Biomass Polygeneration System for the Thermal Conversion of Softwood Waste into Hydrogen and Drop-In Biofuels

In order to keep the +1.5 °C over-temperature, previously predicted with high confidence by IPPC Sixth Assessment, as minimal as feasible, it is more than vital to achieve a low-emission energy system. Polygeneration systems based on thermochemical processes involve biomass conversion in multi-output of bioenergy carriers and chemicals. Due to reduced energy input and input/output diversification, polygeneration energy systems are considered interesting pathways that can increase competitiveness of biomass-derived products. The proposed route of fast pyrolysis, sorption-enhanced biochar gasification and crude bio-oil hydrodeoxygenation to produce drop-in biofuel and hydrogen is examined. Both kinetic and equilibrium approaches were implemented in Aspen Plus to take into account the effect of the major operating parameters on the process performance and then validated against the literature data. Results show how the process integration leads to improved mass conversion yield and increases overall energy efficiency up to 10%-points, reaching the maximum value of 75%. Among the various parameters investigated, pyrolysis temperature influences mainly the products distribution while Steam/Biochar and Sorbent/Biochar affect the energy conversion efficiency.