Parallel Session 19 – Gasification and liquefaction pathways to biofuels and biochemicals

Thursday 24 October 2024, 14.00-15.30 BRT

Moderator: Berend Vreugdenhil (TNO, The Netherlands)

Speakers:

Selected conclusions and key messages:

  • Fast pyrolysis is a mature technology. There is an installed capacity of around 170 ktons per year, primarily directed to the use of pyrolysis oil as boiler fuel. Hydrothermal liquefaction shows highly dynamic development, with commercial demonstration units currently being commissioned. It has a high liquid yield and is also efficient for sludges or high moisture feedstocks. Both technologies can play an important role in the energy transition. They enable a de-coupling of biogenic residue supply and fuel use locations and can produce relevant bio-based commodities for all anticipated hard-to-abate sectors.
  • Bio-oil can be co-processed in existing petroleum refineries. Co-processing is a pathway for quickly introducing renewable carbon into transportation fuel industry and would utilize a multi-trillion-dollar infrastructure already in place worldwide. It can provide carbon credits for refiners and a decarbonization strategy for petroleum refineries. Nevertheless, there is a scale problem with lignocellulosic biorefineries typically producing around 1% of a medium sized petroleum refinery. Finding sufficient supplies of biogenic feedstocks will be challenging at refinery scale.
  • The major question in co-processing is where the bio-carbon goes to in the end products. Tests were performed at NREL with stabilized fast pyrolysis bio-oil (FPBO) and Fischer-Tropsch (FT) wax inserted in the Fluid Catalytic Cracker (FCC). It is clear that bio-carbon doesn’t follow the distribution of fossil carbon in the end product. Adding easily craked feedstocks such as FT wax results in higher gas yields with about equal bio-carbon distribution to gases and liquids (70% of the fossil carbon ends up in the liquid phase). Very little bio-carbon ends up on the catalyst or in the aqueous phase. In the case of heavier feedstocks such as stabilized bio-oil, most of the bio-carbon goes to the liquids (which is positive), but a significant amount ends up as coke-on-catalyst (which is undesirable). The choice of catalyst does make a difference. Blending strategies with different types of biogenic feedstocks to optimize the bio-carbon distribution will be complex but necessary to maximize specific fuel-related credits (like jetfuel). Small differences can have a massive economic impact.
  • BTG in the Netherlands started a test unit for the fractionation of FPBO. An aqueous extractant (water) is added to the FPBO causing separation between a water soluble fraction (wet pyrolytic sugars) and a water non-soluble fraction (liquid pyrolytic lignin). Water may be removed from the wet sugars to produce concentrated pyrolytic sugars. The liquid pyrolytic lignin can be further processed to produce solid pyrolytic lignin together with light phenolics. BTG Bioliquids is working on the development of a marine fuel, a low viscosity oil-in-water emulsified synthetic biofuel consisting for up to 40% bio components such as pyrolytic sugars produced by BTG Bioliquids; 40-50% fossil residuals; and 10% water. The fuel would have a similar GHG reduction and a similar cost as B24/B30 and provides an alternative to limited UCO & FAME supply.
  • Experiments have been done by VTT in Finland to operate a circulating fluidized bed (CFB) gasifier in flexible mode. The plant would have two operating modes: (1) co-production of biomethane, biochar and heat (45% conversion to biomethane, 25% to biochar and 10% to usable heat); and (2) maximised production of biomethane and heat ( 70% conversion to biomethane and 15 % to heat). The conclusion was that the CFB gasifier can be operated flexibly with woody residues under both modes of the FlexSNG process. Shifting between operational modes is simple and can be achieved by adjusting the operating temperature and the oxygen-to-biomass feed ratio.

 

Integration of bio-oil in the FCC of a petroleum refinery (from presentation of Robert Baldwin, NREL).