Hydrothermal carbonization of simulated food waste for recovery of fatty acids and nutrients

Hydrothermal carbonization of combined food waste: A critical evaluation of emergent products

Hydrothermal carbonization (HTC) increasingly appears as an eco-friendly method for managing food waste (FW). In this work, a combination of FW was subjected to HTC, and products were critically evaluated. This involved a lab-scale pressure reactor and optimization of HTC conditions: temperature (220-340 °C) and residence time (90-260 min) via central composite design type of response surface methodology (CCD-RSM). Results showed varying temperatures and residence time to impact the hydrochar (HC) and hydrothermal carbonization aqueous phase (HTC-AP) properties. Although HC produced through HTC exhibited lower ash content (<2%) despite higher fixed carbon (>55 %) with respect to the raw FW, the heating value of HC ranged from 19.2 to 32.5 MJ/kg. Temperature primarily influenced FW conversion, affecting carbonaceous properties. Saturated fatty acids (SFA) were found to be predominant in the HTC-AP under all tested operating conditions (77.3, 48.4, and 37.1 wt% for HTC at 340, 280, and 220 °C in 180 min, respectively). Total phosphorus recovery in HC and HTC-AP respectively peaked at 340 °C and 220 °C in 180 min. The study concludes that HTC holds promise for energy-dense biofuel production, nutrient recovery, and fostering a circular economy.

Tackling municipal solid waste crisis in India: Insights into cutting-edge technologies and risk assessment

Municipal Solid Waste (MSW) management is a pressing global concern, with increasing interest in Waste-to-Energy Technologies (WTE-T) to divert waste from landfills. However, WTE-T adoption is hindered by financial uncertainties. The economic benefits of MSW treatment and energy generation must be balanced against environmental impact. Integrating cutting-edge technologies like Artificial Intelligence (AI) can enhance MSW management strategies and facilitate WTE-T adoption. This review paper explores waste classification, generation, and disposal methods, emphasizing public awareness to reduce waste. It discusses AI's role in waste management, including route optimization, waste composition forecasting, and process parameter optimization for energy generation. Various energy production techniques from MSW, such as high-solids anaerobic digestion, torrefaction, plasma pyrolysis, incineration, gasification, biodegradation, and hydrothermal carbonization, are examined for their advantages and challenges. The paper emphasizes risk assessment in MSW management, covering chemical, mechanical, biological, and health-related risks, aiming to identify and mitigate potential adverse effects. Electronic waste (E-waste) impact on human health and the environment is thoroughly discussed, highlighting the release of hazardous substances and their contribution to air, soil, and water pollution. The paper advocates for circular economy (CE) principles and waste-to-energy solutions to achieve sustainable waste management. It also addresses complexities and constraints faced by developing nations and proposes strategies to overcome them. In conclusion, this comprehensive review underscores the importance of risk assessment, the potential of AI and waste-to-energy solutions, and the need for sustainable waste management to safeguard public health and the environment.

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.

Hydrothermal carbonization of Typha australis: Influence of stirring rate

According to existing literature, there are no conclusive results on the impact of stirring on hydrothermal carbonization (HTC); some studies report a significant impact on the product's properties, while others indicate no influence. This study investigates the influence of stirring rate on several responses and properties of HTC products, including solid mass yield, solid carbon fraction, surface area, surface functional groups, morphology, and the fate of inorganic elements during HTC. Waste biomass was introduced as a feedstock to a 2 L HTC reactor, where the effects of temperature (180-250 °C), residence time (4-12 h), biomass to water (B/W) ratio (1-10%), and stirring rate (0-130 rpm) were investigated. The findings of this study conclusively indicated that the stirring rate does not influence any of the studied responses or properties of hydrochar under the selected experimental conditions used in this study. Nevertheless, the results indicated that a low-stirring rate (5 RPM) is enough to slightly enhanced the heating-up phase of the HTC reactor. For future research, it is recommended to examine the impact of stirring rate on the HTC of other types of biomass using the methodology developed in this study.

