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The catalytic gasification of different individual plastics and their mixtures with a dolomite supported Ni catalyst was evaluated in a drop-tube fixed-bed reactor. The influence of the Ni loading level and the interactions of mixed plastics during steam gasification were both examined. A 5 wt % NiO/dolomite catalyst gave the highest degree of carbon conversion for all evaluated plastics and mixtures. A mixture of the four types of plastic that matched the estimated weight ratio of real plastic waste revealed a lower gas yield than predicted, suggesting their interaction during gasification. The mixtures which contain high-density polyethylene or low-density polyethylene at 0.75 wt/wt led to a reduced gas production, while polystyrene increased it, especially in the polystyrene–polypropylene binary mixture with a markedly higher H2, CO, and CO2 production level than that expected. Thus, it would be beneficial to screen plastic types prior to the generation of suitable gas products.

In this study, the response surface methodology and simplex-lattice design were applied to investigate the effect of biomass constituents on the kinetics of biomass combustion, important information for process design. The synthetic biomass made from pure cellulose, xylan and Organosolv lignin was used instead of real biomass for this purpose. The combustion process was employed using thermogravimetric analyzer. The results obtained from three different kinetic models including Kissinger-Akahira-Sunose, Ozawa-Flynn-Wall and Analytical Method were provided and compared. According to the analysis of variances (ANOVA), the higher cellulose and hemicellulose fraction provided greater activation energy and frequency factor. The proposed regression models with high R 2 coefficient indicated that the predicted kinetic values and experimental data agreed very well. The contour plots generated from the proposed models were also provided in this study. They were used to observe the influence of biomass components on each kinetic parameter.

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We evaluated two-step hydrothermal liquefaction in a semi-continuous reactor for recovery of both nutrients and biocrude from the alga Coelastrum sp. in direct comparison with a one-step process. The influence of the operating temperature, pressure and water flow rate was investigated by means of a 2 k factorial experimental design and response surface methodology. The two-step process gave a higher total biocrude yield (~36 wt% (daf. basis)) and nutrient recovery level in terms of nitrogen containing compounds (~60 wt% of the protein content in the original algae as ammonium and nitrate ions and protein/polypeptides) than the single-step process. The highest biocrude yield was achieved at first-step temperature of 473 K, second-step temperature of 593 K, pressure of 200 bar and water flow rate of 0.5 mL/min.