Narrow Results

A significant amount of hydrogen is required for hydroprocessing processes to satisfy the needs of petroleum refinery, natural gas cleaning, and biofuel upgrading. The first section of this chapter introduces the background of hydrogen production technologies. The second section reviews resources that can be used to manufacture hydrogen. The third section provides an overview of the current development of methane reforming, gasification, electrolysis, and other technologies. The last section concludes the chapter and presents the future trends.

Urgent efforts and appropriate measures to utilise food waste (FW) for holistic exploitation of resources are needed. This chapter briefly reviews the global FW generation scenario among several selected high economic and low developing countries. It further highlights the common globally adopted treatment techniques, such as landfilling, composting, heat–moisture reaction, and anaerobic digestion, their challenges, and associated merits for FW treatment. This review discusses considerations for optimal resource generation from FW and highlights the selection of three conceptual routes. The first route proposes anaerobic digestion and pyrolysis, where valuable products such as biochar can serve as additives in anaerobic digestion for optimal biogas production and stabilised digestates. In addition, in the upstream coupling section, pyro-oil and syngas can be used in anaerobic digestion for biomethanation enhancement. The performance of the syngas biomethanation in anaerobic digestion reflects on hydrogen and carbon monoxide concentrations. A higher concentration of hydrogen could accelerate the carbon monoxide degradation rate and vice versa. The second route offers a direction for high water content FW valorisation via hydrothermal carbonation (HTC) combined with anaerobic digestion and vice versa to obtain hydrochar and valuable products, such as hydro-oil, high biogas, and enriched digestates. Previous studies showed that hydrochar could mitigate ammonia in anaerobic digestion and enhance methane generation compared with pyrochar. For high hydrogen syngas generation, the gasification technique coupled with anaerobic digestion was proposed for FW and associated residues in the third route, thus offering sustainability towards increased bioenergy production. This review stimulates the possibility for the development of the baseline approach on FW and associated residues in different technology (anaerobic digestion, pyrolysis, HTC, and gasification) combinations for optimal resource recovery.

Plastics have become one of the most integral parts of our day-to-day lives; however, after use, plastic waste accumulates on land and in water bodies, which wreaks havoc in the environment by releasing toxic gases. As the usage of plastic increases, it will result in the depletion of natural resources and greater difficulties in managing plastic waste. Accordingly, in this chapter, we focus on various types of resources, such as fuel, gas, energy, and electricity, which are recovered from plastic waste through different waste management technologies such as primary, secondary, tertiary, and quaternary recycling. This chapter is set forth by critically evaluating different types of plastic waste technologies, the products, and their byproducts formed during tertiary treatment. Material and resource recovery of different types of waste plastics through gasification and pyrolysis offers significant environmental benefits by promoting resource extraction and reducing the associated environmental impacts linked to the extraction process.

The characteristics of biomass air-steam gasification in a fluidized bed for hydrogen-rich gas production are studied through a series of experiments. Coconut shell had been taken as a representative biomass and air-steam had been used as the fluidizing and gasifying media. The effects of reactor temperature, steam-to-biomass ratio (S/B), Equivalence ratio (ER) on gas composition and gas yield are investigated. From the experimental results, it can be seen that the higher reactor temperature, the proper ER, proper steam-to-biomass ratio (S/B), and smaller biomass particle size will contribute to more hydrogen production. The goal is to investigate the effects of temperatures in the range between 600 to 900 °C, steam to biomass ratios in the range of 0 to 2.6 on gas composition of the product gas. Gasification temperature was found to be the most influential factor. Increasing the temperature resulted in increases in hydrogen and methane contents. Compared with biomass air gasification, the introduction of steam improved gas quality. However, excessive steam would lower gasification temperature and so degrade fuel gas quality.