Acid tar pits represent some of the most heavily contaminated land and are widespread in the UK, and globally. They pose significant challenges to remediate, with options typically consisting of financially and logistically expensive mixing and/or moving of contamination and disruption to surrounding areas. Phytoremediation offers a great opportunity to remediate hydrocarbon-related pollution, but many studies take place at small spatial and temporal scales and in controlled conditions. Here we present the monitoring results of a large-scale field trial (30 m × 16 m area) of willow (Salix) phytoremediation of an acid tar pit at Cinderhill, UK. Results show that tars had not degraded since deposition in the 1970s before the trial but, after planting with willow spilling, evidence of degradation was clear, with a reduction in n-alkane and PAH concentrations. After 2 years, tar breakdown was only recorded in close association with willow root systems, but after 3 years was documented in tars not targeted by root growth. Willow also stabilised the tar pit surface, altered its topography and enabled the establishment of a diverse understory flora and, along with initial liming of the area, contributed to reduced surface pH from highly acidic to neutral. eDNA of microbial communities in tars near willow roots were highly distinct from tars away from roots, and surrounding soils. The community around willow roots included species known to process PAHs and hydrocarbons, and also to include species that aid vegetation growing in stressful environments. This holistic assessment of the phytoremediation of an acid tar pit indicates its significant potential as a remediation option. Challenges and unforeseen issues during the trial, future work, and knowledge gaps are discussed.

This study evaluated the application of biochar for internal carbonation curing (ICC) and its effects on CO2 uptake, phase assemblage, pore structure, mechanical performance, and overall CO2 emission of cementitious materials. Four commercially available biochars were systematically compared under a unified testing protocol, and, within this application-oriented candidate screening, the biochar with a more balanced ICC-relevant CO2 uptake and post-adsorption retention performance under air purging (retaining 4.8 wt.% CO2) was selected for ICC investigation. Results showed that ICC enabled effective CO2 fixation at early hydration, producing calcite-dominated carbonate phases. With 10% replacement, the ICC mixture achieved a CO2 uptake of 4.6% after 1 day, 47.9% higher than the control. These carbonates not only provided nucleation sites to accelerate hydration-product precipitation but also promoted the formation of hemicarboaluminate (Hc), leading to a 4.2% reduction in total porosity after 1 day. Consequently, the refined microstructure enhanced compressive strength, with the 10% ICC mixture showing gains of 21.9% and 7.3% after 1 and 28 days versus the corresponding virgin biochar mixture. At this dosage, net CO2 emission was 413 kg CO2 t-1 (64.1% of the control), confirming the carbon-mitigation potential of biochar-based ICC. These findings highlight the importance of post-adsorption CO2 holding behavior in governing effective internal CO2 availability and elucidate the hydration-carbonation synergy induced by CO2-adsorbed biochar, demonstrating the feasibility of ICC to promote in-situ CO2 mineralization while mitigating the strength penalty associated with biochar incorporation, thereby supporting a viable pathway to high-performance, low-carbon construction materials.

Zeolites, as one of the most versatile classes of catalysts, exhibit remarkable potential in CO2 chemistry and play a pivotal role in advancing the circular carbon economy. Owing to their unique physicochemical properties, zeolites serve as excellent platforms for catalytic CO2 valorisation, particularly in hydrogenation reactions. They act as multifunctional catalyst supports, enabling the anchoring of metal active sites through diverse strategies, such as nanoparticle encapsulation and single-atom stabilisation, while also providing additional functionalities for tandem catalytic processes. Consequently, metal-zeolite catalyst systems effectively promote the conversion of CO2 into both C1 products (e.g., CO, CH4, and methanol) and high-value multi-carbon products (e.g., oxygenates, olefins, and aromatics). Recent research efforts have therefore focused on enhancing these catalytic systems by tailoring zeolite characteristics, including pore structure and acidity. In this review, we present a comprehensive overview of zeolite-based CO2 hydrogenation, highlighting the multiple roles of zeolites within metal-zeolite catalysts, the modification strategies employed, and the mechanistic insights underlying improved performance. We further discuss structure-performance correlations, assess industrial prospects, and outline future research directions. This work provides a timely overview of state-of-the-art metal-zeolite catalysts for CO2 hydrogenation, serving as a valuable reference for the continued development of CO2 valorisation technologies.

