Natural and biocompatible composite materials combined with large-scale digital fabrication can enable environmentally friendly bio-inspired construction. This work includes a robotically controlled additive-manufacturing system that deposits chitosan. We demonstrate the approach by designing, building, and evaluating the mechanics and controls of a three-chamber motor-driven extrusion system. Composite objects fabricated using our technology display graded properties and feature sizes ranging from micro-to-macroscale. The constructs may be chemically stabilized or dissolved in water and recycled within minutes. Applications include the fabrication of fully recyclable products or temporary architectural components such as tent structures with graded mechanical and optical properties.