Improved human lifestyle and industrialization has led to unsustainable linear economies with overexploitation of resources and waste accumulation. Hence, the need of a paradigm shift from linear to circular economies where wastes are considered as resources. Microbial conversion has been among the waste management strategies attracting immense research and development interest. This is related to the diversity of the microbial world that opens the possibility to convert a wide range of low-value substrates into a panoply of value-added products. For instance, filamentous fungi are able to growth on substrates of variable composition, where a nutritious macroscopic filamentous structure, easily recovered from the medium, is produced as a result of nutrient assimilation. If edible filamentous fungi are used for the valorization of municipal and industrial sidestreams, residuals and wastes, a positive impact can be attained on e.g. the establishment of circular economies and concomitantly on the environment, and on shortage concerns of protein sources due to population growth forecasts. The talk will give an overview of the type of substrates that can be used and value-added products that can be produced through fungal conversion. Examples will include sidestreams and residuals from bioethanol, dairy, fish, paper and pulp, and agricultural sectors. Emphasis will also be given to industrial integration strategies of fungal-based processes that can lead to new value-added products, increased production yields and energy savings.