Modern technology in food processing industries has led to increased food production and as a consequence, also of food by-products and waste. Generation of by-products and waste which consists primarily of organic residues of processed raw materials during processing is unavoidable. These residues can cause pollution, management and economic problems. Instead of throwing and landfilling these by-products and waste, there is an increasing interest to turn these waste and by-products into useful products. Therefore, different methods to use food industrial residues as a source of high valueadded products are under development. Current methods for further utilisation of product-specific by-products and waste have developed along traditional lines and been closely bound to develop the best useful management methods. Two general methods of traditional by-products and waste utilisation include the use of the waste and by-products either as animal feed or as fertilizer. Current valorization, a relatively new concept in the field of industrial residue management promoting the principle of sustainable development, has been developed to produce industrial chemicals, micronutrients, enzymes, and precious metabolites that have industrial value. These products are mainly produced by chemical and biotechnological processes. In addition, part of these residues is used to produce bio-energy through a vast range of processes including chemical, thermochemical and biochemical treatments. As a result, a healthy environment and sustainable development are ensured. In this chapter, two main processes, i.e., enzyme treatment and fermentation for the valorization of food waste and by-products, are discussed. Especially, fundamental principles and highlighting findings of concerned studies are focused at.