuous manner. • Costs of methane in different scenarios range from 60 to 161.6 €/MWh. [ABSTRACT FROM AUTHOR]

Steam methane reforming (SMR) process is facing serious greenhouse effect problems because of the significant CO 2 emissions. To reduce pollution caused by gaseous emissions, desalination wastewater can be used because it contains highly concentrated useful mineral ions such as Ca2+, Mg2+, and Na+ , which react with carbonate ions. This study proposes a novel SMR process for carbon-neutral hydrogen production integrated with desalination wastewater-based CO 2 utilization. A process model for the design of a novel SMR process is proposed; it comprises the following steps: (1) SMR process for hydrogen production; and (2) desalination wastewater recovery for CO 2 utilization. In the process model, the CO 2 from the SMR process was captured using the Na+ ion, and the captured ionic CO 2 was carbonated using the Ca2+ and Mg2+ ions in desalination wastewater. The levelized cost of hydrogen (LCOH) was assessed to demonstrate the economic feasibility of the proposed process. Therefore, 94.5 % of the CO 2 from the SMR process was captured, and the conversion of MgCO 3 and CaCO 3 was determined to be 60 % and 99 %, respectively. In addition, the CO 2 emission via the proposed process was determined to be 0.016 kgCO 2 /kgH 2 , and the LCOH was calculated to be 2.6 USD/kgH 2. [Display omitted] • Steam reforming process was integrated with desalination wastewater process. • Feed stock restriction of the pollutant absorbent is possible to be solved. • Environmental contamination by desalination wastewater is prevented. • 94 % of CO 2 from the steam reforming process is capture and utilized. • Levelized cost of hydrogen production was 2.6 USD/kgH 2 by CO 2 and SO x utilization. [ABSTRACT FROM AUTHOR]

A series of porous organic polymers (denoted as PBP- x) possessing various functional groups was synthesized via Friedel–Crafts alkylation followed by post-synthetic functionalization using amine and sulfonic groups. These functionalized porous polymers were incorporated into an in-house polyimide to fabricate mixed-matrix membranes for CO 2 /N 2 separation. Gas permeation testing revealed that these functionalized porous fillers substantially improved the CO 2 separation performance. Moreover, optimizing both the functionality and pore structure of the porous fillers was found to drastically improve the CO 2 /N 2 separation performance. In particular, the addition of 10 wt% PBP-menm (menm = 1,2-methylethylenediamine) induced an ultrahigh CO 2 permeability of 2988 barrers (158% higher than that of a pure polymer membrane), thus realizing excellent performance that surpasses the Robeson upper bound for CO 2 /N 2 separation. [Display omitted] • Porous organic polymers possessing various functional groups were synthesized. • Defect-free mixed-matrix membranes comprising these functionalized porous fillers were successfully fabricated. • Optimizing both functionality and pore structure of porous fillers led to enhanced CO 2 transport. • The performance of the membrane with the optimum filler surpassed the Robeson upper bound for CO 2 /N 2 separation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A sustainable conversion of plantation waste into syngas was achieved using CO 2 (key greenhouse gas). • CO 2 served a partial oxidant reacting with volatile pyrogenic products evolved from rubber tree residue, leading to enhancement of syngas, especially CO. • Oxidative functionality of CO 2 on syngas production was intensified in the presence of a nickel-based catalyst (Ni/Al 2 O 3). • Integrated process of catalytic pyrolysis and water–gas shift reaction notably increased H 2 productivity. This study introduces the sustainable recovery of energy from plantation waste by converting rubber tree residue (RTR) into syngas through carbon dioxide (CO 2)-assisted pyrolysis. The investigation centers on elucidating the specific impact of CO 2 on the pyrolysis of rubber tree residue, emphasizing its significant influence on enhancing syngas production. At temperatures ≥ 500 °C, CO 2 engages with volatile matters (VMs) released during the thermolysis of rubber tree residue, increasing carbon monoxide (CO) yields. To further optimize the process, catalytic pyrolysis setups incorporating additional heat (600 °C) and a nickel-based catalyst (Ni/Al 2 O 3) were implemented. These experimental configurations substantially increased syngas production from 19.51 to 24.24 mmol g−1, particularly amplifying CO yields under CO 2 conditions 2.58-fold compared to nitrogen (N 2) conditions. This enhancement is attributed to the partial oxidation of volatile matters facilitated by CO 2. Additionally, the Ni/Al 2 O 3 catalyst played a pivotal role in expediting the gas-phase homogeneous reaction of CO 2 with volatile matters, leading to further improved syngas production. Indeed, the syngas yield in the catalytic pyrolysis in the presence of CO 2 was 24.24 mmol g−1, which increased by 1.24 times in reference to the result under the N 2 environment. The identified functional role of CO 2 presents an opportunity to enhance the sustainability of waste management by optimizing carbon utilization and generating value-added products. [ABSTRACT FROM AUTHOR]

• Novel waste energy recovery process for carbon capture and storage was developed. • Waste cold and hot energy from liquefied natural gas plant is recovered. • Net power generation can increased by 16% compared to base process. • Net profit can increased by 75% compared to base process. In an liquefied natural gas (LNG) power plant, the amine scrubbing and CO 2 liquefaction process are generally employed for CO 2 capture and storage (CCS) because it is suitable for large-scale plants. However, a large amount of hot and cold energy is required for CO 2 absorption, regeneration and liquefaction. As a solution, the waste LNG cold energy from the LNG regasification process and waste hot energy from natural gas combined cycle (NGCC), which are generally disposed into the seawater, can be recovered and utilized for the abovementioned purposes. Hence, this study suggested a novel process for waste hot and cold energy recovery of the LNG power plants for CCS. The suggested process model consists of the following four steps: LNG regasification, natural gas combined cycle, CO 2 capture and regeneration and CO 2 liquefaction. In the process model, the waste LNG cold energy is recovered at the lean amine cooler in the CO 2 capture process and each heat exchanger in the CO 2 liquefaction process. Furthermore, for CO 2 regeneration, the waste hot energy from NGCC is recovered at the stripper reboiler. The exergy and economic analyses were addressed to evaluate the economic feasibility of energy conversion of the proposed process. As a result, compared to the base process, the net power generation and exergy efficiency of the proposed process increased by 16% and 8%, respectively. In addition, the net profit of the proposed process increased by 75%, indicating high economic feasibility. The overall energy efficiency and economic feasibility using waste cold and hot energy were observed to increase, which resulted in decreased fuel usage. Therefore, we believe that the proposed approach can contribute significantly to the economic improvements and environmental protection efforts. [ABSTRACT FROM AUTHOR]