Lignin powder, obtained from an abundant and low-cost source, straw, through a low-environmental impact process, steam explosion, was used for the preparation of blends with a biodegradable polyester, poly (F.-caprolactone) (PCL), with an innovative technique, high-energy ball milling. Lignin strongly stabilized PCL against UV radiation. The modulus of the blends increased with the addition of lignin; nevertheless, the elongation at breaking decreased. Through thermal characterization (differential scanning calorimetry and dynamic mechanical analysis), lignin and PCL were found to be immiscible. (C) 2008 Wiley Periodicals, Inc.