Fast pyrolysis of Saccharina japonica alga in a fixed-bed reactor for bio-oil production

•Fas pyrolysis of Saccharina japonica was conducted in a fixed-bed reactor.•Effects of pyrolysis temperature and sweeping-gas flow rate were investigated.•The highest liquid yield was obtained at the temperature in range of 350–500°C with a sweeping gas flow rate of 300ml/min.•The HHVs of pyrolysis bio-oils from S. japonica were in the range of 32.97–33.26MJ/kg. Macro-algae are recognized as a potential feedstock for renewable energy and fuel production. Saccharina japonica is a kind of macro-algae that has been extensively cultivated in Korea. Through pyrolysis, S. japonica can be converted into bio-oil, gas, and char. In this study, we investigated the fast pyrolysis of S. japonica in a fixed-bed reactor at different temperatures from 350 to 550°C with sweeping-gas flow rates of 100, 300, and 500ml/min. As the pyrolysis temperature was increased from 350°C to 500°C, the bio-oil yields decreased while the gas yields increased. The highest liquid yield (40.91wt%) was obtained at a pyrolysis temperature of 350°C with a sweeping-gas velocity of 300ml/min. The major compositions in the bio-oil were di-anhydromannitol (34.45%), iso-sorbide (19.84%), and 2-methyl furyl ketone (8.43%). The gas products (including CO, CO2, H2, and hydrocarbon gases from C1 to C4), were analyzed by gas chromatography with an FID and a TCD. The bio-chars contained a high carbonaceous content can be used as a pollution-free solid fuel or for the production of activated carbon and other chemicals.