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End of life packaging is nowadays one of the major environmental problems due to its short usage time, the low biodegradability, and the big volume occupied. In this context, gasification is one of the most promising chemical recycling techniques. Some non-recyclable or non-compostable waste gasification plants are already operating such as Enerkem Alberta Biofuels in Canada or the Sierra’s FastOx Pathfinder in California. In this review, we have examined works about plastic gasification from the last fifteen years with a specific focus on polyolefin (PP, PE), plastics mix, and co-gasification of plastic with biomass. For each of these, the best operating conditions were investigated. A very in-depth section was dedicated to supercritical water gasification (SCWG). The most used reactors in gasification processes are fluidized bed reactors together with air or steam as gasifying agents. Tar removal is commonly performed using olivine, dolomite, or nickel based catalysts. SCWG has numerous advantages including the inhibition of tar and coke formation and can be used to remove microplastics from the marine environment. In co-gasification of plastic material with coal or biomass, synergistic effects are observed between the raw materials, which improve the performance of the process, allowing to obtain higher gas yields and a syngas with a high energy content.

Experiments of co-gasification of spirit-based distillers’ grains (SDG) and sewage sludge (SS) were carried out with red mud (RM) by using a self-designed fixed-bed gasifier. The effects of RM addition, gasification reaction temperature, SS and SDG blending ratio and other factors on the gasification reaction characteristics and synergism were investigated. The results are as follow: RM had catalytic effect on SS and SDG co-gasification, which can enhance the gasification reaction and H 2 yield; increasing the temperature can enhance the gasification reaction and reduce the syngas H 2 /CO; with the increase of SDG, the H 2 yield gradually grew; with the rise of SS, the gasification reaction gradually augmented. The catalytic mechanism was mainly due to the redox cycle of Fe 2 O 3 in RM, which can promote the water transfer reaction. At the same time, the eutectic mixture of K, Na, Ca, Fe and other metal elements at high temperatures was the main reason for the synergistic effect.

In this study, a thermogravimetry approach was employed to investigate the thermal parameters of waste polypropylene (PP), mixed wood biomass (WB), cardboard (CB), and their blends during co-gasification under oxidative conditions at varying heating rates. The resulting data were used to quantify the mass loss profiles for each feedstock and to assess the effects of blending on process temperatures (onset and end), residual mass, and activation energies. Activation energies (Ea) were determined using three iso-conversional methods: Friedman, Kissinger–Akahira–Sunose (KAS), and Numerical Optimization. Among the feedstocks, PP exhibited the highest thermal stability. When blended with either CB or WB, both onset and end temperatures significantly (p < 0.05) increased with rising PP content. These trends were consistent at heating rates of 20 and 40 °C/min. In contrast, CB/WB blends showed no notable variation in onset temperature across blend ratios at either heating rate. However, PP/CB blends exhibited significantly lower residual masses (up to a six-fold decrease) with increasing PP content. Since both PP and WB individually yielded very low residual mass (<2 wt%), increasing PP content in PP/WB blends did not significantly affect the residual mass. Overall, higher heating rates shifted thermal decomposition into higher temperature regimes in both individual and blended feedstocks, but had no impact on residual mass. The Ea of WB was the highest (138–139 kJ/mol), followed by CB (113–116 kJ/mol) and PP (56–63 kJ/mol). The blending of PP/CB and CB/WB resulted in reduced Ea values compared to the pure feedstocks, indicating a positive synergistic effect during co-gasification. In essence, the co-gasification of mixed plastic waste presents a promising strategy for sustainable waste management and energy recovery.

This study assessed the entrained flow co-gasification characteristics of coal and biomass using thermodynamic equilibrium modelling. The model was validated against entrained flow gasifier data published in the literature. The gasification performance was evaluated under different operating conditions, such as equivalence ratio, temperature, pressure and coal to biomass ratio. It is observed that the lower heating value (LHV) and cold gas efficiency (CGE) increase with increasing temperature until the process reaches a steady state. The effect of pressure on syngas composition is dominant only at non-steady state conditions (<1100 °C). The variation in syngas composition is minor up to the blending of 50% biomass (PB50). However, the PB50 shows a higher LHV and CGE than pure coal by 12%and 18%, respectively. Overall, biomass blending of up to 50% favours gasification performance with an LHV of 12 MJ/kg and a CGE of 78%.

