Ancient biomass is the main source for petrochemicals including plastics, which are inherently difficult to be degraded, increasingly polluting the earth's ecosystem including our oceans. To reduce the consumption by substituting or even replacing most of the petrochemicals with degradable and renewable materials is inevitable and urgent for a sustainable future. We report here a unique strategy to directly convert biomass DNA, at a large scale and with low cost, to diverse materials including gels, membranes, and plastics without breaking down DNA first into building blocks and without polymer syntheses. With excellent and sometimes unexpected, useful properties, we applied these biomass DNA materials for versatile applications for drug delivery, unusual adhesion, multifunctional composites, patterning, and everyday plastic objects. We also achieved cell-free protein production that had not been possible by petrochemical-based products. We expect our biomass DNA conversion approach to be adaptable to other biomass molecules including biomass proteins. We envision a promising and exciting era coming where biomass may replace petrochemicals for most if not all petro-based products.