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Impact of biowaste reducers on continuous solar-driven hematite reduction for carbon–neutral co-production of iron and syngas
(2026-09-15)
Chuayboon, Srirat
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Abanades, Stéphane
Green iron production using bio-reducers and solar energy offers a promising alternative pathway towards carbon–neutral metallurgy. However, the types of raw bio-reducers play an important role in hematite reduction performance. An experimental investigation of continuous hematite reduction with seven agricultural biowastes was conducted in a solar reactor to unravel the impact of bio-reducer types and shapes (pellets and particles) on conversion performance and efficiency at 900–1200 °C. As a result, the most promising biowaste reducers were betel nut, palm oil empty fruit bunch, and beech wood due to their high volatile and carbon content, followed by bagasse, coconut fiber, and particle board. Conversely, rice husk was found to be inappropriate because of low gasification activity due to high ash content. No significant impact of reactant shape between particles and pellets was observed, pointing out that the reactor can accommodate various biomass feedstocks. The syngas yield varied in the range of 23.2–56.9 mmol/g<inf>dry_biomass</inf>, and simultaneous high-purity iron production was confirmed by XRD and SEM/EDS. High process efficiency was demonstrated with maximum carbon conversion of 83.1%, oxygen conversion of 100%, and energy upgrade factor up to 1.00. The solar-to-fuel energy efficiency reached 13.2% at 1200 °C, highlighting the remarkable conversion performance of waste biomass and solar energy to clean syngas fuel and renewable iron.
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Comprehensive analysis of on-sun catalytic reforming of methane with a hydroxyapatite-supported nickel catalyst in a tubular solar reactor
(2026-07-22)
Chuayboon, Srirat
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Kulporm, Ratikorn
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O-Thong, Sompong
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Pham Minh, Doan
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Abanades, Stéphane
Methane reforming offers a suitable pathway for greenhouse gas utilization, but its implementation is hindered by catalyst deactivation due to carbon deposition and thermal sintering. This study shows that hydroxyapatite serves as a stable catalytic support for solar-driven dry, steam, and dual reforming. The influence of oxidizer type and concentration (H<inf>2</inf>O, CO<inf>2</inf>, H<inf>2</inf>O/CO<inf>2</inf> mixture) is experimentally investigated at 800 °C in a tubular solar reactor. A hydroxyapatite-supported nickel catalyst (Ni/HA) achieves methane conversion exceeding 95% with 95% H<inf>2</inf> and 96% CO selectivity. An excess of oxidant (oxidant/CH<inf>4</inf> mole ratio of 1.2-1.5) is recommended to promote CH<inf>4</inf> conversion, improve solar reactor performance, and prevent carbon formation and catalyst deactivation. Through sequential on-sun experimental runs, energy upgrade factor above 1.5 and solar-to-fuel efficiency over 20% are attained, demonstrating high catalytic performance stabilized by the metal dispersion on the support. Dual reforming exhibits the highest syngas yield and performance, with minimized carbon formation and H<inf>2</inf>/CO ratio approaching 2.0. Catalyst characterization (XRD, FTIR, SEM, TEM/EDX) confirms high thermal/chemical stability of Ni/HA under solar heating conditions. These results demonstrate compatibility of Ni/HA catalyst with solar methane reforming, providing a high-efficiency sustainable system for converting greenhouse gases into syngas.
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Complete solar thermal direct reduction of iron ore by hydrogen in a particle-fed reactor under concentrated sunlight
(2026-06-01)
Abanades, Stéphane
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Garcia, Roger
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Chuayboon, Srirat
Solar iron production from H<inf>2</inf>-based direct reduction of iron ore was investigated in a continuously particle-fed reactor for performance analysis. Concentrated solar energy was used as the external source of high-temperature process heat and hydrogen was used as reductant, thereby enabling decarbonation of the iron-making process. The solar reactor featured a rotary kiln composed of a refractory conical cavity, in which the reacting particles were injected and extracted under a flow of H<inf>2</inf> reductant, subjected to real concentrated solar irradiation. The reactor was experimentally tested under both continuous and semi-continuous operation modes to determine and compare the key performance metrics. The on-sun experiments focused on unraveling the effect of the cavity material and operating mode on the process performance including H<inf>2</inf> consumption, particle conversion, and iron product purity. A cavity made of mullite appeared unfavorable for continuous particle flow due to agglomeration and adherence to the walls. Conversely, boron nitride promoted particle flowability while totally eliminating adhesion to the walls. In continuous mode, the conversion was kinetically limited due to a low particle residence time in the cavity. Semi-continuous operation was thus tested with cavity rotation turned off during injection and rotation turned on for particles extraction, which warranted a high-enough reaction duration with particle conversion approaching completion. Maximum conversion up to 99 % was achieved with complete recovery yield of the converted product at the reactor outlet. Characterization of solid products (XRD, SEM/EDX) confirmed the successful production of pure sponge iron. Further scaling-up of the solar reactor concept with longer cavity length will enhance the particle residence time, thereby favoring their conversion in continuous mode.
