Energy Content of the Products from Pyrolysis of Residual Biomass

In this work, the energy associated to the pyrolysis products of different biomass types (acacia, gorse, giant reed, olive pomace, and eucalyptus sawdust) in fixed-bed batch-reactor, were analyzed. For this purpose, pyrolysis experiments at 450 °C of peak temperature and 10 °C/min of heating rate were performed. For each experiment, the mass of biomass, biochar, and bio-oil were quantified, and by difference, the mass of permanent gas was calculated. The biomass and biochar ultimate analysis (CHNOS), and the permanent gas composition (H2, CH4, CO, CO2, C2H4, C2H6, C3H8) were determined. The bio-oil ultimate analysis (CHNOS) was calculated based on mass balance to the biomass pyrolysis process. According to the results, for the pyrolysis of different feedstocks, the biochar yield was between 0.27 and 0.36 kgbiochar·kg-1biomass,db, the bio-oil yield was between 0.51 and 0.68 kgbio-oil·kg-1biomass,db and the gas yield was between 0.19 and 0.27 kggas·kg-1biomass,db. Regarding composition of the biochar, the carbon content was between 75.3 and 81.8 wt%, the hydrogen content was between 2.80 and 3.20 wt%, and the oxygen content was between 9.10 and 20.0 wt%. The volumetric composition of the permanent gas was mainly consisting of CO and CO2, around 87%v. In relation to the ultimate composition of the bio-oil, the carbon content was between 25.97 and 35.25 %wt, the oxygen content was between 52.51 and 60.01 %wt and the hydrogen content was between 9.99 and 12.89 %wt. According to the balance of energy associated to pyrolysis products, the specific energy content of biochar was between 7.39 and 10.52 MJ·kg-1 dry biomass, the energy content of permanent gas was between 1.01 and 1.64 MJ·kg-1 dry biomass, and the energy content of bio-oil was around 4.67 and 8.07 MJ·kg-1 dry biomass. The information obtained is relevant to support the design and scale-up of pyrolysis processes and to assess the energy integration and sustainability of pyrolysis processes.
Proceedings of the 30th European Biomass Conference and Exhibition, 9-12 May 2022, Online, pp. 954-959