This study investigated the thermochemical reaction characteristics of petrochemical wastewater sludge, wood pellets, and their blends. Owing to the high calorific value and the low sulfur, nitrogen, and ash contents, wood pellets effectively compensate for the low heating value of sludge, thereby enhancing co‐combustion and co‐gasification performance. Thermogravimetric (TG) analysis of the combustion showed that the addition of wood pellets increased volatile matter release and resulted in two distinct weight loss peaks during the char combustion stage. An increase in the blending ratio (BR) significantly enhanced the combustion characteristics and combustibility indices, exhibiting a positive synergistic effect, particularly at BR30% and BR50%. TG analysis of gasification showed that as the BR increased, two weight loss peaks appeared in a single reaction stage, and both comprehensive gasification and devolatilization indices improved significantly, with the most pronounced synergistic effect observed at BR50%. Kinetic analysis indicated that the addition of wood pellets increased the activation energy in the volatile release region while reducing the activation energy in the fixed carbon (FC) reaction region. In laboratory‐scale (10 kW th ) and 100 kW th ‐scale fluidized bed combustion and gasification experiments, the reaction temperature and gas emissions of the fluidized bed reached a stable state with increasing BR. Notably, in the 100 kW th ‐scale fluidized bed system, the blended fuel demonstrated long‐term stable operation at BR85%, effectively reducing CO, NO x , and SO 2 emissions. In the gasification experiments, the use of olivine as a catalyst enhanced the hydrogen yield in syngas, and the co‐combustion of syngas with liquefied petroleum gas (LPG) met the fixed‐source emission standards. The results showed that co‐combusting or co‐gasifying sludge and wood pellets can effectively reduce sludge volume while recovering energy. This study integrated TG analysis with experiments on both lab‐scale (10 kW th ) and 100 kW th fluidized bed systems, emphasizing their complementary roles. Lab‐scale tests often require parameter adjustments when scaled up, whereas 100 kW th ‐scale trials yield results closer to practical applications. These findings support the feasibility and sustainability of sludge‐to‐energy technologies.

Gasification is an efficient process to obtain valuable products from biomass with several potential applications, which has received increasing attention over the last decades. Further development of gasification technology requires innovative and economical gasification methods with high efficiencies. Various conventional mechanisms of biomass gasification as well as new technologies are discussed in this paper. Furthermore, co-gasification of biomass and coal as an efficient method to protect the environment by reduction of greenhouse gas (GHG) emissions has been comparatively discussed. In fact, the increasing attention to renewable resources is driven by the climate change due to GHG emissions caused by the widespread utilization of conventional fossil fuels, while biomass gasification is considered as a potentially sustainable and environmentally-friendly technology. Nevertheless, social and environmental aspects should also be taken into account when designing such facilities, to guarantee the sustainable use of biomass. This paper also reviews the life cycle assessment (LCA) studies conducted on biomass gasification, considering different technologies and various feedstocks.

Shortage of feedstock supply often happens in biomass gasification. Thus, the cogasification of blended biomass is a potential option to maintain feedstock supply for continuous gasification operations. The aim of this study is to investigate the effects of biomass blending ratio and biomass particle size on the syngas quality and performance of the co-gasification process. The co-gasification of wood chips/coconut shells was carried out in a downdraft gasifier at a 400 L/min airflow rate. The biomass blending ratio varies at 80/20, 50/50 and 20/80 (w/w) with biomass particle sizes of 5-10, 10-25 and 25- 50 mm. The results show that small particle size favours gas composition. The highest H2 (10.91%), CO (25.60%), and CH4 (2.79%) levels were obtained from the 5-10 mm particle size at 80/20, 50/50, and 20/80 blending ratios, respectively. Higher HHV and gas yield were obtained at the 20/80 blending ratio with the 5-10 and 10-25 mm particle sizes, respectively. Cold gas efficiency varies from 54.37 to 65.52%. The trend shows that at smaller particle sizes, cold gas efficiency is higher, while in most cases, carbon conversion efficiency was found to be more than 90% during co-gasification. The syngas quality and performance of co-gasification were more sensitive to biomass particle size as compared to the blending ratio.

