Catalytic pyrolysis of brown algae using carbon dioxide and oyster shell

Pilot-scale co-processing of lignocellulosic biomass, algae, shellfish waste via thermochemical approach: Recent progress and future directions

Thermal co-processing of lignocellulosic and aquatic biomass, such as algae and shellfish waste, has shown synergistic effects in producing value-added energy products with higher process efficiency than the traditional method, highlighting the importance of scaling up to pilot-scale operations. This article discusses the design and operation of pilot-scale reactors for torrefaction, pyrolysis, and gasification, as well as the key parameters of co-processing biomass into targeted and improved quality products for use as fuel, agricultural application, and environmental remediation. Techno-economic analysis reveals that end product selling price, market dynamics, government policies, and biomass cost are crucial factors influencing the sustainability of thermal co-processing as a feasible approach to utilize the biomass. Because of its simplicity, pyrolysis allows greater energy recovery, while gasification has the highest net present value (profitability). Integration of liquefaction, hydrothermal, and fermentation pre-treatment technology has the potential to increase energy efficiency while reducing process residues.

Biological-Based Produced Water Treatment Using Microalgae: Challenges and Efficiency

Produced water (PW) is the most significant waste stream generated in the oil and gas industries. The generated PW has the potential to be a useful water source rather than waste. While a variety of technologies can be used for the treatment of PW for reuse, biological-based technologies are an effective and sustainable remediation method. Specifically, microalgae, which are a cost-effective and sustainable process that use nutrients to eliminate organic pollutants from PW during the bioremediation process. In these treatment processes, microalgae grow in PW free of charge, eliminate pollutants, and generate clean water that can be recycled and reused. This helps to reduce CO2 levels in the atmosphere while simultaneously producing biofuels, other useful chemicals, and added-value products. As such, this review focuses on PW generation in the oil and gas industry, PW characteristics, and examines the available technologies that can be used for PW remediation, with specific attention to algal-based technologies. In addition, the various aspects of algae growth and cultivation in PW, the effect of growth conditions, water quality parameters, and the corresponding treatment performance are presented. Lastly, this review emphasizes the bioremediation of PW using algae and highlights how to harvest algae that can be processed to generate biofuels for added-value products as a sustainable approach.

Effect of eggshell- and homo-type Ni/Al2O3 catalysts on the pyrolysis of food waste under CO2 atmosphere

This study highlights the potential of pyrolysis of food waste (FW) with Ni-based catalysts under CO₂ atmosphere as an environmentally benign disposal technique. FW was pyrolyzed with homo-type Ni/Al₂O₃ (Ni-HO) or eggshell-type Ni/Al₂O₃ (Ni-EG) catalysts under flowing CO₂ (50 mL/min) at temperatures from 500 to 700 °C for 1 h. A higher gas yield (42.05 wt%) and a lower condensable yield (36.28 wt%) were achieved for catalytic pyrolysis with Ni-EG than with Ni-HO (34.94 wt% and 40.06 wt%, respectively). In particular, the maximum volumetric content of H₂ (21.48%) and CO (28.43%) and the lowest content of C₂-C₄ (19.22%) were obtained using the Ni-EG. The formation of cyclic species (e.g., benzene derivatives) in bio-oil was also effectively suppressed (24.87%) when the Ni-EG catalyst and CO₂ medium were concurrently utilized for the FW pyrolysis. Accordingly, the simultaneous use of the Ni-EG catalyst and CO₂ contributed to altering the carbon distribution of the pyrolytic products from condensable species to value-added gaseous products by facilitating ring-opening reactions and free radical mechanisms. This study should suggest that CO₂-assisted catalytic pyrolysis over the Ni-EG catalyst would be an eco-friendly and sustainable strategy for disposal of FW which also provides a clean and high-quality source of energy.

Fabrication of porous carbon derived from cotton/polyester waste mixed with oyster shells: Pore-forming process and application for tetracycline removal

Porous carbon was fabricated from cotton/polyester-based textile wastes as a carbon source coupled with oyster shells for tetracycline removal. The preparation conditions were optimized and detailed characterization was conducted to study the effects of oyster shells on cotton/polyester pyrolysis. The optimal pyrolysis temperature (900 °C), pyrolysis time (1 h) and mass ratio (OS/CPW of 1:1) were determined using the Box-Behnken experiment. The best porous carbon reached a surface area of 645.05 m²/g. Oyster shells acted as templates to produce cotton/polyester-based porous carbon and a possible pore-forming process was proposed. CaO was converted from CaCO₃, which played the dominant role in developing the mesoporous structure. CO₂ gas released from CaCO₃ promoted the creation of micropore structure. In addition, the impurites of oyster shells acted as the dispersing agent inhibiting CaCO₃ and CaO aggregation and growth. Fe₂O₃ and K₂O from impurities reacted with the carbon skeleton to increase microporosity. Finally, the well-developed and uniform porous carbon was obtained. The first-pseudo order model and Langmuir isotherms were suitable. The maximum adsorption capacity of PC-OS-900 was 515.17 mg/g which competed with other waste-based adsorbents. The TET adsorption mechanism was related to pore distribution, hydrogen bonds, π-π EDA interactions and electrostatic interactions.

Effect of lime mud on the reaction kinetics and thermodynamics of biomass pyrolysis

The solid waste from papermaking factory, lime mud (LM), was previously demonstrated as an effective catalyst in biomass pyrolysis. Since understanding the kinetics and thermodynamics is the critical step for pyrolysis development, thereby the effect of LM on the kinetics and thermodynamics for biomass pyrolysis was systematically investigated in this study. More specifically, two representative biomasses, herbaceous corncob and woody aspen sawdust, were blended with LM at different mass ratio of 0:0, 0.5:1, 1:1, and 2:1. Based on this, pyrolysis was conducted through thermogravimetry under nitrogen atmosphere. The kinetic parameters of activation energy and pre-exponential factor were calculated by iso-conventional method. While the Avrami theory was used to determine the reaction order. Thermodynamic parameters were also calculated and compared with those of non-catalytic pyrolysis.

Pyrolysis of food waste over a Pt catalyst in CO2 atmosphere

In this study, a method of disposing food waste is introduced via catalytic pyrolysis under CO₂ condition. The catalyst and CO₂ hindered the generation of condensable compounds, leading to enhancing non-condensable gas generation. However, they did not affect the amount of solid residues left after the thermal reaction. The amount of condensable cyclic compounds was reduced when the catalyst and/or CO₂ were used. The enhancement of non-condensable gas production and reduction of cyclic compounds formation were maximized when the Pt catalyst and CO₂ were simultaneously applied to the pyrolysis of food waste. For instance, approximately 67.3 % less cyclic compounds, including benzene derivatives, were generated at 700 °C in the presence of the catalyst under a CO₂ atmosphere compared to non-catalytic conditions without CO₂. The results suggest that a CO₂-assisted catalytic pyrolysis is as environmentally benign disposal method for food waste.