The protein poly-L-leucine has been used as a model compound for the nitrogen in biomass fuels. It was pyrolysed in a fluidised bed at 700 and 800 degreesC and the pyrolysis gases were analysed with a FT-IR spectrometer. HCN, NH3 and HNCO were identified as the main nitrogen-containing species, while neither NO nor N2O were found among the pyrolysis gases. At 700 degreesC, as much as 58% of the nitrogen content was converted into HCN and 31% into NH3. The HCN/NH3 ratio increased from about 1.9 at 700 degreesC to above 2.2 at 800 degreesC. Pyrolysis of another protein, poly-L-proline, at 800 degreesC gave a HCN/NH3 ratio close to 10. This revealed that the protein's amino acid composition has a marked impact on the composition of the pyrolysate. (C) 2002 Elsevier Science Ltd. All rights reserved.