Biochar has high potential for long-term atmospheric carbon storage in terrestrial environments, contributing to meeting the UK and global greenhouse gas emission reduction targets. This study investigates the greenhouse gas emissions and techno-economics associated with biochar produced from food waste anaerobic digestate using hydrothermal carbonisation followed by high-temperature post carbonisation. Owing to high moisture contents, digestates are challenging to valorise. However, these low-value feedstocks have steady availability with minimal competition for other applications. The study focuses on food waste digestate supply, biochar production, biochar agricultural field application, and transportation activities. Minimising digestate transport through co-locating biochar production facilities with anaerobic digestion displayed greenhouse gas mitigation costs of < £100 tCO 2 eq −1 (125 USD tCO 2 eq −1 ). The 88% stable carbon fraction of the biochar, which is resistant to degradation in soil, is primarily responsible for the effective removal of atmospheric greenhouse gases. This results in net emissions reductions of 1.15–1.20 tCO 2 eq per tonne of biochar, predominantly due to the long-term storage of durable carbon (1.7 tCO 2 eq per tonne of biochar). Using 50% of the UK’s projected available food waste digestate by 2030 offers a sequester potential of 93 ktCO 2 eq p.a., requiring 28 biochar facilities at 20 kt p.a. capacity. Sensitivity analysis emphasises the influence of the gate fee charged to process digestate, highlighting its importance for economic success of the biochar production. Further studies are needed to investigate the potential technology enhancements to reduce fossil-fuel use and provide greater certainty of the co-benefits of biochar application in agricultural soil. Graphical Abstract

Synthesis of chloromethyl ethylene carbonate (CMEC) via CO2 cycloaddition to epichlorohydrin (ECH) has been investigated using a simple metal-free and halide-free catalyst comprising 4-dimethylamino pyridine (DMAP) and N-H type hydrogen bond donors (HBDs). Combining DMAP and 1,3-diphenyl thiourea (DPTU) had the strongest synergistic effect, which resulted in the highest improvement in CMEC yield. DMAP/DPTU was active in the presence of a simulated flue gas (15 % C02 in N2) at low temperatures (30 - 60 degrees C), reaching a high CMEC yield (93 %) and selectivity (98 %) at 40 degrees C in 24 h. The presence of O2 in simulated flue gas had no effect on catalytic activity; however, excessive H2O in the reactor had a negative effect, resulting in low yield and selectivity. The reaction obeyed pseudo-first-order kinetics in terms of ECH, DMAP, and DPTU concentrations. The addition of DPTU increased the observed rate constant (kobs) by a factor of 1.52 while decreasing the activation energy (Ea) of the reaction by 7.37 kJ/mol, indicating that the synergistic action of DPTU (HBD) and DMAP (nucleophile) influenced catalytic performance. The positive enthalpy (Delta H`) and Gibbs free energy (Delta G`) values indicate an endergonic and kinetically controlled reaction.

Carbon dioxide removal (CDR) at gigaton-scale is essential to meet the Paris climate goals. Relevant CDR rates can only be achieved through the co-deployment of multiple CDR approaches. However, synergisms between different CDR methods and joint co-benefits beyond CDR have seldom been investigated. The combination of pyrogenic carbon (PyC) and enhanced weathering of minerals (Mi) for carbon capture and storage (CCS), in short PyMiCCS, presents a potentially synergetic and multifunctional approach that may be achieved by either co-application of biochar and rock powder to soils or the co-pyrolysis of biomass and rock powder before soil use. Here, we mixed biomass (wood; straw) with 10 to 50 wt% silicate rock powder (namely basanite or diabase) for co-pyrolysis to produce twelve different rock-enhanced (RE-)biochars. Products were subject to physico-chemical characterization, including an assessment of carbon yield and proxies for biochar persistence. Rock-enhanced biochars showed higher nutrient content, liming- and C-sink potential but lower solid-state electrical conductivity and porosity compared to pure biochars. Co-pyrolysis resulted in a coating of rock particles with secondary char but did not affect the net carbon yield. The thermal stability of wood-based RE-biochars (+10 wt% rock) was higher than that of pure woody biochars. However, the underlying mechanism and implications for biochar persistence in the environment need further investigation. Despite the addition of rock powder, the short-term release of ions from the ash fraction remains dominated by cations and anions of biogenic (biochar) origin. Therefore, it is still unclear whether the pyrogenic coating influences rock weathering. Co-pyrolysis with rock dust opens further options for designing biochar properties and to produce novel composite materials catering for multifunctional CDR.

