How do novel and conventional agri-food wastes, co-products and by-products improve soil functions and soil quality?

•Low value agri-food wastes, co-products and by-products (AFWCBs) improve soil quality.•Insect frass residues suppress plant disease, increase microbial activities and immobilize N.•Digestates, duckweed and rice bran compost release N immediately after application.•AFWCBs play roles in closing the nitrogen and carbon cycle.