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Impact of different agricultural biomass residues on the performance of continuous solar-steam gasification
(2025-11-02)
Chuayboon, Srirat
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Abanades, Stéphane
Solar-driven biomass gasification represents a promising avenue for sustainable carbon-neutral fuel production. Nevertheless, the types of raw biomass materials play a vital role in continuous solar gasification performance. In this study, continuous solar-steam gasification with various agricultural crop residues was experimentally carried out in a 1.5 kW<inf>th</inf> solar gasifier to investigate the influence of biomass types on performance and efficiency under different operating temperatures up to 1400 °C. Seven agricultural residues were used as feedstocks, including oil palm wastes (palm mesocarp fiber, palm empty fruit bunch, and palm kernel shell), bagasse, betel nut, coconut fiber, and rice husks. Results demonstrated that the system can effectively perform with all biomass types with high-quantity and high-quality syngas production. The process revealed exceptional performance and efficiency, including the total maximum syngas yield range of 67.9–81.5 mmol/g<inf>dry biomass</inf>, reaching 81.4–95.2 % of the theoretical total syngas yields, maximum energy upgrade factor (1.05–1.35), reaching 94.2–97.3 % of the theoretical values, and maximum carbon conversion (87.2–96.9 %). The feedstock types showed a significant influence on gasification outcomes. Palm oil empty fruit bunch, betel nut, and palm mesocarp fiber were promising candidates for solar gasification with their high volatile content and significant decomposition potential, followed by coconut fiber and bagasse. Nevertheless, palm kernel shell and rice husk were found to be unsuitable biomasses for continuous solar-steam gasification because of the issues of reduced gasification activity and reaction rate limitations, due to a high density for palm kernel shell and a high ash content for rice husk. A temperature of 1300 °C was recommended to carry out continuous solar-steam gasification, leading to the maximum solar-to-fuel energy conversion efficiency in the range 13.7–18.9 %. This study provides insights into the influence of agricultural residue types on the solar-steam gasification process, while assisting in the proper biomass residue selection for efficient continuous solar gasification.
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Carbon capture through solar-driven CO2 gasification of oil palm empty fruit bunch to produce syngas and biochar
(2025-05-15)
Al-Muraisy, Saqr A.A.
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Chuayboon, Srirat
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Soares, Lais Americo
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Buijnsters, J. G.
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Ismail, Shahrul bin
Oil palm empty fruit bunch (OPEFB) is an abundant organic waste in Malaysia that is often disposed of through field burning. A previous study has shown that solar-driven steam gasification of OPEFB can produce hydrogen-rich syngas with an energy upgrade factor of 1.2 and a carbon conversion efficiency of 95.1 %. Beyond its potential as a biofuel, OPEFB can also act as a carbon sink, capturing photosynthetically stored carbon. This study explores the potential of amplifying OPEFB's negative carbon emissions through solar-driven gasification, using CO<inf>2</inf> as the gasifying agent. In this work, a Central Composite Design (CCD) approach was employed to assess the influence of temperature (1100–1300 °C) and CO<inf>2</inf>/OPEFB molar ratio (1.6–3.0) on H<inf>2</inf>/CO molar ratio and energy upgrade factor, with a constant OPEFB flow rate of 1.8 g/min. The results demonstrated that at an energy upgrade factor of 1.4, 94.9 % of the total carbon was converted into syngas with a H<inf>2</inf>/CO molar ratio of 0.3. The maximum observed net carbon capture yield of 0.4 g C/g OPEFB was achieved at 1300 °C and a CO<inf>2</inf>/OPEFB molar ratio of 3.0. The remaining carbon (94.4–95.7 wt %) was converted into biochar with low heavy metal content, which has potential as a soil enhancer.