This study examines the effect of high water pressure (up to 900 bar) on hydrocarbon generation from Type-I kerogen-rich source rocks and compares the results with previously observed effects on Type-II and Type-III kerogens. An immature Type-I oil shale sample from the Duwi Formation, Egypt, was pyrolysed under anhydrous, low-pressure hydrous, and high water-pressure conditions at 320 degrees C (end of bitumen generation) and 350 degrees C (oil window) for 6 and 24 h, respectively. Pyrolysis at 320 degrees C showed that bitumen generation was promoted in the presence of water under lowpressure hydrous compared to anhydrous conditions but retarded at high water pressures. At 350 degrees C, oil generation was also retarded by increasing pressure, with maximum oil yield at 500 bar before dropping by 72% at 900 bar. Lower bitumen yields at 500 bar and higher yields at 900 bar confirm more retention of oil and bitumen in the rock at higher pressure. High water pressure systematically decreased hydrocarbon gas yields, with a more prominent effect at 320 degrees C because of temperature's dominant impact over pressure at 350 degrees C. Similarly, non- hydrocarbon gas yields decreased as water pressure increased, with maximum yields under anhydrous and low-pressure hydrous conditions. The retardation effect on bitumen generation was less significant than that on oil and gas generation. This study highlights pressure's impact on petroleum generation, particularly in overpressured basins. Elevated pressures on Type-I kerogen source rocks retard oil expulsion, and the retained oil and bitumen within the rock can be directly cracked to gas, suggesting that under such conditions, oil yields may be lower, while unconventional gas resources are likely to be more abundant.

The paper examines the design and techno-economic risk assessment of a carbon capture and storage (CCS) process using silica-polyethyleneimine (Si-PEI) as a solid sorbent. This CCS process was integrated into a cement plant with an annual production of one million tonnes of clinker, representing the EU's average plant size. The study benchmarks the Si-PEI CCS process against the monoethanolamine (MEA) CCS process, assuming both systems capture 90 % of the plant's annual emissions. Aspen Plus models, validated through literature and experiments, simulated the CCS processes. A preliminary hazard analysis assessed technical risks, while economic risks were quantified using the Monte Carlo method, considering uncertainties in feedstock supply cost, cement selling price, solvent/sorbent cost, energy cost, and emission allowance price. The Si-PEI CCS unit emerged as the most favourable investment, being less expensive and technically safer than the MEA CCS unit due to its modular design and lower operating temperature. The economic advantage is attributed to the lower operation temperature (120 degrees C vs. 150 degrees C) and lower regeneration energy requirement (2.85 GJ/tonne CO2 vs. 4.25 GJ/tonne CO2). Maintaining a purge rate below 0.03 % is crucial for the solid sorbent's benefits over the MEA CCS process.

Solid sorbents based on silica and polyethyleneimine (PEI) are intensively investigated in the field of carbon capture and storage (CCS). Pyrolysis was proposed as a thermal process to recover the pure silica from exhausted sorbents and convert PEI into potentially useful products, such as alkylated pyrazines. A GC-MS method based on internal standardisation with 2-methoxypyrazine was developed and evaluated to determine the concentration of six pyrazines in the pyrolysis oils of exhausted silica-PEI sorbent pyrolysed at 400, 500, 600 and 650 degrees C. The most abundant pyrazines were 2-ethyl and 2,3-dimethyl, occurring at concentrations of 5-28 mg g-1, followed by pyrazine, 2-methyl, 2-ethyl-3-methyl and 2-propylpyrazine. The GC-MS results were compared to those from a HPLC-DAD method using the Welch's test. The 37 % discrepancy of concentrations was attributed to spectral interference in LC-DAD. GC was slightly less precise than HPLC, calibration errors were lower and enabled the identification of highly alkylated pyrazines. Both methods provided comparable values of total pyrazine yields (around 4-7 % by weight).