Phosphorus recovery from aqueous product of hydrothermal carbonization of cow manure

The work studies the recovery of nutrients (phosphorus and nitrogen) from the process water of acid-assisted hydrothermal carbonization (HTC) of cow manure. Three organic acids (formic acid, oxalic acid, and citric acid) and sulfuric acid were evaluated as additives in HTC. Using 0.3 M sulfuric acid, more than 99% of phosphorus and 15.6% of nitrogen from manure are extracted and dissolved during HTC at 170 °C with 10 min reaction time in a batch reactor. Nutrients (mainly phosphorus) were recovered through precipitation from process water by raising the ionic strength of the solution by addition of salts of magnesium and ammonia, and by raising the pH to 9.5. Subsequently, phosphorus-rich solids were recovered containing almost all (greater than 95%) of the dissolved phosphorus in the sulfuric and formic acid assisted runs. Morphology and qualitative chemical analysis of the precipitates were determined. It is shown by XRD that the precipitate formed from process water generated by HTC with oxalic acid is crystalline, although the diffraction pattern could not be matched with any expected substance.

A strategic review on sustainable approaches in municipal solid waste management andenergy recovery: Role of artificial intelligence,economic stability andlife cycle assessment

The consumption of energy levels has increased in association with economic growth and concurrently increased the energy demand from renewable sources. The need under Sustainable Development Goals (SDG) intends to explore various technological advancements for the utilization of waste to energy. Municipal Solid Waste (MSW) has been reported as constructive feedstock to produce biofuels, biofuel carriers and biochemicals using energy-efficient technologies in risk freeways. The present review contemplates risk assessment and challenges in sorting and transportation of MSW and different aspects of conversion of MSW into energy are critically analysed. The circular bioeconomy of energy production strategies and management of waste are also analysed. The current scenario on MSW and its impacts on the environment are elucidated in conjunction with various policies and amendments equipped for the competent management of MSW in order to fabricate a sustained environment.

Bioresource Upgrade for Sustainable Energy, Environment, and Biomedicine

We conceptualize bioresource upgrade for sustainable energy, environment, and biomedicine with a focus on circular economy, sustainability, and carbon neutrality using high availability and low utilization biomass (HALUB). We acme energy-efficient technologies for sustainable energy and material recovery and applications. The technologies of thermochemical conversion (TC), biochemical conversion (BC), electrochemical conversion (EC), and photochemical conversion (PTC) are summarized for HALUB. Microalgal biomass could contribute to a biofuel HHV of 35.72 MJ Kg-1 and total benefit of 749 $/ton biomass via TC. Specific surface area of biochar reached 3000 m2 g-1 via pyrolytic carbonization of waste bean dregs. Lignocellulosic biomass can be effectively converted into bio-stimulants and biofertilizers via BC with a high conversion efficiency of more than 90%. Besides, lignocellulosic biomass can contribute to a current density of 672 mA m-2 via EC. Bioresource can be 100% selectively synthesized via electrocatalysis through EC and PTC. Machine learning, techno-economic analysis, and life cycle analysis are essential to various upgrading approaches of HALUB. Sustainable biomaterials, sustainable living materials and technologies for biomedical and multifunctional applications like nano-catalysis, microfluidic and micro/nanomotors beyond are also highlighted. New techniques and systems for the complete conversion and utilization of HALUB for new energy and materials are further discussed.

Hydrothermal Conversion of Food Waste to Carbonaceous Solid Fuel-A Review of Recent Developments

This review critically discussed recent developments in hydrothermal carbonization (HTC) of food waste and its valorization to solid fuel. Food waste properties and fundamentals of the HTC reactor were also covered. The review further discussed the effect of temperature, contact time, pressure, water-biomass ratio, and heating rate on the HTC of food waste on the physiochemical properties of hydrochar. Literature review of the properties of the hydrochar produced from food waste in different studies shows that it possesses elemental, proximate, and energy properties that are comparable to sub-bituminous coal and may be used directly as fuel or co-combusted with coal. This work conclusively identified the existing research gaps and provided recommendation for future investigations.

