The ZELDA project aims to develop a new generation of entirely bio-based alternatives to chemical pesticides for crop protection. Through a zero-waste biorefinery concept, ZELDA will fully valorise lignocellulosic biomasses such as birchwood, grape and tomato residues, and wheat straw into safe, sustainable formulations that combine cellulose, hemicellulose and lignin, to produce immune-eliciting products. Developed under a Safe and Sustainable by Design (SSbD) framework, ZELDA biosolutions will mimick a natural photogenic process to strengthen plant defences against fungal and bacterial pathogens, while promoting plant growth and acting directly as microbicides as secondary effects. ZELDA also integrates digital and AI-based precision farming tools to optimise field application, reduce waste, and enhance environmental performance. The efficacy od these bio-based solutions will be validated from lab to field on tomato, grape, and cereals across different Europe’s pedo-climatic agricultural regions.