Which one among the following groups of items contains only biodegradable items ?

Biodegradable substances are those that can be broken down by natural processes, such as microbial action, into simpler compounds [5]. Option 4 consists of cow-dung, paddy-husk, and vegetable wastes, all of which are organic materials derived from plants and animals that decompose naturally [2]. Cow-dung and vegetable wastes are specifically categorized as 'wet waste' or biodegradable organic matter [6]. In contrast, other options contain non-biodegradable materials: glass [3], iron-scrap (metal) [3], and plastic [4]. While sewage is biodegradable [3], plastic and leather (especially chemically treated) in option 3 are resistant to rapid microbial decomposition. Therefore, only the group containing cow-dung, paddy-husk, and vegetable wastes consists entirely of biodegradable items that can be effectively managed through processes like composting or bio-methanation [6].

Sources

1. [5] https://mohua.gov.in/pdf/627b8318adf18Circular-Economy-in-waste-management-FINAL.pdf
2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 5.12.2. Plastics as a Waste Material in Land Environment > p. 97
3. [6] https://pmc.ncbi.nlm.nih.gov/articles/PMC3352250/
4. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 12: Major Crops and Cropping Patterns in India > Glossary > p. 101
5. [4] https://swachhbharatmission.ddws.gov.in/sites/default/files/Technical-Notes/Biodegradable_Waste_Management_Manual_English.pdf