The pyrolysis of two brown macroalgae (Undaria pinnatifida and Laminaria japonica) and one red macroalgae (Porphyra tenera) was investigated for the production of bio-oil within the temperature range of 300-600 degrees C. Macroalgae differ from lignocellulosic land biomass in their constitutional compounds and high N, S and ash contents. The maximum production of bio-oil was achieved at 500 degrees C. with yields between 37.5 and 47.4 wt.%. The main compounds in bio-oils vary between macroalgae and are greatly different from those of land biomass, especially in the presence of many nitrogen-containing compounds. Of the gaseous products. CO(2) was dominant, while C(1)-C(4) hydrocarbons gradually increasing at 400 degrees C and above. The pretreatment of macroalgae by acid washing effectively reduced the ash content. The pyrolysis of macroalgae offers a new opportunity for feedstock production; however, the utilization of bio-oil as a fuel product needs further assessment. (C) 2010 Elsevier Ltd. All rights reserved.