Hydrothermal carbonization of kitchen waste: An analysis of solid and aqueous products and the application of hydrochar to paddy soil

Hydrothermal carbonization (HTC) technology can potentially be used to safely and sustainably utilize kitchen waste (KW). However, the characteristics of HTC solid products (hydrochar) and aqueous products (HAP) based on different types of KW have not yet been clarified. Here, four types of KW, cellulose-based (CL), skeleton-based (SK), protein-based (PT), and starch-based (ST) KW, were used for HTC at 180 °C, 220 °C, and 260 °C. The basic physicochemical properties and structures of hydrochars and HAP were analyzed, and the effects of different hydrochars on rice growth were characterized. HTC decreased the H/C and O/C of KW. All hydrochars were acidic (3.12 to 6.78) and the pH values increased with the HTC temperature, while high HTC temperature reduced the porosity of hydrochars. HTC promoted the enrichment of total carbon (up to 78.1 %), total nitrogen (up to 62.6 %), and total phosphorus (up to 171.6 %) in KW. More carbon (60.7-88.0 %) and nitrogen (up to 87.4 %) were present in the hydrochars than in the HAP. The relative content of C_1s increased and O_1s decreased in CL and ST hydrochars as the HTC temperature increased, while the opposite pattern was observed for SK and PT hydrochars. The dissolved organic matter (DOM) of different hydrochars and HAP were mainly humus-like substances. The biodegradability of the DOM in HAP was often higher than the corresponding hydrochar, and their DOM biodegradability increased with the HTC temperature. The content of heavy metals from different hydrochars did not exceed the relevant thresholds of fertilizer standards. Rice grain yield increased by 3.7-11.1 % in the hydrochar treatments without phosphate fertilizer addition compared with the control treatment. The results of this study provide new theoretical and empirical insights into the potential for HTC technology to be used for the recycling of KW and its products in the agricultural environment.

Hydrothermal carbonization of food waste as sustainable energy conversion path

Every day, a large amount of food waste (FW) is released into the environment, causing financial loss and unpredictable consequences in the world, highlighting the urgency of finding a suitable approach to treating FW. As moisture content makes up 75% of the FW, hydrothermal carbonization (HTC) is a beneficial process for the treatment of FW since it does not require extensive drying. Moreover, the process is considered favorable for carbon sequestration to mitigate climate change in comparison with other processes because the majority of the carbon in FW is integrated into hydrochar. In this work, the reaction mechanism and factors affecting the HTC of FW are scrutinized. Moreover, the physicochemical properties of products after the HTC of FW are critically presented. In general, HTC of FW is considered a promising approach aiming to attain simultaneously-two core benefits on economy and energy in the sustainable development strategy.

The fourth industrial revolution in the food industry-part II: Emerging food trends

The food industry has recently been under unprecedented pressure due to major global challenges, such as climate change, exponential increase in world population and urbanization, and the worldwide spread of new diseases and pandemics, such as the COVID-19. The fourth industrial revolution (Industry 4.0) has been gaining momentum since 2015 and has revolutionized the way in which food is produced, transported, stored, perceived, and consumed worldwide, leading to the emergence of new food trends. After reviewing Industry 4.0 technologies (e.g. artificial intelligence, smart sensors, robotics, blockchain, and the Internet of Things) in Part I of this work (Hassoun, Aït-Kaddour, et al. 2022. The fourth industrial revolution in the food industry-Part I: Industry 4.0 technologies. Critical Reviews in Food Science and Nutrition, 1-17.), this complimentary review will focus on emerging food trends (such as fortified and functional foods, additive manufacturing technologies, cultured meat, precision fermentation, and personalized food) and their connection with Industry 4.0 innovations. Implementation of new food trends has been associated with recent advances in Industry 4.0 technologies, enabling a range of new possibilities. The results show several positive food trends that reflect increased awareness of food chain actors of the food-related health and environmental impacts of food systems. Emergence of other food trends and higher consumer interest and engagement in the transition toward sustainable food development and innovative green strategies are expected in the future.