Hydrothermal carbonization of household wet waste - characterization of hydrochar and process wastewater stream

Hydrothermal pretreatment of press mud: Characterization and potential application of hydrochar and process water

In the present study, press mud (PM), a major waste by-product from sugar industries, was subjected to hydrothermal pretreatment (HTP) to create resource recovery opportunities. The HTP process was performed with the PM samples in a laboratory scale high pressure batch reactor (capacity = 0.7 L) at 160 °C and 200 °C temperatures (solids content = 5 % and 30 %). The pretreatment resulted in separation of solid and liquid phases which are termed as solid hydrochar (HC) and process water (PW), respectively. High heating value (HHV) of HC was ∼14-18 MJ kg-1, slightly higher than that of PM (14 MJ kg-1). The thermogravimetric analysis showed about 1.5-1.7 times higher heat release from HC burning compared to that observed from combustion of PM. Apart from this, the HC and PM showed no phytotoxicity during germination of mung bean (Vigna radiata). Moreover, the biochemical methane potential test on the PW showed a generation of 167-245 mL biogas per gram of chemical oxygen demand added. Hence, the HTP offers several resource recovery opportunities from PM which may also reduce the risks of environmental degradation.

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.

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.

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.

Eco-Friendly Detoxification of Congo Red Dye from Water by Citric Acid Activated Bioadsorbents Consisting of Watermelon and Water Chestnuts Peels Collected from Indigenous Resources

The native peels of two cheap, locally available adsorbents, watermelon (PWM) and water chestnuts (PWC), were chemically processed with different chemicals as modifying agents for the determination and assessment of their adsorption ability for the removal and clearance of harmful, venomous, and pernicious Congo red (CGR), as an acidic nature anionic dye, from the aqueous system. In successive batch experiments, the citric acid-treated peels CPWM and CPWC have shown more promising adsorption performance than their raw and untreated peel counterparts due to the availability of additional adsorption active binding sites evidenced through FT-IR and SEM characterizations. In the Langmuir and Temkin models, the correlation coefficients ( $R^2$ ) for the adsorptive removal of CGR on CPWM, PWM, CPWC, and PWC are very close to unity, 0.99 for each case of adsorption performance. Furthermore, the $q_{\max }$ nonlinear statistical results for the elimination of CGR on citric acid-treated adsorbents (CPWM and CPWC) are 8.3 and 7.95 mg/g whereas for their unmodified forms (PWM and PWC) are 2.23 and 4.32 mg/g, respectively, reflecting homogenous and monolayer adsorption mechanism. The greater values of $B_T$ 1.4 and 1.3 J/mole, for adsorptive removal of dye on CPWM and CPWC, respectively, as compared to their unmodified forms PWM and PWC which are 0.53 and 0.55 J/mole, respectively, indicate the stronger adsorbate-adsorbent associations. The mechanism follows the pseudo second order in the better mode, while thermodynamic statics for ΔH0,ΔG0, ΔS0, and ΔE0, indicate spontaneous and exothermic behavior of adsorption. This study tends to suggest that citric acid-modified adsorbents CPWM and CPWC may indeed be exploited efficiently to eliminate Congo red dye from wastewater.