The large and growing volume of tire waste and sewage sludge requires disposal, for which thermochemical processes such as gasification can be used. Co-gasification of these two waste products allows the tire char to be used as a charge stabilizer and the sewage sludge to improve reactivity and efficiency. The purpose of this study was to evaluate the effect of the composition of a waste tire char and sewage sludge fuel blend on the gasification process, using steam as the gasification agent. Tests were carried out for tire char, municipal sewage sludge, and blends of the two in ratios of 90:10 and 67:33. An analysis of the materials used was carried out (ultimate and proximate analysis as well as ash composition), and isothermal measurements of steam gasification were taken using the thermal volumetric method for temperatures of 800, 850, and 900 °C at an elevated pressure of 1 MPa. On the basis of the results, the formation curves of the main gasification products (H2, CO, CO2, and CH4) were created, the curves for the degree of carbon conversion were plotted, the reactivity indexes were determined for different degrees of conversion (0.25, 0.5, and 0.75), and the quantity and composition of the resulting gas were analyzed. Using the grain model, the kinetic parameters (activation energy and pre-exponential factor) of the gasification reaction were calculated. The addition of municipal sewage sludge had a positive effect on the reactivity of tire char and increased the efficiency of gasification, because it contained components that act as catalysts in the gasification process. There was a favorable effect from the addition and higher amount of sewage sludge on lowering both the activation energy (49.5 kJ/mol and 89.2 kJ/mol for 90:10 and 67:33 blends, respectively) and the pre-exponential factor. A significant improvement in reactivity, with a high degree of conversion and the best gas composition, was obtained for a 90:10 blend at 900 °C.

Willow is a promising biomass resource for addressing the challenges of securing stable domestic biomass fuels in Japan and utilising abandoned agricultural land. Among the willow species, Salix pet-susu Kimura KKD (known as ezonokinu willow, EW) stands out for its growth, high production, storage stability, production stability, and business stability. Previous studies have investigated fuel characterisation through gasification (co-gasification) of various biomass mixtures to enhance feedstock flexibility for gasifier commercialisation. However, the synergistic effects of co-gasification using fuels containing EW blended with Japanese cedar, a commonly planted forest species in Japan, remain unexplored. Therefore, this study explored CO2 co-gasification with different blend ratios of EW/cedar blended char and evaluated the fuel characteristics for each blend ratio to elucidate the synergistic effects. The prepared char samples were utilised in the CO2 gasification test with TG-DTA as the analyser. The results suggest that in the initial stages of the willow/cedar blended char co-gasification reaction, pore size and specific surface area significantly influence the reaction rate. Subsequent stages of the reaction are influenced by the promoting and inhibiting effects of inorganic components, which impact co-gasification. The synergy factor results for the willow/cedar blended char co-gasification suggest a reaction pathway.

Co-gasification of biomass and plastics can utilize two renewable resources to improve the yield and quality of syngas. In this work, the steam co-gasification of lignin (LG) and polyethylene (PE) was explored by reactive force field molecular dynamics. Co-gasification accelerates the decomposition of macromolecular components and enhances the fragmentation and conversion of char and tar. The synergistic interactions between LG and PE promote the scission of C–C/C-O bonds and the release of radicals, which engender a significant increase in H 2 /CO yields and a decrease in CO 2 emissions. The qualitative agreement between the variation trend of major gases concentrations and the experimental data confirms the reliability of simulation results. The LG linkage bonds α/β/γ-O-4 dominate the formation of alkane, olefin, and alkyne gases without much impact on the H 2 /CO/CO 2 content. Despite the distinct linkage structures, the initial reaction pathways of three LG dimers are similar. The Cα/Cβ/Cγ-O bonds are the primary reaction sites to produce two phenylpropane skeletons. The intermediate fragments undergo hydrogen abstraction, demethylation, group migration, rearrangement, hydrogen transfer, and isomerization reactions to generate aromatic hydrocarbons, short-chain hydrocarbons, and cyclopentadienyl aliphatic ring structures. The formation of H 2 , CO, CO 2 , and CH 4 is attributed to the homolysis, deoxygenation, disproportionation, hydrogen abstraction, and reforming reactions of C 1-4 H x O y radicals. This work aims to elucidate the exhaustive reaction mechanisms of LG-PE steam co-gasification at the molecular level, which are not accessible only through experimental methods.