Municipal solid waste management in India: From waste disposal to recovery of resources?

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.

Alkali-activation is effective municipal solid waste incineration fly ash (MSWIFA) solidification/stabilization (S/S) technology. Percolation and migration of heavy metals in MSWIFA S/S matrix is a complicated and slow process. Here, several alkali-activated MSWIFA samples are selected to comparatively investigate the long-term leaching behavior and environmental availability of Pb, Zn and Cd when exposed in different erosion environment. Acid environment posed the more serious destroy to MSWIFA S/S matrices. RAC demonstrated that potential risk level of heavy metals is higher in acid rain environment, and Cd, Zn showed the prominent risk. When soaked in acid rain solution, the surface of alkali-activated MSWIFA S/S matrices was cracked seriously and a large number of hardened slurry peeled off. However, more stable structural properties and lower heavy metal leachability can be found in alkali-activated MSWIFA/aluminosilicate. The immobilization efficiency of Pb, Zn and Cd were all above 99.0%. Microstructure and morphology results indicated that there is new phase Friedel's salts generated and much more amorphous substance such as C-(A)-S-H gel with incorporation of aluminosilicate, which all contributed much to the formation of compact and stable microstructure, then significantly facilitated the encapsulation of heavy metal. These findings will provide theoretical basis and new insight for resource utilization and security landfill of MSWIFA.

In this work, a surface dielectric barrier discharge (SDBD) plasma-based source powered by a bipolar pulsed power supply is reported. This source has been tested for the decomposition of toluene and benzene in an enclosed environment of size 12 ft³. Study has been performed to compare decomposition of toluene and benzene on various combinations of the applied voltages and frequencies. For about 60 min of continuous operation of the SDBD source, a decomposition efficiency of 99.7% (toluene) and 74.8% (benzene) has been achieved. For the effective generation of reactive species, the ground electrode of the SDBD source is coated with TiO₂ nanoparticles. Optical emission spectroscopy diagnostic has also been used to estimate the electron temperature, which is found to be in the range of 3–6 eV. Consequently, the high energetic electrons produced via the SDBD source are the primary reason to activate the catalyst instead of ultra-violet (UV) light. The results further showed that the developed SDBD source produces powerful, immediate discharge and energetic electrons, which could be efficiently used for volatile organic compounds (VOCs) degradation. The need for feed gas, pellets and/or differential pressure has been eliminated by the developed SDBD source from the known conventional methods for VOCs decomposition.

Few studies have been done about engineered facilities related to waste collection, treatment, and disposal in the waste management sectors across Nepal. The decision support system is not well established, resulting in poor planning and execution of waste management. Available data for performing a life cycle assessment (LCA) is limited. We used an LCA model to investigate waste management options for Nepal's capital, Kathmandu. We also tested the hypothesis that exclusion from the LCA model of variables for which there was no data would make no difference in the management rankings. The assessment was based on three scenarios: business as usual, including collection, transportation, and landfilling; recycling; and conjunctive disposal comprised of composting and landfilling. The LCA methodology we used includes detailed unit processes and quantified values of various resources and emissions to compute the impact level on the environment. The contribution of the collection, transportation, landfilling, and recycling was calculated as global warming potential, acidification potential, eutrophication potential, and fuel energy consumption for each scenario. Scenario 3 ranked higher than scenarios 1 and 2 based on available data. The results were based on the environmental burden of metric tons of municipal solid waste handled at landfills, regardless of what was recycled and composted. Scenario 3 yielded minimum environmental impacts and was a cost-efficient option. Using a range of literature values for the missing variables, it was shown that the excluded variables made no difference in the scenario rankings. The study successfully employed the LCA as a decision-making tool in waste management in Kathmandu, which can be useful for other cities in developing countries.

As a technology, a Heat Melt Refuse Compactor (HMRC) has been developed to process municipal solid waste by converting into tiles and on-site valuable products. The HMRC compacts, heats the solid waste to 200°C and recovers the water from the MSW. The heating causes volatile contaminants to be released into the air. The model has evaluated the design and testing parametrs for MSW processing and analysis. HMRC testing has demonstrated water recovery upto 99%, waste volume reduction upto 80%, tile stabilization for long-term, passive separation of liquid/gas phase, and operations with low maintenance cost.

Heat melt refuse compactor has designed to compress by compaction process, encapsulate the waste bi-product, residual gas/water at atmoshpheric pressure, waste volume reduction and microbial stabilization. The model design shows the benefit of a heat melt refuse compactor on-site use by converting the solid waste into valuable products with thermal and compression technique. HMRC model has processed ∼1300 kg of solid waste; which produced ∼700 kg of tile, recovered ∼400 kg of water, and ∼200 kg of gaseous and residual waste. The compression ratio (Cc) of solid waste has been estimated with a compression cell with a diameter between 65 to 100 mm, mesoscale data for a diameter of 195 mm to 265 mm and high-scale data for a diameter of 300 to 400 mm. Cc is a more sensitive variable in formation of bi-products from MSW. Ground base HMRC has designed for Cc stress ranges from 20 to 300 kPa to function within the physical and environmental constraints.E-control contaminant removal mechanism keeps the environment clean and safe.