Book excerpt: This book is a comprehensive guide to bioconversion approaches based on microorganisms and enzymes for the valorization of underused wastes of diverse categories to produce new products. Optimized conditions for microbial and enzymatic valorization are discussed, along with related biotechnological considerations, environmental considerations, bioprocess development, obstacles, and future outlooks. Biofuels, bioenergy, and other platform chemicals are only some of the products that can be produced through this book's explanation of the microbiological processes involved in the bioconversion and valorization of wastes.