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Chemical Looping CH4 Reforming Through Isothermal Two-Step Redox Cycling of SrFeO3 Oxygen Carrier in a Tubular Solar Reactor
(2025-03-01)
Abanades, Stéphane
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Wang, Xinhe
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Chuayboon, Srirat
The chemical looping reforming of methane using an SrFeO<inf>3</inf> oxygen carrier to produce synthesis gas from solar energy was experimentally investigated and validated. High-temperature solar heat was used to provide the reaction enthalpy, and therefore the methane feedstock was entirely dedicated to producing syngas. The two-step isothermal process encompassed partial perovskite reduction with methane (partial oxidation of CH<inf>4</inf>) and exothermic oxidation of SrFeO<inf>3-δ</inf> with CO<inf>2</inf> or H<inf>2</inf>O splitting under the same operating temperature. The oxygen carrier material was shaped in the form of a reticulated porous foam structure for enhancing heat and mass transfer, and it was cycled in a solar-heated tubular reactor under different operating parameters (temperature: 950–1050 °C, methane mole fraction: 5–30%, and type of oxidant gas: H<inf>2</inf>O vs. CO<inf>2</inf>). This study aimed to assess the fuel production capacity of the two-step process and to demonstrate the potential of using strontium ferrite perovskite during solar cycling for the first time. The maximum H<inf>2</inf> and CO production rates during CH<inf>4</inf>-induced reduction were 70 and 25 mL/min at 1000 °C and 15% CH<inf>4</inf> mole fraction. The increase in both the cycle temperature and the methane mole fraction promoted the reduction step, thereby enhancing syngas yields up to 569 mL/g during reduction at 1000 °C under 30% CH<inf>4</inf> (778 mL/g including both cycle steps), and thus outperforming the performance of the benchmark ceria material. In contrast, the oxidation step was not significantly affected by the experimental conditions and the material’s redox performance was weakly dependent on the nature of the oxidizing gas. The syngas yield remained above 200 mL/g during the oxidation step either with H<inf>2</inf>O or CO<inf>2</inf>. Twelve successive redox cycles with stable patterns in the syngas production yields validated material stability. Combining concentrated solar energy and chemical looping reforming was shown to be a promising and sustainable pathway toward carbon-neutral solar fuels.
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Green iron and syngas production via continuous solar-driven agricultural waste biomass gasification combined with iron(III) oxide reduction
(2024-10-15)
Chuayboon, Srirat
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Abanades, Stéphane
The production of renewable synthetic fuels and chemicals from solar energy and agricultural waste biomass is considered. Solar thermochemical conversion processes offer a promising pathway to a sustainable fuel economy and green chemical industry. This study investigates the continuous solar-driven gasification of agricultural biomass (betel nut waste) combined with iron oxide (Fe<inf>2</inf>O<inf>3</inf>) reduction to produce carbon-neutral syngas and green metallic iron in a single process. A thermodynamic analysis of the system was initially conducted to predict the distribution of equilibrium products. Then, on-sun continuous processing was experimentally carried out under different operating conditions, including betel/Fe<inf>2</inf>O<inf>3</inf> molar ratios (0.56–1.5) and temperatures (900–1200 °C) to evaluate the process feasibility and reliability. As a result, solar gasification of betel nut waste combined with Fe<inf>2</inf>O<inf>3</inf> reduction performed exceptionally well with continuous reactant particles feeding, demonstrating a feasible pathway for producing green iron and high-quality syngas. The maximum syngas yield reached 63.3 mmol/g<inf>dry_betel</inf>, approaching its theoretical value, and high-purity Fe was simultaneously produced. The process demonstrated high efficiency, with maximum carbon conversion approaching 98 %, energy upgrade factor up to 1.26, and solar-to-fuel energy conversion efficiency up to 14.4 %, highlighting remarkable conversion performance of biomass and solar energy to chemicals.