The cement industry accounts for almost 7 % of anthropogenic carbon dioxide emissions globally. Therefore, it is imperative to identify innovative solutions to mitigate carbon dioxide emissions from the cement industry.This study aims to evaluate and compare the technical and environmental aspects of integrating two post-combustion carbon capture processes (CCS) into a cement plant: the conventional monoethanolamine (MEA)-based CCS process and the novel silica-alkoxylated polyethyleneimine (SPEI)-based CCS process. Three scenarios were considered: (i) a reference cement plant without CCS, (ii) the conventional MEA-based CCS system integrated into a cement plant and (iii) the novel SPEI-based CCS system integrated into a cement plant. The technical evaluation results showed that the regeneration energy requirements for the conventional MEA and novel SPEI-based CCS processes were 3.53 GJ/tonne CO2 and 2.36 GJ/tonne CO2, respectively, to achieve a capture rate of 90 %. However, the performance of MEA-based carbon capture processes can be improved by using advanced amine formulations that offer lower regeneration heat requirements at 3.3 GJ/tonne CO2, although this is still higher than the SPEI-based carbon capture processes.The novel SPEI-based CCS process showed superior environmental performance compared to the conventional MEA-based CCS process. The endpoint single score was conducted which showed that the SPEI-based CCS process had a lower impact on human health, ecosystems, and resources (7 %, 9 %, and 26 % lower, respectively) compared to the MEA-based CCS process.

Poly(ethylene imine) is a family of polymers with a high content of amine groups employed in various appli-cations and widely investigated as CO2 adsorbents in carbon capture and sequestration. In this study, five branched polyethylenimines (PEIs) of different molecular weights were analysed by Py-GC-MS to gather infor-mation on the chemical structure of the principal thermal degradation products. All the PEIs produced pyroly-sates with a similar chemical composition characterised by the occurrence of ethylenediamine, diethylenetriamine, piperazine, N-ethylaminepiperazine, pyrazine, 2-methylpyrazine, 2,3-dimethylpyrazine, 2-ethylpyrazine. Oligomeric ethylene polyamines were volatilised or evolved after chain scission of the PEI backbone. Pyrolysates also contained minor amounts of alkylated pyrroles, imidazoles, pyridines and other compounds that could not be identified. Pyrolysis products were formed at 300 degrees C, and their abundance increased markedly from 400 degrees to 600 degrees C. Pyrolysis of PEIs at 500 degrees C in the presence of mesoporous silica favoured cyclisation and aromatisation, enhancing the production of alkylated pyrazines. These compounds are of po-tential interest in the food industry as flavour-enhancing additives.

There is a limited understanding of the critical impact moisture has on shale gas resource estimation by affecting gas adsorption and pore structure. Laboratory experiments on dry and 95% relative humidity (R.H.) isolated kerogens are combined with Grand Canonical Monte Carlo (GCMC) and Molecular Dynamic (MD) simulations for kerogen models, including matrix and slits (0.5, 1.0, 1.5, and 2.0 nm) with a range of moisture contents (0-42 wt % on a total organic carbon content (TOC) basis) to better understand how moisture impacts methane adsorp-tion. Higher methane adsorption capacities (Qm) and micropore volumes (Vmicro) are observed for simulated kerogens since all pores in GCMC are accessible. Moisture has a negative effect on Qm, displaying 'rapid', 'gentle', and 'slow' stages with increasing moisture in simulation. Reductions in Qm (61-75%) and Vmicro (88-93%) are obtained for isolated kerogens containing moisture of 38-70 wt% TOC with up to 56% of the moisture in micropores. The same Qm and Vmicro reductions can be reached for the simulated kerogens with moisture contents of 4-24 wt% TOC for matrix and slits. The relative coordination number (Cr) from MD simulation indicates water has a stronger affinity than methane for all functional groups with preferred sorption sites like carboxyl (COOH) under reservoir conditions. The microporosity controls condensed water cluster size. Water adsorbed in ultra-micropores (<0.7 nm) leads to 'rapid' reduction, the 'gentle' Qm reduction stage arises from water condensing, and filling of remaining pores at the highest moisture is related to the 'slow' Qm reduction stage. Therefore, water reduces the methane adsorption capacity of kerogen mainly by occupying and blocking the pore volume rather than competing directly with methane for sorption sites.

