Hydrothermal carbonization of food waste as sustainable energy conversion path

Advancements in Lignin Valorization for Energy Storage Applications: Sustainable Technologies for Lignin Extraction and Hydrothermal Carbonization

The conversion of industrial waste lignin into sustainable carbon materials is an essential step towards reducing dependency on fossil fuels and mitigating environmental impacts. This review explores various aspects of lignin utilization, with particular focus on the extraction of lignin and the application of lignin-derived carbon materials in energy storge applications. The review explores advanced chemical methods to improve the efficiency of biomass conversion, detailing emerging technologies for lignin extraction from various biomasses using innovative solvents and techniques, such as Ionic Liquids and Deep Eutectic Solvents (DESs). Additionally, it discusses the parameters that impact the hydrothermal carbonization (HTC) process. The produced hydrochar shows potential for use as optimized precursors for energy storage applications. This review also considers the implications of these technologies for environmental sustainability and the circular economy, suggesting future research directions to enhance and scale these processes for global impact. This comprehensive analysis highlights the critical role of advanced biomass conversion technologies in achieving sustainability and outlines pathways for future lignin-based carbon materials innovations.

Catalyst-Enhancing Hydrothermal Carbonization of Biomass for Hydrochar and Liquid Fuel Production-A Review

The research impact of catalysts on the hydrothermal carbonization (HTC) process remains an ongoing debate, especially regarding the quest to enhance biomass conversion into fuels and chemicals, which requires diverse catalysts to optimize bio-oil utilization. Comprehensive insights and standardized analytical methodologies are crucial for understanding HTC's potential benefits in terms of biomass conversion stages. This review seeks to understand how catalysts enhance the HTC of biomass for liquid fuel and hydrochar production, drawing from the following key sections: (a) catalyst types applied in HTC processes; (b) biochar functionality as a potential catalyst; (c) catalysts increasing the success of HTC process; and (d) catalyst's effect on the morphological and textural character of hydrochar. The performance of activated carbon would greatly increase via catalyst action, which would progress the degree of carbonization and surface modification, alongside key heteroatoms. As catalytic HTC technology advances, producing carbon materials for thermochemical activities will become more cost-effective, considering the ever-growing demands for high-performance thermochemical technologies.

Biochar mediated high-rate anaerobic bioreactors: A critical review on high-strength wastewater treatment and management

Treatment of high-strength wastewater is critical for the aquatic environment and receiving water bodies around the globe. Untreated or partially treated high-strength wastewater may cause severe damage to the existing water bodies. Various high-rate anaerobic bioreactors have been developed in the last decades for treating high-strength wastewater. High-rate anaerobic bioreactors are effective in treating industrial wastewater and provide energy in the form of methane as well. However, the physical or chemical properties of high-strength industrial wastewater, sometimes, disrupt the functioning of a high-rate anaerobic bioreactor. For example, the disintegration of granular sludge in up flow anaerobic sludge blanket reactor or membrane blocking in an anaerobic membrane bioreactor are the results of a high-strength wastewater treatment which hamper the proper functioning and may harm the wastewater treatment plant economically. Biochar, if added to these bioreactors, may help to alleviate the ill-functioning of high-rate anaerobic bioreactors. The primary mechanisms by biochar work in these bioreactors are direct interspecies electron transfer, microbial immobilization, or gene level alternations in microbial structure. The present article explores and reviews the recent application of biochar in a high-rate anaerobic bioreactor treating high-strength industrial wastewater.

Renewable and efficient removal of arsenic from contaminated water by modified biochars derived from As-enriched plant

There were limited researches on the scientific disposal of As-enriched plants, and how to reduce the available As content in the processed products and improve the utilization value were the key. In this study, the effect and mechanism of biochar produced by the As-enriched Pteris vittate before and after modification on the removal of As(III) in water were studied. The results indicated that the available As contents of Fe-BC300 and Fe-BC500 were reduced by 78.7 % and 91.9 % compared to original biochars, respectively. Modified biochars not only had a large adsorption capacity for As(III) (50.3 and 39.7 mg/g), but also can efficiently oxidize As(III) to As(V). The removal rate of As(III) by modified biochar was still higher than 50% after 3 cycles. The increase of the point of zero charge and the introduction of Fe were the main reasons for its efficient adsorption and oxidation of As(III).

Hydrothermal carbonization of food waste for sustainable biofuel production: Advancements, challenges, and future prospects

With the improvement of living standards, food waste (FW) has become one of the most important organic solid wastes worldwide. Owing to the high moisture content of FW, hydrothermal carbonization (HTC) technology that can directly utilize the moisture in FW as the reaction medium, is widely used. Under mild reaction conditions and short treatment cycle, this technology can effectively and stably convert high-moisture FW into environmentally friendly hydrochar fuel. In view of the importance of this topic, this study comprehensively reviews the research progress of HTC of FW for biofuel synthesis, and critically summarizes the process parameters, carbonization mechanism, and clean applications. Physicochemical properties and micromorphological evolution of hydrochar, hydrothermal chemical reactions of each model component, and potential risks of hydrochar as a fuel are highlighted. Furthermore, carbonization mechanism of the HTC treatment process of FW and the granulation mechanism of hydrochar are systematically reviewed. Finally, potential risks and knowledge gaps in the synthesis of hydrochar from FW are presented and new coupling technologies are pointed out, highlighting the challenges and prospects of this study.