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Carbon-neutral synfuel production via continuous solar H2O and CO2 gasification of oil palm empty fruit bunch
(2023-10-15)
Chuayboon, Srirat
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Abanades, Stéphane
Solar gasification offers a promising carbon-neutral pathway to thermochemically convert waste biomass and solar energy into synfuel. In this study, a thermodynamic analysis of solar gasification of oil palm empty fruit bunch (EFB) with H<inf>2</inf>O and CO<inf>2</inf> gasifying agents was first performed to predict equilibrium product distribution. Subsequently, on-sun continuous solar gasification of EFB was experimentally carried out in a solar particle-fed gasifier to evaluate the influence of gasifying agent types (H<inf>2</inf>O and CO<inf>2</inf>), gasifying agent/EFB molar ratios (1.8–3.4), temperatures (1050–1350 °C), and to assess overall process feasibility and reliability. As a result, solar EFB gasification performed efficiently with both H<inf>2</inf>O and CO<inf>2</inf> gasifying agents under continuous on-sun operation. Syngas product composition and gasification reaction rate strongly depended on gasifying agent type. Increasing temperature enhanced syngas yield and quality, and changed the CO/H<inf>2</inf> mole ratio, especially in EFB + CO<inf>2</inf> gasification. A gasifying agent/EFB molar ratio of 2.6 (slight excess of gasifying agents) and a temperature of 1300 °C were shown to be optimal for continuous solar EFB gasification. The maximum total syngas yield above 76 mmol/g<inf>dry_EFB</inf>, syngas lower heating value above 22 kJ/g<inf>dry_EFB</inf>, and energy upgrade factor above 1.37 were achieved from both EFB + H<inf>2</inf>O and EFB + CO<inf>2</inf> gasification, which closely approached their theoretical equilibrium values. The maximum carbon conversion exceeding 93% and solar-to-fuel energy conversion efficiency up to 19.3% were achieved, demonstrating efficient EFB-to-synfuel conversion performance. Continuous solar EFB gasification with both H<inf>2</inf>O and CO<inf>2</inf> was thus established to be a reliable process for EFB waste biomass valorization into high-quality and carbon-neutral synfuel.
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Comparative Performance Evaluation of Solar-Driven Methane Reforming with ZnO for Co-Production of Syngas and Metallic Zn
(2023-10-06)
Chuayboon, Srirat
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Abanades, Stéphane
Solar-driven methane reforming with ZnO for co-production of hydrogen-rich syngas and metallic Zn was demonstrated in a flexible solar thermochemical reactor prototype fully powered by highly concentrated sunlight under batch and continuous operation. This process provides a practical way to store solar energy into the chemical products while reducing reliance on conventional energy resources that emit CO2 and other pollutants. On-sun experiments were conducted using various operating parameters, including temperature (900-950 °C), pressure (0.15–0.90 bar) and inlet ZnO feeding rate (0.5–1.0 g/min), in both batch and continuous operation, to demonstrate solar reactor flexibility and reliability. The ZnO+CH4 reaction performance between batch and continuous operation was studied and compared. As a result, reducing pressure to vacuum condition improved the net ZnO conversion and lowered side methane cracking reaction, but favored CO2 yield because of insufficient gas residence time. Rising ZnO feeding rate under a constant CH4/ZnO molar ratio of 1.5 promoted Zn and syngas yields. In comparison, continuous operation outperformed batch operation in terms of higher ZnO conversion, higher syngas yield, and reduced methane cracking. Both batch and continuous operation yielded high-purity metallic Zn with a well-crystallized structure and micrometric size particles, thus exhibiting suitable reactor performance for the solar thermochemical methane-driven ZnO reduction process.
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Solar metallurgical process for high-purity Zn and syngas production using carbon or biomass feedstock in a flexible thermochemical reactor
(2023-05-05)
Chuayboon, Srirat
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Abanades, Stéphane
Co-production of high-purity Zn and syngas via carbothermal reduction of ZnO was performed in a directly-irradiated concentrated solar reactor, thereby converting and storing intermittent sunlight into high-value chemical fuels and commodities. On-sun experiments were carried out by varying operating parameters including solid carbonaceous feedstocks (either solid carbon or beech wood biomass) in batch and continuous modes at 950–1350 °C, demonstrating solar reactor flexibility and robustness. Decreasing pressure (150–400 hPa) promoted both ZnO reduction rate and net ZnO conversion above 78%, thus enhancing Zn production yield. Nevertheless, CO selectivity decreased because of rising CO<inf>2</inf> due to the residence time decrease. A remarkable increase in gas production rates/yields, CO selectivity, and reaction extent was highlighted when increasing temperature during continuous pellets reactant injection. Furthermore, utilizing wood biomass as a sustainable green reducer was proved to be an attractive choice to produce both metallic Zn and high-quality syngas in a single process consisting of biomass gasification with solid ZnO. Zn content exceeding 90 wt% was demonstrated for both batch and continuous tests, unveiling high reactor performance for the metallurgical process. The energy content of the feedstock was upgraded by the solar power input (maximum energy upgrade factor up to 1.2), and the maximum solar-to-fuel energy conversion efficiency up to ∼ 6% was achieved with continuous reactant injection. The high-purity Zn can be further used to produce fuel via CO<inf>2</inf>-splitting in a complete and fast reaction.

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