Oil refineries are responsible for -5% of total global CO2 emissions and approximately 25-35% of these emissions are released from a single unit called Fluid Catalytic Cracking (FCC). Chemical Looping Combustion (CLC) has been recently proposed as a novel CO2 capture method from the regenerator of FCC units as an integrated process of CLC-FCC. In this study, for the first time, the combustion behaviour of three types of cokes, a model FCC coke (which is a low volatile semi-anthracite coal), and cokes deposited on commercial FCC catalysts by nhexadecane cracking and Vacuum Gas Oil, were comprehensively investigated with oxygen carriers (Co3O4, CuO, and Mn2O3) in a fixed-bed reactor at 700-850 degrees C. The results demonstrate that a high coke combustion efficiency was achieved with CuO (98 vol %), Co3O4 (91 vol %), and Mn2O3 (91 vol %) at 800 degrees C for 30 min. CuO was the most effective oxygen carrier, at temperatures greater than 750 degrees C for 45 min of residence time. These are the regeneration conditions used in the conventional FCC regenerators.

Abstract Grasslands (natural, semi-natural and improved) occupy approximately one-third of the terrestrial biosphere and are key for global ecosystem service provision, storing up to 30% of soil organic carbon (SOC). To date, most research on soil carbon (C) sequestration has focused on croplands where the levels of native soil organic matter (SOM) are typically low and significant potential exists to replenish SOM stocks. However, with the renewed push to achieve “net zero” C emissions by 2050, grasslands may offer an additional C store, utilising tools such as biochar. Here, we critically evaluate the potential for biochar as a technology for increasing grassland C stocks, identifying a number of practical, economic, social and legislative challenges that need to be addressed before the widescale adoption of biochar may be achieved. We critically assess the current knowledge within the field of grassland biochar research in the context of ecosystem service provision and provide opinions on the applicability of biochar as an amendment to different types of grassland (improved, semi-improved and unimproved) and the potential effect on ecosystem provision using a range of application techniques in the topsoil and subsoil. We concluded that the key question remains, is it possible for managed grasslands to store more C, without causing a loss in additional ecosystem services? To address this question future research must take a more multidisciplinary and holistic approach when evaluating the potential role of biochar at sequestering C in grasslands to mitigate climate change. Graphical Abstract

The objective of this work was to perform the techno-economic analysis for the integration of two post-combustion carbon capture technologies into cement plants, namely monoethanolamine (MEA) scrubbing-based and silica-alkoxylated polyethyleneimine (SPEI) adsorbent-based processes. The key performance indicators were investigated, including emission abatement, energy performance, break-even selling price, CO2 capture and avoidance cost. The technical evaluation showed that the conventional MEA and SPEI-based processes required 3.53 GJ/tonne CO2 and 2.36 GJ/tonne CO2 of regeneration energy when achieving 90% of CO2 capture rate, respectively. In addition, the specific primary energy consumption for CO2 avoided was estimated at 6.5 GJ/tonne CO2 for the MEA-based and 4.3 GJ/tonne CO2 for the SPEI-based process. The CO2 capture costs of MEA and SPEI-based processes were estimated at 61.4 and 49.8 €/tonne CO2, respectively. Meanwhile, the CO2 avoidance cost of MEA and SPEI processes were estimated at 84.7 and 62.2 €/tonne CO2 respectively. The economic evaluation indicated that the cost of clinker production was increased by 108% with the integration of the solvent-based MEA-based and 84% for the SPEI-based processes. However, in the case, the maximum heat of 53.9 MWth is recovered from the reference cement plant, the costs of CO2 capture and CO2 avoidance for both the MEA and SPEI-based processes would be reduced. The CO2 capture costs of MEA and SPEI-based processes would decrease to 48.0 and 35.6 €/tonne CO2, respectively. Additionally, the CO2 avoidance costs for the MEA and SPEI-based processes would be reduced to 57.5 and 44.5 €/tonne CO2, respectively.