Food waste biorefinery towards circular economy in Australia

Staggering amounts of food waste are produced in Australia, and this review provides food waste based biorefinery opportunities in moving towards a circular economy in Australia. The current food waste scenario in Australia including an overview of primary food waste sources, government regulation, and current management practices is presented. The major food waste streams include fruit and vegetable (waste from wine grapes, citrus, apple, potato, and tomato), nuts (almond processing waste), seafood (Fish waste), dairy whey, sugarcane bagasse, and household and businesses. The composition of these waste streams indicated their potential for use in biorefineries to produce value-added products via various pathways combining direct extraction and biological and thermochemical conversion. Finally, the efforts made in Australia to utilize food waste as a resource, as well as the challenges and future directions to promote the development of concrete and commercially viable technologies for food waste biorefinery, are described.

Intelligent approaches for sustainable management and valorisation of food waste

Food waste (FW) is a severe environmental and social concern that today's civilization is facing. Therefore, it is necessary to have an efficient and sustainable solution for managing FW bioprocessing. Emerging technologies like the Internet of Things (IoT), Artificial Intelligence (AI), and Machine Learning (ML) are critical to achieving this, in which IoT sensors' data is analyzed using AI and ML techniques, enabling real-time decision-making and process optimization. This work describes recent developments in valorizing FW using novel tactics such as the IoT, AI, and ML. It could be concluded that combining IoT, AI, and ML approaches could enhance bioprocess monitoring and management for generating value-added products and chemicals from FW, contributing to improving environmental sustainability and food security. Generally, a comprehensive strategy of applying intelligent techniques in conjunction with government backing can minimize FW and maximize the role of FW in the circular economy toward a more sustainable future.

Enhanced co-digestion of sewage sludge and food waste using novel electrochemical anaerobic membrane bioreactor (EC-AnMBR)

Membrane fouling remains a big challenge hindering the wide-application of anaerobic membrane bioreactor (AnMBR) technology. In this study, an electrochemical anaerobic membrane bioreactor (EC-AnMBR) was developed by coupling electrochemical regulation to enhance co-digestion of sewage sludge and food waste and mitigate membrane fouling. The highest methane production (0.12 ± 0.02 L/L_reactor/day) and net energy recovery (31.82 kJ/day) were achieved under the optimum conditions of 0.8 V, hydraulic retention time of 10 days and solids retention time of 50 days. Electrochemical regulation accelerated the mineralization of high-molecular-weight organics and reinforced the membrane antifouling ability by inducing electrostatic repulsive force and electrochemical oxidation. Besides, symbiotic relationships among functional microorganisms (Spirochaetes, Methanolinea, etc.) were enhanced, improving the hydrolysis and methanogenesis processes of complex organics and the long-term stability. This study confirms the technical feasibility of EC-AnMBR in treating high-solid biowastes, and provides the fundamental data to support its application in real-world scenarios.

Hydrothermal conversion of biomass to fuels, chemicals and materials: A review holistically connecting product properties and marketable applications

Biomass is a renewable and carbon-neutral resource with good features for producing biofuels, biochemicals, and biomaterials. Among the different technologies developed to date to convert biomass into such commodities, hydrothermal conversion (HC) is a very appealing and sustainable option, affording marketable gaseous (primarily containing H₂, CO, CH₄, and CO₂), liquid (biofuels, aqueous phase carbohydrates, and inorganics), and solid products (energy-dense biofuels (up to 30 MJ/kg) with excellent functionality and strength). Given these prospects, this publication first-time puts together essential information on the HC of lignocellulosic and algal biomasses covering all the steps involved. Particularly, this work reports and comments on the most important properties (e.g., physiochemical and fuel properties) of all these products from a holistic and practical perspective. It also gathers vital information addressing selecting and using different downstream/upgrading processes to convert HC reaction products into marketable biofuels (HHV up to 46 MJ/kg), biochemicals (yield >90 %), and biomaterials (great functionality and surface area up to 3600 m²/g). As a result of this practical vision, this work not only comments on and summarizes the most important properties of these products but also analyzes and discusses present and future applications, establishing an invaluable link between product properties and market needs to push HC technologies transition from the laboratory to the industry. Such a practical and pioneering approach paves the way for the future development, commercialization and industrialization of HC technologies to develop holistic and zero-waste biorefinery processes.