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In the current scenario in many cities, huge quantities of biowaste solid matter are generated, making it a big challenge to keep our cities smart/clean without creating health issues. The second challenge is to mitigate solid biowastes from municipalities, and it needs systematic valorization/conversion approaches to transform/generate them into clean/least carbon-emitting fuel sources. This effort can help make smart cities with additional amounts of energy generation that can be used by each citizen for their daily energy needs. In the cities, biowastes are reported as food waste (from domestic kitchens and restaurant/hotel), green plant residues (from parks and other cleaning activities), and other miscellaneous sources. Due to the huge generation of these biowastes, the respective cities can look dirtier and also show a poor level of development. So, people from municipal authorities and some research groups have to start converting this biowaste solid matter into renewable and sustainable energy that can help reduce this biowaste accumulation through the promotion of sustainable bioenergy sources. In valorization approaches, biological (anaerobic digestion) and thermochemical (like pyrolysis) processes are common, and these can be applied to biowaste mitigation to minimize the negative impact on the environment and its components. In India, some states, like Madhya Pradesh, have put efforts into creating biogases like green hydrogen from their cities generated biowastes. In this review, we emphasize the different sources of biowaste in cities with their volumes/quantities, factors/activities for generations, and mitigation approaches for biowaste conversion into fuels with the promotion of sustainable goal achievement. Now that waste matters, effort is put into a take-home concept/message regarding the conversion/recovery, and extraction of waste into energy/other valuable products for home needs. It helps keep cities clean, smart, and rich in revenue sources.
Sarangi et al. (Wed,) studied this question.