The search for alternative ways to give a second life to materials paved the way for detailed investigation into three silica-polyethylenimine (Si-PEI) materials for the purpose of CO2 adsorption in carbon capture and storage. A solvent extraction procedure was investigated to recover degraded PEIs and silica, and concomitantly, pyrolysis was evaluated to obtain valuable chemicals such as alkylated pyrazines. An array of thermal (TGA, Py-GC-MS), mechanical (rheology), and spectroscopical (ATR-FTIR, 1H-13C-NMR) methods were applied to PEIs extracted with methanol to determine the relevant physico-chemical features of these polymers when subjected to degradation after use in CO2 capture. Proxies of degradation associated with the plausible formation of urea/carbamate moieties were revealed by Py-GC-MS, NMR, and ATR-FTIR. The yield of alkylpyrazines estimated by Py-GC-MS highlighted the potential of exhausted PEIs as possibly valuable materials in other applications.

Recent exploration in the Nile Delta Basin has led to major oil and gas discoveries; however, source-reservoir relationships in the onshore part of the basin are still ambiguous. This work involves a comprehensive geochemical assessment of possible Oligocene-Pliocene source rocks, using TOC/Rock-Eval pyrolysis and gas chromatography-mass spectrometry. The aim is to investigate quantity, quality, thermal maturity, sources, and depositional paleoenvironment of the disseminated organic matter, and to correlate rock samples with hydro-carbons retrieved from the study area. Moreover, the chemical and isotopic compositions of gases were employed to examine origin, maturity, mixing and secondary alteration processes. Results reveal fair to good organic richness (TOC similar to 1 wt%) for the Oligocene-Pliocene rocks, with the highest TOC content from the Oligocene Tineh Formation. The kerogen is generally gas-prone Type-III and to a lesser extent Type-IV and Type-II/III. Molecular and biomarker results indicate mixed source facies with variable contributions from higher plants, algae, bacteria, and plankton, deposited under suboxic to anoxic nearshore marine or lacustrine depositional settings. Significant biomarkers include elevated C26/C25 tricyclic terpane ratios (0.82-3.62), low C31 homohopane (22R)/C30 hopane ratios (0.17-0.63), and low oleanane and gamma-cerane contents. Maturity-related biomarkers, Rock-Eval Tmax and vitrinite reflectance values are consistent and suggest immature to early mature rock samples. Molecular and isotopic compositions of mud gases indicate complex origins and mixing histories ranging from primary microbial to pure thermogenic, where thermogenic processes dominate the pre-Miocene intervals. Chemometric analysis of 18 source-related biomarker ratios for rock extracts revealed four genetic families. Hierarchical cluster analysis (HCA) of biomarker data for rock extracts and condensate oils from the onshore Nile Delta indicates no correlation between Miocene-Pliocene rocks and condensates or oils in the area. Therefore, pre-Miocene source rocks are suggested to be the most probable candidates for hydrocarbons in the onshore Nile Delta.

