NOVELTY - System for solid state fermentation of fungus comprises several separate fermentation units placed next to each other, where size of at least one dimension of each unit is accommodated to provide conditions for aerobic fermentation of the fungus without the need to install in the unit forced aeration, forced agitation or active cooling of the fungal culture.    USE - For biodegradation/bioremediation of polluted biomass. The fermentation product may be used as a component of microbial cultivation medium, for generation of energy, e.g. as fuel for combustion ovens, as animal feed, for soil enhancement; as bioremediation agent, for environment enhancing soil treatment, as a biofilter in aqueous environments and/or watersheds, as water retention device in e.g. low soil-humidity areas or in dykes to prevent flooding, as a raw material for paper and cardboard producing industries, as a feed for a microbial fuel cell, for heavy and precious metal recovery, for bionanotechnology applications.    ADVANTAGE - The system is simple, does not require extensive engineering and can be easily scaled up to any desired scale. The substrate does not need to be completely sterile. The fungus is adapted to degrade a particular substrate by serial transfer and growth of the fungus on the particular substrate, to enrich for strains with an improved growth performance on the substrate. The dimension of the unit is such that it circumvents heat build-up in the fungal culture present in the unit due to fungal growth and metabolism and to maintain aerobic metabolism throughout the culture. The arrangement of movable units for loading and/or unloading provides flexibility and optimal use of the available space.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for biodegradation of a substrate comprising biomass involving bringing the substrate in the form of particles having diameter 15 mm; adjusting the moisture content of the substrate to obtain a dry matter content of 40-90 wt.%; inoculating the substrate with an inoculum of a fungus; incubating substrate with the fungus in the system for a period to achieve partial degradation of the substrate; further processing mass of fungus and degraded substrate as desired.