**Waste Residues**

Waste residues refer to the by-products that are left over from industrial, agricultural, commercial, or domestic processes that have used up the primary product. These residues can include a wide range of materials such as biomass leftovers, ash from combustion processes, slags from metal smelting, spent catalysts, tailings from mining and milling operations, and sludges from water treatment. While they are often seen as a disposal challenge, waste residues can also be a resource, as they sometimes contain valuable materials that can be recycled or repurposed. In the energy sector, certain waste residues can be utilized as feedstock for the production of bioenergy or biofuels, thus contributing to a more circular economy and reducing the environmental impact of waste.

For more information about waste residues, please refer to the following sources:

1. **United States Environmental Protection Agency (EPA)**
The EPA provides comprehensive information on various types of waste, including waste residues, how they are managed, and how they can be utilized in a sustainable manner.
URL: (https://www.epa.gov/sustainable-management-food/types-wastes-and-residuals-recovered-food-waste)

2. **The World Bank – What a Waste 2.0: A Global Snapshot of Solid Waste Management to 2050**
This report offers an extensive overview of waste generation and management worldwide, which includes discussions on waste residues and their potential impacts on sustainability and resource efficiency.
URL: (https://www.worldbank.org/en/news/immersive-story/2018/09/20/what-a-waste-2-0-a-global-snapshot-of-solid-waste-management-to-2050)