Abstract Effective regeneration of adsorbents is considered as one of the essential qualities for commercial use. However, most of the studies have only reported the adsorption properties and overlooked the reuse of adsorbents. In this study, we determined the regenerability and reusability of fly‐ash derived zeolite (FADZ) NaP1. These adsorbents have become popular to remove pollutants from water, including toxic metals, since they are less expensive, compared to their counterparts, and can be synthesized from a waste product. We evaluated the efficiency of copper (Cu2+) ions recovery from water using multiple regeneration solutions due to medium adsorption selectivity towards Cu2+. We determined the time required for the regeneration using acid, base, and salt solutions. The suitable pH and solution while maintaining the structure of the zeolite were studied. Up to 90% recovery was achieved via three successive regenerations, each taking 3 h using 3 M KCl and 3 M NaCl solutions. X‐ray diffraction (XRD) and fluorescence showed changes in structure after regeneration at pH < 5 and contact time <6 h. The desorption kinetics using KCl solutions can be described by pseudo‐second order model. Freundlich model represents the desorption of Cu2+ ions better than the Langmuir model due to regression coefficient (R2) values in the range of 0.998–1.0. Results suggest a strong ion exchange mechanism as the main driving force for desorption. The type of anions (such as Cl− and OH−) in solution influences regeneration in addition to the exchanging cation.

Chemical looping combustion (CLC) is an advanced combustion process in which the combustion reaction splits into two parts; in the first reaction metal oxides are used as oxygen suppliers for fuel combustion and then in the second reaction, reduced metal oxides are re-oxidised in an air reactor. Although this technology could be applicable for the safe implication of "low-temperature oxidation of hydrogen", there is limited understanding of oxygen carrier reduction stages and the oxidation mechanism of hydrogen throughout the process. The novelty of this research lies in its pioneering investigation of low-temperature oxidation of hydrogen through chemical looping technology as a safe and alternative heating system, using three distinct metal oxide oxygen carriers: CuO, Co3O4, and Mn2O3. The oxidation of hydrogen over these oxygen carriers was comprehensively studied in a fixed-bed reactor operating at 200-450 degrees C. XRD analysis demonstrates that CuO directly reduced to metallic Cu at 200-450 degrees C, instead of following a sequential reduction step CuO & RARR;Cu4O3 & RARR;Cu2O & RARR;Cu throughout the temperature. Co3O4 was reduced to a mixture CoO and Co at 450 degrees C, which may refer to a sequential reduction step Co3O4 & RARR;CoO & RARR;Co with increasing the temperature. Decreasing the reduction temperature led to an elevation in CoO formation. Mn2O3 can also reduce to a mixture of Mn3O4 and MnO at temperatures between 250 and 400 degrees C. Compared to temperature, the increase in the residence time did not show any further reduction in Mn2O3. SEM results showed that most of the metal oxide particles were evenly dispersed on the supports. Based on the experimental results, a potential reduction stage of CuO, Co3O4 and Mn2O3 was proposed for low-temperature hydrogen oxidation, which could be a potential application for space heating using safe hydrogen combustion.

Lignin from pulping is recovered in a wet form, making it ideal for hydrothermal carbonisation (HTC). This study investigates the effects of temperature (200-280 & DEG;C), residence time (1-6 h), and water to biomass mass ratio (2:1-6:1) on the composition of the resultant biocoal and the extent of alkaline and alkaline metal removal during HTC of pine Kraft lignin (PKL). Consistent with studies on other biomass materials, temperature exhibited the most significant effect on biocoal yield and properties, followed by residence time showing a marginal effect and varying the water to lignin mass only affecting alkaline and alkaline earth metals removal. Biocoal yields were in the range of 76-95 % (80-97 % on a carbon basis) and, compositionally, the biocoal obtained corresponded to sub-bituminous (220-260 & DEG;C) and high volatile bituminous coals (280 & DEG;C). Gas yields are low with the gas comprising mainly CO2 (98 v/v). The optimum temperature, time and biomass to water ratio for alkaline and alkaline earth metals removal was 260 & DEG;C, 3 h and 5:1 under which 93-95 % for sodium (Na) and potassium (K) and 75-80 % for magnesium (Mg) and calcium (Ca) removal were achieved. Solid-state C-13 Nuclear Magnetic Resonance (NMR) revealed that during HTC, the oxygen-containing bonds of esters, ethers, and carboxylic groups were dissociated to produce lower-molecular weight including phenolic compounds dissolved in the process water. These findings have shown that the HTC is a promising alternative thermochemical route for coalification of wet PKL to a low ash coal-like fuel similar to sub-bituminous coal in rank that has potential applications for carbonisation.