I am agree with Shalini Gupta ,you need to follow all required steps in solid waste management. It is very crucial to take care for e- waste , and non recyclable waste.

You may focus on high-quantity solid waste materials whose landfilling is gradually increasing with respect to the production increment. Furthermore, you may classify the solid waste types in terms of, for example, industry, hazards, and recycling. Hope that this serves you well.

We have case studies of urban Area (City with population 5 million) where we have carried out Awareness and Daily Action Program in 172 schools with 170,000 High School Students over 10 years. The project (Sagarmitra OR Friends of Oceans) grew from 150 students to 172,000 between 2011 and 2021. We have also worked with small villages with up to 250 families and have experience about how rural and urban families segregate Plastic Waste from their homes and after collecting it for a month as dry plastic waste hand it over to us and allied agencies. We buy the aggregate plastic (41 tons from Jan to April 2021 & approx 100 tons purchased and sent for recycling last year 2020). The weakest link in recycling is the lack of recollection of clean and dry waste plastic at source. We have made a breakthrough in behavior change - that is quantified. Good luck with your search for a theme. Hope this helps. Please note - as 2020 was a covid pandemic year the schools were closed by 15th march. We adapted to collecting waste plastic from Housing Societies and Businesses. The graphic gives an outline of 2020 and 3 months of 2021.