The characterization of lignin char and its reactivity towards the formation of polycyclic aromatic hydrocarbons (PAHs) were studied. The char was prepared by pyrolyzing lignin at atmospheric pressure and temperatures ranging from 150 to 550 degreesC under both pyrolytic and oxidative (5% oxygen in helium) atmospheres. The chemical composition of char was characterized by Fourier transform infrared spectroscopy (FTIR), cross-polarization magic angle spinning C-13 nuclear magnetic resonance spectroscopy (CPMAS C-13 NMR), and energy-dispersive X-ray spectroscopy. The surface area of the char was measured by Brunauer-Emmett-Teller method and surface morphology obtained by scanning electron microscopy (SEM). The char yield in pyrolysis decreased rapidly with an increase in temperature until 400 degreesC, after which there was a gradual decrease in the yield to ca. 40% at 750 degreesC. In oxidative atmosphere, the char yield decreased to ca. 15% at 550 degreesC. The surface area of the char was low with a maximum of 5 m(2)/g. SEM analysis indicated that the pyrolysis led to the formation of melt, liquid phase, vesicles, precipitates of inorganic salts and surface etching. These structures decomposed rapidly at high temperatures. FTIR and NMR studies showed a gradual decrease in the amounts of OH and CH3 with increasing temperature. At 550 degreesC, most IR bands, except those due to the aromatic CH and OH stretches, disappeared resulting in mainly aromatic char. Both the H/C and O/C ratios of the char decreased with increase in temperature. Although the data on char reactivity was limited, it indicated that surface area, presence of inorganics and aromaticity of char may be important factors in PAH formation. These chars have low reactivity, compared to chars from other biomass constituents, such as chlorogenic acid, pectin and cellulose, probably due to the highly cross-linked and refractory nature of the lignin char. (C) 2004 Elsevier Ltd. All rights reserved.