Spent cultivation substrate (SCS) is growing medium which stays after cultivation of mushrooms or vegetables and for many years was considered as a problematic waste product from farming. However recently in the new transition to sustainable, circular farming systems it is seen as a valuable product which could be recycled. In the scope of the VegWaMus CirCrop project we have focused on recycling spent mushroom substrate (SMS) into growing medium or growing medium additives for vegetables and subsequent mushroom cultivation. We also investigated reuse spent growing substrate (SGS) and crop waste from greenhouse tomato production into new cultivation substrate via composting, vermicomposting and co-composting. The SMS after mushroom cultivation was firstly air dried or used in its fresh form for tomato and lettuce growing medium additive and was characterised by high organic matter content, low bulk density, high pH and soluble slats content. SMS substrates was rich in macro and micro elements important from nutritional point of view and their content generally decreased in following order K, Ca, Na, Mg, Mn, Fe, Si, Zn, Cu, Se and Mo. The content of heavy metals was acceptable.

Whereas SGS showed also acceptable heavy metals content, and could be potentially used in horticulture for subsequent greenhouse vegetables cultivation. However composting or co composting with additional waste products is recommended to eliminate potential pests and due to high mineral salt content. SGS has good composting potential with sufficiently high C/N ration and organic mater content (50-65%) to heat up during composting. SGS can be also targeted for the direct use in outdoor agriculture and landscaping as soil fertility amendment.